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Sample records for thermal degradation studies

  1. Study of thermal degradation of vanadium and titanium acetylacetonate derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Dyagileva, L.M.; Tsyganova, E.I.; Mar' in, V.P.; Aleksandrov, Yu.A. (Gor' kovskij Gosudarstvennyj Univ. (USSR). Nauchno-Issledovatel' skij Inst. Khimii)

    1982-09-01

    Kinetics and products of vanadium (+3), vanadyl (+3) and titanium (+3) acetylacetonates thermal degradation have been studied in vapor phase in the closed system at 300-470 deg C. Gaseous composition of pyrolysis has been determined at different levels of decomposition. It is supposed that vanadium and metal vanadium mixed oxides become vanadium (+3) pyrolysis products. It is shown that metal oxidation level does not affect the thermal degradation rate. Central atom substitution leads to the change in thermal stability. Titanium (+3) acetylacetate derivatives are less stable than vanadium (+3) ones.

  2. Study of the thermal degradation of citrus seeds

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Montoya, V. [Centro de Quimica, Instituto de Ciencias, Universidad Autonoma de Puebla, Apdo. Postal J-55, Puebla 72570, Pue (Mexico); Instituto Nacional del Carbon, CSIC, Apartado 73, E-33080 Oviedo (Spain); Montes-Moran, M.A. [Instituto Nacional del Carbon, CSIC, Apartado 73, E-33080 Oviedo (Spain); Elizalde-Gonzalez, M.P. [Centro de Quimica, Instituto de Ciencias, Universidad Autonoma de Puebla, Apdo. Postal J-55, Puebla 72570, Pue (Mexico)

    2009-09-15

    The citrus seeds are one of the principal residues in the juice industry and their utilization can decrease significantly the problems of their final disposal. In this work the thermal degradation of three Mexican citrus seeds: orange (Citrus sinensis), lemon (Citrus Limon) and grapefruit (Citrus paradisi) was studied in nitrogen atmosphere. The two components (embryo and husk) of the seeds were characterized separately. The results showed that the thermal effects are very similar between the three embryos and the three husks. The embryos show higher degradability, superior content of nitrogen and higher heating value than the husks. The thermal degradation of the components of the three seeds is completed at 600 C and it is considered to be a global process derived from the decomposition of their principal components (cellulose, hemicellulose and lignin). The results suggest that mixing the three entire seeds will not lead to a severe deviation from their individual thermal behavior and that the industry could apply them for carbonization purposes. (author)

  3. Thermal Degradation Studies of Polyurethane/POSS Nanohybrid Elastomers

    Energy Technology Data Exchange (ETDEWEB)

    Lewicki, J P; Pielichowski, K; TremblotDeLaCroix, P; Janowski, B; Todd, D; Liggat, J J

    2010-03-05

    Reported here is the synthesis of a series of Polyurethane/POSS nanohybrid elastomers, the characterization of their thermal stability and degradation behavior at elevated temperatures using a combination of Thermal Gravimetric Analysis (TGA) and Thermal Volatilization Analysis (TVA). A series of PU elastomers systems have been formulated incorporating varying levels of 1,2-propanediol-heptaisobutyl-POSS (PHIPOSS) as a chain extender unit, replacing butane diol. The bulk thermal stability of the nanohybrid systems has been characterized using TGA. Results indicate that covalent incorporation of POSS into the PU elastomer network increase the non-oxidative thermal stability of the systems. TVA analysis of the thermal degradation of the POSS/PU hybrid elastomers have demonstrated that the hybrid systems are indeed more thermally stable when compared to the unmodified PU matrix; evolving significantly reduced levels of volatile degradation products and exhibiting a {approx}30 C increase in onset degradation temperature. Furthermore, characterization of the distribution of degradation products from both unmodified and hybrid systems indicate that the inclusion of POSS in the PU network is directly influencing the degradation pathways of both the soft and hard block components of the elastomers: The POSS/PU hybrid systems show reduced levels of CO, CO2, water and increased levels of THF as products of thermal degradation.

  4. Thermal degradation kinetics and antimicrobial studies of terpolymer resins

    Directory of Open Access Journals (Sweden)

    Abdul R. Burkanudeen

    2016-09-01

    Full Text Available The terpolymer (ASF was synthesized by condensation of anthranilic acid and salicylic acid with formaldehyde in the presence of glacial acetic acid as a catalyst at 140 ± 2 °C for 6 h with varying proportions of reactants. The terpolymer ASF-I was characterized by elemental analysis, FTIR, 1H NMR and 13C NMR spectroscopy. The thermal decomposition behavior of ASF-I, II and III terpolymers was studied using thermogravimetric analysis (TGA in a static nitrogen atmosphere at a heating rate of 20 °C/min. Freeman–Carroll, Sharp–Wentworth and Phadnis–Deshpande methods were used to calculate the thermal activation energy (Ea the order of reaction (n, entropy change (ΔS, free energy change (ΔF, apparent entropy (S∗ and frequency factor (Z. Phadnis–Deshpande method was used to propose the thermal degradation model for the decomposition pattern of ASF-I terpolymer resin. The order of the decomposition reaction was found to be 0.901. The thermal activation energy determined with the help of these methods was in good agreement with each other. The ASF-I, II and III resins were tested for their inhibitory action against pathogenic bacteria and fungi. The resins show potent inhibitory action against bacteria, such as Escherichia coli, Klebsiella, Staphylococcus aureus and Pseudomonas aeruginosa and fungi viz. Aspergillus flavus, Aspergillus niger, Penicillium sp., Candida albicans, Cryptococcus neoformans and Mucor sp.

  5. Studies on Thermal Degradation Behavior of Siliceous Agriculture Waste (Rice Husk, Wheat Husk and Bagasse)

    National Research Council Canada - National Science Library

    Syed H. Javed; Umair Aslam; Mohsin Kazmi; Masooma Rustam; Sheema Riaz; Zahid Munir

    2015-01-01

    Various siliceous agriculture waste (SAW) such as rice husk, wheat husk and bagasse have been investigated to study their thermal degradation behavior using Thermogravimetric Analyzer (TGA) technique...

  6. Thermal Degradation Studies of A Polyurethane Propellant Binder

    Energy Technology Data Exchange (ETDEWEB)

    Assink, R.A.; Celina, M.; Gillen, K.T.; Graham, A.C.; Minier, L.M.

    1999-06-12

    The thermal oxidative aging of a crosslinked hydroxy-terminated polybutadiene (HTPB)/isophorone diisocyanate (IPDI) based polyurethane rubber, used as a polymeric binder in solid propellant grain, was investigated at temperatures from 25 C to 125 C. The changes in tensile elongation, polymer network properties and chain dynamics, mechanical hardening and density were determined with a range of techniques including modulus profiling, solvent swelling, NMR relaxation and O{sub 2} permeability measurements. We critically evaluated the Arrhenius methodology that is commonly used with a linear extrapolation of high temperature aging data using extensive data superposition and highly sensitive oxygen consumption experiments. The effects of other constituents in the propellant formulation on aging were also investigated. We conclude that crosslinking is the dominant process at higher temperatures and that the degradation involves only limited hardening in the bulk of the material. Significant curvature in the Arrhenius diagram of the oxidation rates was observed. This is similar to results for other rubber materials.

  7. Thermal Degradation Study of Decabromodiphenyl Ether. Translating Thermo-Analytical Results into Optimal Chromatographic Conditions

    Directory of Open Access Journals (Sweden)

    Dumitras Mihai

    2016-12-01

    Full Text Available This study aims to investigate the thermal degradation behavior of decabrominated diphenyl ether (BDE 209, a flame retardant (FR which accounts for more than 90% of the total polybrominated diphenyl ethers reported for indoor dust samples collected from Eastern Romania. Simultaneous TG/DTA was applied under various heating rate and atmospheres. The results of this study showed that BDE 209 undergoes thermal degradation in a single step, regardless of the heating rate or atmosphere, with an initial degradation temperature between 297 and 330 °C, depending on the heating rate, and a partial overlapping of melting and thermal degradation in the initial stages which might suggest that the common degradation noticed for the higher brominated FRs analysis might also occur during sample preparation or during injection of the extracts in the GC systems and not necessarily during column elution. The main findings of this research were aimed at designing proper GC analytical methods for the selected halogenated contaminants.

  8. Physics Based Electrolytic Capacitor Degradation Models for Prognostic Studies under Thermal Overstress

    Science.gov (United States)

    Kulkarni, Chetan S.; Celaya, Jose R.; Goebel, Kai; Biswas, Gautam

    2012-01-01

    Electrolytic capacitors are used in several applications ranging from power supplies on safety critical avionics equipment to power drivers for electro-mechanical actuators. This makes them good candidates for prognostics and health management research. Prognostics provides a way to assess remaining useful life of components or systems based on their current state of health and their anticipated future use and operational conditions. Past experiences show that capacitors tend to degrade and fail faster under high electrical and thermal stress conditions that they are often subjected to during operations. In this work, we study the effects of accelerated aging due to thermal stress on different sets of capacitors under different conditions. Our focus is on deriving first principles degradation models for thermal stress conditions. Data collected from simultaneous experiments are used to validate the desired models. Our overall goal is to derive accurate models of capacitor degradation, and use them to predict performance changes in DC-DC converters.

  9. A study of poly(vinyl alcohol thermal degradation by thermogravimetry and differential thermogravimetry

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    Julián Esteban Barrera

    2010-04-01

    Full Text Available The thermal degradation of poly(vinyl alcohol (PVA having different degrees of hydrolysis and molecular weights was studied by thermogravimetry (TGA and differential thermogravimetry (DTGA. Four degradation events were identified whose intensity was related to the degree of hydrolysis. It was verified that the solid-state degradation mechanism for high hydrolysis degrees corresponded to eliminating water-forming side groups in stoichiometric amounts. The presence of acetate groups and lower melting points delayed the polymer’s thermal decomposition at lower hydrolysis degrees. There was no direct correlation in these samples between weight-loss during the first degradation event and the stoichiometric quantities which would be produced by eliminating the side groups. Reaction order and energy activation value qualitative coincidence was found by evaluating experimental data by using Freeman-Carroll and Friedman kinetic models.

  10. A study of poly(vinyl alcohol thermal degradation by thermogravimetry and differential thermogravimetry

    Directory of Open Access Journals (Sweden)

    Julián Esteban Barrera

    2007-05-01

    Full Text Available The thermal degradation of poly(vinyl alcohol (PVA having different degrees of hydrolysis and molecular weights was studied by thermogravimetry (TGA and differential thermogravimetry (DTGA. Four degradation events were identified whose intensity was related to the degree of hydrolysis. It was verified that the solid-state degradation mechanism for high hydrolysis degrees corresponded to eliminating water-forming side groups in stoichiometric amounts. The presence of acetate groups and lower melting points delayed the polymer’s thermal decomposition at lower hydrolysis degrees. There was no direct correlation in these samples between weight-loss during the first degradation event and the stoichiometric quantities which would be produced by eliminating the side groups. Reaction order and energy activation value qualitative coincidence was found by evaluating experimental data by using Freeman-Carroll and Friedman kinetic models.

  11. On the Influence of the Sample Absorptivity when Studying the Thermal Degradation of Materials

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    Pascal Boulet

    2015-08-01

    Full Text Available The change in absorptivity during the degradation process of materials is discussed, and its influence as one of the involved parameters in the degradation models is studied. Three materials with very different behaviors are used for the demonstration of its role: a carbon composite material, which is opaque, almost grey, a plywood slab, which is opaque and spectral-dependent and a clear PMMA slab, which is semitransparent. Data are analyzed for virgin and degraded materials at different steps of thermal degradation. It is seen that absorptivity and emissivity often reach high values in the range of 0.90–0.95 with a near-grey behavior after significant thermal aggression, but depending on the materials of interest, some significant evolution may be first observed, especially during the early stages of the degradation. Supplementary inaccuracy can come from the heterogeneity of the incident flux on the slab. As a whole, discrepancies up to 20% can be observed on the absorbed flux depending on the degradation time, mainly because of the spectral variations of the absorption and up to 10% more, depending on the position on the slab. Simple models with a constant and unique value of absorptivity may then lead to inaccuracies in the evaluation of the radiative flux absorption, with possible consequences on the pyrolysis analysis, especially for properties related to the early step of the degradation process, like the time to ignition, for example.

  12. On the Influence of the Sample Absorptivity when Studying the Thermal Degradation of Materials.

    Science.gov (United States)

    Boulet, Pascal; Brissinger, Damien; Collin, Anthony; Acem, Zoubir; Parent, Gilles

    2015-08-21

    The change in absorptivity during the degradation process of materials is discussed, and its influence as one of the involved parameters in the degradation models is studied. Three materials with very different behaviors are used for the demonstration of its role: a carbon composite material, which is opaque, almost grey, a plywood slab, which is opaque and spectral-dependent and a clear PMMA slab, which is semitransparent. Data are analyzed for virgin and degraded materials at different steps of thermal degradation. It is seen that absorptivity and emissivity often reach high values in the range of 0.90-0.95 with a near-grey behavior after significant thermal aggression, but depending on the materials of interest, some significant evolution may be first observed, especially during the early stages of the degradation. Supplementary inaccuracy can come from the heterogeneity of the incident flux on the slab. As a whole, discrepancies up to 20% can be observed on the absorbed flux depending on the degradation time, mainly because of the spectral variations of the absorption and up to 10% more, depending on the position on the slab. Simple models with a constant and unique value of absorptivity may then lead to inaccuracies in the evaluation of the radiative flux absorption, with possible consequences on the pyrolysis analysis, especially for properties related to the early step of the degradation process, like the time to ignition, for example.

  13. Thermal degradation study of silicon carbide threads developed for advanced flexible thermal protection systems

    Science.gov (United States)

    Tran, Huy Kim; Sawko, Paul M.

    1992-01-01

    Silicon carbide (SiC) fiber is a material that may be used in advanced thermal protection systems (TPS) for future aerospace vehicles. SiC fiber's mechanical properties depend greatly on the presence or absence of sizing and its microstructure. In this research, silicon dioxide is found to be present on the surface of the fiber. Electron Spectroscopy for Chemical Analysis (ESCA) and Scanning Electron Microscopy (SEM) show that a thin oxide layer (SiO2) exists on the as-received fibers, and the oxide thickness increases when the fibers are exposed to high temperature. ESCA also reveals no evidence of Si-C bonding on the fiber surface on both as-received and heat treated fibers. The silicon oxide layer is thought to signal the decomposition of SiC bonds and may be partially responsible for the degradation in the breaking strength observed at temperatures above 400 C. The variation in electrical resistivity of the fibers with increasing temperature indicates a transition to a higher band gap material at 350 to 600 C. This is consistent with a decomposition of SiC involving silicon oxide formation.

  14. Thermal degradation and morphological studies on raw and reinforced polyacrylic rubbers

    Science.gov (United States)

    Sasikala, A.; Kala, A.

    2017-05-01

    Poly acrylate rubbers (ACM) of today are saturated copolymers of monomeric acrylic esters and reactive cure site monomers. ACM elastomer have also found use in vibration damping due to its excellent resilience. Other applications include textiles, adhesives, and coatings. Two state of Poly acrylic raw and reinforced Rubber are analyzed using FTIR spectroscopy, Optical Microscopy, DSC and TGA measurements. With the objective of determined the mechanical strength, Thermal analysis on TGA and DSC studies show that, the thermal degradation temperature Tg of the sample material is obtained and activation energy is also calaulated by Broido, Horowitz - Metzger, Piloyan-Novikova and Coats Redfern methods which are found.

  15. A theoretical and experimental study of the thermal degradation of biomass

    Energy Technology Data Exchange (ETDEWEB)

    Groenli, Morten G.

    1996-12-31

    This thesis relates to the thermal degradation of biomass covering a theoretical and experimental study in two parts. In the first part, there is presented an experimental and modeling work on the pyrolysis of biomass under regimes controlled by chemical kinetics, and the second part presents an experimental and modeling work on the pyrolysis of biomass under regimes controlled by heat and mass transfer. Five different celluloses, and hemicellulose and lignin isolated from birch and spruce have been studied by thermogravimetry. The thermo grams of wood species revealed different weight loss characteristics which can be attributed to their different chemical composition. The kinetic analysis gave activation energies between 210 and 280 kJ/mole for all the celluloses, and a model of independent parallel reactions was successfully used to describe the thermal degradation. In the second part of the thesis there is presented experimental and modeling work on the pyrolysis of biomass under regimes controlled by heat and mass transfer. The effect of heating conditions on the product yields distribution and reacted fraction was investigated. The experiments show that heat flux alters the pyrolysis products as well as the intra particle temperatures to the greatest extent. A comprehensive mathematical model which can simulate drying and pyrolysis of moist wood is presented. The simulation of thermal degradation and heat transport processes agreed well with experimental results. 198 refs., 139 figs., 68 abs.

  16. Degradation of polysorbates 20 and 80: studies on thermal autoxidation and hydrolysis.

    Science.gov (United States)

    Kishore, Ravuri S K; Pappenberger, Astrid; Dauphin, Isabelle Bauer; Ross, Alfred; Buergi, Beatrice; Staempfli, Andreas; Mahler, Hanns-Christian

    2011-02-01

    The purpose of this work was to study the mechanistic pathways of degradation of polysorbates (PS) 20 and PS80 in parenteral formulations. The fate of PS in typical protein formulations was monitored and analyzed by a variety of methods, including (1)H NMR, high-performance liquid chromatography/evaporative light scattering detection, and ultraviolet-visible spectroscopy. Oxidative degradation of PS in neat raw material was studied using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and headspace gas chromatography-mass spectrometry. TGA-DSC studies revealed that autoxidation via a radical mechanism is dominated by statistical random scission in PS20 and PS80. Thermal initiation of radical formation occurs at the polyoxyethylene (POE) as well as the olefin sites. In PS80, radical initiation at the olefinic site precedes initiation at the POE site, leading to modified degradation profile. Corresponding to these results, in aqueous formulations, a surge peroxide content was detected in PS20-containing samples and in higher concentrations in those containing PS80. Hydrolysis in aqueous formulations, as followed by (1)H NMR, was found to have a half-life of 5 months at 40°C. On the basis of the obtained results, PSs degrade mainly via autoxidation and also via hydrolysis at higher temperatures. Further studies are required to investigate on potential effects of degradation on surface activity and protein stability in PS-containing formulations. Copyright © 2010 Wiley-Liss, Inc.

  17. Thermal degradation of glucosinolates in red cabbage

    NARCIS (Netherlands)

    Oerlemans, K.; Barrett, D.M.; Bosch Suades, C.; Verkerk, R.; Dekker, M.

    2006-01-01

    Thermal degradation of individual glucosinolates within the plant matrix was studied. Red cabbage samples were heated at different temperatures for various times. To rule out the influence of enzymatic breakdown and to focus entirely on the thermal degradation of glucosinolates, myrosinase was

  18. Study of Curing Kinetics and Thermal Degradation of UV Curable Epoxy Acrylate Resin

    Directory of Open Access Journals (Sweden)

    Amrita Sharma

    2008-01-01

    Full Text Available Blends of epoxy acrylate resins (acid values 3, 6.5 & 10 mg KOH/gm Solid with monofunctional monomers (ethoxylated phenol monoacrylate were prepared by physical mixing, having weight ratio 50:50. These blends were cured by using UV radiations in presence of photo initiator (Darocure 1173. The thermal degradation kinetics of these resin blends were studied, using thermo gravimetric analysis in nitrogen atmosphere at a heating rate of 10°C/min. by applying Coats-Red fern equation. According to the analysis, all the coating films degrade in two steps. In the first step of degradation kinetics, R2M follows 1.75 order (n=1.75 and all other coating films follow second order (n=2 kinetics. In second step, R2M & R3M follow half order (n=0.5 kinetics and R1M follow first order (n=1 degradation kinetics. Order of the reaction is obtained on the basis of best fit analysis, and all the parameters were confirmed by regression analysis. From the reaction order, value of activation energy (E and pre exponential factor (Z were calculated by the slop and intercept of the plot between X and Y, respectively.

  19. Thermal degradation of organics for pyrolysis in space: Titan's atmospheric aerosol case study

    Science.gov (United States)

    He, Jing; Buch, Arnaud; Carrasco, Nathalie; Szopa, Cyril

    2015-03-01

    Pyrolysis coupled with mass spectry is among the instrumentation the most implemented in planetary exploration probes to analyze the chemical composition of extraterrestrial solid samples. It is used to analyze the volatile species which can be thermally extracted from the samples, including the organic fraction which is of primary interest for astrobiological purposes. However the thermal degradation of these organic materials, which can be very complex in nature or very different from organics commonly present on Earth, is badly known. This leads to a restriction in the optimization of space instrumentation, and in the interpretation of the measurements. In the present work we propose a complete overview of the thermal degradation processes studied on a model of complex organic material produced in an extraterrestrial environment, i.e. laboratory analogues of Titan's atmospheric aerosols. The thermal evolution of the studied analogues is monitored by following their mass loss, the emitted heating flux, and the evolution of their chemical composition through infrared spectroscopy and elemental analysis. The gaseous products released from the material are also analyzed by mass spectrometry, allowing to better constrain the mechanisms of chemical evolution of the samples. The complex organic material analyzed is found not to be fully decomposed when heated up to about 800 °C, with the evidence that nitrogen is still deeply incorporated in the remaining graphitic carbon nitride residue. The most appropriate pyrolysis temperature to chemically probe the studied material is found to be about 450 °C because at this temperature are detected the largest gaseous molecules which should be the most representative ones of the material pyrolyzed.

  20. Nylon separators. [thermal degradation

    Science.gov (United States)

    Lim, H. S.

    1977-01-01

    A nylon separator was placed in a flooded condition in K0H solution and heated at various high temperatures ranging from 60 C to 110 C. The weight decrease was measured and the molecular weight and decomposition product were analyzed to determine: (1) the effect of K0H concentration on the hydrolysis rate; (2) the effect of K0H concentration on nylon degradation; (3) the activation energy at different K0H concentrations; and (4) the effect of oxygen on nylon degradation. The nylon hydrolysis rate is shown to increase as K0H concentration is decreased 34%, giving a maximum rate at about 16%. Separator hydrolysis is confirmed by molecular weight decrease in age of the batteries, and the reaction of nylon with molecular oxygen is probably negligible, compared to hydrolysis. The extrapolated rate value from the high temperature experiment correlates well with experimental values at 35 degrees.

  1. Thermal battery degradation mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Missert, Nancy A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Brunke, Lyle Brent [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-09-01

    Diffuse reflectance IR spectroscopy (DRIFTS) was used to investigate the effect of accelerated aging on LiSi based anodes in simulated MC3816 batteries. DRIFTS spectra showed that the oxygen, carbonate, hydroxide and sulfur content of the anodes changes with aging times and temperatures, but not in a monotonic fashion that could be correlated to phase evolution. Bands associated with sulfur species were only observed in anodes taken from batteries aged in wet environments, providing further evidence for a reaction pathway facilitated by H2S transport from the cathode, through the separator, to the anode. Loss of battery capacity with accelerated aging in wet environments was correlated to loss of FeS2 in the catholyte pellets, suggesting that the major contribution to battery performance degradation results from loss of active cathode material.

  2. Theoretical studies on thermal degradation reaction mechanism of model compound of bisphenol A polycarbonate.

    Science.gov (United States)

    Huang, Jinbao; He, Chao; Li, Xinsheng; Pan, Guiying; Tong, Hong

    2018-01-01

    Density functional theory methods (DFT) M062X have been used to investigate the thermal degradation processes of model compound of bisphenol A polycarbonate (MPC) and to identify the optimal reaction paths in the thermal decomposition of bisphenol A polycarbonate (PC). The bond dissociation energies of main bonds in MPC were calculated, and it is found that the weakest bond in MPC is the single bond between the methylic carbon and carbon atom and the second weakest bond in MPC is the single bond between oxygen atom and the carbonyl carbon. On the basis of computational results of kinetic parameters, a mechanism is proposed where the hydrolysis (or alcoholysis) reaction is the main degradation pathways for the formation of the evolved products, and the homolytic cleavage and rearrangement reactions are the competitive reaction pathways in the thermal degradation of PC. The proposed mechanism is consistent with experimental observations of CO2, bisphenol A and 1,1-bis(4-hydroxyphenyl)-ethane as the main degradation products, together with a small amount of CO, alkyl phenol and diphenyl carbonate. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Thermal degradation of injectable epinephrine.

    Science.gov (United States)

    Church, W H; Hu, S S; Henry, A J

    1994-05-01

    The degradation of epinephrine in USP injectable cartridges was investigated under different heating conditions. Epinephrine (EPI) and EPI sulfonic acid (EPI-SA) levels in 1:10,000 (0.1 mg/mL) EPI injectable solutions subjected to either cyclical (65 degrees C for 8 hr/d for 4 to 12 weeks) or constant (65 degrees C for 7 days) heating were determined using high-pressure liquid chromatography with diode array and electrochemical detection. Constant (169 total hours of heat exposure) heating resulted in complete degradation of both compounds and dark brown discoloration of the solution. Cyclical heating (672 total hours of heat exposure) resulted in a 31% reduction in EPI concentration and a 225% increase in EPI-SA concentration with no discoloration of the solution. In laboratory-prepared solutions, the degradation of EPI and the formation of EPI-SA was found to be dependent on sodium metabisulfite concentration and the duration of cyclical heating. These results indicate that the thermal stability of EPI and the formation of EPI-SA depends on the method of heat exposure and the amount of bisulfite present in the solution.

  4. Study of Aramid Fiber/Polychloroprene Recycling Process by Thermal Degradation

    Directory of Open Access Journals (Sweden)

    Igor Dabkiewicz

    2016-07-01

    Full Text Available Aramid fiber is an important polymer applied as reinforcement in high-performance composites, which, due its exceptional properties, becomes an excellent impact absorption material. It has been broadly utilized in aeronautic industry and ballistic protection. In aircrafts, it is mainly used in secondary structures, such as fairings, floor panels, and bullet proof structures in helicopters, whereas, in ballistic protection industry, it is applied in automotive armor and bullet proof vest. Under environmental perspective, it is worrying the development and application of composites, which generate proportional discards of these materials, whether originated from manufacturing process, spare parts or end of life cycle. High-performance composite materials like those using aramid fiber are generally difficult to recycle due to their properties and the difficulty for the separation of the components, making their recycling economically unviable. From the characteristics of composite materials and environmental viewpoint, this paper presents a new aramid fiber recycling process. The main objective of this research was to study different recycling methods in aramid fibers/Neoprene® composites. To promote the Neoprene® degradation, it was used a pyrolysis oven with controlled atmosphere and CO 2 injection. For the degraded separation, it was designed a mechanical washing machine in which the most degraded separation occurred. To complete the materials separation, it was employed a manual cleaning process, and, at least to prove the efficacy of the process, it was applied a tensile test in the yarns.

  5. Study on Thermal Degradation Characteristics and Regression Rate Measurement of Paraffin-Based Fuel

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    Songqi Hu

    2015-09-01

    Full Text Available Paraffin fuel has been found to have a regression rate that is higher than conventional HTPB (hydroxyl-terminated polybutadiene fuel and, thus, presents itself as an ideal energy source for a hybrid rocket engine. The energy characteristics of paraffin-based fuel and HTPB fuel have been calculated by the method of minimum free energy. The thermal degradation characteristics were measured for paraffin, pretreated paraffin, HTPB and paraffin-based fuel in different working conditions by the using differential scanning calorimetry (DSC and a thermogravimetric analyzer (TGA. The regression rates of paraffin-based fuel and HTPB fuel were tested by a rectangular solid-gas hybrid engine. The research findings showed that: the specific impulse of paraffin-based fuel is almost the same as that of HTPB fuel; the decomposition temperature of pretreated paraffin is higher than that of the unprocessed paraffin, but lower than that of HTPB; with the increase of paraffin, the initial reaction exothermic peak of paraffin-based fuel is reached in advance, and the initial reaction heat release also increases; the regression rate of paraffin-based fuel is higher than the common HTPB fuel under the same conditions; with the increase of oxidizer mass flow rate, the regression rate of solid fuel increases accordingly for the same fuel formulation.

  6. Application of thermal analysis methods on the study of PE thermal degradation and the influence of Mg (OH) sub 2 as fire retardant

    CERN Document Server

    Zarringhalam-Moghaddam, A

    2002-01-01

    Fire retardation effects of Mg(OH) sub 2 on PE was studied utilizing DTA, TGA and DSC methods. Reductions on reaction peak area and mass loss rate with the addition of Mg(OH) sub 2 were observed as indication of retardation effects of Mg(OH) sub 2 on PE. Cone calorimeter tests were performed on samples to verify the thermo analytical results. It was concluded that when Mg(OH) sub 2 is present it effectively modified the degradation behavior of PE and the thermal analyses are useful and rapid methods to study the retardation effects.

  7. Mechanical, Thermal Degradation, and Flammability Studies on Surface Modified Sisal Fiber Reinforced Recycled Polypropylene Composites

    Directory of Open Access Journals (Sweden)

    Arun Kumar Gupta

    2012-01-01

    Full Text Available The effect of surface treated sisal fiber on the mechanical, thermal, flammability, and morphological properties of sisal fiber (SF reinforced recycled polypropylene (RPP composites was investigated. The surface of sisal fiber was modified with different chemical reagent such as silane, glycidyl methacrylate (GMA, and O-hydroxybenzene diazonium chloride (OBDC to improve the compatibility with the matrix polymer. The experimental results revealed an improvement in the tensile strength to 11%, 20%, and 31.36% and impact strength to 78.72%, 77%, and 81% for silane, GMA, and OBDC treated sisal fiber reinforced recycled Polypropylene (RPP/SF composites, respectively, as compared to RPP. The thermogravimetric analysis (TGA, differential scanning calorimeter (DSC, and heat deflection temperature (HDT results revealed improved thermal stability as compared with RPP. The flammability behaviour of silane, GMA, and OBDC treated SF/RPP composites was studied by the horizontal burning rate by UL-94. The morphological analysis through scanning electron micrograph (SEM supports improves surface interaction between fiber surface and polymer matrix.

  8. Mechanistic Study on the Degradation of Thermal Barrier Coatings Induced by Volcanic Ash Deposition

    Science.gov (United States)

    Arai, Masayuki

    2017-08-01

    Thermal stress generated on thermal barrier coatings (TBCs) by volcanic ash (VA) deposition was assessed measuring the tip deflection of a multilayered beam structure as a function of temperature. The TBC in this study was deposited onto the surface of a blade utilized in a land-based gas turbine which is composed of 8 wt.%Y2O3-ZrO2/CoNiCrAlY on a Ni-based superalloy. The VA-deposited TBC sample was heated at 1453 K, and the effect of VA deposition on TBC delamination was examined in comparison with a TBC sample without VA deposition as a reference. On the basis of the VA attack damage mechanism which was investigated via the tip deflection measurement and a comprehensive microstructure examination, a damage-coupled constitutive model was proposed. The proposed model was based on the infiltration of the molten VA inside pores and phase transformations of yttria -tabilized zirconia in the TBC system. The numerical analysis results, which were simulated utilizing the finite element code installing the developed constitutive model, showed us that VA attack on the TBC sample induced near-interfacial cracks because of a significant increasing in the coating stress.

  9. Degradation Characterization of Thermal Interface Greases

    Energy Technology Data Exchange (ETDEWEB)

    Major, Joshua [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Narumanchi, Sreekant V [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Paret, Paul P [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Blackman, Gregory [DuPont; Wong, Arnold [DuPont; Meth, Jeffery [DuPont

    2018-02-12

    Thermal interface materials (TIMs) are used in power electronics packaging to minimize thermal resistance between the heat generating component and the heat sink. Thermal greases are one such class. The conformability and thin bond line thickness (BLT) of these TIMs can potentially provide low thermal resistance throughout the operation lifetime of a component. However, their performance degrades over time due to pump-out and dry-out during thermal and power cycling. The reliability performance of greases through operational cycling needs to be quantified to develop new materials with superior properties. NREL, in collaboration with DuPont, has performed thermal and reliability characterization of several commercially available thermal greases. Initial bulk and contact thermal resistance of grease samples were measured, and then the thermal degradation that occurred due to pump-out and dry-out during temperature cycling was monitored. The thermal resistances of five different grease materials were evaluated using NREL's steady-state thermal resistance tester based on the ASTM test method D5470. Greases were then applied, utilizing a 2.5 cm x 2.5 cm stencil, between invar and aluminum plates to compare the thermomechanical performance of the materials in a representative test fixture. Scanning Acoustic microscopy, thermal, and compositional analyses were performed periodically during thermal cycling from -40 degrees C to 125 degrees C. Completion of this characterization has allowed for a comprehensive evaluation of thermal greases both for their initial bulk and contact thermal performance, as well as their degradation mechanisms under accelerated thermal cycling conditions.

  10. Degradation Characterization of Thermal Interface Greases

    Energy Technology Data Exchange (ETDEWEB)

    DeVoto, Douglas J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Major, Joshua [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Paret, Paul P [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Blackman, Gregory S. [DuPont Experimental Station; Wong, Arnold [DuPont Experimental Station; Meth, Jeffery S. [DuPont Experimental Station

    2017-07-27

    Thermal interface materials (TIMs) are used in power electronics packaging to minimize thermal resistance between the heat generating component and the heat sink. Thermal greases are one such class. The conformability and thin bond line thickness (BLT) of these TIMs can potentially provide low thermal resistance throughout the operation lifetime of a component. However, their performance degrades over time due to pump-out and dry-out during thermal and power cycling. The reliability performance of greases through operational cycling needs to be quantified to develop new materials with superior properties. NREL, in collaboration with DuPont, has performed thermal and reliability characterization of several commercially available thermal greases. Initial bulk and contact thermal resistance of grease samples were measured, and then the thermal degradation that occurred due to pump-out and dry-out during temperature cycling was monitored. The thermal resistances of five different grease materials were evaluated using NREL's steady-state thermal resistance tester based on the ASTM test method D5470. Greases were then applied, utilizing a 2.5 cm x 2.5 cm stencil, between invar and aluminum plates to compare the thermomechanical performance of the materials in a representative test fixture. Scanning Acoustic microscopy, thermal, and compositional analyses were performed periodically during thermal cycling from -40 degrees Celcius to 125 degrees Celcius. Completion of this characterization has allowed for a comprehensive evaluation of thermal greases both for their initial bulk and contact thermal performance, as well as their degradation mechanisms under accelerated thermal cycling conditions.

  11. Degradation Characterization of Thermal Interface Greases: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    DeVoto, Douglas J [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Major, Joshua [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Paret, Paul P [National Renewable Energy Laboratory (NREL), Golden, CO (United States); Blackman, G. S. [DuPont Experimental Station; Wong, A. [DuPont Experimental Station; Meth, J. S. [DuPont Experimental Station

    2017-08-03

    Thermal interface materials (TIMs) are used in power electronics packaging to minimize thermal resistance between the heat generating component and the heat sink. Thermal greases are one such class. The conformability and thin bond line thickness (BLT) of these TIMs can potentially provide low thermal resistance throughout the operation lifetime of a component. However, their performance degrades over time due to pump-out and dry-out during thermal and power cycling. The reliability performance of greases through operational cycling needs to be quantified to develop new materials with superior properties. NREL, in collaboration with DuPont, has performed thermal and reliability characterization of several commercially available thermal greases. Initial bulk and contact thermal resistance of grease samples were measured, and then the thermal degradation that occurred due to pump-out and dry-out during temperature cycling was monitored. The thermal resistances of five different grease materials were evaluated using NREL's steady-state thermal resistance tester based on the ASTM test method D5470. Greases were then applied, utilizing a 2.5 cm x 2.5 cm stencil, between invar and aluminum plates to compare the thermomechanical performance of the materials in a representative test fixture. Scanning Acoustic microscopy, thermal, and compositional analyses were performed periodically during thermal cycling from -40 degrees Celcius to 125 degrees Celcius. Completion of this characterization has allowed for a comprehensive evaluation of thermal greases both for their initial bulk and contact thermal performance, as well as their degradation mechanisms under accelerated thermal cycling conditions.

  12. Analysis of thermally-degrading, confined HMX

    Energy Technology Data Exchange (ETDEWEB)

    Hobbs, M.L.; Schmitt, R.G.; Renlund, A.M.

    1996-12-01

    The response of a thermally-degrading, confined HMX pellet is analyzed using a Reactive Elastic-Plastic (REP) constitutive model which is founded on the collapse and growth of internal inclusions resulting from physical and chemical processes such as forced displacement, thermal expansion, and/or decomposition. Axial stress predictions compare adequately to data. Deficiencies in the model and future directions are discussed.

  13. A kinetic study of the thermal degradation of cetyltrimethylammonium bromide inside the mesoporous SBA-3 molecular sieve

    Directory of Open Access Journals (Sweden)

    DJORDJE STOJAKOVIC

    2007-12-01

    Full Text Available The thermal degradation of cetyltrimethylammonium bromide (CTMAB inside the mesoporous SBA-3 was studied under non-isothermal conditions. There are two distinct and complex kinetic processes which partly overlap, each consisting of one dominant and three minor individual processes. The two dominant processes can be described by the Sestak–Berggren model. The main decomposition step (the first dominant process involves the overcoming of weak interactions between CTMAB and the silica network and proceeds with a lower Ea value (116±2 kJ mol‑1 than the second dominant process (153±5 kJ mol-1, which can be explained by the size reduction of the pore openings due to the contraction of the SBA-3 unit cell caused by the removal of CTMAB.

  14. Thermogravimetric assessment of thermal degradation in asphaltenes

    Energy Technology Data Exchange (ETDEWEB)

    Barneto, Agustín García, E-mail: agustin.garcia@diq.uhu.es [Department of Chemical Engineering, Physical Chemistry and Organic Chemistry, University of Huelva, Huelva (Spain); Carmona, José Ariza [Department of Chemical Engineering, Physical Chemistry and Organic Chemistry, University of Huelva, Huelva (Spain); Garrido, María José Franco [CEPSA, RDI Centre, Madrid (Spain)

    2016-03-20

    Graphical abstract: - Highlights: • Asphaltenes content of visbreaking streams in oil refinery can be measured by using TGA. • Deconvoluting TGA curves allows the thermal-based composition of asphaltenes to be elucidated. • Asphaltenes cracking involves acceleratory stages compatible with autocatalytic kinetic. • Activation energy during asphaltenes pyrolysis increased with increasing temperature. • Activation energy remained almost constant at 200–225 kJ/mol during oxidative cracking. - Abstract: Monitoring asphaltenes is very important with a view to optimizing visbreaking units in oil refineries. Current analyses based on selective dissolution in different solvents are slow, so new, more expeditious methods for measuring asphaltenes are required to facilitate fuel-oil production. In this work, we studied the thermal degradation of asphaltenes as the potential basis for a thermogravimetric method for their monitoring in visbreaking streams. The thermal degradation of asphaltenes occurs largely from 400 to 500 °C; the process is quite smooth in an inert environment but involves several fast mass loss events in the air. Kinetic parameters for characterizing the process were determined by using two model-free methods and the modified Prout–Tompkins kinetic equation to examine asphaltene thermolysis. Both types of methods showed the activation energy to increase during pyrolysis but to remain almost constant during cracking in the presence of oxygen or even diminish during char oxidation. Deconvoluting the thermogravimetric profiles revealed that asphaltene thermolysis in the air cannot be accurately described in terms of an nth order kinetic model because it involves some acceleratory phases. Also, thermogravimetric analyses of visbreaking streams revealed that char production in them is proportional to their asphaltene content. This relationship enables the thermogravimetric measurement of asphaltenes.

  15. Thermal degradation process of polysulfone aramid fiber

    OpenAIRE

    Zhu Fang-Long; Feng Qian-Qian; Xin Qun; Zhou Yu

    2014-01-01

    Polysulfone aramid fiber is one kind of high temperature fibers. In the paper, thermal degradation behavior and kinetics of polysulfone aramid fiber were investigated by thermogravimetric analysis and differential thermogravimetric at different heating rates under nitrogen and air, respectively. The experimental results show that its initial degradation temperature is 375°C in nitrogen and 410°C in air at heating rate of 10 K/min. When temperature went to 8...

  16. Thermally triggered degradation of transient electronic devices.

    Science.gov (United States)

    Park, Chan Woo; Kang, Seung-Kyun; Hernandez, Hector Lopez; Kaitz, Joshua A; Wie, Dae Seung; Shin, Jiho; Lee, Olivia P; Sottos, Nancy R; Moore, Jeffrey S; Rogers, John A; White, Scott R

    2015-07-01

    Thermally triggered transient electronics using wax-encapsulated acid, which enable rapid device destruction via acidic degradation of the metal electronic components are reported. Using a cyclic poly(phthalaldehyde) (cPPA) substrate affords a more rapid destruction of the device due to acidic depolymerization of cPPA. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Model systems for the study of MSWI fly ash thermal degradation. Kinetics of active carbon-silica gel mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Collina, E.; Lasagni, M.; Pitea, D. [Universita Milano-Bicocca, Milano (Italy); Barilli, L. [CAP Gestione s.p.a., Milano (Italy)

    2004-09-15

    The thermal behavior of MSWI fly ash and model systems was studied in batch experiments in air. A global parameter, Total Organic Carbon (TOC), was used to measure the decrease of reagent concentration in time. As for the thermal degradation of organic carbon on MSWI fly ash, the only reaction product was CO2 it was shown that the carbon for the reactions didn't come from adsorbed organic compounds but from the native carbon matrix of MSWI fly ash. The TOC vs time data were well fitted by the deconvolution treatment and a generalized kinetic model for oxidation of fly ash native carbon was developed. It was shown that the measured conversion of native carbon in fly ashes to CO{sub 2} product is the result of two simultaneous reactions taking place at the fly ash surface: the first reaction is the direct impingement of oxygen onto vacant carbon active sites leading to an immediate carbon gasification; the second one is the dissociative oxygen chemisorption followed by the C(O) complex intermediate gasification. The rate determining step is the intermediate oxidation. The model was validated using kinetic data for four native fly ashes, three from danish and one from italian municipal solid waste incinerators for temperatures ranging from 200 C to 600 C. In the thermal treatment of C-SiO{sub 2} model mixture, the only reaction product was CO{sub 2}. TOC versus time data were well fitted with a single exponential, indicating a first-order reaction. The Arrhenius and Eyring plots showed a piecewise linear trend, thus indicating a change in the reaction rate-determining step. Based on the activation and thermodynamic parameters, the following hypothesis were made: (i) in the lower temperature range (LTR), the direct oxydation reaction is the ratelimiting step; (ii) in the higher temperature range (HTR), the oxygen adsorption and the diffusion processes of surface oxygen complexes are the rate-limiting step. The goal of the studies which followed was to collect new

  18. Thermal degradation process of polysulfone aramid fiber

    Directory of Open Access Journals (Sweden)

    Zhu Fang-Long

    2014-01-01

    Full Text Available Polysulfone aramid fiber is one kind of high temperature fibers. In the paper, thermal degradation behavior and kinetics of polysulfone aramid fiber were investigated by thermogravimetric analysis and differential thermogravimetric at different heating rates under nitrogen and air, respectively. The experimental results show that its initial degradation temperature is 375°C in nitrogen and 410°C in air at heating rate of 10 K/min. When temperature went to 800°C, the fiber loses all mass in air. The mass losses in the stage showed that degradation of polysulfone aramid occurs in two-step process as could be concluded by the presence of two distinct exothermic peaks in differential thermogravimetric curves.

  19. COMPARATIVE KINETICS STUDY OF THE THERMAL AND THERMO-OXIDATIVE DEGRADATION OF A POLYSTYRENE-CLAY NANOCOMPOZITE BY TGA AND DSC

    Directory of Open Access Journals (Sweden)

    Ion Dranca

    2010-12-01

    Full Text Available The methods of thermogravimetry (TGA and differential scanning calorimetry (DSC have been used to study the thermal and thermo-oxidative degradation of polystyrene (PS and a PS-clay nanocomposite. An advanced isoconversional method has been applied for kinertic analysis. Introduction of the clay phase increasers the activation energy and affects the total heat of degradation, which suggests a change in the reaction mechanism. The obtained kinetic data permit a comparative assessment of the fire resistance of the studied materials

  20. Thermal Degradation of Thermoplastic Polyurethane Modified with Polycarbonate

    Energy Technology Data Exchange (ETDEWEB)

    Kwon, H.J. [Inha University, Inchon (Korea); Cha, Y.J. [BAIKSAN CO. LTD., Ansan (Korea); Choe, S.J. [Inha University, Inchon (Korea)

    2000-05-01

    Thermal degradation of thermoplastic polyurethane modified polycarbonate has been investigated by means of DSC, GPC and FT-IR techniques. The polyurethanes used in this study are TPU-35 and TPU-53 containing 35.5 and 53.4 wt % of hard segments, respectively. The more content of hard segment, the higher the glass transition temperature (T{sub g}) of TPU was observed. On the other hand, the T{sub g} of the TPU modified PC decreased with the content of TPU and the annealing temperature regardless of the hard segment contents. The latter behavior may arise from the thermal degradation of TPU upon annealing process: the observed thermal degradation temperatures were at 240 and 250 deg. C D for the PC/TPU-35 and PC/TPU-53, respectively. The molecular weight, molecular weight distribution and viscosity agree well with the DSC measurement, which implicates a thermal degradation of TPU. In addition, thermal stability of the TPU modified PC linearly decreased with an incorporation of TPU. Transesterification or any interaction was not observed using FT-IR: the evidence was no frequency shift or any variance between the carbonyl stretching and NH group. For the specimens prepared below the degradation temperature, the enhancement of the thickness dependent impact strength of the PC/TPU blend was observes, and the morphology of the two blends was compared. (author). 19 refs., 2 tabs., 12 figs.

  1. Photo, thermal and chemical degradation of riboflavin

    Directory of Open Access Journals (Sweden)

    Muhammad Ali Sheraz

    2014-08-01

    Full Text Available Riboflavin (RF, also known as vitamin B2, belongs to the class of water-soluble vitamins and is widely present in a variety of food products. It is sensitive to light and high temperature, and therefore, needs a consideration of these factors for its stability in food products and pharmaceutical preparations. A number of other factors have also been identified that affect the stability of RF. These factors include radiation source, its intensity and wavelength, pH, presence of oxygen, buffer concentration and ionic strength, solvent polarity and viscosity, and use of stabilizers and complexing agents. A detailed review of the literature in this field has been made and all those factors that affect the photo, thermal and chemical degradation of RF have been discussed. RF undergoes degradation through several mechanisms and an understanding of the mode of photo- and thermal degradation of RF may help in the stabilization of the vitamin. A general scheme for the photodegradation of RF is presented.

  2. [DNA degradation during standard alkaline of thermal denaturation].

    Science.gov (United States)

    Drozhdeniuk, A P; Sulimova, G E; Vaniushin, B F

    1976-01-01

    Essential degradation 8 DNA (up to 10 per cent) with liberation of acid-soluble fragments takes place on the standard alkaline (0,01 M sodium phosphate, pH 12, 60 degrees, 15 min) or thermal (0.06 M sodium phosphate buffer, pH 6.8, 102 degrees C, 15 min) denaturation. This degradation is more or less selective: fraction of low molecular weight fragments, isolated by hydroxyapatite cromatography and eluted by 0.06 M sodium phosphate buffer, pH 6.8 is rich in adenine and thymine and contains about 2 times less 5-methylcytosine than the total wheat germ DNA. The degree of degradation of DNA on thermal denaturation is higher than on alkaline degradation. Therefore while studying reassociation of various DNA, one and the same standard method of DNA denaturation should be used. Besides, both the level of DNA degradation and the nature of the resulting products (fragments) should be taken into account.

  3. Synthesis and thermal degradation Kinetics of D - (+ - galactose containing polymers

    Directory of Open Access Journals (Sweden)

    Fehmi Saltan

    2013-01-01

    Full Text Available In this study, it is investigated the synthesis and characterizations of polymerizable vinyl sugars. Carbohydrate containing polymers were synthesized via free radical polymerization. Thermal behavior of polymer derivatives was analyzed by using DSC and TG. Molecular weight dispersion of polymer derivatives was also analyzed with GPC. Molecular structures were analyzed by FT-IR and 1H-NMR spectrophotometer. We found that molecular weight of copolymers could effect to the thermal stability. According to TG data related to the copolymers, molecular weight of polymers increased while the thermal stability decreased. Thermogravimetric analysis of polymers also investigated. The apparent activation energies for thermal degradation of carbohydrate containing polymers were obtained by integral methods (Flynn - Wall - Ozawa, Kissinger - Akahira - Sunose, and Tang.

  4. Thermal degradation kinetics and solid state, temperature ...

    Indian Academy of Sciences (India)

    WINTEC

    Phenothiazine derivatives belong to a big group of aromatic compounds. These derivatives are substituted in ... Elemental analysis for carbon, hydrogen, nitrogen and sulphur were done using Vario EL III CHNS ... The aim of the kinetic study of thermal analysis data is to find out the most probable kinetic model which best ...

  5. Single gene retrieval from thermally degraded DNA

    Indian Academy of Sciences (India)

    Unknown

    To simulate single gene retrieval from ancient DNA, several related factors have been investigated. By monitoring a. 889 bp polymerase chain reaction (PCR) product and genomic DNA degradation, we find that heat and oxygen. (especially heat) are both crucial factors influencing DNA degradation. The heat influence ...

  6. Single gene retrieval from thermally degraded DNA

    Indian Academy of Sciences (India)

    To simulate single gene retrieval from ancient DNA, several related factors have been investigated. By monitoring a 889 bp polymerase chain reaction (PCR) product and genomic DNA degradation, we find that heat and oxygen (especially heat) are both crucial factors influencing DNA degradation. The heat influence ...

  7. Paracetamol degradation in aqueous solution by non-thermal plasma

    Science.gov (United States)

    Baloul, Yasmine; Aubry, Olivier; Rabat, Hervé; Colas, Cyril; Maunit, Benoît; Hong, Dunpin

    2017-08-01

    This study deals with paracetamol degradation in water using a non-thermal plasma (NTP) created by a dielectric barrier discharge (DBD). The effects of the NTP operating conditions on the degradation were studied, showing that the treatment efficiency of the process was highly dependent on the electrical parameters and working gas composition in the reactor containing the aqueous solution. A conversion rate higher than 99% was reached with an energy yield of 12 g/kWh. High resolution mass spectrometry (HRMS) measurements showed that the main species produced in water during the process were nitrogen compounds, carboxylic acids and aromatic compounds. Contribution to the topical issue "The 15th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XV)", edited by Nicolas Gherardi and Tomáš Hoder

  8. Kinetics study of metaxalone degradation under hydrolytic, oxidative and thermal stress conditions using stability-indicating HPLC method

    Directory of Open Access Journals (Sweden)

    Vamsi Krishna Marothu

    2012-12-01

    Full Text Available An isocratic stability indicating RP-HPLC–UV method is presented for the determination of metaxalone (MET in the presence of its degradation products. The method uses Dr. Maisch C18 column (250 mm×4.6 mm, 5 μm with mobile phase consisting of acetonitrile–potassium dihydrogen orthophosphate buffer with 4 mL of 0.4% triethyl amine (pH 3.0; 10 mM (58:42, v/v at a flow rate of 1.0 mL/min. pH of the buffer was adjusted with o-phosphoric acid. UV detection was performed at 225 nm. The method was validated for specificity, linearity, precision, accuracy, limit of detection, limit of quantification and robustness. The calibration plot was linear over the concentration range of 1–100 μg/mL having a correlation coefficient (r2 of 0.999. Limits of detection and quantification were 0.3 and 1 μg/mL, respectively. Intra-day and inter-day precision (% RSD was 0.65 and 0.79 respectively. The proposed method was used to investigate the degradation kinetics of MET under different stress conditions employed. Degradation of MET followed a pseudo-first-order kinetics, and rate constant (K, time left for 50% potency (t1/2, and time left for 90% potency (t90 were calculated. Keywords: Metaxalone, Degradation kinetics, RP-HPLC–UV

  9. Spectral and Thermal Degradation of Melamine Cyanurate

    Directory of Open Access Journals (Sweden)

    V. Sangeetha

    2013-01-01

    Full Text Available Melamine cyanurate, an organic crystalline complex was, synthesized by evaporation of an aqueous solution containing equimolar quantities of melamine and cyanuric acid. The synthesized compound has been subjected to various characterizations like Powder XRD, FT-IR, TG-DTG, SEM, and SHG. The presence of sharp diffraction peaks in the XRD confirms that the products are highly crystalline. The average particle size was calculated using the Debye-Scherrer formula, and it was found to be 3.067 μm. Thermal behavior of the grown crystal has been studied by TG-DTG analysis. From TG-DTG, it is found that the title crystal possesses good thermal stability. The activation energy was calculated using the Broido, Coats-Redfern, and Horowitz-Metzger methods. A sharp peak exothermic peak at 405.40°C was assigned as the melting point of the title material. SEM reveals the morphology of the synthesized salt. No detectable signal was observed during the Kurtz-Perry technique.

  10. Interfacial thermal degradation in inverted organic solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Greenbank, William; Hirsch, Lionel; Wantz, Guillaume; Chambon, Sylvain, E-mail: sylvain.chambon@ims-bordeaux.fr [University of Bordeaux, CNRS, Bordeaux INP, IMS, UMR 5218, F-33405 Talence (France)

    2015-12-28

    The efficiency of organic photovoltaic (OPV) solar cells is constantly improving; however, the lifetime of the devices still requires significant improvement if the potential of OPV is to be realised. In this study, several series of inverted OPV were fabricated and thermally aged in the dark in an inert atmosphere. It was demonstrated that all of the devices undergo short circuit current-driven degradation, which is assigned to morphology changes in the active layer. In addition, a previously unreported, open circuit voltage-driven degradation mechanism was observed that is highly material specific and interfacial in origin. This mechanism was specifically observed in devices containing MoO{sub 3} and silver as hole transporting layers and electrode materials, respectively. Devices with this combination were among the worst performing devices with respect to thermal ageing. The physical origins of this mechanism were explored by Rutherford backscattering spectrometry and atomic force microscopy and an increase in roughness with thermal ageing was observed that may be partially responsible for the ageing mechanism.

  11. Degradation Behavior of Thermal Stabilized Polyacrylonitrile Fibers

    Directory of Open Access Journals (Sweden)

    LEI Shuai

    2017-05-01

    Full Text Available In the temperature range of 300-800℃, 40%-50% of the mass lost during the processing of polyacrylonitrile based carbon fiber (PANCF. Understanding the degradation behavior will be valuable in understanding the formation mechanism of pseudo-graphite structure, and providing theoretic basis for producing high performance carbon fiber and increasing the carbonization yield. The simulation of the degradation progress was carried out on the thermogravimetric analyzer (TGA, the results show that there are two degradation steps for PAN fiber stabilized in air, and controlled by cyclization coefficient and oxygen content. The cyclization coefficient and oxygen content are effective to the density of carbon fiber by influencing the degradation behavior, which cause defects in the fiber. The higher cyclization coefficient leads to form less structural defects and higher density of the fiber; on the contrary, the higher oxygen content leads to form more structural defects and lower density of the fiber.

  12. Development of method for identification of compounds emitted during thermal degradation of binders used in foundry

    Directory of Open Access Journals (Sweden)

    A. Bobrowski

    2011-07-01

    Full Text Available The aim of the research was to develop a method for identification of compounds emitted during thermal degradation of binders used in foundry. Research were performed with the use of Certified Reference Materials mixtures of semi-volatiles compounds with furfuryl alcohol and aldehyde. Furfuryl-urea resin samples were also used. Station for thermal degradation of materials used in foundry was designed and made. Thermal degradation process conditions and gas chromatograph coupled with high resolution mass spectrometry operating conditions were established. Organic compounds emitted during degradation were identified. The paper briefly represents the range of study and the results obtained for furfuryl-urea resin thermal degradation. Significant information about volatile and semi-volatile organic compounds emitted in different temperatures is also discussed.

  13. Thermal properties of degraded lowland peat-moorsh soils

    Science.gov (United States)

    Gnatowski, Tomasz

    2016-04-01

    Soil thermal properties, i.e.: specific heat capacity (c), thermal conductivity (K), volumetric heat capacity (C) govern the thermal environment and heat transport through the soil. Hence the precise knowledge and accurate predictions of these properties for peaty soils with high amount of organic matter are especially important for the proper forecasting of soil temperature and thus it may lead to a better assessment of the greenhouse gas emissions created by microbiological activity of the peatlands. The objective of the study was to develop the predictive models of the selected thermal parameters of peat-moorsh soils in terms of their potential applicability for forecasting changes of soil temperature in degraded ecosystems of the Middle Biebrza River Valley area. Evaluation of the soil thermal properties was conducted for the parameters: specific heat capacity (c), volumetric heat capacities of the dry and saturated soil (Cdry, Csat) and thermal conductivities of the dry and saturated soil (Kdry, Ksat). The thermal parameters were measured using the dual-needle probe (KD2-Pro) on soil samples collected from seven peaty soils, representing total 24 horizons. The surface layers were characterized by different degrees of advancement of soil degradation dependent on intensiveness of the cultivation practises (peaty and humic moorsh). The underlying soil layers contain peat deposits of different botanical composition (peat-moss, sedge-reed, reed and alder) and varying degrees of decomposition of the organic matter, from H1 to H7 (von Post scale). Based on the research results it has been shown that the specific heat capacity of the soils differs depending on the type of soil (type of moorsh and type of peat). The range of changes varied from 1276 J.kg-1.K-1 in the humic moorsh soil to 1944 J.kg-1.K-1 in the low decomposed sedge-moss peat. It has also been stated that in degraded peat soils with the increasing of the ash content in the soil the value of specific heat

  14. Degradation of thermally-cured silicone encapsulant under terrestrial UV

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Can; Miller, David C.; Tappan, Ian A.; Dauskardt, Reinhold H.

    2016-12-01

    Concentrator photovoltaic (CPV) modules operate in extreme conditions, including enhanced solar flux, elevated operating temperature, and frequent thermal cycling. Coupled with active environmental species such as oxygen and moisture, the operating conditions pose a unique materials challenge for guaranteeing operational lifetimes of greater than 25 years. Specifically, the encapsulants used in the optical elements are susceptible to environmental degradation during operation. For example, the interfaces must remain in contact to prevent optical attenuation and thermal runaway. We developed fracture mechanics based metrologies to characterize the adhesion of the silicone encapsulant and its adjacent surfaces, as well as the cohesion of the encapsulant. Further, we studied the effects of weathering on adhesion using an outdoor concentrator operating in excess of 1100 times the AM1.5 direct irradiance and in indoor environmental chambers with broadband ultraviolet (UV) irradiation combined with controlled temperature and humidity. We observed a sharp initial increase in adhesion energy followed by a gradual decrease in adhesion as a result of both outdoor concentrator exposure and indoor UV weathering. We characterized changes in mechanical properties and chemical structures using XPS, FTIR, and DMA to understand the fundamental connection between mechanical strength and the degradation of the silicone encapsulant. We developed physics based models to explain the change in adhesion and to predict operational lifetimes of the materials and their interfaces.

  15. Thermal degradation kinetics of bixin in an aqueous model system.

    Science.gov (United States)

    Rios, Alessandro de O; Borsarelli, Claudio D; Mercadante, Adriana Z

    2005-03-23

    The kinetics of the thermal degradation of the natural cis carotenoid bixin in a water/ethanol (8:2) solution was studied as a function of temperature (70-125 degrees C), using high-performance liquid chromatography. The curves for the decay of bixin and formation of products (e.g., di-cis and all-trans isomers and a C17 degradation compound) did not adjust well to a first-order rate law, but very good fits were obtained using a biexponential model. This mathematical modeling gave the rate constant values for the formation of the primary products from bixin, and the energy barrier for each step was obtained. The di-cis isomers were formed immediately (15 kcal/mol) together with the decay of bixin, followed by a slow consumption, indicating their role as reaction intermediates. In fact, the di-cis isomers could easily revert to bixin (Ea approximately 3 kcal/mol) or yield the primary C17 degradation product, with an energy barrier of 6.5 kcal/mol. In turn, 24 kcal/mol was necessary for the Bix --> all-trans step, explaining its slower formation.

  16. synthesis, characterization and thermal degradation of oligo

    African Journals Online (AJOL)

    Preferred Customer

    more than 60 years because of useful properties such as paramagnetism, semiconductivity, and electrochemical properties. Because of these properties, they are used to prepare composites having high thermal stability [1], graphite materials, adhesives, epoxy oligomer and block copolymers, photoresists [2], and materials ...

  17. The thermal properties of a carbon nanotube-enriched epoxy: Thermal conductivity, curing, and degradation kinetics

    KAUST Repository

    Ventura, Isaac Aguilar

    2013-05-31

    Multiwalled carbon nanotube-enriched epoxy polymers were prepared by solvent evaporation based on a commercially available epoxy system and functionalized multiwalled carbon nanotubes (COOH-MWCNTs). Three weight ratio configurations (0.05, 0.5, and 1.0 wt %) of COOH-MWCNTs were considered and compared with neat epoxy and ethanol-treated epoxy to investigate the effects of nano enrichment and processing. Here, the thermal properties of the epoxy polymers, including curing kinetics, thermal conductivity, and degradation kinetics were studied. Introducing the MWCNTs increased the curing activation energy as revealed by differential scanning calorimetry. The final thermal conductivity of the 0.5 and 1.0 wt % MWCNT-enriched epoxy samples measured by laser flash technique increased by up to 15% compared with the neat material. The activation energy of the degradation process, investigated by thermogravimetric analysis, was found to increase with increasing CNT content, suggesting that the addition of MWCNTs improved the thermal stability of the epoxy polymers. © 2013 Wiley Periodicals, Inc.

  18. Determination of Polymers Thermal Degradation by Color Change Analysis

    Directory of Open Access Journals (Sweden)

    Andrés Felipe Rojas González

    2016-01-01

    Full Text Available Context: It has been observed that thermal degradation of thermoplastic polymers, when they are reprocessed by injection, extrusion and extrusion / injection, undergo color changes in the product, although it not has been established as this change occurs. Method: It analyzed the effect on thermal degradation caused by polymer type, processing type, polymer grade, rotation speed of the extrusion screw and number of reprocessing, which is quantified by the color change using an empirical equation, with experimental data obtained by analysis through a microcolor colorimeter. Results: It was found that the color change analysis provides information about progress of the thermal degradation and stability of thermoplastic polymers, which are undergoing to multiple reprocessing events and processes. Conclusions: It was established that this technique can be implemented as a simple and efficient measure of thermoplastic products quality control, according to their color change.

  19. Broccoli glucosinolate degradation is reduced performing thermal treatment in binary systems with other food ingredients

    NARCIS (Netherlands)

    Giambanelli, E.; Verkerk, R.; Fogliano, V.; Capuano, E.; Antuono, D' L.F.; Oliviero, T.

    2015-01-01

    Glucosinolate (GL) stability has been widely studied in different Brassica species. However, the matrix effect determined by the presence of other ingredients occurred in many broccoli-based traditional recipes may affect GL thermal degradation. In this study, the matrix effect on GL thermal

  20. Thermal Degradation of Filler/PP Composite and Its Depression

    Science.gov (United States)

    Hosoi, Hiroshi; Funami, Fumiyasu; Yasuda, Naoki; Nomura, Manabu; Yui, Hiroshi; Ikuta, Nobuo

    To examine thermal degradation accelerated by filling inorganic particles in polypropylene (PP), the composites were made with three types of inorganic powders : talc, magnesium hydroxide, and mica. They were easily degraded with the fillers in this order in the thermal aging test. A commercial heat resistance agent, ‘Plenlizer MK-400’, was added while making the composites. The degradation resistance of the agent remarkably appeared in the reverse order. That is, thermal degradation was most depressed in talc-filled composite with the agent. In another experience, soxhlet extraction was carried out to the filler with an organic solvent, o-xylene, that was able to dissolve PP. A lot of inorganic ions were detected in the extractant. In particular, the detected amount of aluminum ion increased in the order of talc, magnesium hydroxide, and mica. This order was the same as the fillers indicated by the degree of degradation. Infrared analysis of the agent with inorganic ions in chloroform showed that the peaks due to the agent were much stronger with aluminum ion than those with iron ion. These results suggested that a cause of degradation was aluminum ion dispersed from particles to PP matrix during the molding.

  1. Thermal degradation of PVC: A review.

    Science.gov (United States)

    Yu, Jie; Sun, Lushi; Ma, Chuan; Qiao, Yu; Yao, Hong

    2016-02-01

    This review summarized various chemical recycling methods for PVC, such as pyrolysis, catalytic dechlorination and hydrothermal treatment, with a view to solving the problem of energy crisis and the impact of environmental degradation of PVC. Emphasis was paid on the recent progress on the pyrolysis of PVC, including co-pyrolysis of PVC with biomass/coal and other plastics, catalytic dechlorination of raw PVC or Cl-containing oil and hydrothermal treatment using subcritical and supercritical water. Understanding the advantage and disadvantage of these treatment methods can be beneficial for treating PVC properly. The dehydrochlorination of PVC mainly happed at low temperature of 250-320°C. The process of PVC dehydrochlorination can catalyze and accelerate the biomass pyrolysis. The intermediates from dehydrochlorination stage of PVC can increase char yield of co-pyrolysis of PVC with PP/PE/PS. For the catalytic degradation and dechlorination of PVC, metal oxides catalysts mainly acted as adsorbents for the evolved HCl or as inhibitors of HCl formation depending on their basicity, while zeolites and noble metal catalysts can produce lighter oil, depending the total number of acid sites and the number of accessible acidic sites. For hydrothermal treatment, PVC decomposed through three stages. In the first region (T<250°C), PVC went through dehydrochlorination to form polyene; in the second region (250°C

  2. Thermal Degradation Kinetics of Sugarcane Bagasse and Soft Wood Cellulose

    Directory of Open Access Journals (Sweden)

    Samson M. Mohomane

    2017-10-01

    Full Text Available The properties of untreated sugar cane bagasse (SCB and soft wood (SW and their respective celluloses were investigated. The celluloses indicated improved crystallinity index values and decreased concentration of lignin and hemicellulose compared to their untreated counterparts. Three degradation models, Kissinger-Akahira-Sunose (KAS, Flynn-Wall-Ozawa (OFW, and Kissinger (KGR methods were employed to determine apparent activation energy values. Generally, the thermal degradation processes of both sugarcane bagasse and soft wood included dehydration, degradation of hemicellulose and cellulose, whereas the lignin degraded from the degradation temperature of hemicellulose to the end of the cellulose. The apparent activation energy values obtained from the OFW and KAS models vary with the degree of conversion, and showed similar trends. The activation energies obtained by KGR were relatively lower than those obtained from the KAS and OFW methods.

  3. modelling of thermal degradation kinetics of ascorbic acid in ...

    African Journals Online (AJOL)

    Administrator

    dried, cooked, canned and frozen fruit and vegetables are a ... Samuel E. Agarry, Biochemical Engineering Research Laboratory, Department of Chemical .... Table 1: Rate Constants for Thermal Degradation of Ascorbic Acid in Potato and Pawpaw at Various. Temperatures. Food Material. T oC. ) (min. 10. 1. 3. −. −. xK. T.

  4. Control of Several Emissions during Olive Pomace Thermal Degradation

    Directory of Open Access Journals (Sweden)

    Teresa Miranda

    2014-10-01

    Full Text Available Biomass plays an important role as an energy source, being an interesting alternative to fossil fuels due to its environment-friendly and sustainable characteristics. However, due to the exposure of customers to emissions during biomass heating, evolved pollutants should be taken into account and controlled. Changing raw materials or mixing them with another less pollutant biomass could be a suitable step to reduce pollution. This work studied the thermal behaviour of olive pomace, pyrenean oak and their blends under combustion using thermogravimetric analysis. It was possible to monitor the emissions released during the process by coupling mass spectrometry analysis. The experiments were carried out under non-isothermal conditions at the temperature range 25–750 °C and a heating rate of 20 °C·min−1. The following species were analysed: aromatic compounds (benzene and toluene, sulphur emissions (sulphur dioxide, 1,4-dioxin, hydrochloric acid, carbon dioxide and nitrogen oxides. The results indicated that pollutants were mainly evolved in two different stages, which are related to the thermal degradation steps. Thus, depending on the pollutant and raw material composition, different emission profiles were observed. Furthermore, intensity of the emission profiles was related, in some cases, to the composition of the precursor.

  5. Thermal degradation of polymer systems having liquid crystalline oligoester segment

    Directory of Open Access Journals (Sweden)

    Renato Matroniani

    Full Text Available Abstract Block copolymers and blends comprised by liquid crystalline oligoester and polystyrene were prepared and their thermal stability were characterized by thermogravimetric analysis (TGA. The samples have shown three main decomposition temperatures due to (1 lost of flexible chain and decomposition of mesogenic segment, (2 decomposition of polystyrene and (3 final decomposition of oligoester rigid segment. Both copolymers and polymer blends presented lower thermal stability compared to polystyrene and oligoester. The residual mass after heating at 600 °C in copolymers and polymer blends were lower than those found in the oligoesters. A degradative process of aromatic segments of oligoester induced by decomposition of polystyrene is suggested.

  6. Theoretical investigation on degradation behaviors of spectral properties of thermal control coatings induced by charged particles

    Energy Technology Data Exchange (ETDEWEB)

    Han, Yuge; Ma, Wei; Xuan, Yimin, E-mail: ymxuan@mail.njust.edu.cn

    2013-10-01

    The degradation of spectral properties of thermal control coatings on spacecrafts is investigated in this paper. By studying their physical components and geometry structure, the factors which determine the spectral properties of the coatings are founded. A theoretical model for calculating the spectral absorptance of coatings is proposed based on the Mie's theory and Stratified Media theory. Mathematical expressions are introduced for accounting for the effect of the complicated environment. Based on these work, a predicting model for the degradation of spectral absorptance properties of the coatings is established. To validate this model, the predicted degradation performance of spectral properties of zinc oxide based coatings under electrons and protons exposure are compared with the experimental data. A good agreement is found at the wavelength between 250 nm and 2500 nm. Finally, a useful approach for predicting the degradation behaviors of thermal control coatings on spacecrafts in orbit is established.

  7. Non-isothermal kinetics of thermal degradation of chitosan

    Directory of Open Access Journals (Sweden)

    Georgieva Velyana

    2012-08-01

    Full Text Available Abstract Background Chitosan is the second most abundant nitrogen containing biopolymer in nature, obtained from the shells of crustaceans, particularly crabs, shrimp and lobsters, which are waste products of seafood processing industries. It has great potential application in the areas of biotechnology, biomedicine, food industries, and cosmetics. Chitosan is also capable of adsorbing a number of metal ions as its amino groups can serve as chelation sites. Grafted functional groups such as hydroxyl, carboxyl, sulfate, phosphate, and amino groups on the chitosan have been reported to be responsible for metal binding and sorption of dyes and pigments. The knowledge of their thermal stability and pyrolysis may help to better understand and plan their industrial processing. Results Thermogravimetric studies of chitosan in air atmosphere were carried out at six rates of linear increasing of the temperature. The kinetics and mechanism of the thermal decomposition reaction were evaluated from the TG data using recommended from ICTAC kinetics committee iso-conversional calculation procedure of Kissinger-Akahira-Sunose, as well as 27 mechanism functions. The comparison of the obtained results showed that they strongly depend on the selection of proper mechanism function for the process. Therefore, it is very important to determine the most probable mechanism function. In this respect the iso-conversional calculation procedure turned out to be the most appropriate. Conclusion Chitosan have excellent properties such as hydrophilicity, biocompatibility, biodegradability, antibacterial, non-toxicity, adsorption application. The thermal degradation of chitosan occurs in two stages. The most probable mechanism function for both stages is determined and it was best described by kinetic equations of n-th order (Fn mechanism. For the first stage, it was established that n is equal to 3.0 and for the second stage – to 1.0 respectively. The values of the

  8. Modelling thermal degradation of zearalenone in maize bread during baking.

    Science.gov (United States)

    Numanoglu, E; Yener, S; Gökmen, V; Uygun, U; Koksel, H

    2013-01-01

    The thermal degradation of zearalenone (ZEA) was investigated using a crust-like model, representing maize bread, which was prepared with naturally contaminated maize flour. Model samples were heated under isothermal conditions at the temperature range of 100-250°C. No reduction was observed at 100°C. Thermal degradation rate constants (k) were calculated as 0.0017, 0.0143 and 0.0216 min(-1) for 150, 200 and 250°C, respectively. Maize bread baked at 250°C for 70 min was used to test the capability of model kinetic data for the prediction of ZEA reduction. The time-temperature history in the crust and crumb parts was recorded separately. Partial degradation of ZEA at each time interval was calculated by means of the corresponding k-values obtained by using the Arrhenius equation, and the total reduction occurring at the end of the entire baking process was predicted. The reduction in the crumb and crust of bread was also experimentally determined and found to be consistent with the predicted values. It was concluded that the kinetic constants determined by means of the crust-like model could be used to predict the ZEA reduction occurring during baking of maize bread.

  9. Thermolysis kinetics and thermal degradation compounds of alliin.

    Science.gov (United States)

    Chen, Zixing; Xu, MingJiao; Wang, Chao; Zhou, Hua; Fan, Lokyee; Huang, Xuesong

    2017-05-15

    To investigate thermolysis kinetics and identify degradation compounds, alliin solutions were heated at 60, 80, and 89°C. The degradation compounds of alliin were identified by high performance liquid chromatography-mass spectrometry (HPLC-MS), tandem mass spectrometry (MS/MS) and ultra-pressure liquid chromatography-high resolution mass spectrometry (UPLC-HRMS). The results showed that the thermal degradation kinetic of alliin could be described by a first-order reaction and k=4.38×1017exp (-142494/RT), where k is the reaction rate constant, min-1; R is gas constant; T is the absolute temperature, K. Degraded compounds, including S-allyl-l-cysteine and ethers, such as allyl alanine disulfide, allyl alanine trisulfide, allyl alanine tetrasulfide, dialanine disulfide (cysteine), dialanine trisulfide and dialanine tetrasulfide, were identified by HPLC-MS, MS/MS and UPLC-HRMS. Allyl alanine tetrasulfide was identified for the first time in alliin. The results show that alliin is unstable and significant numbers of organosulfur compounds are generated under high temperature treatment. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Using kinetic models to predict thermal degradation of fire-retardant-treated plywood roof sheathing

    Science.gov (United States)

    Patricia Lebow; Jerrold E. Winandy; Patricia K. Lebow

    2003-01-01

    Between 1985-1995 a substantial number of multifamily housing units in the Eastern and Southern U.S. experienced problems with thermally degraded fire-retardant-treated (FRT) plywood roof sheathing. A series of studies conducted at the USDA Forest Service, Forest Products Laboratory (FPL), examined the materials, chemical mechanisms, and process implications and has...

  11. Progress in Characterizing Thermal Degradation of Ethylene-Propylene Rubber

    Energy Technology Data Exchange (ETDEWEB)

    Fifield, Leonard S. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Huang, Qian [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Childers, Matthew I. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Correa, Miguel [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Shin, Yongsoon [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Zwoster, Andy [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-08-26

    Ethylene-propylene rubber (EPR) is one of the two most common nuclear cable insulation materials. A large fraction of EPR-insulated cables in use in the nuclear industry were manufactured by The Okonite Company. Okoguard® is the name of the medium voltage thermoset EPR manufactured by The Okonite Company. Okoguard® has been produced with silane-treated clay filler and the characteristic pink color since the 1970’s. EPR is complex material that undergoes simultaneous reactions during thermal aging including oxidative and thermal cleavage and oxidative and thermal crosslinking. This reaction complexity makes precise EPR service life prediction from accelerated aging using approaches designed for single discreet reactions such as the Arrhenius approach problematic. Performance data and activation energies for EPR aged at conditions closer to service conditions will improve EPR lifetime prediction. In this report pink Okoguard® EPR insulation material has been thermally aged at elevated temperatures. A variety of characterization techniques have been employed to track material changes with aging. It was noted that EPR aged significant departure in aging behavior seemed to occur at accelerated aging temperatures between 140°C and 150°C at around 20 days of exposure. This may be due to alternative degradation mechanisms being accessed at this higher temperature and reinforces the need to perform accelerated aging for Okoguard® EPR service life prediction at temperatures below 150°C.

  12. Degradation studies of SMRM teflon

    Science.gov (United States)

    Liang, Ranty H.; Oda, Keri L.; Chung, Shirley Y.; Gupta, Amitava

    1986-01-01

    Teflon samples returned from the Solar Max Satellite (SMS) suffered noticeable damage such as cracking and yellowing. This is in contrast to teflon exposed aboard STS-5 and STS-8 which showed no detectable changes. Selected teflon tape samples from SMS were studied to evaluate the extent and mechanism of degradation. ESCA studies revealed that these teflon samples contain hydrocarbon segments which were susceptible to oxygen atom degradation. Mechanical measurements also showed bulk property changes as a result of LEO exposure. A molecular model of material and energetic oxygen atom interaction was proposed. SMS data and the importance of developing correlation between accelerated exposure data from STS and ground-based testing and real time data will be presented.

  13. Rapid estimation of glucosinolate thermal degradation rate constants in leaves of Chinese kale and broccoli (Brassica oleracea) in two seasons.

    Science.gov (United States)

    Hennig, Kristin; Verkerk, Ruud; Bonnema, Guusje; Dekker, Matthijs

    2012-08-15

    Kinetic modeling was used as a tool to quantitatively estimate glucosinolate thermal degradation rate constants. Literature shows that thermal degradation rates differ in different vegetables. Well-characterized plant material, leaves of broccoli and Chinese kale plants grown in two seasons, was used in the study. It was shown that a first-order reaction is appropriate to model glucosinolate degradation independent from the season. No difference in degradation rate constants of structurally identical glucosinolates was found between broccoli and Chinese kale leaves when grown in the same season. However, glucosinolate degradation rate constants were highly affected by the season (20-80% increase in spring compared to autumn). These results suggest that differences in glucosinolate degradation rate constants can be due to variation in environmental as well as genetic factors. Furthermore, a methodology to estimate rate constants rapidly is provided to enable the analysis of high sample numbers for future studies.

  14. Thermal Degradation Characteristics of Oil Filled Cable Joint with Extremely Degraded tan δ Oil

    Science.gov (United States)

    Ide, Kenichi; Nakade, Masahiko; Takahashi, Tohru; Nakajima, Takenori

    Much of oil filled (OF) cable has been used for a long time for 66∼500kV extra high voltage cable. Sometimes we can see extremely degraded tanδ oil (several tens % of tanδ, for example) in joint box etc. The calculation results of tanδ on a simple combination model of paper/oil show that, tanδ of oil impregnated paper with such a high tanδ oil is extremely high and it must result in a thermal breakdown. However such an event has not taken place up to the present in actually operated transmission line. This fact suggests that some suppression mechanism of tanδ has acted in the degraded tanδ oil impregnated paper insulation. Therefore we investigated the tanδ characteristics of oil impregnated paper with extremely high tanδ oil in detail. In addition, based on the investigation results, we developed a simulation method of heat generation by dielectric loss in OF cable joint (which has degraded tanδ oil).

  15. Thermal and chemical degradation of inorganic membrane materials. Topical report

    Energy Technology Data Exchange (ETDEWEB)

    Krishnan, G.N.; Sanjurjo, A.; Wood, B.J.; Lau, K.H.

    1994-04-01

    This report describes the results of a literature review to evaluate the long-term thermal and chemical degradation of inorganic membranes that are being developed to separate gaseous products produced by the gasification or combustion of coal in fixed-, fluidized-, and entrained-bed gasifiers, direct coal-fired turbines, and pressurized-fluidized-bed combustors. Several impurities, such as H{sub 2}S, NH{sub 3}, SO{sub 2}, NO{sub x}, and trace metal compounds are generated during coal conversion, and they must be removed from the coal gas or the combustor flue gas to meet environmental standards. The use of membranes to separate these noxious gases is an attractive alternative to their removal by sorbents such as zinc titanate or calcium oxide. Inorganic membranes that have a high separation efficiency and exhibit both thermal and chemical stability would improve the economics of power generation from coal. The U.S. Department of Energy is supporting investigations to develop inorganic membranes for separating hydrogen from coal gas streams and noxious impurities from hot coal- and flue-gas streams. Membrane materials that have been investigated in the past include glass (silica), alumina, zirconia, carbon, and metals (Pd and Pt).

  16. Bio-based barium alginate film: Preparation, flame retardancy and thermal degradation behavior.

    Science.gov (United States)

    Liu, Yun; Zhang, Chuan-Jie; Zhao, Jin-Chao; Guo, Yi; Zhu, Ping; Wang, De-Yi

    2016-03-30

    A bio-based barium alginate film was prepared via a facile ionic exchange and casting approach. Its flammability, thermal degradation and pyrolysis behaviors, thermal degradation mechanism were studied systemically by limiting oxygen index (LOI), vertical burning (UL-94), microscale combustion calorimetry (MCC), thermogravimetric analysis (TGA) coupled with Fourier transform infrared analysis (FTIR) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). It showed that barium alginate film had much higher LOI value (52.0%) than that of sodium alginate film (24.5%). Moreover, barium alginate film passed the UL-94 V-0 rating, while the sodium alginate film showed no classification. Importantly, peak of heat release rate (PHRR) of barium alginate film in MCC test was much lower than that of sodium alginate film, suggested that introduction of barium ion into alginate film significantly decreased release of combustible gases. TG-FTIR and Py-GC-MS results indicated that barium alginate produced much less flammable products than that of sodium alginate in whole thermal degradation procedure. Finally, a possible degradation mechanism of barium alginate had been proposed. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. Thermal behavior and pyrolytic degradation kinetics of polymeric mixtures from waste packaging plastics

    Directory of Open Access Journals (Sweden)

    R. Tuffi

    2018-01-01

    Full Text Available The thermal behavior and pyrolytic kinetic analysis of main waste polymers (polypropylene (PP, polyethylene film (PE, poly(ethylene terephthalate (PET, polystyrene (PS and three synthetic mixtures representing commingled postconsumer plastics wastes (CPCPWs output from material recovery facilities were studied. Thermogravimetry (TG pyrolysis experiments revealed that the thermal degradation of single polymers and the synthetic mixture enriched in PP occurred in one single step. The other two mixtures underwent a two-consecutive, partially overlapping degradation steps, whose peaks related to the first-order derivative of TG were deconvoluted into two distinct processes. Further TG experiments carried out on binary mixtures (PS/PP, PET/PP, PET/PEfilm and PP/PEfilm showed a thermal degradation reliance on composition, structure and temperatures of single polymer components. A kinetic analysis was made for each step using the Kissinger-Akahira-Sunose (KAS method, thus determining almost constant activation energy (Ea for pyrolysis of PS, PET, PP and PE film in the range 0.25<α<0.85, unlike for pyrolysis of CPCPWs, with particular reference to CPCPW1 and the second step of CPCPW2 and CPCPW3, both ascribable to degradation of PP and PE film. To account for the reliability of these values the integral isoconversional modified method developed by Vyazovkin was also applied.

  18. Toluene degradation by non-thermal plasma combined with a ferroelectric catalyst.

    Science.gov (United States)

    Liang, Wen-Jun; Ma, Lin; Liu, Huan; Li, Jian

    2013-08-01

    Degradation of toluene in a gas by non-thermal plasma with a ferroelectric catalyst was studied at normal temperature and atmospheric pressure. Spontaneous polarization material (BaTiO3) and photocatalyst (TiO2) were added into plasma system simultively. Toluene degradation efficiency and specific energy density during the discharge process were investigated. Furthermore, byproducts and degradation mechanisms of toluene were also investigated. The toluene degradation efficiency increased when non-thermal plasma technology was combined with the catalyst. The toluene degradation efficiencies of the different catalysts tested were in the following order: BaTiO3/TiO2>BaTiO3>TiO2>no catalyst. A mass ratio of 2.38:1 was optimum for the BaTiO3 and TiO2 catalyst. The outlet gas was analyzed by gas chromatography and Fourier transform infrared spectroscopy, and the main compounds detected were CO2, H2O, O3 and benzene ring derivatives. Copyright © 2013 Elsevier Ltd. All rights reserved.

  19. Thermal Contributions to the Degradation of Ground-Laboratory- and Space-Irradiated Teflon Investigated

    Science.gov (United States)

    deGroh, Kim K.; Martin, Morgana

    2003-01-01

    The Hubble Space Telescope (HST) is covered with two primary types of thermal control materials, radiators and multilayer insulation blankets, which passively control temperatures during orbit. Both of these thermal control materials utilize back-surface metalized Teflon FEP (DuPont, fluorinated ethylene propylene) as the exterior (spacefacing) layer because of its excellent optical properties (low solar absorptance and high thermal emittance). The aluminized-FEP (Al-FEP) outermost layer of the multilayer insulation blankets on the HST has become embrittled while in space, resulting in severe on-orbit cracking (see the photographs). During the second servicing mission, an extremely embrittled piece of Al-FEP was retrieved that had curled, exposing the backsurface aluminum to space (see the photograph on the right). Because the aluminum surface has a lower thermal emittance than the FEP, this curled piece reached 200 C during orbit, 150 C higher than the nominal temperature extreme. To better understand the effect of temperature on the rate of degradation, and on the mechanism of degradation, of this insulation material in the low-Earth-orbit environment, researchers at the NASA Glenn Research Center conducted experiments to determine the effect of heating on the degradation of FEP that has been irradiated in a ground laboratory facility or in space on the HST. For this study, Teflon FEP retrieved from the HST during the third servicing mission after 9.7 years of space exposure was provided to Glenn by the NASA Goddard Space Flight Center.

  20. Calcium-Magnesium-Aluminosilicate (CMAS) Infiltration and Cyclic Degradations of Thermal and Environmental Barrier Coatings in Thermal Gradients

    Science.gov (United States)

    Zhu, Dongming; Harder, Bryan; Smialek, Jim; Miller, Robert A.

    2014-01-01

    In a continuing effort to develop higher temperature capable turbine thermal barrier and environmental barrier coating systems, Calcium-Magnesium-Aluminosilicate (CMAS) resistance of the advanced coating systems needs to be evaluated and improved. This paper highlights some of NASA past high heat flux testing approaches for turbine thermal and environmental barrier coatings assessments in CMAS environments. One of our current emphases has been focused on the thermal barrier - environmental barrier coating composition and testing developments. The effort has included the CMAS infiltrations in high temperature and high heat flux turbine engine like conditions using advanced laser high heat flux rigs, and subsequently degradation studies in laser heat flux thermal gradient cyclic and isothermal furnace cyclic testing conditions. These heat flux CMAS infiltration and related coating durability testing are essential where appropriate CMAS melting, infiltration and coating-substrate temperature exposure temperature controls can be achieved, thus helping quantify the CMAS-coating interaction and degradation mechanisms. The CMAS work is also playing a critical role in advanced coating developments, by developing laboratory coating durability assessment methodologies in simulated turbine engine conditions and helping establish CMAS test standards in laboratory environments.

  1. Application of non-thermal plasma reactor and Fenton reaction for degradation of ibuprofen

    Energy Technology Data Exchange (ETDEWEB)

    Marković, Marijana [Center of Chemistry, Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Studentski trg 12-16, 11000 Belgrade (Serbia); Jović, Milica; Stanković, Dalibor [Innovation Center, Faculty of Chemistry, University of Belgrade, P.O. Box 51, 11058 Belgrade 118 (Serbia); Kovačević, Vesna [Faculty of Physics, University of Belgrade, P.O. Box 44, 11000 Belgrade (Serbia); Roglić, Goran [Faculty of Chemistry, University of Belgrade, P.O. Box 51, 11058 Belgrade 118 (Serbia); Gojgić-Cvijović, Gordana [Center of Chemistry, Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Studentski trg 12-16, 11000 Belgrade (Serbia); Manojlović, Dragan, E-mail: manojlo@chem.bg.ac.rs [Faculty of Chemistry, University of Belgrade, P.O. Box 51, 11058 Belgrade 118 (Serbia)

    2015-02-01

    Pharmaceutical compounds have been detected frequently in surface and ground water. Advanced Oxidation Processes (AOPs) were reported as very efficient for removal of various organic compounds. Nevertheless, due to incomplete degradation, toxic intermediates can induce more severe effects than the parent compound. Therefore, toxicity studies are necessary for the evaluation of possible uses of AOPs. In this study the effectiveness and capacity for environmental application of three different AOPs were estimated. They were applied and evaluated for removal of ibuprofen from water solutions. Therefore, two treatments were performed in a non-thermal plasma reactor with dielectric barrier discharge with and without a homogenous catalyst (Fe{sup 2+}). The third treatment was the Fenton reaction. The degradation rate of ibuprofen was measured by HPLC-DAD and the main degradation products were identified using LC–MS TOF. Twelve degradation products were identified, and there were differences according to the various treatments applied. Toxicity effects were determined with two bioassays: Vibrio fischeri and Artemia salina. The efficiency of AOPs was demonstrated for all treatments, where after 15 min degradation percentage was over 80% accompanied by opening of the aromatic ring. In the treatment with homogenous catalyst degradation reached 99%. V. fischeri toxicity test has shown greater sensitivity to ibuprofen solution after the Fenton treatment in comparison to A. salina. - Highlights: • Twelve ibuprofen degradation products were identified in total. • The degradation percentage differed between treatments (DBD/Fe{sup 2+} was 99%). • In DBD/Fe{sup 2+} only aliphatic degradation products were identified. • V. fischeri was sensitive to ibuprofen solution after the Fenton treatment. • A. salina showed no toxic effect when exposed to all post treatment solutions.

  2. Aging Effects and Estimating Degradation Mechanisms of Thermally Upgraded Paper in Mineral Oil

    Science.gov (United States)

    Miyagi, Katsunori; Oe, Etsuo; Yamagata, Naoki

    The life of a transformer is limited to the deterioration of its solid insulation. Winding conductors and other solid insulation materials in oil-immersed transformers have been insulated using cellulose products. For many years, manufacturers have met the needs of special applications by designing transformers using thermally upgraded materials to achieve lighter weight, higher power density and increased life. Recently, the effect of thermally upgraded insulation on diagnostic techniques such as gas-in oil analysis, and their indication of insulation degradation have been reviewed. This paper describes evaluations of the thermal degradation characteristics and decomposition reactions in mineral transformer oil of amine-impregnated thermally upgraded paper insulation. The thermal resistance of the thermally upgraded paper is evaluated by comparison with Kraft paper insulation. Further, aging degradation mechanisms of decompositional degradation of the thermally upgraded paper due to aging in mineral transformer oil are proposed.

  3. Degradation of Thermal Barrier Coatings from Deposits and Its Mitigation

    Energy Technology Data Exchange (ETDEWEB)

    Nitin Padture

    2011-12-31

    Ceramic thermal barrier coatings (TBCs) used in gas-turbine engines afford higher operating temperatures, resulting in enhanced efficiencies and performance. However, in the case of syngas-fired engines, fly ash particulate impurities that may be present in syngas can melt on the hotter TBC surfaces and form glassy deposits. These deposits can penetrate the TBCs leading to their failure. In experiments using lignite fly ash to simulate these conditions we show that conventional TBCs of composition 93wt% ZrO{sub 2} + 7wt% Y{sub 2}O{sub 3} (7YSZ) fabricated using the air plasma spray (APS) process are completely destroyed by the molten fly ash. The molten fly ash is found to penetrate the full thickness of the TBC. The mechanisms by which this occurs appear to be similar to those observed in degradation of 7YSZ TBCs by molten calcium-magnesium-aluminosilicate (CMAS) sand and by molten volcanic ash in aircraft engines. In contrast, APS TBCs of Gd{sub 2Zr{sub 2}O{sub 7} composition are highly resistant to attack by molten lignite fly ash under identical conditions, where the molten ash penetrates ~25% of TBC thickness. This damage mitigation appears to be due to the formation of an impervious, stable crystalline layer at the fly ash/Gd{sub 2}Zr{sub 2}O{sub 7} TBC interface arresting the penetrating moltenfly- ash front. Additionally, these TBCs were tested using a rig with thermal gradient and simultaneous accumulation of ash. Modeling using an established mechanics model has been performed to illustrate the modes of delamination, as well as further opportunities to optimize coating microstructure. Transfer of the technology was developed in this program to all interested parties.

  4. Spectroscopic Study of the Thermal Degradation of PVP-capped Rh and Pt Nanoparticles in H2 and O2 Environments

    Energy Technology Data Exchange (ETDEWEB)

    Borodko, Yuri; Lee, Hyun Sook; Joo, Sang Hoon; Zhang, Yawen; Somorjai, Gabor A.

    2009-09-15

    Poly(N-vinylpyrrolidone) (PVP) capped platinum and rhodium nanoparticles (7-12 nm) have been studied with UV-VIS, FTIR and Raman spectroscopy. The absorption bands in the region 190-900 nm are shown to be sensitive to the electronic structure of surface Rh and Pt atoms as well as to the aggregation of the nanoparticles. In-situ FTIR-DRIFT spectroscopy of the thermal decay of PVP stabilized Rh and Pt nanoparticles in H{sub 2} and O{sub 2} atmospheres in temperatures ranging from 30 C-350 C reveal that decomposition of PVP above 200 C, PVP transforms into a 'polyamidpolyene' - like material that is in turn converted into a thin layer of amorphous carbon above 300 C. Adsorbed carbon monoxide was used as a probing molecule to monitor changes of electronic structure of surface Rh and Pt atoms and accessible surface area. The behavior of surface Rh and Pt atoms with ligated CO and amide groups of pyrrolidones resemble that of surface coordination compounds.

  5. Estimate carbon emissions from degraded permafrost with InSAR and a soil thermal model

    Science.gov (United States)

    Zhou, Z.; Liu, L.

    2016-12-01

    Climate warming, tundra fire over past decades has caused degradation in permafrost widely and quickly. Recent studies indicate that an increase in degradation could switch permafrost from a carbon sink to a source, with the potential of creating a positive feedback to anthropogenic climate warming. Unfortunately, Soil Organic Carbon (SOC) emissions from degraded permafrost unquantified, and limit our ability to understand SOC losses in arctic environments. This work will investigate recent 10 years of data already collected at the Anaktuvuk River fire (both ground and remote sensed), and will employ a soil thermal model to estimate SOC emission in this region. The model converts the increases in Active Layer Thickness (ALT), as measured by InSAR, to changes in Organic Layer Thickness (OLT), and SOC. ALOS-1/2 L-band SAR dataset will be used to produce the ATL changes over the study area. Soil prosperities (e.g. temperature at different depth, bulk density) will be used in the soil thermal model to estimate OLT changes and SOC losses. Ground measurement will validate the InSAR results and the soil thermal model. A final estimation of SOC emission will be produced in Anaktuvuk River region.

  6. Degradation mechanism and thermal stability of urea nitrate below the melting point

    Energy Technology Data Exchange (ETDEWEB)

    Desilets, Sylvain, E-mail: sylvain.desilets@drdc-rddc.gc.ca [Defence R and D Canada, Valcartier, 2459 Pie-XI Blvd North, Val-Belair, Quebec, Canada G3J 1X5 (Canada); Brousseau, Patrick; Chamberland, Daniel [Defence R and D Canada, Valcartier, 2459 Pie-XI Blvd North, Val-Belair, Quebec, Canada G3J 1X5 (Canada); Singh, Shanti; Feng, Hongtu; Turcotte, Richard [Canadian Explosives Research Laboratory, 1 Haanel Dr. Ottawa, Quebec, Canada K1A 1M1 (Canada); Anderson, John [Defence R and D Canada, Suffield, Box 4000, stn Main, Medicine Hat, Alberta, Canada T1A 8K6 (Canada)

    2011-07-10

    Highlights: {yields} Decomposition mechanism of urea nitrate. {yields} Spectral characterization of the decomposition mechanism. {yields} Thermal stability of urea nitrate at 50, 70 and 100 {sup o}C. {yields} Chemical balance of decomposed products released. - Abstract: Aging and degradation of urea nitrate below the melting point, at 100 {sup o}C, was studied by using thermal analysis and spectroscopic methods including IR, Raman, {sup 1}H and {sup 13}C NMR techniques. It was found that urea nitrate was completely degraded after 72 h at 100 {sup o}C into a mixture of solids (69%) and released gaseous species (31%). The degradation mechanism below the melting point was clearly identified. The remaining solid mixture was composed of ammonium nitrate, urea and biuret while unreacted residual nitric and isocyanic acids as well as traces of ammonia were released as gaseous species at 100 {sup o}C. The thermal stability of urea nitrate, under extreme storage conditions (50 {sup o}C), was also examined by isothermal nano-calorimetry.

  7. Thermal degradation features of peppermint oil in a binary system with Β- cyclodextrin

    Directory of Open Access Journals (Sweden)

    I. A. Omelchenko

    2016-04-01

    Full Text Available Aim. One of the most promising ways of changing physical and chemical properties of the active pharmaceutical ingredient is an encapsulation on a molecular level with the use of cyclodextrins. This makes it possible to create products with the desired activity and controlled distribution in the body. Methods and results. We have studied the thermal decomposition of peppermint oil in binary systems with β-cyclodextrin. It has been found that the thermal degradation of mechanical mixture and inclusion complex of the «host-guest» with the composition of 1:1 passes through different mechanisms. Conclusions. It is shown that the given data of thermal stability are useful for the identification of an inclusion complex «β-CD – peppermint oil» and assessing its complexation, and for the development of technology of medicinal forms of supramolecular complex of β-cyclodextrin and peppermint oil

  8. Ultrasonic and Thermal Pretreatments on Anaerobic Digestion of Petrochemical Sludge: Dewaterability and Degradation of PAHs

    Science.gov (United States)

    Zhou, Jun; Xu, Weizhong; Wong, Jonathan W. C.; Yong, Xiaoyu; Yan, Binghua; Zhang, Xueying; Jia, Honghua

    2015-01-01

    Effects of different pretreatment methods on sludge dewaterability and polycyclic aromatic hydrocarbons (PAHs) degradation during petrochemical sludge anaerobic digestion were studied. Results showed that the total biogas production volume in the thermal pretreatment system was 4 and 5 times higher than that in the ultrasound pretreatment and in the control system, and the corresponding volatile solid removal efficiencies reached 28%, 15%, and 8%. Phenanthrene, paranaphthalene, fluoranthene, benzofluoranthene, and benzopyrene removal rates reached 43.3%, 55.5%, 30.6%, 42.9%, and 41.7%, respectively, in the thermal pretreatment system, which were much higher than those in the ultrasound pretreatment and in the control system. Moreover, capillary suction time (CST) of sludge increased after pretreatment, and then reduced after 20 days of anaerobic digestion, indicating that sludge dewaterability was greatly improved after anaerobic digestion. The decrease of protein and polysaccharide in the sludge could improve sludge dewaterability during petrochemical sludge anaerobic digestion. This study suggested that thermal pretreatment might be a promising enhancement method for petrochemical sludge solubilization, thus contributing to degradation of the PAHs, biogas production, and improvement of dewaterability during petrochemical sludge anaerobic digestion. PMID:26327510

  9. Mass spectrometric comparison of swift heavy ion-induced and anaerobic thermal degradation of polymers

    Science.gov (United States)

    Lima, V.; Hossain, U. H.; Walbert, T.; Seidl, T.; Ensinger, W.

    2018-03-01

    The study of polymers irradiated by highly energetic ions and the resulting radiation-induced degradation is of major importance for space and particle accelerator applications. The mechanism of ion-induced molecular fragmentation of polyethylene, polyethyleneimine and polyamide was investigated by means of mass spectrometry and infrared spectroscopy. The results show that the introduction of nitrogen and oxygen into the polymer influences the stability rendering aliphatic polymers with heteroatoms less stable. A comparison to thermal decomposition data from literature reveals that ion-induced degradation is different in its bond fracture mechanism. While thermal degradation starts at the weakest bond, which is usually the carbon-heteroatom bond, energetic ion irradiation leads in the first step to scission of all types of bonds creating smaller molecular fragments. This is due to the localized extreme energy input under non-equilibrium conditions when the ions transfer kinetic energy onto electrons. These findings are of relevance for the choice of polymers for long-term application in both space and accelerator facilities.

  10. Hydrogen and Carbon Black Production from the Degradation of Methane by Thermal Plasma

    Directory of Open Access Journals (Sweden)

    Leila Cottet

    2014-05-01

    Full Text Available Methane gas (CH4 is the main inducer of the so called greenhouse gases effect. Recent scientific research aims to minimize the accumulation of this gas in the atmosphere and to develop processes capable of producing stable materials with added value. Thermal plasma technology is a promising alternative to these applications, since it allows obtaining H2 and solid carbon from CH4, without the parallel formation of byproducts such as CO2 and NOx. In this work, CH4 was degraded by thermal plasma in order to produce hydrogen (H2 and carbon black. The degradation efficiency of CH4, selectivity for H2 production as well as the characterization of carbon black were studied. The best results were obtained in the CH4 flow rate of 5 L min-1 the degradation percentage and the selectivity for H2 production reached 98.8 % and 48.4 %, respectively. At flow rates of less than 5 L min-1 the selectivity for H2 production increases and reaches 91.9 %. The carbon black has obtained amorphous with hydrophobic characteristics and can be marketed to be used in composite material, and can also be activated chemically and/or physically and used as adsorbent material.

  11. NDE of degradation of thermal barrier coating by means of impedance spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ogawa, Kazuhiro; Minkov, Dorian; Shoji, Tetsuo [Tohoku Univ., Research Inst. for Fracture Technology, Sendai (Japan); Sato, Minoru; Hashimoto, Hideo [Tohoku Electric Power Co. Inc., Sendai (Japan)

    1999-04-01

    Nondestructive evaluation of thermal barrier coating (TBC) degradation during service operation has received a wide attention for service life prediction of advanced gas turbines. In this work, TBC on nickel base superalloy degraded at various degrees by thermal aging is investigated. Particularly, TBC and Metal-Chromium-Aluminum-Yttrium alloy (MCrAlY) (M indicates iron (Fe), cobalt (Co), nickel (Ni) or these combinations) bond coating interface where a detrimental reaction takes place and forms various reaction products during thermal aging, is studied in detail. Formation kinetics and physical properties of the reaction layer are evaluated by means of Impedance Spectroscopy (IS). Specimens aged at higher temperature and a longer aging time shows larger impedance. The impedance behavior of TBC and bond coating is found to be markedly changed by the formation of the reaction layer. Physical properties and thickness of the reaction layer are evaluated using the change of the impedance. A mechanistic interpretation of the cause of change in the physical properties and IS behavior are described. (Author)

  12. A full-scale study on thermal degradation of polychlorinated dibenzo- p-dioxins and dibenzofurans in municipal solid waste incinerator fly ash and its secondary air pollution control in China.

    Science.gov (United States)

    Gao, Xingbao; Ji, Bingjing; Yan, Dahai; Huang, Qifei; Zhu, Xuemei

    2017-04-01

    Degradation of polychlorinated dibenzo- p-dioxins and dibenzofurans in municipal solid waste incinerator fly ash is beneficial to its risk control. Fly ash was treated in a full-scale thermal degradation system (capacity 1 t d-1) to remove polychlorinated dibenzo- p-dioxins and dibenzofurans. Apart from the confirmation of the polychlorinated dibenzo- p-dioxin and dibenzofuran decomposition efficiency, we focused on two major issues that are the major obstacles for commercialising this decomposition technology in China, desorption and regeneration of dioxins and control of secondary air pollution. The toxic equivalent quantity values of polychlorinated dibenzo- p-dioxins and dibenzofurans decreased to solid waste incinerator economiser, and then co-processed in the air pollution control system. The degradation furnace released relatively large amounts of cadmium, lead and polychlorinated dibenzo- p-dioxins and dibenzofurans compared with the municipal solid waste incinerator, but the amounts emitted to the atmosphere did not exceed the Chinese national emission limits. Thermal degradation can therefore be used as a polychlorinated dibenzo- p-dioxin and dibenzofuran abatement method for municipal solid waste incinerator source in China.

  13. Thermally induced degradation of sulfur-containing aliphatic glucosinolates in broccoli sprouts (Brassica oleracea var. italica) and model systems.

    Science.gov (United States)

    Hanschen, Franziska S; Platz, Stefanie; Mewis, Inga; Schreiner, Monika; Rohn, Sascha; Kroh, Lothar W

    2012-03-07

    Processing reduces the glucosinolate (GSL) content of plant food, among other aspects due to thermally induced degradation. Since there is little information about the thermal stability of GSL and formation of corresponding breakdown products, the thermally induced degradation of sulfur-containing aliphatic GSL was studied in broccoli sprouts and with isolated GSL in dry medium at different temperatures as well as in aqueous medium at different pH values. Desulfo-GSL have been analyzed with HPLC-DAD, while breakdown products were estimated using GC-FID. Whereas in the broccoli sprouts structural differences of the GSL with regard to thermal stability exist, the various isolated sulfur-containing aliphatic GSL degraded nearly equally and were in general more stable. In broccoli sprouts, methylsulfanylalkyl GSL were more susceptible to degradation at high temperatures, whereas methylsulfinylalkyl GSL were revealed to be more affected in aqueous medium under alkaline conditions. Besides small amounts of isothiocyanates, the main thermally induced breakdown products of sulfur-containing aliphatic GSL were nitriles. Although they were most rapidly formed at comparatively high temperatures under dry heat conditions, their highest concentrations were found after cooking in acidic medium, conditions being typical for domestic processing.

  14. Thermal Degradation of Streptomycin Residues in Honey During Storage

    Directory of Open Access Journals (Sweden)

    Monica Cristina Cara

    2013-01-01

    Full Text Available In Europe there is an increasing emphasis on the quality control of honey, especially on maximum limits of veterinary drug residues (particularly antibiotics permitted in it. Streptomycin is an aminoglycoside antibiotic used in apiculture to protect bees against a variety of brood diseases. Romanian authorities have included it in the National Monitoring Program for honey manufacturers. In this study, an enzyme-linked immunosorbent assay (ELISA screening test was validated as a detection method of streptomycin residues in honey. The ELISA experimental results were compared to those obtained by using an HPLC method. The values generated by the two methods were very close to each other. This fact certifies that ELISA method can be successfully used for quantitative detection of the amount of streptomycin in honey samples. Following validation, three types of honey (polyfloral, lime and acacia were analyzed for streptomycin content after exposure to 4, 22, 30, 40 or 70 °C for 20 weeks. The results show that streptomycin mass fraction decreased with time and with the increase of temperature in all honey samples. The data collected were used to fit a second-order multiple linear regression model for predicting the degradation of streptomycin in honey samples as a function of temperature and storage period. Values of the calculated statistical indicators confirm a good predictive capability of mathematical and statistical models.

  15. Comparative Performance of Three Magnesium Compounds on Thermal Degradation Behavior of Red Gum Wood

    Directory of Open Access Journals (Sweden)

    Yiqiang Wu

    2014-01-01

    Full Text Available The effect of basic magnesium carbonate (BMC, magnesium hydroxide (MH, and magnesium chloride hydrate (MCH on thermal degradation of red gum wood was studied using cone calorimetry, Thermogravimetric-differential scanning calorimetry (TG-DSC analysis, and X-ray diffraction (XRD characterization. The results showed common fire retardation actions of the three compounds by releasing incombustible gas and/or water vapor to dilute combustible gas in the flaming zone, and by converting to MgO, which had a satisfactory protective wall effect on the wood. Individually, BMC absorbed heat from the wood at the pre-decomposition stage and, thus, slowed down wood pyrolysis process. It slightly increased the char yield by charring in both the charring stage and the char calcination stage. MH lost water at about 270 °C, close to the temperature at which wood thermally degraded. MH rendered wood char quickly, and the compact char layer impeded further carbonization and burning of inner wood. MCH promoted charring with Mg2+ as a Lewis acid, and increased wood char yield. MCH also released Cl· free radical and HCl at 167 °C, which easily coordinated with combustion reaction radical, and slowed down, even inhibited, the combustion chain reaction.

  16. Thermal degradation analysis of pongamia pinnata oil as alternative ...

    Indian Academy of Sciences (India)

    In this paper the feasibility of non-edible pongamia pinnata oil (PPO) as an alternative liquid dielectric which can be used in distribution transformers is examined. Hence, electrical, physical and chemical properties have been measured for thermally aged (with and without catalytic added) pongamia pinnata oil (PPO) and ...

  17. Modelling of Thermal Degradation Kinetics of Ascorbic Acid in ...

    African Journals Online (AJOL)

    Ascorbic acid (vitamin C) loss in thermally treated pawpaw and potato was modelled mathematically. Isothermal experiments in the temperature range of 50 -80 oC for the drying of pawpaw and 60 -100 oC for the blanch-drying of potato were utilized to determine the kinetics of ascorbic acid loss in both fruit and vegetable.

  18. Modelling of thermal degradation kinetics of ascorbic acid in ...

    African Journals Online (AJOL)

    Ascorbic acid (vitamin C) loss in thermally treated pawpaw and potato was modelled mathematically. Isothermal experiments in the temperature range of 50 -80 oC for the drying of pawpaw and 60 -100 oC for the blanch-drying of potato were utilized to determine the kinetics of ascorbic acid loss in both fruit and vegetable.

  19. Thermal degradation analysis of pongamia pinnata oil as alternative ...

    Indian Academy of Sciences (India)

    T Mariprasath

    Abstract. In this paper the feasibility of non-edible pongamia pinnata oil (PPO) as an alternative liquid dielectric which can be used in distribution transformers is examined. Hence, electrical, physical and chemical properties have been measured for thermally aged (with and without catalytic added) pongamia pinnata oil.

  20. Thermal degradation kinetics of polylactic acid/acid fabricated cellulose nanocrystal based bionanocomposites.

    Science.gov (United States)

    Monika; Dhar, Prodyut; Katiyar, Vimal

    2017-11-01

    Cellulose nanocrystals (CNC) are fabricated from filter paper (as cellulosic source) by acid hydrolysis using different acids such as sulphuric (H2SO4), phosphoric (H3PO4), hydrochloric (HCl) and nitric (HNO3) acid. The resulting acid derived CNC are melt mixed with Polylactic acid (PLA) using extruder at 180°C. Thermogravimetric (TGA) result shows that increase in 10% and 50% weight loss (T10, T50) temperature for PLA-CNC film fabricated with HNO3, H3PO4 and HCl derived CNC have improved thermal stability in comparison to H2SO4-CNC. Nonisothermal kinetic studies are carried out with modified-Coats-Redfern (C-R), Ozawa-Flynn-Wall (OFW) and Kissinger method to predict the kinetic and thermodynamic parameters. Subsequently prediction of these parameter leads to the proposal of thermal induced degradation mechanism of nanocomposites using Criado method. The distribution of Ea calculated from OFW model are (PLA-H3PO4-CNC: 125-139 kJmol(-1)), (PLA-HNO3-CNC: 126-145 kJmol(-1)), (PLA-H2SO4-CNC: 102-123 kJmol(-1)) and (PLA-HCl-CNC: 140-182 kJmol(-1)). This difference among Ea for the decomposition of PLA-CNC bionanocomposite is probably due to various acids used in this study. The Ea calculated by these two methods are found in consonance with that observed from Kissinger method. Further, hyphenated TG-Fourier transform infrared spectroscopy (FTIR) result shows that gaseous products such as CO2, CO, lactide, aldehydes and other compounds are given off during the thermal degradation of PLA-CNC nanocomposite. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Thermal and IR studies on copper doped polyvinyl alcohol

    Indian Academy of Sciences (India)

    5 mol% PVA : mol% Cu2+ polymer films were prepared by casting process. Thermal transitions and thermal degradation of samples with respect to copper concentration were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Increase in glass transition temperature as ...

  2. Thermal degradation kinetics and estimation of lifetime of radiation grafted polypropylene films

    Science.gov (United States)

    Mandal, Dev K.; Bhunia, Haripada; Bajpai, Pramod K.; Bhalla, Vinod Kumar

    2017-07-01

    In this research work, thermal stability and degradation behavior of acrylic acid grafted polypropylene (PP-g-PAAc) films were investigated by using thermogravimetric (TGA) analysis at four different heating rates 5, 10, 15 and 20 °C/min over a temperature range of 40-550 °C in nitrogen atmosphere. The kinetic parameters namely activation energy (Ea), reaction order (n) and frequency factor (Z) were calculated by three multiple heating rate methods. The thermal stability of PP-g-PAAc films is found to decrease with increase in degree of grafting. The TGA data and thermal kinetic parameters were also used to predict the lifetime of grafted PP films. The estimated lifetime of neat PP as well as grafted PP decreased with increase in temperature by all the three methods. Studies also indicated that Ea and lifetime of PP-g-PAAc films decreased with increase in degree of grafting, which may also be helpful in biodegradation of grafted PP films.

  3. An investigation about the solid state thermal degradation of acetylsalicylic acid: polymer formation

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Edna M. de A; Melo, Dulce M. de A; Moura, Maria de F.V. de; Farias, Robson F. de

    2004-05-06

    An investigation about the thermal degradation of acetylsalicylic acid (ASA) is performed. It is verified that the thermal degradation of ASA produces not only salicylic acid (SA) and acetic acid (AA) as products but also an ASA polymer, which is transparent and solid. And also verified that the temperature in which the polymer is obtained influences its physical consistence (solid or semi-solid). Furthermore, the ASA polymer is very stable from a thermic point of view, as verified by TG and DSC analysis. X-ray diffraction patterns obtained for the ASA polymer show that it exhibits a low crystallinity.

  4. Thermal degradation of poly({alpha}-methylstyrene) in solution. [Quarterly report, July--September 1995

    Energy Technology Data Exchange (ETDEWEB)

    Madras, G.; Smith, J.M.; McCoy, B.J.

    1995-11-11

    The thermal degradation of poly({alpha}-methylstyrene) in solution was investigated at various temperatures (150-225 C) and polymer concentrations (2.00-20.0 g/L) at 6.8 MPa (1000 psig). The molecular weight distributions (MWDs) of the reacted polymer at these conditions were examined at four different residence times. Experimental data indicated that the polymer degraded to its monomer, {alpha}-methylstyrene. No other degradation products were observed. Continuous-mixture kinetics was used to examine the MWDs and to obtain the rate coefficient for degradation and its activation energy. The rate was first-order in polymer concentration with a rate constant at 225 C of 0.01 min{sup {minus} 1} and an activation energy of 66.5 kJ/mol (16.0 kcal/mol). The maximum conversion observed at 275 C was 1.2%. Hydrogen-donor solvent, tetralin, had no effect on the degradation.

  5. Four new degradation products of doxorubicin: An application of forced degradation study and hyphenated chromatographic techniques

    Directory of Open Access Journals (Sweden)

    Dheeraj Kaushik

    2015-10-01

    Full Text Available Forced degradation study on doxorubicin (DOX was carried out under hydrolytic condition in acidic, alkaline and neutral media at varied temperatures, as well as under peroxide, thermal and photolytic conditions in accordance with International Conference on Harmonization (ICH guidelines Q1(R2. It was found extremely unstable to alkaline hydrolysis even at room temperature, unstable to acid hydrolysis at 80 °C, and to oxidation at room temperature. It degraded to four products (O-I–O-IV in oxidative condition, and to single product (A-I in acid hydrolytic condition. These products were resolved on a C8 (150 mm×4.6 mm, 5 µm column with isocratic elution using mobile phase consisting of HCOONH4 (10 mM, pH 2.5, acetonitrile and methanol (65:15:20, v/v/v. Liquid chromatography–photodiode array (LC–PDA technique was used to ascertain the purity of the products noted in LC–UV chromatogram. For their characterization, a six stage mass fragmentation (MS6 pattern of DOX was outlined through mass spectral studies in positive mode of electrospray ionization (+ESI as well as through accurate mass spectral data of DOX and the products generated through liquid chromatography–time of flight mass spectrometry (LC–MS–TOF on degraded drug solutions. Based on it, O-I–O-IV were characterized as 3-hydroxy-9-desacetyldoxorubicin-9-hydroperoxide, 1-hydroxy-9-desacetyldoxorubicin-9-hydroperoxide, 9-desacetyldoxorubicin-9-hydroperoxide and 9-desacetyldoxorubicin, respectively, whereas A-I was characterized as deglucosaminyl doxorubicin. While A-I was found to be a pharmacopoeial impurity, all oxidative products were found to be new degradation impurities. The mechanisms and pathways of degradation of doxorubicin were outlined and discussed.

  6. Thermal oxidative degradation of wood modified with aminophenylborates

    Directory of Open Access Journals (Sweden)

    Klyachenkova Olga

    2016-01-01

    Full Text Available Comparative thermal analysis in the presence of oxygen was carried out for samples of native pine wood and wood samples modified with aminophenylborates. Significant decrease in the amount of heat released during thermal decomposition of the modified samples was established, which is due to the increase of carbonaceous residues on the surface. Reduction of heat release during decomposition of the modified samples may be explained by the lower yield of combustible volatile products as well as by thin film of boron oxide, formed on the surface of the modified wood, that partially reflects heat flow. Produced upon the modifier decomposition water vapor and inert nitrogen oxides dilute gaseous mixture near the wood surface and isolate it from oxygen. This enhances fire-resistance of wood modified with mono- and diethanolamine(N→Bphenylborates. Hydroxyl group at the sixth carbon atom of the glucopyranose ring of cellulose participates in reactions of cellulose modification, which prevents formation of flammable levoglucosan and, consequently, improves the fire-resistance of the modified wood.

  7. MMOD Protection and Degradation Effects for Thermal Control Systems

    Science.gov (United States)

    Christiansen, Eric

    2014-01-01

    Micrometeoroid and orbital debris (MMOD) environment overview Hypervelocity impact effects & MMOD shielding MMOD risk assessment process Requirements & protection techniques - ISS - Shuttle - Orion/Commercial Crew Vehicles MMOD effects on spacecraft systems & improving MMOD protection - Radiators Coatings - Thermal protection system (TPS) for atmospheric entry vehicles Coatings - Windows - Solar arrays - Solar array masts - EVA Handrails - Thermal Blankets Orbital Debris provided by JSC & is the predominate threat in low Earth orbit - ORDEM 3.0 is latest model (released December 2013) - http://orbitaldebris.jsc.nasa.gov/ - Man-made objects in orbit about Earth impacting up to 16 km/s average 9-10 km/s for ISS orbit - High-density debris (steel) is major issue Meteoroid model provided by MSFC - MEM-R2 is latest release - http://www.nasa.gov/offices/meo/home/index.html - Natural particles in orbit about sun Mg-silicates, Ni-Fe, others - Meteoroid environment (MEM): 11-72 km/s Average 22-23 km/s.

  8. Mechanisms Underpinning Degradation of Protective Oxides and Thermal Barrier Coatings in High Hydrogen Content (HHC) - Fueled Turbines

    Energy Technology Data Exchange (ETDEWEB)

    Mumm, Daniel

    2013-08-31

    The overarching goal of this research program has been to evaluate the potential impacts of coal-derived syngas and high-hydrogen content fuels on the degradation of turbine hot-section components through attack of protective oxides and thermal barrier coatings. The primary focus of this research program has been to explore mechanisms underpinning the observed degradation processes, and connections to the combustion environments and characteristic non-combustible constituents. Based on the mechanistic understanding of how these emerging fuel streams affect materials degradation, the ultimate goal of the program is to advance the goals of the Advanced Turbine Program by developing materials design protocols leading to turbine hot-section components with improved resistance to service lifetime degradation under advanced fuels exposures. This research program has been focused on studying how: (1) differing combustion environments – relative to traditional natural gas fired systems – affect both the growth rate of thermally grown oxide (TGO) layers and the stability of these oxides and of protective thermal barrier coatings (TBCs); and (2) how low levels of fuel impurities and characteristic non-combustibles interact with surface oxides, for instance through the development of molten deposits that lead to hot corrosion of protective TBC coatings. The overall program has been comprised of six inter-related themes, each comprising a research thrust over the program period, including: (i) evaluating the role of syngas and high hydrogen content (HHC) combustion environments in modifying component surface temperatures, heat transfer to the TBC coatings, and thermal gradients within these coatings; (ii) understanding the instability of TBC coatings in the syngas and high hydrogen environment with regards to decomposition, phase changes and sintering; (iii) characterizing ash deposition, molten phase development and infiltration, and associated corrosive

  9. Effect of demineralization on the physiochemical structure and thermal degradation of acid treated indigenous rice husk

    Directory of Open Access Journals (Sweden)

    Aslam Umair

    2016-09-01

    Full Text Available Energy generation from biomass presents some serious problems like slagging, fouling and corrosion of boilers. To address these problems, demineralization of biomass is performed using different leaching agents. This study is focused on determining the influence of leaching agents and leaching time on the physiochemical structure of rice husk during demineralization. Dilute (5% wt solutions of HCl and H2SO4 were used for the demineralization of rice husk separately with leaching time of 15, 60 and 120 minutes. It is shown that H2SO4 exhibited higher removal of alkali and alkaline earth metals (AAEM comparatively as depicted by the 34.2% decrease in ash content along with an increase of 7.10% in the heating value. The acid has been seen to induce more notable changes in physiochemical structure as depicted by the FTIR spectra and SEM micrographs. The thermal degradation behavior of the demineralized rice husk has also been reported.

  10. PVT Degradation Studies: Acoustic Diagnostics

    Energy Technology Data Exchange (ETDEWEB)

    Dib, Gerges [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Tucker, Brian J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Kouzes, Richard T. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Smith, Philip J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2017-04-01

    Under certain environmental conditions, polyvinyl toluene (PVT) plastic scintillator has been observed to undergo internal fogging. This document reports on a study of acoustic techniques to determine whether they can provide a diagnostic for the fogging of PVT. Different ultrasound techniques were employed for detecting the level of internal fogging in PVT, including wave velocity measurements, attenuation, nonlinear acoustics, and acoustic microscopy. The results indicate that there are linear relations between the wave velocity and wave attenuation with the level of internal fogging. The effects of fogging on ultrasound wave attenuation is further verified by acoustic microscopy imaging, where regions with fog in the specimen demonstration higher levels of attenuation compared to clear regions. Results from the nonlinear ultrasound measurements were inconclusive due to high sensitivities to transducer coupling and fixture variabilities.

  11. Thermal stability and degradation kinetics of polyphenols and polyphenylenediamines enzymatically synthesized by horseradish peroxidase

    Energy Technology Data Exchange (ETDEWEB)

    Park, Hansol; Ryu, Keungarp [University of Ulsan, Ulsan (Korea, Republic of); Kwon, Oyul [Seoul National University of Science and Technology, Seoul (Korea, Republic of)

    2015-09-15

    Various substituted phenols and phenylenediamines were enzymatically polymerized by horseradish peroxidase in 80% (v/v) organic solvents-aqueous buffer (100 mM sodium acetate, pH 5) mixtures with H{sub 2}O{sub 2} as the oxidant. The thermal stability of the polymers was investigated by thermogravimetric analysis (TGA) and represented by the char yield (wt% of the initial polymer mass) after being heated at 800 .deg. C. Poly(p-phenylphenol) had the highest thermal stability among the synthesized polymers with a char yield of 47 wt%. The polymers containing amino groups such as poly(p-aminophenol) and polyphenylenediamines were also shown to possess high thermal stabilities. The activation energies for the thermal degradation of the polymers determined by derivative thermogravimetric analysis (DTG) using Horowitz-Metzger's pseudo-first-order kinetics were in the range between 23-65 kJ/mol and comparable to those of the chemically synthesized polymers. Dynamic structural changes of the enzymatically synthesized polymers upon heating were studied by differential scanning calorimetry (DSC). The DSC curves of poly(p-phenylphenol) showed a broad exothermic peaks between 150-250 .deg. C, indicating that the polymer undergoes complex structural transitions in the temperature range. On the other hand, the DSC curves of the poly(p-aminophenol) and the poly(p-phenylenediamine) which contain amino groups showed strong sharp endothermic peaks near 150 .deg. C, implying that these polymers possess homogeneous oriented structures which undergo a concerted structural disintegration upon heating.

  12. A metabolomics approach to identify factors influencing glucosinolate thermal degradation rates in Brassica vegetables.

    Science.gov (United States)

    Hennig, K; de Vos, R C H; Maliepaard, C; Dekker, M; Verkerk, R; Bonnema, G

    2014-07-15

    Thermal processing of Brassica vegetables can lead to substantial loss of potential health-promoting glucosinolates (GLs). The extent of thermal degradation of a specific GL varies in different vegetables, possibly due to differences in the composition of other metabolites within the plant matrices. An untargeted metabolomics approach followed by random forest regression was applied to identify metabolites associated to thermal GL degradation in a segregating Brassica oleracea population. Out of 413 metabolites, 15 were associated with the degradation of glucobrassicin, six with that of glucoraphanin and two with both GLs. Among these 23 metabolites three were identified as flavonols (one kaempferol- and two quercetin-derivatives) and two as other GLs (4-methoxyglucobrassicin, gluconasturtiin). Twenty quantitative trait loci (QTLs) for these metabolites, which were associated with glucoraphanin and glucobrassicin degradation, were identified on linkage groups C01, C07 and C09. Two flavonols mapped on linkage groups C07 and C09 and co-localise with the QTL for GL degradation determined previously. Copyright © 2014 Elsevier Ltd. All rights reserved.

  13. Gas chromatographic-mass spectrometric analysis of some potential toxicants amongst volatile compounds emitted during large-scale thermal degradation of poly(acrylonitrile-butadiene-styrene) plastic.

    Science.gov (United States)

    Shapi, M M; Hesso, A

    1991-01-02

    A number of compounds emitted during the thermal degradation of plastics are potentially toxic. This study was aimed at identifying the volatile compounds emitted during large-scale thermal degradation of poly(acrylonitrile-butadiene-styrene). About 5 g of the sample were degraded at between 25 and 470 degrees C in air and nitrogen in a device that can simulate temperature-programmed thermogravimetry. The volatiles were collected in dichloromethane using the solvent trap technique. Some of the 92 compounds identified by gas chromatography-mass spectrometry were found to have no hitherto documented toxicological profiles, even though they are potentially dangerous.

  14. Influence of enzyme and chemical adsorption on the thermal degradation path for eucalyptus pulp

    Energy Technology Data Exchange (ETDEWEB)

    Barneto, Agustin G., E-mail: agustin.garcia@diq.uhu.es [Chemical Engineering Department, El Carmen Campus, University of Huelva, 21071 Huelva (Spain); Valls, Cristina [Textile and Paper Engineering Department, Universitat Politecnica de Catalunya, Colom 11, E-08222 Terrassa (Spain); Ariza, Jose [Chemical Engineering Department, El Carmen Campus, University of Huelva, 21071 Huelva (Spain); Roncero, M. Blanca [Textile and Paper Engineering Department, Universitat Politecnica de Catalunya, Colom 11, E-08222 Terrassa (Spain)

    2013-01-10

    Highlights: Black-Right-Pointing-Pointer Enzymes and chemicals adsorption changes thermal degradation path of cellulose. Black-Right-Pointing-Pointer Adsorptions on pulp fibres increase their amorphous cellulose content. Black-Right-Pointing-Pointer Charring/volatilization ratio of pulp is affected by adsorptions. - Abstract: Changes in thermal degradation path of eucalyptus pulp support enzymes (laccase from Trametes villosa) and chemicals (Tris-HCl or tartrate-tartaric buffer) adsorption on cellulose during biobleaching, thereby increasing cellulose amount that degrades at low temperature and decreasing the apparent crystallinity (ApC) of cellulose crystallites. Changes in ApC, which can be assessed by thermogravimetric analysis -but not X-ray diffraction spectroscopy-affect cellulose volatilization; thus, the higher ApC is, the lower is char production and the higher the volatilization temperature. A linear relationship between ApC and the volatilization/charring ratio (V/C) was observed in this work.

  15. Pyrite-enhanced methylene blue degradation in non-thermal plasma water treatment reactor

    Energy Technology Data Exchange (ETDEWEB)

    Benetoli, Luis Otavio de Brito, E-mail: luskywalcker@yahoo.com.br [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil); Cadorin, Bruno Mena; Baldissarelli, Vanessa Zanon [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil); Geremias, Reginaldo [Departamento de Ciencias Rurais, Universidade Federal de Santa Catarina (UFSC), Curitibanos, SC (Brazil); Goncalvez de Souza, Ivan [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil); Debacher, Nito Angelo, E-mail: debacher@qmc.ufsc.br [Departamento de Quimica, Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil)

    2012-10-30

    Highlights: Black-Right-Pointing-Pointer We use O{sub 2} as the feed gas and pyrite was added to the non-thermal plasma reactor. Black-Right-Pointing-Pointer The methylene blue removal by NTP increased in the presence of pyrite. Black-Right-Pointing-Pointer The total organic carbon content decreased substantially. Black-Right-Pointing-Pointer The acute toxicity test showed that the treated solution is not toxic. Black-Right-Pointing-Pointer The dye degradation occurs via electron impact as well as successive hydroxylation. - Abstract: In this study, methylene blue (MB) removal from an aqueous phase by electrical discharge non-thermal plasma (NTP) over water was investigated using three different feed gases: N{sub 2}, Ar, and O{sub 2}. The results showed that the dye removal rate was not strongly dependent on the feed gas when the electrical current was kept the same for all gases. The hydrogen peroxide generation in the water varied according to the feed gas (N{sub 2} < Ar < O{sub 2}). Using O{sub 2} as the feed gas, pyrite was added to the reactor in acid medium resulting in an accentuated increase in the dye removal, which suggests that pyrite acts as a Fenton-like catalyst. The total organic carbon (TOC) content of the dye solution decreased slightly as the plasma treatment time increased, but in the presence of the pyrite catalyst the TOC removal increased substantially. The acute toxicity test using Artemia sp. microcrustaceans showed that the treated solution is not toxic when Ar, O{sub 2} or O{sub 2}-pyrite is employed. Electrospray ionization mass spectrometry analysis (ESI-MS) of the treated samples indicated that the dye degradation occurs via high energy electron impact as well as successive hydroxylation in the benzene rings of the dye molecules.

  16. Degradation of Teflon(trademark) FEP Following Charged Particle Radiation and Rapid Thermal Cycling

    Science.gov (United States)

    Townsend, Jacqueline; Powers, Charles; Viens, Michael; Ayres-Treusdell, Mary; Munoz, Bruno

    1999-01-01

    During the Second Servicing Mission (SM2) of the Hubble Space Telescope (HST) severe degradation was observed on the outer layer of the thermal control blankets. Astronaut observations and photographs revealed large cracks in the metallized Teflon(trademark) FEP (fluorinated ethylene propylene), the outer layer of the multi-layer insulation (MLI), in many locations around the telescope. In an effort to understand what elements of the space environment might cause such damage, pristine Teflon(trademark) FEP was tested for durability to radiation and thermal cycling. Specimens were subjected to electron and proton fluences comparable to those experienced by HST and were subsequently thermal cycled in a custom-built rapid thermal cycle chamber. Tensile tests of the specimens showed that radiation followed by thermal cycling significantly reduced the ultimate strength and elongation of Teflon(trademark) FEP.

  17. Degradation of Teflon(tm) FEP Following Charged Particle Radiation and Rapid Thermal Cycling

    Science.gov (United States)

    Townsend, Jacqueline; Powers, Charles; Viens, Michael; Ayres-Treusdell, Mary; Munoz, Bruno

    1998-01-01

    During the Second Servicing Mission (SM2) of the Hubble Space Telescope (HST) severe degradation was observed on the outer layer of the thermal control blankets. Astronaut observations and photographs revealed large cracks in the metallized Teflon(R) FEP (fluorinated ethylene propylene), the outer layer of the multi-layer insulation (MLI), in many locations around the telescope. In an effort to understand what elements of the space environment might cause such damage, pristine Teflon(R) FEP was tested for durability to radiation and thermal cycling. Specimens were subjected to electron and proton fluences comparable to those experienced by HST and were subsequently thermal cycled in a custom-built rapid thermal cycle chamber. Tensile tests of the specimens showed that radiation followed by thermal cycling significantly reduced the ultimate strength and elongation of Teflon(R) FEP.

  18. Cholesterol and stigmasterol within a sunflower oil matrix: Thermal degradation and oxysterols formation.

    Science.gov (United States)

    Barriuso, Blanca; Ansorena, Diana; Poyato, Candelaria; Astiasarán, Iciar

    2015-07-01

    The characteristics of the lipid matrix surrounding sterols exert a great influence in their thermal oxidation process. The objective of this work was to assess the oxidation susceptibility of equal amounts of cholesterol and stigmasterol within a sunflower oil lipid matrix (ratio 1:1:200) during heating (180°C, 0-180min). Remaining percentage of sterols was determined and seven sterol oxidation products (SOPs) were analysed for each type of sterol along the heating treatment. Evolution of the fatty acid profile and vitamin E content of the oil was also studied. Overall oxidation status of the model system was assessed by means of Peroxides Value (PV) and TBARS. PV remained constant from 30min onwards and TBARS continued increasing along the whole heating treatment. Degradation of both cholesterol and stigmasterol fitted a first order curve (R(2)=0.937 and 0.883, respectively), with very similar degradation constants (0.004min(-1) and 0.005min(-1), respectively). However, higher concentrations of oxidation products were found from cholesterol (79μg/mg) than from stigmasterol (53μg/mg) at the end of the heating treatment. Profile of individual oxidation products was similar for both sterols, except for the fact that no 25-hydroxystigmasterol was detected. 7α-Hydroxy and 7-keto-derivatives were the most abundant SOPs at the end of the treatment. PUFA and vitamin E suffered a significant degradation along the process, which was correlated to sterols oxidation. Copyright © 2015 Elsevier Inc. All rights reserved.

  19. Investigation on Thermal Degradation Process of Polymer Solar Cells Based on Blend of PBDTTT-C and PC70BM

    Directory of Open Access Journals (Sweden)

    Yu Ning

    2014-01-01

    Full Text Available The effects of thermal treatment on the photovoltaic performance of conventional and inverted polymer solar cells (PSCs based on the combination of poly[(4,8-bis-(2-ethylhexyloxy-benzo[1,2-b;4,5-b′]dithiophene-2,6-diyl-alt-(4-(2-ethylhexanoyl-thie-no[3,4-b]thiophene-2,6-diyl] (PBDTTT-C and [6,6]-phenyl C70-butyric acid methyl ester (PC70BM are investigated. The transient photoconductivity, the absorption spectra, and the transmission electron microscopy (TEM images have been employed to study the thermal degradation of the inverted PSCs. The degradation is attributed to the inefficient charge generation and imbalance in charge-carrier transport, which is closely associated with the morphological evolution of the active layer with prolonged heating time.

  20. Thermal and pH degradation kinetics of anthocyanins in natural food colorant prepared from black rice bran.

    Science.gov (United States)

    Loypimai, Patiwit; Moongngarm, Anuchita; Chottanom, Pheeraya

    2016-01-01

    The study of the stability of anthocyanins in food colorant powder is important to predict the quality changes occurring as the food products are processed, to prevent and control the degradation of the anthocyanins. The objectives of this study were to identify anthocyanin components in natural food colorants obtained from black rice bran, and investigate their thermal stability at 60, 80, and 100 °C, pH stability from 2.0 to 5.0 and also their correlation with visual color, L (*), C (*), and h°. Results showed that only six types of anthocyanins, cyanidin-3-O-glucoside, cyanidin-3-O-rutinoside, delphinidin, cyanidin, pelargonidin and malvidin were present in raw black rice bran (BRB) and black rice bran colorant powder (BCP). The thermal degradation of both the visual color and the anthocyanin content in the BCP followed a first-order kinetic reaction model. The temperature-dependent degradation was adequately fitted to the Arrhenius equation. In terms of the pH stability, increasing pH values resulted in lower activation energies (E a ) and higher half-life (t 1/2 ) values for both color parameters and individual anthocyanins when heating from 60 to 100 °C. Moreover, the degradation rate constant (k) increased with increasing temperature and pH value. The degradation of cyanidin-3-O-glucoside and total anthocyanins showed a strong positive correlation with C (*). The changes in visual color may be used as an on-line quality control indicator during thermal processing of food products containing rice bran colorants which have high anthocyanin content.

  1. Thermal stability and degradation of poly (N-phenylpropionamide homopolymer and copolymer of N-phenylpropionamide with methyl methacrylate

    Directory of Open Access Journals (Sweden)

    M.A. Diab

    2017-05-01

    Full Text Available Different concentrations of copolymer of (N-phenylpropionamide (PA with methyl methacrylate (MMA were prepared and the reactivity ratio values of copolymerization were calculated using the 1H-NMR technique. Thermal analysis of the copolymers showed that the thermal stability is an intermediate between poly(N-phenylpropionamide and poly(methyl methacrylate homopolymers. Thermal degradation products of the PPA were identified by GC–MS techniques. It seems that the mechanism of degradation of PPA homopolymer is characterized by free radical formation followed by recombination along the backbone chain. The activation energies of the thermal degradation of the copolymers were calculated using the Arrhenius relationship.

  2. In Situ Monitoring the Thermal Degradation of PCPDTBT Low Band Gap Polymers with Varying Alkyl Side-Chain Patterns

    OpenAIRE

    Marin, Lidia; Penxten, Huguette; Van Mierloo, Sarah; Carleer, Robert; Lutsen, Laurence; Vanderzande, Dirk; Maes, Wouter

    2013-01-01

    The degradation pattern of a series of low band gap PCPDTBT polymers under thermal stress is investigated by in situ UV-vis and FT-IR techniques combined with thermal degradation analysis. Thermogravimetric analysis is used to predetermine the decomposition intervals, revealing that thermolysis occurs in two stages. TG-TD-GC/MS shows that loss of the alkyl side chains predominantly happens within the first temperature regime and degradation of the polymer backbone occurs thereafter. UV-vis sp...

  3. Charge Transport and Photocurrent Generation Characteristics in Dye Solar Cells Containing Thermally Degraded N719 Dye Molecules

    DEFF Research Database (Denmark)

    Andersen, A. R.; Halme, J.; Lund, T.

    2011-01-01

    By deliberately introducing the thermally degraded form of the dye solar cell sensitizer N719 in dye-sensitized solar cells (DSCs) using synthetically prepared N719-TBP ([Ru(L-H)(2)(NCS)(4-tert-butylpyridine)](-+)N-(Bu)(4)), we have investigated the devastating influence of this ligand substitution...... product (N719-TBP) on the performance parameters of the cells. Two types of dyed solar cells, based on either N719 or N719-TBP, have been characterized employing standard current-voltage (I-V) performance test, UV-vis optical spectroscopy, incident photon to current efficiency (IPCE), and electrochemical...... in the substitution product. The observations made in this study of DSC cells dyed with the substitution product, representing a worst case scenario of cells with 100% degraded dye, are in agreement with the characteristics of N719-dyed solar cells degraded at 85 degrees C, where the effect of ligand substitution...

  4. Fractionation and physicochemical characterization of lignin from waste jute bags: Effect of process parameters on yield and thermal degradation.

    Science.gov (United States)

    Ahuja, Dheeraj; Kaushik, Anupama; Chauhan, Ghanshyam S

    2017-04-01

    In this work lignin was extracted from waste jute bags using soda cooking method and effect of varying alkali concentration and pH on yield, purity, structure and thermal degradation of lignin were studied. The Lignin yield, chemical composition and purity were assessed using TAPPI method and UV-vis spectroscopy. Yield and purity of lignin ranged from 27 to 58% and 50-94%, respectively for all the samples and was maximum for 8% alkali concentration and at pH 2 giving higher thermal stability. Chemical structure, thermal stability and elementary analysis of lignin were studied using FTIR, (H)NMR, thermo gravimetric analysis (TGA) and Elemental analyzer. FTIR and (H)NMR results showed that core structure of lignin starts breaking beyond 10% alkali concentration. S/G ratio shows the dominance of Syringyl unit over guaiacyl unit. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Experimental study and kinetic modeling of the thermal degradation of aromatic volatile organic compounds (benzene, toluene and xylene-para) in methane flames; Etude experimentale et modelisation cinetique de la degradation thermique des composes organiques volatils aromatiques benzenes, toluene et para-xylene dans des flammes de methane

    Energy Technology Data Exchange (ETDEWEB)

    Dupont, L.

    2001-02-01

    This study treats of the thermal degradation of a family of aromatic volatile organic compounds (VOCs) in laminar premixed methane flames at low pressure. The experimental influence of benzene, toluene and xylene-para on the structure of a reference methane flame has been studied. The molar fraction profiles of the stable and reactive, aliphatic, aromatic and cyclic species have been established by the coupling of the molecular beam sampling/mass spectroscopy technique with the gas chromatography/mass spectroscopy technique. Temperature profiles have been measured using a covered thermocouple. A detailed kinetic mechanism of oxidation of these compounds in flame conditions has been developed. Different available sub-mechanisms have been used as references: the GDF-Kin 1.0 model for the oxidation of methane and the models of Tan and Franck (1996) and of Lindstedt and Maurice (1996) in the case of benzene and toluene. In the case of para-xylene, a model has been developed because no mechanisms was available in the literature. These different mechanisms have been refined, completed or adjusted by comparing the experimental results with those obtained by kinetic modeling. The complete kinetic mechanism, comprising 156 chemical species involved in 1072 reactions allows to reproduce all the experimental observations in a satisfactory manner. The kinetic analysis of reactions velocity has permitted to determine oxidation kinetic schemes for benzene, toluene, xylene-para and for the cyclopentadienyl radical, main species at the origin of the rupture of the aromatic cycle. Reactions of recombination with the methyl radicals formed during methane oxidation, of the different aromatic or aliphatic radicals created during the oxidation of aromatics, play an important role and lead to the formation of several aromatic pollutants (ethyl-benzene for instance) or aliphatic pollutants (butadiene or penta-diene for instance) in flames. (J.S.)

  6. Magnetically driven rotation of thermal plasma jet for non-degradable CF{sub 4} treatment

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Sooseok, E-mail: choi@chemenv.titech.ac.jp [Department of Nuclear Engineering, Seoul National University (Korea, Republic of); Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology (Japan); Hong, Sang Hee; Kim, Sungwoo [Department of Nuclear Engineering, Seoul National University (Korea, Republic of); Park, Dong-Wha [Department of Chemical Engineering and Regional Innovation Center for Environmental Technology of Thermal Plasma, Inha University (Korea, Republic of); Watanabe, Takayuki [Department of Environmental Chemistry and Engineering, Tokyo Institute of Technology (Japan)

    2012-11-15

    Effects of an externally applied magnetic field on the thermal plasma treatment of non-degradable greenhouse gas were investigated. Tetrafluoromethane (CF{sub 4}) was decomposed as a waste gas, because it is the most stable species among perfluorocompounds and has the highest global warming potential. A permanent magnet equipped on the exit region of a hollow electrode plasma torch produced azimuthal Lorentz force to drive rotational motions of the arc root and the thermal plasma jet. In order to sustain a stable arc discharge, the position of the permanent magnet was determined by numerical analysis on the temperature distribution according to the length of arc column. Forcibly swirling motion of thermal plasma jet was observed in accordance with the strength of applied magnetic field. Increased destruction and removal efficiency of CF{sub 4} was measured in torch operation with the externally applied magnetic field due to the enhanced entrainment of waste gas into the thermal plasma jet.

  7. Monitoring chemical degradation of thermally cycled glass-fibre composites using hyperspectral imaging

    Science.gov (United States)

    Papadakis, V. M.; Müller, B.; Hagenbeek, M.; Sinke, J.; Groves, R. M.

    2016-04-01

    Nowadays, the application of glass-fibre composites in light-weight structures is growing. Although mechanical characterizations of those structures are commonly performed in testing, chemical changes of materials under stresses have not yet been well documented. In the present work coupon tests and Hyperspectral Imaging (HSI) have been used to categorise possible chemical changes of glass-fibre reinforced polymers (GFRP) which are currently used in the aircraft industry. HSI is a hybrid technique that combines spectroscopy with imaging. It is able to detect chemical degradation of surfaces and has already been successfully applied in a wide range of fields including astronomy, remote sensing, cultural heritage and medical sciences. GFRP specimens were exposed to two different thermal loading conditions. One thermal loading condition was a continuous thermal exposure at 120°C for 24h, 48 h and 96h, i.e. ageing at a constant temperature. The other thermal loading condition was thermal cycling with three different numbers of cycles (4000, 8000, 12000) and two temperature ranges (0°C to 120°C and -25°C to 95°C). The effects of both conditions were measured using both HSI and interlaminar shear (ILSS) tests. No significant changes of the physical properties of the thermally cycled GFRP specimens were detected using interlaminar shear strength tests and optical microscopy. However, when using HIS, differences of the surface conditions were detected. The results showed that the different thermal loading conditions could be successfully clustered in different colours, using the HSI linear unmixing technique. Each different thermal loading condition showed a different chemical degradation level on its surface which was indicated using different colours.

  8. A method to calculate thermal conductivity of a nonperiodic system, bamboo Si1-xGex nanowire with axially degraded components

    Science.gov (United States)

    Xia, Minggang; Han, Jinyun; Cheng, Zhaofang; Zhang, Shengli; Li, Baowen

    2017-10-01

    For a nonperiodic system, a bamboo Si1-xGex nanowire with axially degraded components, it is impossible to obtain its phonon dispersion relations through lattice dynamic or the first principle calculation. Therefore, we present a simple and available method to solve this problem. At first, the Si1-xGex nanowire with axially degraded component is divided into several sections according to its component distribution like bamboos' sections formed in the growth process. For each section with a given x value, we constructed a pseudo-cell to calculate its phonon dispersion relations. Thermal conductances of junctions and of each section are then calculated by the phonon mismatch model and the phonon transmission probability with diffusive and ballistic portions. The dependences of thermal conductivity on the length of each section and the gradient of degraded component between sections are presented. We studied thermal conductivity dependence on temperature, length and diameter of the Si1-xGex nanowire with axially degraded component. And we found κ l0.8, in which the exponent 0.8 is ascribed to the competition between phonons ballistic and diffusive transport. Furthermore, thermal conductivities along axial (100), (110), and (111) directions are discussed in detail. The method provides a simple and available tool to study thermal conductivity of a non-period system, such as a quasiperiodic superlattice or a nanowire with axially degraded component.

  9. Thermal degradation, antioxidant and antimicrobial activity of the synthesized allicin and allicin incorporated in gel

    OpenAIRE

    Ilić Dušica P.; Nikolić Vesna D.; Nikolić Ljubiša B.; Stanković Mihajlo Z.; Stanojević Ljiljana P.

    2010-01-01

    The main carriers of the pharmacological activity of garlic (Allium sativum L.) are organic sulfur compounds, the most important among them being allicin, a sulfenic acid thioester, or allylthiosulfonate. In this paper, the identification of synthesized and purified allicin was determined by using various spectroscopic methods (UV/VIS, FTIR, NMR). A HPLC method was developed for the detection and determination of the allicin content. The thermal degradation of allicin by using FTIR method was...

  10. Thermal degradation kinetics of polyketone based on styrene and carbon monoxide

    Energy Technology Data Exchange (ETDEWEB)

    Mu, Jiali, E-mail: jiaqm411@163.com; Fan, Wenjun; Shan, Shaoyun; Su, Hongying; Wu, Shuisheng; Jia, Qingming

    2014-03-01

    Highlights: • The PK were synthesized from carbon monoxide and styrene in the presence of PANI-PdCl{sub 2} catalyst and PdCl{sub 2} catalyst. • The structures and thermal behaviors of PK prepared by homogenous and the supported catalyst were investigated. • The microstructures of PK were changed in the supported catalyst system. • The alternating PK copolymer (PANI-PdCl{sub 2} catalyst) was more thermally stable than PK (PdCl{sub 2} catalyst). • The degradation activation energy values were estimated by Flynn–Wall–Ozawa method and Kissinger method. - Abstract: Copolymerization of styrene with carbon monoxide to give polyketones (PK) was carried out under homogeneous palladium catalyst and polyaniline (PANI) supported palladium(II) catalyst, respectively. The copolymers were characterized by {sup 1}H NMR, {sup 13}C NMR and GPC. The results indicated that the PK catalyzed by the supported catalyst has narrow molecular weight distribution (PDI = 1.18). For comparison purpose of thermal behaviors of PK prepared by the homogeneous and the supported catalyst, thermogravimetric (TG) analysis and derivative thermogravimetric (DTG) were conducted at different heating rates. The peak temperatures (396–402 °C) for PK prepared by the supported catalyst are higher than those (387–395 °C) of PK prepared by the homogeneous catalyst. The degradation activation energy (E{sub k}) values were estimated by Flynn–Wall–Ozawa method and Kissinger method, respectively. The E{sub k} values, as determined by two methods, were found to be in the range 270.72 ± 0.03–297.55 ± 0.10 kJ mol{sup −1}. Structures analysis and thermal degradation analysis revealed that the supported catalyst changed the microstructures of PK, resulting in improving thermal stability of PK.

  11. Thermal degradation of new and aged urethane foam and epon 826 epoxy.

    Energy Technology Data Exchange (ETDEWEB)

    Kruizenga, Alan Michael [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Mills, Bernice E. [Sandia National Lab. (SNL-CA), Livermore, CA (United States)

    2013-08-01

    Thermal desorption spectroscopy was used to monitor the decomposition as a function of temperature for the foam and epoxy as a function of temperature in the range of 60C to 170C. Samples were studied with one day holds at each of the studied temperatures. Both new (FoamN and EpoxyN) and aged (FoamP and EpoxyP) samples were studied. During these ~10 day experiments, the foam samples lost 11 to 13% of their weight and the EpoxyN lost 10% of its weight. The amount of weight lost was difficult to quantify for EpoxyP because of its inert filler. The onset of the appearance of organic degradation products from FoamP began at 110C. Similar products did not appear until 120C for FoamN, suggesting some effect of the previous decades of storage for FoamP. In the case of the epoxies, the corresponding temperatures were 120C for EpoxyP and 110C for EpoxyN. Suggestions for why the aged epoxy seems more stable than newer sample include the possibility of incomplete curing or differences in composition. Recommendation to limit use temperature to 90-100C for both epoxy and foam.

  12. Thermal and pH degradation kinetics of anthocyanins in natural food colorant prepared from black rice bran

    OpenAIRE

    Loypimai, Patiwit; Moongngarm, Anuchita; Chottanom, Pheeraya

    2015-01-01

    The study of the stability of anthocyanins in food colorant powder is important to predict the quality changes occurring as the food products are processed, to prevent and control the degradation of the anthocyanins. The objectives of this study were to identify anthocyanin components in natural food colorants obtained from black rice bran, and investigate their thermal stability at 60, 80, and 100 °C, pH stability from 2.0 to 5.0 and also their correlation with visual color, L*, C*, and h°. ...

  13. Thermal Degradation, Mechanical Properties and Morphology of Wheat Straw Flour Filled Recycled Thermoplastic Composites.

    Science.gov (United States)

    Mengeloglu, Fatih; Karakus, Kadir

    2008-01-24

    Thermal behaviors of wheat straw flour (WF) filled thermoplastic compositeswere measured applying the thermogravimetric analysis and differential scanningcalorimetry. Morphology and mechanical properties were also studied using scanningelectron microscope and universal testing machine, respectively. Presence of WF inthermoplastic matrix reduced the degradation temperature of the composites. One for WFand one for thermoplastics, two main decomposition peaks were observed. Morphologicalstudy showed that addition of coupling agent improved the compatibility between WFs andthermoplastic. WFs were embedded into the thermoplastic matrix indicating improvedadhesion. However, the bonding was not perfect because some debonding can also be seenon the interface of WFs and thermoplastic matrix. In the case of mechanical properties ofWF filled recycled thermoplastic, HDPE and PP based composites provided similar tensileand flexural properties. The addition of coupling agents improved the properties ofthermoplastic composites. MAPE coupling agents performed better in HDPE while MAPPcoupling agents were superior in PP based composites. The composites produced with thecombination of 50-percent mixture of recycled HDPE and PP performed similar with theuse of both coupling agents. All produced composites provided flexural properties requiredby the ASTM standard for polyolefin-based plastic lumber decking boards.

  14. Thermal Degradation, Mechanical Properties and Morphology of Wheat Straw Flour Filled Recycled Thermoplastic Composites

    Directory of Open Access Journals (Sweden)

    Kadir Karakus

    2008-01-01

    Full Text Available Thermal behaviors of wheat straw flour (WF filled thermoplastic compositeswere measured applying the thermogravimetric analysis and differential scanningcalorimetry. Morphology and mechanical properties were also studied using scanningelectron microscope and universal testing machine, respectively. Presence of WF inthermoplastic matrix reduced the degradation temperature of the composites. One for WFand one for thermoplastics, two main decomposition peaks were observed. Morphologicalstudy showed that addition of coupling agent improved the compatibility between WFs andthermoplastic. WFs were embedded into the thermoplastic matrix indicating improvedadhesion. However, the bonding was not perfect because some debonding can also be seenon the interface of WFs and thermoplastic matrix. In the case of mechanical properties ofWF filled recycled thermoplastic, HDPE and PP based composites provided similar tensileand flexural properties. The addition of coupling agents improved the properties ofthermoplastic composites. MAPE coupling agents performed better in HDPE while MAPPcoupling agents were superior in PP based composites. The composites produced with thecombination of 50-percent mixture of recycled HDPE and PP performed similar with theuse of both coupling agents. All produced composites provided flexural properties requiredby the ASTM standard for polyolefin-based plastic lumber decking boards.

  15. Synchronized Analysis of FTIR Spectra and GCMS Chromatograms for Evaluation of the Thermally Degraded Vegetable Oils

    Directory of Open Access Journals (Sweden)

    Siong Fong Sim

    2014-01-01

    Full Text Available Fourier Transform Infrared (FTIR and Gas Chromatography Mass Spectrometry (GCMS are two common instruments used for analysis of edible oils. The output signal is often analysed on the software attached to the workstations. The processing software is usually individualised for a specific source. The output of GCMS cannot be analysed on the FTIR hence analysts often need to juggle between instruments when multiple techniques are employed. This could become exhaustive when a large dataset is involved. This paper reports a synchronised approach for analysis of signal from FTIR and GCMS. The algorithm is demonstrated on a dataset of edible oils to investigate the thermal degradation of seven types of edible oils treated at 100°C and 150°C. The synchronised routines identify peaks present in FTIR and GCMS spectra/chromatograms where the information is subsequently extracted onto peak tables for further analysis. In this study, it is found that palm based products and corn oils were relatively more stable with higher content of antioxidants tocopherols and squalene. As a conclusion, this approach allows simultaneous analysis of signal from multiple sources and samples enhancing the efficiency of the signal processing process.

  16. Thermal and catalytic degradation of polyethylene wastes in the presence of silica gel, 5A molecular sieve and activated carbon.

    Science.gov (United States)

    González, Yovana Sander; Costa, Carlos; Márquez, M Carmen; Ramos, Pedro

    2011-03-15

    A comparative study of thermal and catalytic degradation of polyethylene wastes has been carried out with the aim of obtaining chemical compounds with potential use in the chemical industry and the energy production. Polyethylene wastes were obtained from polyethylene bags used in supermarkets. Catalysts utilized in the study were silica gel, 5A molecular sieve and activated carbon. The pyrolysis was performed in a batch reactor at 450, 500 and 700 °C during 2h for each catalyst. The ratio catalyst/PE was 10% w/w and the solid and gaseous products were analyzed by gas chromatography and mass spectrometry. The optimum operation temperature and the influence of the three catalysts are discussed with regards to the products formed. The best temperature for degradation with silica gel and activated carbon as catalysts was 450 °C and with 5A molecular sieve was 700 °C. Degradation products of PE (solid fraction and gas fraction) are depending on temperature and catalyst used. External surface and structure of catalysts were visualized by Scanning Electron Microscopy (SEM) and the contribution on product distribution is commented. All products from different degradations could be used as feed stocks in chemical industry or in energy production based on the value of heat of combustion for solid fraction (45000 J/g), similar to the heat of combustion of commercial fuels. Copyright © 2011 Elsevier B.V. All rights reserved.

  17. Kinetics of mechanical, thermal and oxidative degradation and solution properties of polymers in relation to their use as polymeric actives in lubricating oils. DGMK-project 149

    Energy Technology Data Exchange (ETDEWEB)

    Klein, J.; Mueller, H.G.

    1979-01-01

    Oxidative and thermal degradation of 10 W/50 multigrade motor oils have been investigated in a laboratory test. Changes of viscosity and of molecular weight distribution of polymers have been studied. Shear degradation of polymers in dilute solution has been studied by following the change of molecular weight distribution curves as a function of time by gel permeation chromatography. Rate constants of the degradation reaction are determined as functions of system parameters as e.g. molecular weight, shear stress and polymer concentration. Mechanical shear degradation is found to be a first order process. Rate of degradation is directly proportional to the hydrodynamic volume of the macromolecules. Measurement of solution properties of polymers in oil shows that polymer coils either expand or contract with increasing temperature depending on their chemical structure. On the basis of these results a new more general concept is presented to explain the mechanism of action of viscosity index improvers.

  18. Thermal/chemical degradation of ceramic cross-flow filter materials

    Energy Technology Data Exchange (ETDEWEB)

    Alvin, M.A.; Lane, J.E.; Lippert, T.E.

    1989-11-01

    This report summarizes the 14-month, Phase 1 effort conducted by Westinghouse on the Thermal/Chemical Degradation of Ceramic Cross-Flow Filter Materials program. In Phase 1 expected filter process conditions were identified for a fixed-bed, fluid-bed, and entrained-bed gasification, direct coal fired turbine, and pressurized fluidized-bed combustion system. Ceramic cross-flow filter materials were also selected, procured, and subjected to chemical and physical characterization. The stability of each of the ceramic cross-flow materials was assessed in terms of potential reactions or phase change as a result of process temperature, and effluent gas compositions containing alkali and fines. In addition chemical and physical characterization was conducted on cross-flow filters that were exposed to the METC fluid-bed gasifier and the New York University pressurized fluidized-bed combustor. Long-term high temperature degradation mechanisms were proposed for each ceramic cross-flow material at process operating conditions. An experimental bench-scale test program is recommended to be conducted in Phase 2, generating data that support the proposed cross-flow filter material thermal/chemical degradation mechanisms. Papers on the individual subtasks have been processed separately for inclusion on the data base.

  19. Effect of various nanofillers on thermal stability and degradation kinetics of polymer nanocomposites.

    Science.gov (United States)

    Choudhury, Anusuya; Bhowmick, Anil K; Ong, Christopher; Soddemann, Matthias

    2010-08-01

    Structure of nanofillers and their subsequent interaction with a polymer is very important in determining thermal stability of polymer nanocomposite. In this paper, we tried to correlate structure of various 0, 1 and 2 dimensional nanofillers with the thermal stability of hydrogenated nitrile butadiene rubber (HNBR) nanocomposites. Organically modified and unmodified layered silicates such as montmorillonite (Cloisite Na+, Cloisite 30B and Cloisite 15A), rod-like fibrous filler (sepiolite) and spherical nanoparticles (nanosilica) were chosen for this purpose. A significant improvement in thermal stability (obtained by thermogravimeric analysis and differential scanning calorimetry) was observed for silica-filled nanocomposites. However, the activation energy of the nanocomposites calculated by different kinetic methods (both non-isothermal and isothermal methods) was found to be significantly high for sepiolite, 30B and silica-filled nanocomposites. The results were explained with the help of structure of the nanofillers, their interaction with the elastomer and the subsequent dispersion, as measured by X-ray diffraction, transmission electron microscopy and atomic force microscopy. From these analyses it was concluded that organically modified montmorillonite, sepiolite and nanosilica increase the thermal stability of the nanocomposite to a great extent due to the interaction of the reactive groups on the surface of these fillers with the polymer and high thermal stability of these inorganic fillers. Finally, degradation mechanism of HNBR in presence of the nanofillers at severe operating temperatures was investigated with the help of FTIR spectroscopy.

  20. Thermal degradation mechanism of addition-cure liquid silicone rubber with urea-containing silane

    Energy Technology Data Exchange (ETDEWEB)

    Fang, Weizhen; Zeng, Xingrong, E-mail: psxrzeng@gmail.com; Lai, Xuejun; Li, Hongqiang; Chen, Wanjuan; Zhang, Yajun

    2015-04-10

    Highlights: • The urea-containing silane was incorporated into addition-cure liquid silicone rubber (ALSR) via hydrosilylation reaction. • The thermal stability of the ALSR was improved by DEUPAS both in nitrogen and air • The TG–FTIR of evolved gases during degradation was performed. • The possible degradation mechanism of the ALSR samples was proposed. - Abstract: The reactive urea-containing silane, (γ-diethylureidopropyl) allyloxyethoxysilane (DEUPAS), was synthesized by the trans-etherification reaction. The chemical structure was characterized by Fourier transform infrared spectrometry (FTIR) and {sup 1}H nuclear magnetic resonance spectrometry ({sup 1}H NMR). Subsequently, DEUPAS was incorporated into addition-cure liquid silicone rubber (ALSR) via hydrosilylation reaction. The thermal stability of the ALSR samples was investigated by thermogravimetry (TG) and thermogravimetry–Fourier transform infrared spectrometry (TG–FTIR). When DEUPAS was incorporated, the temperature of 10% weight loss and 20% weight loss under air atmosphere were respectively increased by 31 °C and 60 °C compared with those of the ALSR without DEUPAS. Meanwhile, the residual weight at 800 °C increased from 33.5% to 58.7%. It was found that the striking enhancement in thermal stability of the ALSR samples was likely attributed to the decomposition of the urea groups to isocyanic acid, which reacted with hydroxyl groups to inhibit the unzipping depolymerization.

  1. Magnetic Susceptibility depending on the Thermal Degradation of HK-40 Steel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jeong Min; Park, Jong Seo; Nahm, Seung Hoon [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Son, De Rac [Hannam University, Daejeon (Korea, Republic of); Kim, Dong Gyun [Kyungpook National University, Daegu (Korea, Republic of); Han, Sang In; Choi, Song Chun [Korea Gas Safety Corporation, Siheung (Korea, Republic of); Ryu, Dae Hyun [Hansei University, Gunpo (Korea, Republic of)

    2004-02-15

    Since the used materials of furnace heater tube with different kinds of thermal degradation were not commonly available, the HK-40 steel specimens were heat-treated isothermally at elevated temperature to simulate the microstructure at the service temperature. HK-40 steel specimens with five different aging time were prepared by isothermal heat treatment at 1050 .deg. C . The characteristics of the magnetic susceptibility have been investigated for the degradation evaluation of HK-40 steel. The magnetic susceptibility at room temperature increases as the extent of degradation of the materials increases. The variation of magnetic susceptibility was compared with the variation of tensile properties and Vickers hardness. To investigate the effect of the microsturctural change on the characteristics of tensile properties, hardness and magnetic susceptibility, the microstructures were examined by a scanning electron microscope(SEM) and the chemical compositions were analyzed by a energy spectrometer of SEM. As a result, the magnetic susceptibility method can be suggested as one of the nondestructive evaluation methods for the degradation of the HK-40 steel

  2. Kinetic and thermodynamic investigation of mancozeb degradation in tomato homogenate during thermal processing.

    Science.gov (United States)

    Certel, Muharrem; Cengiz, Mehmet F; Akçay, Mehmet

    2012-02-01

    The kinetic and thermodynamic parameters of mancozeb degradation in tomato homogenates under the conditions prevailing in the manufacture of tomato products (at 60-100 °C for 0-60 min) were investigated. A gas chromatography-mass spectrometry method was used to analyse residual mancozeb in tomato homogenate. Ethylenethiourea (ETU), the main toxic degradation product of mancozeb, was measured by high-performance liquid chromatography (HPLC)-with photodiode array detector (PDA). The degradation of mancozeb and the formation of ETU in tomato homogenates were adequately described as first-order kinetics. Dependence of the rate constant followed the Arrhenius relationship. Apparent activation energies, temperature coefficients, half time and time to reduce to 90% of the initial value of mancozeb were calculated as kinetic parameters. The thermodynamic parameters of mancozeb were also described as Δg(d) = - 2.440 and 7.074 kJ mol⁻¹; Δh(d) = - 32.555 and - 42.767 kJ mol⁻¹; Δs(d) = - 0.090 and - 0.150 kJ mol⁻¹ K⁻¹; K(e) = 0.414 and 9.797 L g⁻¹ for 333 and 373 K respectively. Current findings may shed light on the reduction of mancozeb residue and its toxic degradation product during thermal processing of tomatoes and may also be valuable in awareness and prevention of potential risks from dietary exposure. Copyright © 2011 Society of Chemical Industry.

  3. Advanced Cell Development and Degradation Studies

    Energy Technology Data Exchange (ETDEWEB)

    J. E. O' Brien; C. M. Stoots; J. S. Herring; R. C. O' Brien; K. G. Condie; M. Sohal; G. K. Housley; J. J. Hartvigsen; D. Larsen; G. Tao; B. Yildiz; V. Sharma; P. Singh; N. Petigny; T. L. Cable

    2010-09-01

    The Idaho National Laboratory (INL) has been researching the application of solid-oxide electrolysis cells for large-scale hydrogen production from steam over a temperature range of 800 to 900ºC. From 2003 – 2009, this work was sponsored by the DOE Nuclear Hydrogen Initiative (NHI). Starting in 2010, the HTE research program has been sponsored by the Next Generation Nuclear Plant (NGNP) program. HTSE research priorities in FY10 are centered on understanding and reducing cell and stack performance degradation to an acceptable level to advance the technology readiness level of HTSE and to justify further large-scale demonstration activities. This report provides a summary of our FY10 experimental program, which has been focused on advanced cell and stack development and degradation studies. Advanced cell and stack development activities are under way at five technology partners: MSRI, Versa Power, Ceramatec, NASA Glenn, and St. Gobain. Performance evaluation of the advanced technology cells and stacks has been performed by the technology partners, by MIT and the University of Connecticut and at the INL HTE Laboratory. Summaries of these development activities and test results are presented.

  4. STUDY OF WHEAT PROTEIN DEGRADATION DURING GERMINATION

    Directory of Open Access Journals (Sweden)

    Eva Michalcová

    2012-06-01

    Full Text Available Glutens, the storage proteins of cereals, play significant role in technological and nutraceutical quality of cereal grains. Whereas the high content of glutens allows making better structure of dough, consummation of foods with high gluten content can cause digestive problems. In our work, we studied ability of wheat proteases to degrade proteins, especially glutens. Wheat grains were germinated for up to seven days at three different temperatures 15, 20, 30 °C and pH 3.0, 4.0, 5.5, 7.0, 8.0. Proteins were fractionated into salt-soluble albumins and globulins, alcohol-soluble gliadins and base-soluble glutenins. In these fractions, protein content and their composition were analyzed by Bradford method and SDS-PAGE (sodium dodecyl sulfate polyacrylamide gel electrophoresis. The results showed that remarkable degradation of glutens started after three days and the lowest concentration was measured at the seventh day of germination of wheat grain at temperature 20 °C, pH 5.5.

  5. Forest degradation and livelihood: a case study of government forest ...

    African Journals Online (AJOL)

    This study examined the effect of forest degradation on livelihood returns in Government forest reserves of Ogun State. Primary data used in the study were obtained in a multi-stage random sampling procedure across non-degraded and degraded forests. Both qualitative and quantitative analytical methods were employed ...

  6. Durability Improvements Through Degradation Mechanism Studies

    Energy Technology Data Exchange (ETDEWEB)

    Borup, Rodney L. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Mukundan, Rangachary [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Spernjak, Dusan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Baker, Andrew M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Lujan, Roger W. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Langlois, David Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Ahluwalia, Rajesh [Argonne National Lab. (ANL), Argonne, IL (United States); Papadia, D. D. [Argonne National Lab. (ANL), Argonne, IL (United States); Weber, Adam Z. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Kusoglu, Ahmet [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Shi, Shouwnen [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); More, K. L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Grot, Steve [Ion Power, New Castle, DE (United States)

    2015-08-03

    The durability of polymer electrolyte membrane (PEM) fuel cells is a major barrier to the commercialization of these systems for stationary and transportation power applications. By investigating cell component degradation modes and defining the fundamental degradation mechanisms of components and component interactions, new materials can be designed to improve durability. To achieve a deeper understanding of PEM fuel cell durability and component degradation mechanisms, we utilize a multi-institutional and multi-disciplinary team with significant experience investigating these phenomena.

  7. Effect of Azo Dyes on the Thermal Degradation of Post-consumer Polyester Fabrics

    Directory of Open Access Journals (Sweden)

    Qin Dan

    2016-01-01

    Full Text Available Thermogravimetric analysis(TGA and pyrolysis gas chromatography mass spectrometry (Py-GC-MS investigations were carried out on the thermal degradation of white and red post-consumer polyester fabrics. The results show that red PET fabrics which was dyed with C.I. Disperse red 167 for its typical azo structure exhibits larger activation energy compared with white PET. The addition of azo dyes displays an inhibiting effect on the deep pyrolysis and the formation of biphenyl and bis(2-hydroxybutyl terephthalate produced by the free radical mechanism.

  8. Effect of Thermal Degradation on High Temperature Ultrasonic Transducer Performance in Small Modular Reactors

    Science.gov (United States)

    Bilgunde, Prathamesh N.; Bond, Leonard J.

    Prototype ultrasonic NDT transducers for use in immersion in coolants for small modular reactors have shown low signal to noise ratio. The reasons for the limitations in performance at high temperature are under investigation, and include changes in component properties. This current work seeks to quantify the issue of thermal expansion and degradation of the piezoelectric material in a transducer using a finite element method. The computational model represents an experimental set up for an ultrasonic transducer in a pulse-echo mode immersed in a liquid sodium coolant. Effect on transmitted and received ultrasonic signal due to elevated temperature (∼200oC) has been analysed.

  9. Tracking thermal degradation on passion fruit juice through Nuclear Magnetic Resonance and chemometrics.

    Science.gov (United States)

    Soares, Marcia Valeria L; Alves Filho, Elenilson G; Silva, Lorena Mara A; Novotny, Etelvino Henrique; Canuto, Kirley Marques; Wurlitzer, Nedio Jair; Narain, Narendra; de Brito, Edy Sousa

    2017-03-15

    Thermal food processing mainly aims to control microorganism in order to extend its shelf life. However, it may induce chemical and nutritional changes in foodstuff. The Nuclear Magnetic Resonance (NMR) coupled to multivariate analysis was used to evaluate the effect of different thermal processing conditions (85 and 140°C for 4; 15; 30; and 60s) on the passion fruit juice using an Armfield pasteurizer. Through this approach it was possible to identify the changes in the juice composition. The temperature and the time lead to a hydrolysis of the sucrose to glucose and fructose. Additionally, juice submitted to 140°C for 60s results in the degradation of the sucrose and the formation of 5-(hydroxymethyl)-2-furfural (HMF). Despite no novel chemical marker has been identified, the 1 H NMR chemometrics approach may contribute in the choice of the temperature and time to be employed in the juice processing. Copyright © 2016 Elsevier Ltd. All rights reserved.

  10. Thermal Degradation Behaviour of Ni(II Complex of 3,4-Methylenedioxaphenylaminoglyoxime

    Directory of Open Access Journals (Sweden)

    Emin Karapınar

    2013-01-01

    Full Text Available Thermal degradation behaviour of the Ni(II complex of 3,4-methylenedioxaphenylaminoglyoxime was investigated by TG, DTA, and DTG at a heating rate of 10°C min−1 under dinitrogen. The acquired experimental data shows that the complex is thermally stable up to 541 K. The pyrolytic decomposition process occurs by melting metal complex and metal oxide remains as final product. The energies of the reactions involved and the mechanism of decomposition at each stage have been examined. The values of kinetic parameters such as activation energy (E, preexponential factor (A and thermodynamic parameters such as enthalpy (ΔH, entropy (ΔS, and Gibbs free energy (ΔG are also evaluated.

  11. Thermal and spectroscopic analysis of organic matter degradation and humification during composting of pig slurry in different scenarios.

    Science.gov (United States)

    Martín-Mata, J; Lahoz-Ramos, C; Bustamante, M A; Marhuenda-Egea, F C; Moral, R; Santos, A; Sáez, J A; Bernal, M P

    2016-09-01

    In this work, different analytical techniques (thermal analysis, (13)C cross-polarization magic angle spinning (CPMAS) NMR and Fourier transform infrared (FT-IR) spectroscopy) have been used to study the organic matter changes during the co-composting of pig slurry with cotton gin waste. To ensure the validity of the findings, the composting process was developed in different scenarios: under experimental pilot plant conditions, using the static pile system, and under real conditions on a pig farm, using the turning pile system. Also, the thermal stability index (R1) was determined before and after an extraction with water, to evaluate the effect of eliminating water-soluble inorganic salts on the thermal analysis. The results of the thermal methods showed the degradation of the most labile organic matter during composting; R1 increased during composting in all piles, without any influence of the presence of water-soluble inorganic ions in the sample. The NMR showed a decrease in the abundance of the carbohydrate molecules and an increase in the aliphatic materials during composting, due to a concentration effect. Also, FT-IR spectroscopy was a useful technique to study the trends of polysaccharides and nitrate, as indicators of organic matter transformations during composting.

  12. The Study of the Microbes Degraded Polystyrene

    Directory of Open Access Journals (Sweden)

    Zhi-Long Tang

    2017-01-01

    Full Text Available Under the observation that Tenebrio molitor and Zophobas morio could eat polystyrene (PS, we setup the platform to screen the gut microbes of these two worms. To take advantage of that Tenebrio molitor and Zophobas morio can eat and digest polystyrene as its diet, we analyzed these special microbes with PS plate and PS turbidity system with time courses. There were two strains TM1 and ZM1 which isolated from Tenebrio molitor and Zophobas morio, and were identified by 16S rDNA sequencing. The results showed that TM1 and ZM1 were cocci-like and short rod shape Gram-negative bacteria under microscope. The PS plate and turbidity assay showed that TM1 and ZM1 could utilize polystyrene as their carbon sources. The further study of PS degraded enzyme and cloning warrants our attention that this platform will be an excellent tools to explore and solve this problem.

  13. Fundamental understanding of the thermal degradation mechanisms of waste tires and their air pollutant generation in a N2 atmosphere.

    Science.gov (United States)

    Kwon, Eilhann; Castaldi, Marco J

    2009-08-01

    The thermal decomposition of waste tires has been characterized via thermo-gravimetric analysis (TGA) tests, and significant mass loss has been observed between 300 and 500 degrees C. A series of gas chromatography-mass spectrometer (GC-MS) measurements, in which the instrument was coupled to a TGA unit, have been carried out to investigate the thermal degradation mechanisms as well as the air pollutant generation including volatile organic carbons (VOCs) and polycyclic aromatic hydrocarbons (PAHs) in a nitrogen atmosphere. In order to understand fundamental information on the thermal degradation mechanisms of waste tires, the main constituents of tires, poly-isoprene rubber (IR) and styrene butadiene rubber (SBR), have been studied under the same conditions. All of the experimental work indicated that the bond scission on each monomer of the main constituents of tires was followed by hydrogenation and gas phase reactions. This helped to clarify the independent pathways and species attributable to IR and SBR during the pyrolysis process. To extend that understanding to a more practical level, a flow-through reactor was used to test waste tire, SBR and IR samples in the temperature range of 500-800 degrees C at a heating rate of approximately 200 degrees C. Lastly, the formation of VOCs (approximately 1-50 PPMV/10 mg of sample) and PAHs (approximately 0.2-7 PPMV/10 mg of sample) was observed at relatively low temperatures compared to conventional fuels, and its quantified concentration was significantly high due to the chemical structure of SBR and IR. The measurement of chemicals released during pyrolysis suggests not only a methodology for reducing the air pollutants but also the feasibility of petrochemical recovery during thermal treatment.

  14. Thermal degradation kinetics of nylon6/GF/crysnano nanoclay nanocomposites by TGA

    Directory of Open Access Journals (Sweden)

    SHAHRYAR PASHAEI

    2011-06-01

    Full Text Available Nylon 6 is extensively used in engineering applications because of its unique characteristics such as low price, low viscosity, high toughness, shelf lubricating behaviour and high chemical resistance. Nanocomposites based on PA-6 were prepared by melt extrusion and an adjacent injection moulding process. Mechanical and thermomechanical properties have been investigated by tensile testing and dynamic mechanical analysis. To evaluate the potential of crysnano nanoclays as a new candidate in the class of nanofillers, the properties of the crysnano nanoclays nanocomposites has been compared to those of glass fiber. Thermal characteristics were performed using thermogravimetric analysis (TGA, differential scanning calorimetry (DSC and dynamic mechanical analysis (DMA. With increase in filler loading, the enthalpy of melting (Hm obtained from DSC curves was reduced as compared to pristine nylon 6. All the nanocompsoites were stable upto 205 °C. Degradation kinetic parameters have been calculated for thermal degradation processes using the composites using three mathematical models, namely Horowitz–Metzger, Coats–Redfern and Broido’s methods.

  15. Pressurized Hot Water Extraction of anthocyanins from red onion: A study on extraction and degradation rates.

    Science.gov (United States)

    Petersson, Erik V; Liu, Jiayin; Sjöberg, Per J R; Danielsson, Rolf; Turner, Charlotta

    2010-03-17

    Pressurized Hot Water Extraction (PHWE) is a quick, efficient and environmentally friendly technique for extractions. However, when using PHWE to extract thermally unstable analytes, extraction and degradation effects occur at the same time, and thereby compete. At first, the extraction effect dominates, but degradation effects soon take over. In this paper, extraction and degradation rates of anthocyanins from red onion were studied with experiments in a static batch reactor at 110 degrees C. A total extraction curve was calculated with data from the actual extraction and degradation curves, showing that more anthocyanins, 21-36% depending on the species, could be extracted if no degradation occurred, but then longer extraction times would be required than those needed to reach the peak level in the apparent extraction curves. The results give information about the different kinetic processes competing during an extraction procedure. Copyright 2010 Elsevier B.V. All rights reserved.

  16. FUV quantum efficiency degradation of cesium iodide photocathodes caused by exposure to thermal atomic oxygen

    Science.gov (United States)

    McPhate, Jason; Anne, Joshi; Bacinski, John; Banks, Bruce; Cates, Carey; Christensen, Paul; Cruden, Brett; Dunham, Larry; Graham, Eric; Hughes, David; Kimble, Randy; Lupie, Olivia; Niedner, Malcolm; Osterman, Steven; Penton, Steven; Proffitt, Charles; Pugel, Diane; Siegmund, Oswald; Wheeler, Thomas

    2011-09-01

    The color dependence of the measured decline of the on-orbit sensitivity of the FUV channel of the HST Cosmic Origins Spectrograph (HST-COS) indicated the principal loss mechanism to be degradation of the cesium iodide (CsI) photocathode of the open-faced FUV detector. A possible cause of this degradation is contamination by atomic oxygen (AO), prompting an investigation of the interaction of AO with CsI. To address this question, opaque CsI photocathodes were deposited on stainless steel substrates employing the same deposition techniques and parameters used for the photocathodes of the HST-COS FUV detector. The as-deposited FUV quantum efficiency of these photocathodes was measured in the 117-174 nm range. Several of the photocathodes were exposed to varying levels of thermalized, atomic oxygen (AO) fluence (produced via an RF plasma). The post AO exposure QE's were measured and the degradation of sensitivity versus wavelength and AO fluence are presented.

  17. Degradation of palm oil refinery wastewaters by non-thermal gliding arc discharge at atmospheric pressure.

    Science.gov (United States)

    Mountapmbeme-Kouotou, P; Laminsi, S; Acayanka, E; Brisset, J-L

    2013-07-01

    The gliding electric discharge in humid air is a source of activated species forming (e.g. (•)OH, (•)NO and their derivatives H2O2, ONO2H and NO3H) which are present in a non-thermal plasma at atmospheric pressure. These species are able to degrade organic pollutants in palm oil refinery wastewaters (PORW). The increase in acidity (pH decrease), conductivity and total dissolved solids (TDS) and the decrease in the total organic carbon (TOC) of PORW samples exposed to the discharge are reported. More than 50% TOC abatement is obtained for 15 min treatment in batch conditions with a laboratory reactor. The organic pollutants of PORW, i.e. mainly fatty acids are degraded according to a pseudo first-order reaction (k* = 0.06 min(-1)). Post discharge reactions are also observed after having switched off the discharge, which suggests that the pseudo first-order (k ≈ 0.05 min(-1)) degradation reactions should be attributed to the diffusion of soluble reactive species, e.g. H2O2 and ONOOH in the liquid target.

  18. Multistep kinetic behavior in the thermal degradation of poly(L-lactic acid): a physico-geometrical kinetic interpretation.

    Science.gov (United States)

    Yoshikawa, Masahiro; Goshi, Yuri; Yamada, Shuto; Koga, Nobuyoshi

    2014-09-25

    A physico-geometrical kinetic interpretation of the thermal degradation of poly(L-lactic acid) (PLLA) is described based on the results of a kinetic study using thermogravimetry (TG) and the microscopic observation of the reaction process. From the physico-geometrical viewpoint, the reaction process is separated into two different stages characterized by a surface reaction of the molten PLLA in the initial reaction stage followed by continuous bubble formation and disappearance in the established reaction stage. The generally reported trend of variation in the apparent activation energy as the reaction advances is explained by the partial overlapping of these two reaction stages. The kinetic rate data obtained using TG were kinetically separated into those for the respective reaction stages by optimizing the kinetic parameters. The significance of the kinetic results is discussed in terms of the physico-geometrical characteristics of the reaction. Such systematic kinetic analyses demonstrate the importance of considering the physico-geometrical perspective when interpreting the kinetic results for the thermal degradation of polymers.

  19. Pressurized-water reactor internals aging degradation study. Phase 1

    Energy Technology Data Exchange (ETDEWEB)

    Luk, K.H. [Oak Ridge National Lab., TN (United States)

    1993-09-01

    This report documents the results of a Phase I study on the effects of aging degradations on pr internals. Primary stressers for internals an generated by the primary coolant flow in the they include unsteady hydrodynamic forces and pump-generated pressure pulsations. Other stressors are applied loads, manufacturing processes, impurities in the coolant and exposures to fast neutron fluxes. A survey of reported aging-related failure information indicates that fatigue, stress corrosion cracking (SCC) and mechanical wear are the three major aging-related degradation mechanisms for PWR internals. Significant reported failures include thermal shield flow-induced vibration problems, SCC in guide tube support pins and core support structure bolts, fatigue-induced core baffle water-jet impingement problems and excess wear in flux thimbles. Many of the reported problems have been resolved by accepted engineering practices. Uncertainties remain in the assessment of long-term neutron irradiation effects and environmental factors in high-cycle fatigue failures. Reactor internals are examined by visual inspections and the technique is access limited. Improved inspection methods, especially one with an early failure detection capability, can enhance the safety and efficiency of reactor operations.

  20. Accelerated degradation studies of encapsulation polymers

    Science.gov (United States)

    Weiss, Karl-Anders; Huelsmann, Jan Philip; Kaltenbach, Thomas; Philipp, Daniel; Schuhmacher, Tanja; Wirth, Jochen; Koehl, Michael

    2008-08-01

    The estimation of PV-modules lifetime facilitates the further development and helps to lower risks for producers and investors. One base for this extensive testing and simulation work is the knowledge of the chemical degradation processes and their kinetics, as well as of the permeation of water and oxygen into the module, especially of the encapsulant. Besides ethylen-vinylacetate copolymer (EVA), which is the dominant material for encapsulation, new materials become available and need the assessment of their properties and the durability impact. Accelerated durability tests were performed on different EVA materials. The paper reports on several measurement methods for analysis of the polymers that were used, FT-IR with attenuated total reflection (ATR), and Raman microscopy, e.g. It is very important to identify degradation products and intermediates in order to identify the leading degradation processes and their kinetics as well as potential interactions between different processes. Another important factor for the degradation of the PV-modules and the concerned polymers in particular is the permeation of reactive substances, especially of water vapor, into and inside the modules. The paper shows results of permeation measurements of the new materials, as well as FEM-based numerical simulations of the humidity diffusion within a PV-module what is an important step towards the calculation of the chemical degradation using numerical simulation tools in the future.

  1. Thermal stress promotes host mitochondrial degradation in symbiotic cnidarians: are the batteries of the reef going to run out?

    Directory of Open Access Journals (Sweden)

    Simon R Dunn

    Full Text Available The symbiotic relationship between cnidarians and their dinoflagellate symbionts, Symbiodinium spp, which underpins the formation of tropical coral reefs, can be destabilized by rapid changes to environmental conditions. Although some studies have concluded that a breakdown in the symbiosis begins with increased reactive oxygen species (ROS generation within the symbiont due to a decoupling of photosynthesis, others have reported the release of viable symbionts via a variety of host cell derived mechanisms. We explored an alternative model focused upon changes in host cnidarian mitochondrial integrity in response to thermal stress. Mitochondria are often likened to being batteries of the cell, providing energy in the form of ATP, and controlling cellular pathway activation and ROS generation. The overall morphology of host mitochondria was compared to that of associated symbionts under an experimental thermal stress using confocal and electron microscopy. The results demonstrate that hyperthermic stress induces the degradation of cnidarian host mitochondria that is independent of symbiont cellular deterioration. The potential sites of host mitochondrial disruption were also assessed by measuring changes in the expression of genes associated with electron transport and ATP synthesis using quantitative RT-PCR. The primary site of degradation appeared to be downstream of complex III of the electron transport chain with a significant reduction in host cytochrome c and ATP synthase expression. The consequences of reduced expression could limit the capacity of the host to mitigate ROS generation and maintain both organelle integrity and cellular energy supplies. The disruption of host mitochondria, cellular homeostasis, and subsequent cell death irrespective of symbiont integrity highlights the importance of the host response to thermal stress and in symbiosis dysfunction that has substantial implications for understanding how coral reefs will survive

  2. Kinetics of the Thermal Degradation of Granulated Scrap Tyres: a Model-free Analysis

    Directory of Open Access Journals (Sweden)

    Félix A. LÓPEZ

    2013-12-01

    Full Text Available Pyrolysis is a technology with a promising future in the recycling of scrap tyres. This paper determines the thermal decomposition behaviour and kinetics of granulated scrap tyres (GST by examining the thermogravimetric/derivative thermogravimetric (TGA/DTG data obtained during their pyrolysis in an inert atmosphere at different heating rates. The model-free methods of Friedman, Flynn-Wall-Ozawa and Coats-Redfern were used to determine the reaction kinetics from the DTG data. The apparent activation energy and pre-exponential factor for the degradation of GST were calculated. A comparison with the results obtained by other authors was made.DOI: http://dx.doi.org/10.5755/j01.ms.19.4.2947

  3. Structure, wettability and thermal degradation of new fluoro-oligomer modified nanoclays.

    Science.gov (United States)

    Valsecchi, R; Viganò, M; Levi, M; Turri, S

    2008-04-01

    Quaternary ammonium salts based on monofunctionalized Perfluoropolyether (PFPE) oligomers were synthesized and used for the cation exchange process of sodium Montmorillonite nanoclays. The new fluoromodified nanoclays were characterized through X-rays diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), termogravimetric analysis (TGA), differential scanning calorimetry (DSC), electronic microscopy (SEM-EDS), and contact angle measurements (CA). In particular XRD showed rather complex patterns (presence of higher order reflections) which allowed the calculation of basal spacings, regularly increasing with the molecular weight of the fluorinated macrocation. Both IR and SEM confirmed the presence of fluorinated segments at clays interface, while TGA showed a limited thermal stability with an onset of degradation temperature which seems not dependent on the molecular weight of the macrocation. CA measurements showed a peculiar behaviour, with evident dynamic hysteresis phenomena and surface tension components quite different from those of commercially available, organomodified clays.

  4. Gas Evolution Qualitative Analyses From Modified Cellulose Mixtures During Thermal Degradation in Air and Argon

    Directory of Open Access Journals (Sweden)

    Zbigniew Zawieja

    2017-09-01

    Full Text Available This paper presents the application of mineral additives, such as expanded perlite, expanded vermiculite and microspheres in items used in founding. Mixed with paper pulp and aluminosilicate resin as a binder, these additives are the base of a mixture patented by the authors, which can be used in the production of pipe shapes and connectors with a circular cross-section in casting systems in the founding industry. These mixtures were subjected to TG thermal degradation during which a quantitative analysis of the emitted fumes was carried out. The analysis did not detect any other compounds other than those formed by the combustion of cellulose materials, which indicated that no chemical reaction took place between the applied additives and cellulose at high temperatures.

  5. Recovery of thermal-degraded ZnO photodetector by embedding nano silver oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Zhan-Shuo [Institute of Microelectronics, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Hung, Fei-Yi, E-mail: fyhung@mail.ncku.edu.tw [Institute of Nanotechnology and Microsystems Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Chen, Kuan-Jen [Institute of Nanotechnology and Microsystems Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); The Instrument Center, National Cheng Kung University, Tainan 701, Taiwan (China); Chang, Shoou-Jinn [Institute of Microelectronics, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Institute of Microelectronics and Department of Electrical Engineering, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China); Hsieh, Wei-Kang; Liao, Tsai-Yu; Chen, Tse-Pu [Institute of Microelectronics, Center for Micro/Nano Science and Technology, National Cheng Kung University, Tainan 701, Taiwan (China)

    2013-08-15

    The degraded performance of annealed ZnO-based photodetector can be recovered by embedding Ag{sub 2}O nanoparticles resulted from the transformation of as-deposited Ag layer. After thermal treatment, the electrons were attracted at the interface between ZnO and Ag{sub 2}O. The excess Ag{sup +} ions form the cluster to incorporate into the interstitial sites of ZnO lattice to create a larger amount of lattice defects for the leakage path. The photo-current of ZnO film with Ag{sub 2}O nanoparticles is less than annealed ZnO film because the photo-induced electrons would flow into Ag{sub 2}O side. ZnO photodetector with the appropriate Ag{sub 2}O nanoparticles possesses the best rejection ratio.

  6. Thermal degradation, antioxidant and antimicrobial activity of the synthesized allicin and allicin incorporated in gel

    Directory of Open Access Journals (Sweden)

    Ilić Dušica P.

    2010-01-01

    Full Text Available The main carriers of the pharmacological activity of garlic (Allium sativum L. are organic sulfur compounds, the most important among them being allicin, a sulfenic acid thioester, or allylthiosulfonate. In this paper, the identification of synthesized and purified allicin was determined by using various spectroscopic methods (UV/VIS, FTIR, NMR. A HPLC method was developed for the detection and determination of the allicin content. The thermal degradation of allicin by using FTIR method was monitored. The method for the production of allicin gel based on Carbopol 940 (poly(acrylic acid was elaborated. The antimicrobial activity of pure allicin and allicin incorporated into gel by using a disk diffusion method was determined. In order to determine the antioxidant activity of allicin DPPH test was done and it was proved that with low concentrations (1 mgcm-3 a high DPPH radicals scavenging capacity (90% was achieved.

  7. Fire performance, microstructure and thermal degradation of an epoxy based nano intumescent fire retardant coating for structural applications

    Energy Technology Data Exchange (ETDEWEB)

    Aziz, Hammad, E-mail: engr.hammad.aziz03@gmail.com; Ahmad, Faiz, E-mail: faizahmad@petronas.com.my; Yusoff, P. S. M. Megat; Zia-ul-Mustafa, M. [Department of Mechanical Engineering, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, Tronoh 31750, Perak (Malaysia)

    2015-07-22

    Intumescent fire retardant coating (IFRC) is a passive fire protection system which swells upon heating to form expanded multi-cellular char layer that protects the substrate from fire. In this research work, IFRC’s were developed using different flame retardants such as ammonium polyphosphate, expandable graphite, melamine and boric acid. These flame retardants were bound together with the help of epoxy binder and cured together using curing agent. IFRC was then reinforced with nano magnesium oxide and nano alumina as inorganic fillers to study their effect towards fire performance, microstructure and thermal degradation. Small scale fire test was conducted to investigate the thermal insulation of coating whereas fire performance was calculated using thermal margin value. Field emission scanning electron microscopy was used to examine the microstructure of char obtained after fire test. Thermogravimetric analysis was conducted to investigate the residual weight of coating. Results showed that the performance of the coating was enhanced by reinforcement with nano size fillers as compared to non-filler based coating. Comparing both nano size magnesium oxide and nano size alumina; nano size alumina gave better fire performance with improved microstructure of char and high residual weight.

  8. In vitro degradation behaviour of biodegradable soy plastics : effects of crosslinking with glyoxal and thermal treatment

    NARCIS (Netherlands)

    Vaz, C.M.; Graaf, de L.A.; Reis, R.L.; Cunha, A.M.

    2003-01-01

    In-vitro degradation of soy-derived protein materials, non-crosslinked (SItp), crosslinked with glyoxal (X-SItp) or submitted to heat treatment (24TT-SItp), was studied with either an isotonic saline solution without enzymatic activity or containing bacterial collagenase. The changes in weight of

  9. Mechanistic study of a diazo dye degradation by Soybean Peroxidase

    OpenAIRE

    Kalsoom, Umme; Ashraf, Syed Salman; Meetani, Mohammed A; Rauf, Muhammad A; Bhatti, Haq Nawaz

    2013-01-01

    Background Enzyme based remediation of wastewater is emerging as a novel, efficient and environmentally-friendlier approach. However, studies showing detailed mechanisms of enzyme mediated degradation of organic pollutants are not widely published. Results The present report describes a detailed study on the use of Soybean Peroxidase to efficiently degrade Trypan Blue, a diazo dye. In addition to examining various parameters that can affect the dye degradation ability of the enzyme, such as e...

  10. Biological monitoring of aromatic diisocyanates in workers exposed to thermal degradation products of polyurethanes.

    Science.gov (United States)

    Rosenberg, Christina; Nikkilä, Kirsi; Henriks-Eckerman, Maj-Len; Peltonen, Kimmo; Engströrm, Kerstin

    2002-10-01

    Exposure to diisocyanates was assessed by biological monitoring among workers exposed to the thermal degradation products of polyurethanes (PURs) in five PUR-processing environments. The processes included grinding and welding in car repair shops, milling and turning of PUR-coated metal cylinders, injection moulding of thermoplastic PUR, welding and cutting of PUR-insulated district heating pipes during installation and joint welding, and heat-flexing of PUR floor covering. Isocyanate-derived amines in acid-hydrolysed urine samples were analysed as perfluoroacylated derivatives by gas chromatography mass spectrometry in negative chemical ionisation mode. The limits of quantification (LOQs) for the aromatic diamines 2,4- and 2,6-toluenediamine (2,4- and 2,6-TDA) and 4,4'-methylenedianiline (4,4'-MDA) were 0.25 nmol l(-1), 0.25 nmol l(-1) and 0.15 nmol l(-1), respectively. The LOQ for the aliphatic diamines hexamethylenediamine (HDA), isophoronediamine (IpDA) and 4,4'-diaminodicyclohexyl methane (4,4'-DDHM) was 5 nmol l(-1). TDA and MDA were detected in urine samples from workers in car repair shops and MDA in samples from workers welding district heating pipes. The 2,4-TDA isomer accounted for about 80% of the total TDA detected. No 2.6-TDA was found in the urine of non-exposed workers. The highest measured urinary TDA and MDA concentrations were 0.79 nmol mmol(-1) creatinine and 3.1 nmol mmol(-1) creatinine, respectively. The concentrations found among non-exposed workers were 0.08 nmol mmol(-1) creatinine for TDA and 0.05 nmol mmol(-1) creatinine for MDA (arithmetic means). Exposure to diisocyanates originating from the thermal degradation of PURs are often intermittent and of short duration. Nevertheless, exposure to aromatic diisocyanates can be identified by monitoring diisocyanate-derived amines in acid-hydrolysed urine samples.

  11. Kinetics of the thermal degradation of patulin in the presence of ascorbic acid.

    Science.gov (United States)

    Kokkinidou, S; Floros, J D; LaBorde, L F

    2014-01-01

    Degradation of the mycotoxin patulin between 25 and 85 °C without and with added ascorbic acid was studied, and the effectiveness of linear and nonlinear models for predicting reaction rates was compared. In agreement with previous reports, ascorbic acid significantly increased (P ≤ 0.05) the rate of patulin degradation at all temperatures studied. The data for patulin degradation in the absence of ascorbic acid were adequately modeled using a zero-order linear kinetic model. However, the predictive abilities of zero and higher-order linear models were not adequate to describe the more complex reactions that likely occurred when ascorbic acid was added. In contrast, the nonlinear Weibull model adequately described the patulin-ascorbic acid reaction throughout the temperature range studied. Zero-order rate constants and Weibull scale values for each of the respective reactions followed the Arrhenius law. Activation energies of 58.7 ± 3.9 and 29.6 ± 1.9 kJ mol⁻¹ for the reaction without and with ascorbic acid, respectively, confirmed decreased patulin stability in the presence of ascorbic acid and suggested that the mechanisms for the 2 degradation reactions were different. © 2013 Institute of Food Technologists®

  12. Degradation in Thermal Properties and Morphology of Polyetheretherketone-Alumina Composites Exposed to Gamma Radiation

    Science.gov (United States)

    Lawrence, Falix; Mishra, Satyabrata; Mallika, C.; Kamachi Mudali, U.; Natarajan, R.; Ponraju, D.; Seshadri, S. K.; Sampath Kumar, T. S.

    2012-07-01

    Sheets of polyetheretherketone (PEEK) and PEEK-alumina composites with micron-sized alumina powder with 5, 10, 15, 20, and 25% by weight were fabricated, irradiated with gamma rays up to 10 MGy and the degradation in their thermal properties and morphology were evaluated. The radicals generated during irradiation get stabilized by chain scission and crosslinking. Chain scission is predominant on the surface and crosslinking is predominant in the bulk of the samples. Owing to radiation damage, the glass transition temperature, T g increased for pure PEEK from 136 to 140.5 °C, whereas the shift in T g for the composites decreased with increase in alumina content and for PEEK-25% alumina, the change in T g was insignificant, as alumina acts as an excitation energy sink and reduces the crosslinking density, which in turn decreased the shift in T g towards higher temperature. Similarly, the melting temperature, T m and enthalpy of melting, Δ H m of PEEK and PEEK-alumina composites decreased on account of radiation owing to the restriction of chain mobility and disordering of structures caused by crosslinks. The decrease in T m and Δ H m was more pronounced in pure PEEK and the extent of decrease in T m and Δ H m was less for composites. SEM images revealed the formation of micro-cracks and micro-pores in PEEK due to radiation. The SEM image of irradiated PEEK-alumina (25%) composite showed negligible micro-cracks and micro-pores, because of the reinforcing effect of high alumina content in the PEEK matrix which helps in reducing the degradation in the properties of the polymer. Though alumina reduces the degradation of the polymer matrix during irradiation, an optimum level of ceramic fillers only have to be loaded to the polymer to avoid the reduction in toughness.

  13. Thermal/chemical degradation of ceramic candle filter materials. Final report, September 1988--October 1994

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1995-01-01

    High-temperature ceramic candle filters are being developed for use in advanced power generation systems such as the Integrated Gasification Combined Cycle (IGCC), Pressurized Fluidized-Bed Combustor (PFBC), and Direct Coal-Fired Turbine (DCFT). The direct firing of coal produces particulate matter which must be removed to meet both environmental and process limitations. The ceramic candles increase the efficiency of the advanced power generation systems and protect downstream equipment from erosion and impingement of particulate matter in the hot exhaust gases. Ceramic candle filters are rigid, closed-ended (capped on one side) porous cylinders which generally have a flange on the open-ended side. The flange at the open end allows the candle to be suspended by a tubesheet in the filter vessel. Candle filters have shown promise, but have also encountered durability problems during use in hostile, high-temperature environments. Limitations in the candle lifetime lower the economic advantages of using candle filters for this application. Candles typically fail by cracking at the flange or in the body of the candle. The objective of this project was to test and analyze ceramic candle filter materials and to evaluate the degradation mechanisms. The tests were conducted such that the effects of each degradation mechanism could be examined. Separately. The overall objective of the project was to: (a) develop a better understanding of the thermal and chemical degradation mechanisms of ceramic candle filter materials in advanced coal utilization projects, (b) develop test procedures, and (c) recommend changes to increase filter lifetime. 15 refs., 67 figs., 17 tabs.

  14. Evaluation of Ultrasonic and Thermal Nondestructive Evaluation for the Characterization of Aging Degradation in Braided Composite Materials

    Science.gov (United States)

    Martin, Richard E.

    2010-01-01

    This paper examines the ability of traditional nondestructive evaluation (NDE) techniques to measure the degradation of braided polymer composite materials subjected to thermal-humidity cycling to simulate aging. A series of braided composite coupons were examined using immersion ultrasonic and pulsed thermography techniques in the as received condition. These same specimens were then examined following extended thermal-humidity cycling. Results of this examination did not show a significant change in the resulting (NDE) signals.

  15. Preparation, Characterization and Thermal Degradation of Polyimide (4-APS/BTDA)/SiO2 Composite Films

    Science.gov (United States)

    Ahmad, Mansor Bin; Gharayebi, Yadollah; Salit, Mohd. Sapuan; Hussein, Mohd. Zobir; Ebrahimiasl, Saeideh; Dehzangi, Arash

    2012-01-01

    Polyimide/SiO2 composite films were prepared from tetraethoxysilane (TEOS) and poly(amic acid) (PAA) based on aromatic diamine (4-aminophenyl sulfone) (4-APS) and aromatic dianhydride (3,3,4,4-benzophenonetetracarboxylic dianhydride) (BTDA) via a sol-gel process in N-methyl-2-pyrrolidinone (NMP). The prepared polyimide/SiO2 composite films were characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) and thermogravimetric analysis (TGA). The FTIR results confirmed the synthesis of polyimide (4-APS/BTDA) and the formation of SiO2 particles in the polyimide matrix. Meanwhile, the SEM images showed that the SiO2 particles were well dispersed in the polyimide matrix. Thermal stability and kinetic parameters of the degradation processes for the prepared polyimide/SiO2 composite films were investigated using TGA in N2 atmosphere. The activation energy of the solid-state process was calculated using Flynn–Wall–Ozawa’s method without the knowledge of the reaction mechanism. The results indicated that thermal stability and the values of the calculated activation energies increased with the increase of the TEOS loading and the activation energy also varied with the percentage of weight loss for all compositions. PMID:22606014

  16. Degradation study of different brands of paracetamol by UV spectroscopy

    Directory of Open Access Journals (Sweden)

    Safila Naveed

    2016-05-01

    Full Text Available Objective: To investgate the forced degradation study for the determination of degradation of the drug substance. Methods: Paracetamol was exposed to different conditions according to International Conference on Harmonization guideline. The amount of degradation product can be calculated with the help of UV spectrophotometer. The official test limits according to British Pharmacopoeia/United States Pharmacopoeia should not less than and should not more than lapelled amount. Forced degradation of drug substance was exposed to acidic and basic medium of panadol. Forced degradation of drug substance of panadol, disprol and calpol were also observed negligible difference in availability on exposure to UV and heat. This method can be used successfully for studying the stress degradation factors. Because this method is less time consuming and simple and cost effective also. Results: The brands i.e. calpol, panadol and disprol, when they come in contact with different degradation parameters (before, acid, base, heat and UV treatments according to statistical analysis, the result showed significant values (P < 0.05 which indicated that there was no degradation in any of the brand. Conclusions: The result indicated there is no degradation found in these brands.

  17. Delamination evaluation of thermal barrier coating on turbine blade owing to isothermal degradation using ultrasonic C-scan image

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ho Girl; Kim, Hak Joon; Song, Sung Jin; Seok, Chang Sung [Dept. of Mechanical Engineering, Sungkyunkwan University, Suwon (Korea, Republic of)

    2016-10-15

    Thermal barrier coating (TBC) is an essential element consisting of a super-alloy base and ceramic coating designed to achieve long operational time under a high temperature and pressure environment. However, the top coat of TBC can be delaminated at certain temperatures with long operation time. As the delamination of TBC is directly related to the blade damage, the coupling status of the TBC should be assured for reliable operation. Conventional studies of nondestructive evaluation have been made for detecting generation of thermally grown oxide (TGO) or qualitatively evaluating delamination in TBC. In this study, the ultrasonic C-scan method was developed to obtain the damage map inside TBC by estimating the delamination in a quantitative way. All specimens were isothermally degraded at 1,100°C with different time, having different partial delamination area. To detect partial delamination in TBC, the C-scan was performed by a single transducer using pulse-echo method with normal incidence. Partial delamination coefficients of 1 mm to 6 mm were derived by the proportion of the surface reflection signal and flaw signal which were theoretical signals using Rogers-Van Buren and Kim's equations. Using the partial delamination coefficients, the partial delamination maps were obtained. Regardless of the partial delamination coefficient, partial delamination area was increased when degradation time was increased in TBC. In addition, a decrease in partial delamination area in each TBC specimen was observed when the partial delamination coefficient was increased. From the portion of the partial delamination maps, the criterion for delamination was derived.

  18. Degradation and Moisture Absorption Study of Potato-starch Linear ...

    African Journals Online (AJOL)

    Composite of linear low density polyethylene (LLDPE) and potato-starch was produced and subjected to degradation studies with the agencies of enzymes, exposure to weather and immersion in water. Enzymatic hydrolysis degraded the matrix to an extent greater than 40% loss in strength and about 20% loss in ...

  19. Growth study on chrysene degraders isolated from polycyclic ...

    African Journals Online (AJOL)

    GRACE

    2006-05-16

    May 16, 2006 ... (Hinchee et al., 1994). The search for suitable degraders of recalcitrant HMW. PAHs for use in bioremediation strategies has warranted this work. In this study, four bacterial isolates isolated from crude oil and wood processing site in Nigeria were evaluated for chrysene degradation potential. To the best.

  20. Formation, characterization, and thermal degradation behavior of a novel tricomponent aggregate of beta-cyclodextrin, ferrocene, and polypropylene glycol.

    Science.gov (United States)

    Song, Le Xin; Du, Fang Yun; Guo, Xue Qing; Pan, Shu Zhen

    2010-02-04

    A tricomponent aggregate PPG-Fc-beta-CD formed by polypropylene glycol (PPG), ferrocene (Fc), and beta-cyclodextrin (beta-CD) was obtained and characterized by a series of physical methods, such as (1)H nuclear magnetic resonance, flame atomic absorption spectrometry, high performance liquid chromatography, UV-vis absorption spectroscopy, thermogravimetry, and gas chromatography coupled to time-of-flight mass spectrometry. First, the tricomponent aggregate exhibited a component ratio of 1:28:32 (PPG/Fc/beta-CD) in the solid state, and showed a completely different order in thermal stability when compared with beta-CD: under a nitrogen atmosphere, beta-CD > PPG-Fc-beta-CD, and in a vacuum, PPG-Fc-beta-CD > beta-CD. Second, the appearance of two peculiar points p and q at the end of TG curve of the aggregate gave a strong impression that the degradation rate further increased after the sharp decomposition of the aggregate reached point p and the amount present in the residual fraction at point q about 780.0 K was lower than 1%, both of which were rather different from those reported previously. This finding implied that the molecular assembly resulting from the binding interaction among Fc, PPG, and beta-CD induced more efficiently the degradation of each of them. Third, an interesting phenomenon was found that the order of thermal release of the three assembled components in PPG-Fc-beta-CD was Fc > beta-CD > PPG. Results of this study provide some insight into an initial attempt to construct a supramolecule among a polymer, a coordination compound, and an organic compound.

  1. Biochemical degradation and physical migration of polyphenolic compounds in osmotic dehydrated blueberries with pulsed electric field and thermal pretreatments.

    Science.gov (United States)

    Yu, Yuanshan; Jin, Tony Z; Fan, Xuetong; Wu, Jijun

    2018-01-15

    Fresh blueberries were pretreated by pulsed electric fields (PEF) or thermal pretreatment and then were subject to osmotic dehydration. The changes in contents of anthocyanins, predominantly phenolic acids and flavonols, total phenolics, polyphenol oxidase (PPO) activity and antioxidant activity in the blueberry samples during pretreatment and osmotic dehydration were investigated. Biochemical degradation and physical migration of these nutritive compounds from fruits to osmotic solutions were observed during the pretreatments and osmotic dehydration. PEF pretreated samples had the least degradation loss but the most migration loss of these compounds compared to thermally pretreated and control samples. Higher rates of water loss and solid gain during osmotic dehydration were also obtained by PEF pretreatment, reducing the dehydration time from 130 to 48h. PEF pretreated and dehydrated fruits showed superior appearance to thermally pretreated and control samples. Therefore, PEF pretreatment is a preferred technology that balances nutritive quality, appearance, and dehydration rate. Published by Elsevier Ltd.

  2. Tailoring the degradation rates of thermally responsive hydrogels designed for soft tissue injection by varying the autocatalytic potential

    Science.gov (United States)

    Zhu, Yang; Jiang, Hongbin; Ye, Sang-Ho; Yoshizumi, Tomo; Wagner, William R.

    2015-01-01

    The ability to modulate the degradation properties of biomaterials such as thermally responsive hydrogels is desirable when exploring new therapeutic strategies that rely on the temporary presence of a placed scaffold or gel. Here we report a method of manipulating the absorption rate of a poly(N-isopropylacrylamide) ((poly(NIPAAm)) based hydrogel across a wide range (from 1 d to 5 mo) by small alterations in the composition. Relying upon the autocatalytic effect, the degradation of poly(NIPAAm-co-HEMA-co-MAPLA), (HEMA=2-hydroxyethyl methacrylate; MAPLA=methacrylate-polylactide) was greatly accelerated by adding a fourth monomer methacrylic acid (MAA) at no more than 2 mol% to obtain poly(NIPAAm-co-HEMA-co-MAPLA-co-MAA) (pNHMMj) where j reflects the MAA molar % in the reactant mixture. MAA residue introduction decreased the pH inside the hydrogels and in surrounding buffered solutions. Accelerated degradation positively correlated with MAA content in pNHMMj polymers, putatively by the accelerated cleavage of MAPLA residues to raise the transition temperature of the polymer above body temperature. Physical properties including thermal transition behavior and initial mechanical strength did not vary significantly with MAA content. A rat hindlimb injection model generally reflected the in vitro observation that higher MAA content resulted in more rapid degradation and cellular infiltration. The strategy of tuning the degradation of thermally responsive hydrogels where degradation or solubilization is determined by their polyester components might be applied to other tissue engineering and regenerative medicine applications where designed biomaterial degradation behavior is needed. PMID:25890745

  3. Study of environmental degradation of silver surface

    Energy Technology Data Exchange (ETDEWEB)

    Aguas, H.; Silva, R.J.C.; Viegas, M.; Pereira, L.; Fortunato, E.; Martins, R. [Materials Science Department, CENIMAT/I3N, FCT-UNL, Campus de Caparica (Portugal)

    2008-05-15

    To evaluate the evolution of a dark film formation on silver surface objects, several coupons were catalogued and place inside a museum, located in an urban area. The changes on these samples were measured by spectroscopic ellipsometry, in periods of months. This technique allows the reduction of the coupons exposure time, in several months, due to its high sensitivity to surface modifications, with acceptable results for the evaluation of its degradation. The thicknesses of the degradation layers and the optical properties of silver oxide, chloride and sulphide reference samples were determined using a mixture of Tauc-Lorentz and Drude models. The composition of the silver corrosion layer was determined by fitting the layer using a Bruggeman Effective Medium Approximation (BEMA) of the three products plus voids. It was found that the thickness of the layer depends in the placement of the coupons, namely, inside or outside displayers. The average film thickness after 6 months was of 180 Aa and 280 Aa, inside and outside the displayers, respectively. The main compounds found in the layers were the silver chlorides and sulphides, which composition changed with the thickness of the layer, and the exposition time. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Synthesis and Thermal Degradation Kinetics of Co(II, Ni(II, Cd(II, Zn(II, Pd(II, Rh(III and Ru(III Complexes with Methylquinolino[3,2-b]benzodiazepine

    Directory of Open Access Journals (Sweden)

    Bennehalli Basavaraju

    2007-01-01

    Full Text Available A series of new complexes formed by the interaction of a new ligand Methylquinolino[3,2-b]benzodiazepine (L with various transition metal ions have been isolated and characterized by elemental analysis and electronic, IR, magnetic moment and conductivity measurements. Thermogravimetric (TG studies of the complexes have been performed in order to establish the mode of their thermal degradation. The thermal degradation was found to proceed in two steps. The kinetics and thermodynamic parameters were computed from the thermal decomposition data.

  5. Tracking degradation in lithium iron phosphate batteries using differential thermal voltammetry

    Science.gov (United States)

    Shibagaki, Toshio; Merla, Yu; Offer, Gregory J.

    2018-01-01

    Diagnosing the state-of-health of lithium ion batteries in-operando is becoming increasingly important for multiple applications. We report the application of differential thermal voltammetry (DTV) to lithium iron phosphate (LFP) cells for the first time, and demonstrate that the technique is capable of diagnosing degradation in a similar way to incremental capacity analysis (ICA). DTV has the advantage of not requiring current and works for multiple cells in parallel, and is less sensitive to temperature introducing errors. Cells were aged by holding at 100% SOC or cycling at 1C charge, 6D discharge, both at an elevated temperature of 45 °C under forced air convection. Cells were periodically characterised, measuring capacity fade, resistance increase (power fade), and DTV fingerprints. The DTV results for both cells correlated well with both capacity and power, suggesting they could be used to diagnose SOH in-operando for both charge and discharge. The DTV peak-to-peak capacity correlated well with total capacity fade for the cycled cell, suggesting that it should be possible to estimate SOC and SOH from DTV for incomplete cycles within the voltage hysteresis region of an LFP cell.

  6. Spectroscopic, thermal and biological studies of coordination ...

    Indian Academy of Sciences (India)

    , thermal and biological studies of coordination compounds of sulfasalazine drug: Mn(II), Hg(II), Cr(III), ZrO(II), VO(II) and Y(III) transition metal complexes. M G Abd El-Wahed M S Refat S M El-Megharbel. Thermal Studies Volume 32 Issue 2 ...

  7. Saccharomyces kluyveri as a model organism to study pyrimidine degradation.

    Science.gov (United States)

    Beck, Halfdan; Dobritzsch, Doreen; Piskur, Jure

    2008-12-01

    The yeast Saccharomyces kluyveri (Lachancea kluyveri), a far relative of Saccharomyces cerevisiae, is not a widely studied organism in the laboratory. However, significant contributions to the understanding of nucleic acid precursors degradation in eukaryotes have been made using this model organism. Here we review eukaryotic pyrimidine degradation with emphasis on the contributions made with S. kluyveri and how this increases our understanding of human disease. Additionally, we discuss the possibilities and limitations of this nonconventional yeast as a laboratory organism.

  8. Thermal degradation of multilayer insulation due to the presence of penetrations

    Science.gov (United States)

    Johnson, W. L.; Kelly, A. O.; Fesmire, J. E.

    2014-01-01

    Invented in the 1950s, cryogenic multilayer insulation (MLI) continues to be studied, tested, and analyzed as it represents a complex system that is integral with the total system to be insulated. Numerous tank and calorimeter tests have been performed using many different insulation approaches. Many different variables have been tested and documented, mainly within the insulation system itself. There are several factors in insulation application that can drive up the heat load on the entire system. These include the treatment of insulation seams, instrumentation wires running through the insulation, and the integration of the insulation with the structures and fluids. Several attempts have been made to identify the performance losses due to structural integration with a real system. Due to the nature of MLI, these were tied to specific programs and configuration dependent. In an effort to understand the complex heat transfer mechanisms surrounding such systems, a series of calorimeter testing coupled with thermal modeling of the calorimeter tests was put into place. Testing showed that a buffer of micro-fiberglass material such as Cryolite is a robust method of closing out MLI penetrations. Additionally, a validated thermal model was used to develop parametric analysis far beyond the limitations of the calorimeter testing. This paper presents the methodology and approach, with experimental data providing the basis for developing the thermal model and its results for applicability to future design cases.

  9. tRNA-dependent cysteine biosynthetic pathway represents a strategy to increase cysteine contents by preventing it from thermal degradation: thermal adaptation of methanogenic archaea ancestor.

    Science.gov (United States)

    Qu, Ge; Wang, Wei; Chen, Ling-Ling; Qian, Shao-Song; Zhang, Hong-Yu

    2009-10-01

    Although cysteine (Cys) is beneficial to stabilize protein structures, it is not prevalent in thermophiles. For instance, the Cys contents in most thermophilic archaea are only around 0.7%. However, methanogenic archaea, no matter thermophilic or not, contain relatively abundant Cys, which remains elusive for a long time. Recently, Klipcan et al. correlated this intriguing property of methanogenic archaea with their unique tRNA-dependent Cys biosynthetic pathway. But, the deep reasons underlying the correlation are ambiguous. Considering the facts that free Cys is thermally labile and the tRNA-dependent Cys biosynthesis avoids the use of free Cys, we speculate that the unique Cys biosynthetic pathway represents a strategy to increase Cys contents by preventing it from thermal degradation, which may be relevant to the thermal adaptation of methanogenic archaea ancestor.

  10. Toxicity evaluations of nanoclays and thermally degraded byproducts through spectroscopical and microscopical approaches.

    Science.gov (United States)

    Wagner, Alixandra; Eldawud, Reem; White, Andrew; Agarwal, Sushant; Stueckle, Todd A; Sierros, Konstantinos A; Rojanasakul, Yon; Gupta, Rakesh K; Dinu, Cerasela Zoica

    2017-01-01

    Montmorillonite is a type of nanoclay that originates from the clay fraction of the soil and is incorporated into polymers to form nanocomposites with enhanced mechanical strength, barrier, and flammability properties used for food packaging, automotive, and medical devices. However, with implementation in such consumer applications, the interaction of montmorillonite-based composites or derived byproducts with biological systems needs to be investigated. Herein we examined the potential of Cloisite Na+ (pristine) and Cloisite 30B (organically modified montmorillonite nanoclay) and their thermally degraded byproducts' to induce toxicity in model human lung epithelial cells. The experimental set-up mimicked biological exposure in manufacturing and disposal areas and employed cellular treatments with occupationally relevant doses of nanoclays previously characterized using spectroscopical and microscopical approaches. For nanoclay-cellular interactions and for cellular analyses respectively, biosensorial-based analytical platforms were used, with induced cellular changes being confirmed via live cell counts, viability assays, and cell imaging. Our analysis of byproducts' chemical and physical properties revealed both structural and functional changes. Real-time high throughput analyses of exposed cellular systems confirmed that nanoclay induced significant toxic effects, with Cloisite 30B showing time-dependent decreases in live cell count and cellular viability relative to control and pristine nanoclay, respectively. Byproducts produced less toxic effects; all treatments caused alterations in the cell morphology upon exposure. Our morphological, behavioral, and viability cellular changes show that nanoclays have the potential to produce toxic effects when used both in manufacturing or disposal environments. The reported toxicological mechanisms prove the extensibility of a biosensorial-based platform for cellular behavior analysis upon treatment with a variety of

  11. LC, LC-MS/MS studies for the identification and characterization of degradation products of hydrochlorothiazide and establishment of mechanistic approach towards degradation

    OpenAIRE

    Mahajan,Anand Avinash; Thaker,Anil Keshavlal; Mohanraj,Krishnapriya

    2012-01-01

    The objective of the present investigation was to separate, identify and characterize the degradation products of hydrochlorothiazide under hydrolytic, oxidative, photolytic and thermal stress conditions as per the International Conference on Harmonization (ICH) guideline Q1A (R2). The drug degraded under acidic, basic, neutral and oxidative stress, while it was stable under photolytic and thermal stress conditions. Two degradation products were formed, which were separated by using HPLC on C...

  12. Photo- and thermal degradation of olive oil measured using an optical fibre smartphone spectrofluorimeter

    Science.gov (United States)

    Hossain, Md Arafat; Canning, John; Cook, Kevin; Ast, Sandra; Jamalipour, Abbas

    2017-04-01

    Degradation of olive oil under light and heat are analysed using an optical fibre based low-cost portable smartphone spectrofluorimeter. Visible fluorescence bands associated with phenolic acids, vitamins and chlorophyll centred at λ 452, 525 and 670 nm respectively are generated using near-UV excitation (LED λex 370 nm), of extra virgin olive oil are degraded more likely than refined olive oil under light and heat exposure. Packaging is shown to be critical when assessing the origin of degradation.

  13. Study on the forced degradation behaviour of ledipasvir: Identification of major degradation products using LC-QTOF-MS/MS and NMR.

    Science.gov (United States)

    Swain, Debasish; Samanthula, Gananadhamu

    2017-05-10

    Ledipasvir, a novel NS5A inhibitor is used in the management of hepatitis C virus infections. The drug was subjected to forced degradation studies as per the conditions prescribed in ICH Q1 (R2) guideline. Ledipasvir degraded in hydrolytic (acid, alkaline and neutral) and oxidative stress conditions. The drug was found to be stable in thermal and photolytic conditions. Eight novel degradation products were obtained and were well separated using an HPLC C18 stationary phase (150×4.6mm, 5μm) and mobile phase composed of formic acid/acetonitrile in gradient elution mode. All the degradation products were characterised using tandem mass spectrometry with a time-of-flight analyser and the major degradation products of hydrolytic and oxidative stress were isolated and their structural confirmation was studied using 1 H and 13 C NMR. A well resolved chromatographic method proposed in this study suggests that the proposed analytical method finds its application as a stability indicating assay method for the drug and can be used in routine analysis. Copyright © 2017. Published by Elsevier B.V.

  14. Electron Barrier Formation at the Organic-Back Contact Interface is the First Step in Thermal Degradation of Polymer Solar Cells

    KAUST Repository

    Sachs-Quintana, I. T.

    2014-03-24

    Long-term stability of polymer solar cells is determined by many factors, one of which is thermal stability. Although many thermal stability studies occur far beyond the operating temperature of a solar cell which is almost always less than 65 °C, thermal degradation is studied at temperatures that the solar cell would encounter in real-world operating conditions. At these temperatures, movement of the polymer and fullerenes, along with adhesion of the polymer to the back contact, creates a barrier for electron extraction. The polymer barrier can be removed and the performance can be restored by peeling off the electrode and depositing a new one. X-ray photoelectron spectroscopy measurements reveal a larger amount of polymer adhered to electrodes peeled from aged devices than electrodes peeled from fresh devices. The degradation caused by hole-transporting polymer adhering to the electrode can be suppressed by using an inverted device where instead of electrons, holes are extracted at the back metal electrode. The problem can be ultimately eliminated by choosing a polymer with a high glass transition temperature. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Synthesis, characterization, thermal degradation and urease inhibitory studies of the new hydrazide based Schiff base ligand 2-(2-hydroxyphenyl-3-{[(E-(2-hydroxyphenylmethylidene]amino}-2,3-dihydroquinazolin-4(1H-one

    Directory of Open Access Journals (Sweden)

    Ikram Muhammad

    2017-12-01

    Full Text Available The novel Schiff base ligand 2-(2-hydroxyphenyl-3-{[(E-(2-hydroxyphenylmethylidene]amino}-2,3-dihydroquinazolin-4(1H-one (H-HHAQ derived from 2-aminobenzhydrazide was synthesized and characterized by elemental analyses, ES+-MS, 1H and 13C{1H}-NMR, and IR studies. The characterization of the ligand was further confirmed by single crystal analysis. The Schiff base ligand was complexed with metal ions like Co(II, Ni(II, Cu(II and Zn(II to obtain the bis-octahedral complexes. The ligand and its metal complexes were also studied for their urease inhibitory activities. All the tested compounds show medium to moderate activities for the enzyme, whereas the copper based complex was found to be much more active against urease with an IC50 = 0.3 ± 0.1 μM±SEM, which is even more potent than the standard thiourea. The IC50 of the cobalt complex was 43.4±1.2 μM±SEM, whereas that of the nickel complex was 294.2±5.0 μM±SEM. The ligand H-HHAQ and the zinc complex were inactive against the tested enzyme.

  16. Crystal structure, thermal behavior and enzymatic degradation of poly(tetramethylene adipate) solution-grown chain-folded lamellar crystals.

    Science.gov (United States)

    Iwata, Tadahisa; Kobayashi, Shiomi; Tabata, Kenji; Yonezawa, Noriyuki; Doi, Yoshiharu

    2004-03-15

    Solution-grown chain-folded lamellar single crystals of poly(tetramethylene adipate) (PTMA) were prepared from a dilute solution of 2-methyl-1-propanol by isothermal crystallization. PTMA crystals were hexagonal-shaped and polyethylene decoration of the crystals resulted in a "six cross-sector" surface morphology and showed that the average direction of chain folding is parallel to the crystal growth planes of [110] and [010]. Chain-folded lamellar crystals gave well-resolved electron diffraction diagrams corresponding to all the equatorial reflections of the X-ray fiber diagram obtained from stretched PTMA melt-quenched film (beta structure). The unit cell parameters of the beta structure of PTMA were determined as a = 0.503 nm, b = 0.732 nm and c (fiber axis) = 1.442 nm with an orthorhombic crystal system. The fiber repeat distance is appropriate for an all-trans backbone conformation for the straight stems. The setting angle, with respect to the a axis, is +/-46 degrees for the corner and center chains. Thermal behavior of lamellar crystals has been investigated by means of transmission electron microscopy (TEM) and atomic force microscopy (AFM). The lamellar thickness at the edges of the crystal increased after thermal treatment with taking the molecular chains into recrystallization parts; the holes then opened up at the thickening front of the crystal. The morphological changes of lamellar crystals after enzymatic degradation by Lipase type XIII from Pseudomonas sp. and water-soluble products were characterized by TEM, AFM, gel permeation chromatography, high performance liquid chromatography and fast atom bombardment mass spectrometry. The degradation progressed mainly from the edges of the lamellar crystals without decreasing the molecular weights and the lamellar thicknesses. The central portion of single crystals was often degraded by enzymatic attacks. This result combined with thermal behavior indicates that the loosely chain-packing region exists

  17. Real-time mass spectroscopy analysis of Li-ion battery electrolyte degradation under abusive thermal conditions

    Science.gov (United States)

    Gaulupeau, B.; Delobel, B.; Cahen, S.; Fontana, S.; Hérold, C.

    2017-02-01

    The lithium-ion batteries are widely used in rechargeable electronic devices. The current challenges are to improve the capacity and safety of these systems in view of their development to a larger scale, such as for their application in electric and hybrid vehicles. Lithium-ion batteries use organic solvents because of the wide operating voltage. The corresponding electrolytes are usually based on combinations of linear, cyclic alkyl carbonates and a lithium salt such as LiPF6. It has been reported that in abusive thermal conditions, a catalytic effect of the cathode materials lead to the formation fluoro-organics compounds. In order to understand the degradation phenomenon, the study at 240 °C of the interaction between positive electrode materials (LiCoO2, LiNi1/3Mn1/3Co1/3O2, LiMn2O4 and LiFePO4) and electrolyte in dry and wet conditions has been realized by an original method which consists in analyzing by mass spectrometry in real time the volatile molecules produced. The evolution of specific gases channels coupled to the NMR reveal the formation of rarely discussed species such as 2-fluoroethanol and 1,4-dioxane. Furthermore, it appears that the presence of water or other protic impurities greatly influence their formation.

  18. Evaluation of the integral methods for the kinetic study of thermally stimulated processes in polymer science

    OpenAIRE

    Pérez-Maqueda, Luis A.; Sánchez-Jiménez, P.E.; Criado, J.M.

    2005-01-01

    This paper reports on the accuracy of the integral methods used for the kinetic analysis of degradation and crystallization of polymers. Integral methods are preferred by many authors over the differential ones because often the experimental data obtained, such as thermal degradation studied by thermogravimetry, are integral and the differentiation of the integral data usually produces an unwilling increase of the noise. A problem of the integral methods is the fact that Arrhenius integral fu...

  19. Part I: In-situ fluorometric quantification of microalgal neutral lipids. Part II: Thermal degradation behavior of investment casting polymer patterns

    Science.gov (United States)

    Zhao, Hongfang

    Research described in this dissertation covers two topics. Part-I is focused on in-situ determination of neutral lipid content of microalgae using a lipophilic fluorescent dye. The traditional Nile red stain-based method for detecting microalgal intracellular lipids is limited due to varying composition and thickness of rigid cell walls. In this study, the addition of dilute acid and heating of solution, were found to greatly enhance staining efficiency of Nile red for microalgal species evaluated. Oil-in-water (O/W) microemulsion stabilized by a non-ionic surfactant was employed as a pseudo-standard that mimics lipid-bearing microalgal cells suspended in water. The average neutral lipid contents determined were very close to the results obtained by traditional gravimetric method and solid phase extraction. Part II of the dissertation explores thermo-physico-chemical properties of polymeric pattern materials, including expanded polystyrene (EPS) foam, polyurethane foam, and epoxy stereolithography (SLA) patterns, that are used in investment casting. Density, elastic modulus, expansion coefficient, thermal degradation behavior, etc. were experimentally investigated for their effects on metal casting quality. The reduction in toxic hydrogen cyanide (HCN) generated during thermal decomposition of polyurethane pattern was achieved by increasing either oxidant level or residence time in heated zone. Thermal degradation kinetics of the pattern materials were examined with a thermogravimetric analysis and activation energies were determined by Kissinger and Flynn-Wall-Ozawa methods.

  20. Thermal and pH degradation kinetics of anthocyanins in natural food colorant prepared from black rice bran

    National Research Council Canada - National Science Library

    Loypimai, Patiwit; Moongngarm, Anuchita; Chottanom, Pheeraya

    2016-01-01

    The study of the stability of anthocyanins in food colorant powder is important to predict the quality changes occurring as the food products are processed, to prevent and control the degradation of the anthocyanins...

  1. Visible light induced degradation of methyl orange using β-Ag0.333V2O5 nanorod catalysts by facile thermal decomposition method

    Directory of Open Access Journals (Sweden)

    R. Saravanan

    2015-09-01

    Full Text Available One dimensional nanorods of β-Ag0.333V2O5 have been synthesized by facile thermal decomposition method without using any additives. The prepared sample was characterized by different physical and chemical techniques such as XRD, FE-SEM, TEM, DRS and XPS. The photocatalytic activity of β-Ag0.333V2O5 catalyst was investigated by studying the degradation of methyl orange (MO in aqueous medium under visible light exposure. The result shows β-Ag0.333V2O5 exhibits outstanding photocatalytic activity under visible light illumination.

  2. Development of forced degradation and stability indicating studies of drugs—A review

    Directory of Open Access Journals (Sweden)

    M Blessy

    2014-06-01

    Full Text Available Forced degradation is a degradation of new drug substance and drug product at conditions more severe than accelerated conditions. It is required to demonstrate specificity of stability indicating methods and also provides an insight into degradation pathways and degradation products of the drug substance and helps in elucidation of the structure of the degradation products. Forced degradation studies show the chemical behavior of the molecule which in turn helps in the development of formulation and package. In addition, the regulatory guidance is very general and does not explain about the performance of forced degradation studies. Thus, this review discusses the current trends in performance of forced degradation studies by providing a strategy for conducting studies on degradation mechanisms and also describes the analytical methods helpful for development of stability indicating method. Keywords: Degradation conditions, Degradation product, Forced degradation, Stability indicating method, Stress testing

  3. Degradation study on optical materials for concentrator photovoltaics

    Science.gov (United States)

    Eltermann, Fabian; Roeder, Kerstin; Wiesenfarth, Maike; Wilde, Juergen; Bett, Andreas W.

    2012-10-01

    In this work the impact of accelerated aging on the spectral transmission and the mechanical robustness of silicone elastomers for concentrator photovoltaic applications was investigated. Therefore, specific test samples were manufactured. The samples were annealed at 150 °C to assure a complete cross-linking. These samples were exposed to humidity freeze, to a pressure cooker test, and to UV light. To investigate optical materials under UVA intensity up to 10 W/cm2 a test setup was developed. Thus, a UV dosage of 10000 kWh/m2 was applied to the silicone samples after thermal treatment. The mean transmission was used as a measure to identify changes in the spectral behavior and was, therefore, compared after the stress tests with the initial value. No total failures but rather degradation was observed, mainly in the range of ultraviolet and visible light. In addition, the shear strengths for the silicone elastomers were compared before and after stress.

  4. Bacterial degradation of recalcitrant PAHs: metabolic studies and application to pyrene degradation in a freshwater sediment

    Energy Technology Data Exchange (ETDEWEB)

    Jouanneau, Y.; Demaneche, S.; Meyer, Ch.; Willison, J.C. [CEA-Grenoble, UMR 5092 CNRS-CEA-UJF, 38 - Grenoble (France)

    2005-07-01

    Cost-effective bio-remediation strategies have been proposed to remove toxic chemicals, including polycyclic aromatic hydrocarbons (PAHs), from contaminated sites. However, the efficiency of these strategies is often limited, due to the resistance of certain chemicals to microbial degradation. Our studies deal with the biodegradation of four-ring PAHs using two recently isolated bacteria, Mycobacterium strain 6PY1, which can mineralize pyrene and phenanthrene, and Sphingomonas strain CHY-1, which mineralizes chrysene and various three-ring PAHs. The metabolic pathways for the biodegradation of PAHs have been investigated using GC-MS to identify and assay metabolites. Also, several enzymes involved in PAH catabolism have been identified by a combination of proteomic and genetic approaches. In Mycobacterium 6PY1, two ring-hydroxylating di-oxygenases which catalyze the initial attack of PAHs have been overproduced in E. coli, isolated and characterized. The selectivity of the two enzymes showed marked differences, since one di-oxygenase preferentially oxidized 2- or 3- ring PAHs whereas the other attacked pyrene and 3-ring PAHs exclusively. In Sphingomonas CHY-1, a single di-oxygenase, called PhnI, was found to convert seven PAHs, including chrysene, to the corresponding dihydro-diols. It is the first enzyme to be described which is able to attack the four-ring PAHs chrysene and benz[a]anthracene.. The fate of pyrene was examined in a sediment taken from a freshwater lake of the French Alps. Experiments were carried out in microcosms containing a layer of sediment which was spiked with {sup 14}C-pyrene. Pyrene mineralization was monitored over 61 days by measuring the {sup 14}CO{sub 2} evolved from the microcosms. Some microcosms were planted with young reeds (Phragmites australis), while other were inoculated with Mycobacterium 6PY1. P. australis reeds promoted a significant increase of pyrene degradation, which most likely resulted from a root-mediated increase of

  5. Characterization of deposits formed on diesel injectors in field test and from thermal oxidative degradation of n-hexadecane in a laboratory reactor

    Directory of Open Access Journals (Sweden)

    Venkataraman Ramya

    2008-12-01

    Full Text Available Abstract Solid deposits from commercially available high-pressure diesel injectors (HPDI were analyzed to study the solid deposition from diesel fuel during engine operation. The structural and chemical properties of injector deposits were compared to those formed from the thermal oxidative stressing of a diesel fuel range model compound, n-hexadecane at 160°C and 450 psi for 2.5 h in a flow reactor. Both deposits consist of polyaromatic compounds (PAH with oxygen moieties. The similarities in structure and composition of the injector deposits and n-hexadecane deposits suggest that laboratory experiments can simulate thermal oxidative degradation of diesel in commercial injectors. The formation of PAH from n-hexadecane showed that aromatization of straight chain alkanes and polycondensation of aromatic rings was possible at temperatures as low as 160°C in the presence of oxygen. A mechanism for an oxygen-assisted aromatization of cylcoalkanes is proposed.

  6. Thermal degradation of sucralose: a combination of analytical methods to determine stability and chlorinated byproducts

    Science.gov (United States)

    de Oliveira, Diogo N.; de Menezes, Maico; Catharino, Rodrigo R.

    2015-04-01

    In the late years, much attention has been brought to the scientific community regarding the safety of sucralose and its industrial applications. Although it is the most used artificial sweetener in foods and pharmaceuticals, many questions still arise on its potential to form chlorinated byproducts in high temperatures, as demonstrated by several recent studies. In the present contribution, we use a combination of differential scanning calorimetry and thermogravimetric analysis coupled with infrared spectroscopy (DSC/TGA/IR), Hot-stage microscopy (HSM) and high-resolution mass spectrometry (HRMS) on samples submitted to water bath at mild temperatures to evaluate a broad spectrum of hazardous compounds formed in the degradation of this product. TGA/IR has revealed that there is effective decomposition in form of CO2 along with the formation of hydrogen chloride and other minor compounds. HSM results have provided accurate information, where the melting of the crystals was observed, followed by decomposition. Chlorinated derivatives, including polychlorinated aromatic hydrocarbons (PCAHs) were also confirmed by HRMS. These findings not only corroborate the suspected instability of sucralose to high temperatures, but also indicate that even exposed to mild conditions the formation of hazardous polychlorinated compounds is observed.

  7. Thermal degradation behaviour of nanoamphiphilic chitosan dispersed poly (lactic acid) bionanocomposite films.

    Science.gov (United States)

    Pal, Akhilesh Kumar; Katiyar, Vimal

    2017-02-01

    In the present study, nano-amphiphilic chitosan termed as chitosan-grafted-oligo l-lactic acid (CH-g-OLLA), is synthesized by microwave initiated insitu condensation polymerization. The synthesized CH-g-OLLA becomes hydrophobic in nature due to chemical bond formation between chitosan backbone and OLLA chains. Further, CH-g-OLLA (30%) bionanocomposite is used as a nanofiller in poly (lactic acid)/chitosan-grafted-oligo l-lactic acid (PLA/CH-g-OLLA) bionanocomposite films. Surface morphology shows a homogeneous dispersion of CH-g-OLLA in the form of spherical aggregates, which vary in the range of ∼20 to 150nm. Non-isothermal degradation kinetics, proposed by Kissinger, Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa and Augis & Bennett models, are utilized to estimate the activation energies (Ea) for PLA, which are 254.1, 260.2, 257.0 and 259.1kJmol-1 respectively. The reduction in Ea values of bionanocomposite films may be elucidated by intermolecular distance and enrichment in chain mobility. The evolved gaseous products like hydrocarbons, carbon dioxide, carbon monoxide and cyclic oligomers are successfully identified with TG-FTIR analysis. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Analysis of annatto (Bixa orellana) food coloring formulations. 2. Determination of aromatic hydrocarbon thermal degradation products by gas chromatography.

    Science.gov (United States)

    Scotter, M J; Wilson, L A; Appleton, G P; Castle, L

    2000-02-01

    Twenty samples of commercial annatto formulations have been analyzed for m-xylene and toluene using ambient alkaline hydrolysis, followed by solvent extraction and capillary gas chromatography. Fifteen of the samples contained annatto during source extraction and processing, resulting in contamination by internal generation of both bixin and norbixin types with aromatic hydrocarbons. Two samples of norbixin of known production history (i. e., thermal versus nonthermal processes) were analyzed specifically to identify possible differences in their degradation component profiles. They were found to differ significantly in m-xylene content, which is consistent with their respective production histories.

  9. Assessment by HPLC of the degradation behavior of acitretin under hydrolytic, oxidative, photolytic and thermal stress conditions

    Directory of Open Access Journals (Sweden)

    Pawan K. Porwal

    2014-12-01

    Full Text Available Acitretin is a photosensitive oral retinoid with very limited data available on its degradation. The official HPLC method for acitretin determination was insufficient to resolve the degradation products generated during stability studies. Therefore, an isocratic RP-HPLC–UV method was developed for the determination of acitretin in the presence of its related impurities and degradation products. Efficient chromatographic separation was achieved on a Thermo beta-basic column C18 (100 mm×4.6 mm, 5 μm with mobile phase containing 0.3% (v/v glacial acetic acid with acetonitrile (ACN and isopropyl alcohol (IPA in an isocratic ratio of 70:30 at a flow rate of 1.0 mL/min with the eluent monitored at 360 nm. The method was validated for specificity, linearity, precision, accuracy and robustness. The calibration plot was linear over the concentration range of 50–150 μg/mL with a correlation coefficient (r2 of 0.999. The proposed method was used to investigate the degradation kinetics of acitretin under the different degradative conditions. The degradation rate constant (K, half-life (t1/2, and t90 were calculated. Degradation of acitretin followed pseudo-first-order kinetics. The drug was found to be less stable under acidic and photolytic degradation conditions: the photolytic degradation constants for acitretin in sunlight and UV light were 0.002698% and 0.0008402% min−1, respectively. The LOD for acitretin and the known impurities were at a level below 0.02%. The method shows consistent recoveries for ACTR (99.8%–101.2% and also for its known impurities (97.2–101.3%. The method was found to be accurate, precise, linear, specific, sensitive, rugged, robust, and useful for characterizing the stability of this chemical.

  10. Data of thermal degradation and dynamic mechanical properties of starch–glycerol based films with citric acid as crosslinking agent

    Directory of Open Access Journals (Sweden)

    Paula González Seligra

    2016-06-01

    Full Text Available Interest in biodegradable edible films as packaging or coating has increased because their beneficial effects on foods. In particular, food products are highly dependents on thermal stability, integrity and transition process temperatures of the packaging. The present work describes a complete data of the thermal degradation and dynamic mechanical properties of starch–glycerol based films with citric acid (CA as crosslinking agent described in the article titled: “Biodegradable and non-retrogradable eco-films based on starch–glycerol with citric acid as crosslinking agent” González Seligra et al. (2016 [1]. Data describes thermogravimetric and dynamical mechanical experiences and provides the figures of weight loss and loss tangent of the films as a function of the temperature.

  11. Data of thermal degradation and dynamic mechanical properties of starch-glycerol based films with citric acid as crosslinking agent.

    Science.gov (United States)

    González Seligra, Paula; Medina Jaramillo, Carolina; Famá, Lucía; Goyanes, Silvia

    2016-06-01

    Interest in biodegradable edible films as packaging or coating has increased because their beneficial effects on foods. In particular, food products are highly dependents on thermal stability, integrity and transition process temperatures of the packaging. The present work describes a complete data of the thermal degradation and dynamic mechanical properties of starch-glycerol based films with citric acid (CA) as crosslinking agent described in the article titled: "Biodegradable and non-retrogradable eco-films based on starch-glycerol with citric acid as crosslinking agent" González Seligra et al. (2016) [1]. Data describes thermogravimetric and dynamical mechanical experiences and provides the figures of weight loss and loss tangent of the films as a function of the temperature.

  12. Study of thermal behavior of phytic acid

    Directory of Open Access Journals (Sweden)

    André Luis Máximo Daneluti

    2013-06-01

    Full Text Available Phytic acid is a natural compound widely used as depigmenting agent in galenic cosmetic emulsions. However, we have observed experimentally that phytic acid, when heated to 150 ºC for around one hour, shows evidence of thermal decomposition. Few studies investigating this substance alone with regard to its stability are available in the literature. This fact prompted the present study to characterize this species and its thermal behavior using thermal analysis (TG/DTG and DSC and to associate the results of these techniques with those obtained by elemental analysis (EA and absorption spectroscopy in the infrared region. The TG/DTG and DSC curves allowed evaluation of the thermal behavior of the sample of phytic acid and enabled use of the non-isothermal thermogravimetric method to study the kinetics of the three main mass-loss events: dehydration I, dehydration II and thermal decomposition. The combination of infrared absorption spectroscopy and elemental analysis techniques allowed evaluation of the intermediate products of the thermal decomposition of phytic acid. The infrared spectra of samples taken during the heating process revealed a reduction in the intensity of the absorption band related to O-H stretching as a result of the dehydration process. Furthermore, elemental analysis results showed an increase in the carbon content and a decrease in the hydrogen content at temperatures of 95, 150, 263 and 380 °C. Visually, darkening of the material was observed at 150 °C, indicating that the thermal decomposition of the material started at this temperature. At a temperature of 380 °C, thermal decomposition progressed, leading to a decrease in carbon and hydrogen. The results of thermogravimetry coupled with those of elemental analysis allow us to conclude that there was agreement between the percentages of phytic acid found in aqueous solution. The kinetic study by the non-isothermal thermogravimetric method showed that the dehydration

  13. Thermal analysis studies of poly(etheretherketone)/hydroxyapatite biocomposite mixtures.

    Science.gov (United States)

    Meenan, B J; McClorey, C; Akay, M

    2000-08-01

    Biocomposite formulations which have the potential to combine the proven mechanical performance of poly(etheretherketone) (PEEK) with the inherent bioactivity of hydroxyapatite (HA), may have a utility as load-bearing materials in a medical implant context. The effect of thermal processing on the relevant properties of the PEEK and/or HA components in any fabricated composite structure is, however, an important consideration for their effective exploitation. This paper reports the results of a detailed thermal characterization study of a series of PEEK/HA mixtures using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and modulated differential scanning calorimetry (MDSC). The TGA analyses show minimal weight loss for all of the mixtures and for a pure PEEK sample up to approximately 530 degrees C. Above this point there is a sharp on-set of decomposition for the PEEK component in each case. The temperature at which this feature occurs varies for each mixture in the approximate range 539-556 degrees C. This observation is supported by the presence of exotherms in the corresponding DSC scans, in the same temperature region, which are also assigned to PEEK decomposition. The temperature at which the degradation on-set occurs is found to decrease with increasing HA contribution. The use of the modulated DSC technique allows a number of important thermal events, not easily identifiable from the data obtained by the conventional method, to be clearly observed. In particular, the glass transition temperature (Tg) of the polymer can now be accurately determined. Using these thermal analysis data, calculations of the % crystallinity of PEEK in the mixtures have been made and compared with that of a 100% polymer sample. From these studies it is evident that the presence of HA does not adversely affect the degree of crystallinity of the PEEK component in the mixtures of interest over the thermal range studied. Copyright 2000 Kluwer Academic

  14. The impact of low-temperature seasonal aquifer thermal energy storage (SATES) systems on chlorinated solvent contaminated groundwater: Modeling of spreading and degradation

    Science.gov (United States)

    Zuurbier, Koen G.; Hartog, Niels; Valstar, Johan; Post, Vincent E. A.; van Breukelen, Boris M.

    2013-04-01

    Groundwater systems are increasingly used for seasonal aquifer thermal energy storage (SATES) for periodic heating and cooling of buildings. Its use is hampered in contaminated aquifers because of the potential environmental risks associated with the spreading of contaminated groundwater, but positive side effects, such as enhanced contaminant remediation, might also occur. A first reactive transport study is presented to assess the effect of SATES on the fate of chlorinated solvents by means of scenario modeling, with emphasis on the effects of transient SATES pumping and applicable kinetic degradation regime. Temperature effects on physical, chemical, and biological reactions were excluded as calculations and initial simulations showed that the small temperature range commonly involved (ΔT < 15 °C) only caused minor effects. The results show that a significant decrease of the contaminant mass and (eventually) plume volume occurs when degradation is described as sediment-limited with a constant rate in space and time, provided that dense non-aqueous phase liquid (DNAPL) is absent. However, in the presence of DNAPL dissolution, particularly when the dissolved contaminant reaches SATES wells, a considerably larger contaminant plume is created, depending on the balance between DNAPL dissolution and mass removal by degradation. Under conditions where degradation is contaminant-limited and degradation rates depend on contaminant concentrations in the aquifer, a SATES system does not result in enhanced remediation of a contaminant plume. Although field data are lacking and existing regulatory constraints do not yet permit the application of SATES in contaminated aquifers, reactive transport modeling provides a means of assessing the risks of SATES application in contaminated aquifers. The results from this study are considered to be a first step in identifying the subsurface conditions under which SATES can be applied in a safe or even beneficial manner.

  15. Mechanical property degradation and microstructural evolution of cast austenitic stainless steels under short-term thermal aging

    Energy Technology Data Exchange (ETDEWEB)

    Lach, Timothy G.; Byun, Thak Sang; Leonard, Keith J.

    2017-12-01

    Mechanical testing and microstructural characterization were performed on short-term thermally aged cast austenitic stainless steels (CASS) to understand the severity and mechanisms of thermal-aging degradation experienced during extended operation of light water reactor (LWR) coolant systems. Four CASS materials – CF3, CF3M, CF8, and CF8M – were thermally aged for 1500 hours at 290 °C, 330 °C, 360 °C, and 400 °C. All four alloys experienced insignificant change in strength and ductility properties but a significant reduction in absorbed impact energy. The primary microstructural and compositional changes during thermal aging were spinodal decomposition of the δ-ferrite into α/ α`, precipitation of G-phase in the δ-ferrite, segregation of solute to the austenite/ ferrite interphase boundary, and growth of M23C6 carbides on the austenite/ferrite interphase boundary. These changes were shown to be highly dependent on chemical composition, particularly the concentration of C and Mo, and aging temperature. A comprehensive model is being developed to correlate the microstructural evolution with mechanical behavior and simulation for predictive evaluations of LWR coolant system components.

  16. Lycopene degradation, isomerization and in vitro bioaccessibility in high pressure homogenized tomato puree containing oil: effect of additional thermal and high pressure processing.

    Science.gov (United States)

    Knockaert, Griet; Pulissery, Sudheer K; Colle, Ines; Van Buggenhout, Sandy; Hendrickx, Marc; Loey, Ann Van

    2012-12-01

    In the present study, the effect of equivalent thermal and high pressure processes at pasteurization and sterilization intensities on some health related properties of high pressure homogenized tomato puree containing oil were investigated. Total lycopene concentration, cis-lycopene content and in vitro lycopene bioaccessibility were examined as health related properties. Results showed that pasteurization hardly affected the health related properties of tomato puree. Only the formation of cis-lycopene during intense thermal pasteurization was observed. Sterilization processes on the other hand had a significant effect on the health related properties. A significant decrease in total lycopene concentration was found after the sterilization processes. Next to degradation, significant isomerization was also observed: all-trans-lycopene was mainly converted to 9-cis- and 13-cis-lycopene. High pressure sterilization limited the overall lycopene isomerization, when compared to the equivalent thermal sterilization processes. The formation of 5-cis-lycopene on the other hand seemed to be favoured by high pressure. The in vitro lycopene bioaccessibility of high pressure homogenized tomato puree containing oil was decreased during subsequent thermal or high pressure processing, whereby significant changes were observed for all the sterilization processes. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Mechanical Properties and Kinetics of Thermal Degradation of Bioplastics based on Straw Cellulose and Whole Wheat Flour

    Directory of Open Access Journals (Sweden)

    Hesam Omrani fard

    2012-12-01

    Full Text Available During  the  past  two  decades  the  use  of  bioplastics,  as  a  suitable  alternative to  petroleum-based  plastics,  has  attracted  researchers'  attention  to  a  great extent.  In  this  study,  the whole wheat four and  straw cellulose at different proportions were mixed with glycerol and bioplastics sheets were obtained by a press type molding machine.  The mechanical  properties  of  samples  were  examined  on compositions prepared by whole wheat weight in three proportions of 70, 60 and 50% and the cellulose in three proportions 75, 70 and 65%. The tensile tests on the samples indicated  that with  lowering  proportions  of  both  four  and  cellulose,  the modulus of elasticity and  tensile  strength of  the bioplastics dropped as well. The maximum modulus of  elasticity  achieved  for  the four  and  cellulose  compositions were 12.5, and 8.6 MPa, and the maximum tensile strengths were 878 and 202 kPa, respectively. The TGA tests indicated that the bioplastics prepared from whole wheat four showed higher temperatures of thermal degradation. The activation energies calculated for the four and cellulose bioplastics, as estimated by Arrhenius type equation, were 133.0 and 63.8 kJ/mol, respectively.

  18. Hydrolytic and thermal degradation of PCL and PCL/Bentonite compounds

    Energy Technology Data Exchange (ETDEWEB)

    Franca, Danyelle Campos; Bezerra, Elieber Barros; Morais, Dayanne Diniz de Souza; Araujo, Edcleide Maria [Universidade Federal de Campina grande (UFCG), PB (Brazil). Departamento de Engenharia de Materiais; Wellen, Renate Maria Ramos, E-mail: wellen.renate@gmail.com [Universidade Federal da Paraiba (UFPB), Joao Pessoa, PB (Brazil). Departamento de Engenharia de Materiais

    2016-05-15

    Poly(ε-caprolactone)/montmorillonite (PCL/MMT) and Poly(εcaprolactone)/organo-modified montmorillonite (PCL/OMMT) compounds at 3% w/w clay content were prepared by melting mixing. The effect of MMT and OMMT on the degradability of PCL injected specimens was investigated in vacuum at 40 deg C for up to 45 days and in aqueous medium at 40 deg C for up to 45 days. Selected specimens were collected after 15, 30 and 45 days of exposure. Microstructural changes were monitored during the degradation experiment by means of melt flow rate (MFR), weight loss, X ray diffraction (XRD), mechanical properties, and scanning electron microscopy (SEM). PCL and its compounds revealed not to be prone to hydrolytic degradation with similar results for MFR of samples exposed in vacuum and water. Gain and loss of weight were observed during experiments, probably due to swelling mechanism taking place in two stages, with the amorphous phase being the first to be swelled followed by the crystalline one. By XRD a new peak corresponding to (002) plane was evident for PCL/OMMT. PCL proved to be resistant to degradation since experiments carried out in vacuum or in aqueous medium for up to 45 days were not enough to affect the mechanical integrity of PCL samples. (author)

  19. Thermal Contributions to the Degradation of Ground Laboratory and Space Irradiated Teflon

    Science.gov (United States)

    deGroh, Kim K.; Martin, Morgana

    2003-01-01

    The aluminized Teflon fluorinated ethylene propylene outer most layer of the multilayer insulation blankets on the Hubble Space Telescope has become embrittled resulting in severe on-orbit cracking. During the second servicing mission, a piece of aluminized fluorinated ethylene propylene was retrieved that had curled, exposing the back-surface aluminum to space. This extremely embrittled piece reached 200 C on-orbit, 150 C higher than the nominal temperature extreme. Therefore, experiments have been conducted to determine the effect of heating on the degradation of fluorinated ethylene propylene that has been irradiated in a ground laboratory facility or in space on Hubble Space Telescope. Samples of pristine, x-ray irradiated and Hubble Space Telescope retrieved fluorinated ethylene propylene were heat treated from 50 to 200 C at 25 C intervals in a high vacuum facility and tensile tested. Density measurements were also obtained. Results indicate that heating does not embrittle non-irradiated Teflon. However, there is a significant dependence of the embrittlement of irradiated Teflon on heating temperature, with near complete loss of elongation at 100 C and higher. Rate of degradation changes, which were consistent with the glass transition temperature for fluorinated ethylene propylene, were present in the data. The results support chain scission as the primary mechanism of degradation of fluorinated ethylene propylene on Hubble Space Telescope, and indicate the significance of the on-orbit temperature of fluorinated ethylene propylene with respect to its degradation in the space environment.

  20. Preparation, spectral and thermal studies of pyrazinecarboxylic ...

    Indian Academy of Sciences (India)

    Unknown

    carboxylic acid) have been prepared by neutralization of aqueous hydrazine hydrate with the respective acids in appropriate molar ratios. The free acids and their hydrazinium salts have been characterized by analytical, IR spectroscopic and thermal studies. IR spectra of all the salts show N–N stretching frequencies of the ...

  1. imide, crystal structure, thermal and dielectric studies

    Indian Academy of Sciences (India)

    IR and Raman spectroscopies and its crystal structure is confirmed by single crystal X-ray diffraction method. The X-ray studies on ... Di-cationic ionic liquids; crystal structure; dielectric; thermal properties. 1. Introduction. The chemistry of ionic ... exposed in various emerging areas as solvents of high tem- perature organic ...

  2. Degradation studies on plasticized PVC films submited to gamma radiation

    Directory of Open Access Journals (Sweden)

    Vinhas Glória Maria

    2003-01-01

    Full Text Available Poly (vinyl chloride, PVC, is a rigid polymer and for several of its applications must be compounded with plasticizing agents. The plasticizers minimize the dipolar interactions, which exist between the polymer's chains, promoting their mobility. In this work we studied the properties of PVC/plasticizer systems submitted to different doses of gamma radiation. We have used four commercial plasticizers amongt them di(2-ethylhexyl phthalate, DEHP, which is present in a great number of commercial applications. The PVC/plasticizer systems have been studied as films made by the solvent evaporation technique. Irradiated and non-irradiated films have been characterized by viscosimetric analysis, mechanical essays and infrared spectroscopy. The results have shown that the rigid, non plasticized, PVC film presented the greatest degradation index, while among the plasticized films the one which presented the larger degradation index due to chain scission was the DEHP plasticized PVC.

  3. Organic matter degradation in Lake Baikal - a sediment trap study

    DEFF Research Database (Denmark)

    Schubert, Carsten J.; Niggemann, Jutta; Lomstein, Bente Aagaard

    represented by chlorins, amino acids, and fatty acids, were preferentially degraded over bulk organic carbon. A wide range of diagenetic indicators has been applied to assess the diagenetic stage of the sediment trap material, including the pigment based Chlorin Index, different amino acid based indicators......Lake Baikal offers a unique opportunity to study water column processes in a freshwater system with conditions similar to oceanic systems, e. g. great water depth and oxygenated water column. Investigations on sediment trap material provide information on the early stages of organic matter...... degradation in the water column. Sediment trap material from 18 different water depths has been analysed for bulk organic matter parameters, including organic carbon and nitrogen isotopic compositions, chlorin concentrations, and Chlorin Indices [1]. Detailed studies focused on the concentration...

  4. Implications of Steam Generator Fouling on the Degradation of Material and Thermal Performance

    Science.gov (United States)

    Turner, Carl W.

    Fouling of steam generators has a significant negative impact on the material and thermal performance the steam generators of pressurized water reactors. Corrosion products that originate from various components in the steam cycle of a nuclear power plant get pumped forward with the feed water to steam generators where they deposit on the tube bundle, tube support structure and the tube sheet. Heavy accumulation of deposit within the steam generator has led to some serious operational problems, including loss of thermal performance, under deposit corrosion, steam generator level oscillations, flow accelerated corrosion of carbon steel tube support plates and the failure of steam generator tubes due to high cycle fatigue.

  5. Thermal Degradation Behavior of Siloxane Elastomer Impregnated Carbon Nanotube Areogel Networks

    Energy Technology Data Exchange (ETDEWEB)

    Lewicki, J P; Worsley, M A

    2010-12-13

    A novel class of nanoporous graphitic carbon foams has been synthesized. Unprecedented properties - electrically conductive, thermally stable (> 1000 C), and mechanically robust. Improved transport properties (DWNT-CA, SWNT-CA) - greater than 100% enhancement in thermal conductivity, 100-400% improvement in electrical conductivity. Rich mechanical deformation behavior (SWNT-CA) - stiff ({approx}100% improvement of elastic modulus), energy dissipation, fracture toughness, and fatigue behavior. Implications for energy-related technologies - hydrogen storage, fusion and fission energy, catalysis, electrochemical energy storage, and composites with foam scaffolds.

  6. Optically Detected Magnetic Resonance and Thermal Activation Spectroscopy Study of Organic Semiconductors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chang-Hwan [Iowa State Univ., Ames, IA (United States)

    2003-01-01

    Organic electronic materials are a new class of emerging materials. Organic light emitting devices (OLEDs) are the most promising candidates for future flat panel display technologies. The photophysical characterization is the basic research step one must follow to understand this new class of materials and devices. The light emission properties are closely related to the transport properties of these materials. The objective of this dissertation is to probe the relation between transport and photophysical properties of organic semiconductors. The transport characteristics were evaluated by using thermally stimulated current and thermally stimulated luminescence techniques. The photoluminescence detected magnetic resonance and photoluminescence quantum yield studies provide valuable photophysical information on this class of materials. OLEDs are already in the market. However, detailed studies on the degradation mechanisms are still lacking. Since both optically detected magnetic resonance and thermal activation spectroscopy probe long-lived defect-related states in organic semiconductors, the combined study generates new insight on the OLED operation and degradation mechanisms.

  7. Speciation of methylmercury in market seafood by thermal degradation, amalgamation and atomic absorption spectroscopy.

    Science.gov (United States)

    Ruiz-de-Cenzano, Manuela; Rochina-Marco, Arancha; Cervera, M Luisa; de la Guardia, Miguel

    2014-09-01

    Sample thermal decomposition followed by mercury amalgamation and atomic absorption has been employed for the determination of methylmercury (MeHg) in fish. The method involves HBr leaching of MeHg, extraction into toluene, and back-extraction into an aqueous l-cysteine solution. Preliminary studies were focused on the extraction efficiency, losses, contaminations, and species interconversion prevention. The limit of detection was 0.018µgg(-1) (dry weight). The intraday precision for three replicate analysis at a concentration of 4.2µgg(-1) (dry weight) was 3.5 percent, similar to the interday precision according to analysis of variance (ANOVA). The accuracy was guaranteed by the use of fortified samples involving 83-105 percent recoveries, and certified reference materials TORT-2 (lobster hepatopancreas) and DORM-3 (dogfish liver), providing 107 and 98 percent recovery of certified values. The greenness of the method was also evaluated with the analytical eco-scale being obtained a final score of 73 points which means an acceptable green analysis. The method was applied to fifty-seven market samples of different fish acquired from local markets in several sampling campaigns. The content of MeHg found varied between 0.0311 and 1.24µgg(-1) (wet weight), with values that involve 33-129 percent of the total mercury content. Some considerations about food safety were also done taking into account data about Spanish fish consume and Tolerable Weekly Intake (TWI) established for MeHg. Copyright © 2014 Elsevier Inc. All rights reserved.

  8. Effect of the Electric Field Frequency on Ascorbic Acid Degradation during Thermal Treatment by Ohmic Heating

    Science.gov (United States)

    Mercali, Giovana Domeneghini; Schwartz, Steven; Marczak, Ligia Damasceno Ferreira; Tessaro, Isabel Cristina; Sastry, Sudhir

    2014-01-01

    In this work, the influence of the electric field frequency and solids content on the degradation kinetics of ascorbic acid during ohmic heating of acerola pulp and acerola serum was investigated. The degradation percentage of ascorbic acid in the pulp after 120 min of heating varied between 12 and 17%. For the serum, the degradation percentage was in the range of 13 and 18%. The results were fitted to the first-order model, and the kinetic rate constants ranged from 1.1 to 1.6 × 10−3 min−1 and from 1.1 to 1.5 × 10−3 min−1 for pulp and serum, respectively. D values ranged between 1480 and 2145 min for the pulp and between 1524 and 1951 min for the serum. A distinct behavior between the kinetic parameters of the pulp and serum in electric field frequencies ranging from 10 to 1000 Hz indicates that the presence of distinct amounts and types of solids might affect the rate of the electron transfer in electrochemical reactions. These variables may also affect the polarization process stimulated by the oscillating electric field. The non-achievement of the equilibrium of the polarization process may have an influence on oxidation reactions, affecting the predisposition to hydrogen donation from the ascorbic acid molecule. PMID:24892902

  9. Impact of modified graphene and microwave irradiation on thermal stability and degradation mechanism of poly (styrene-co-methyl meth acrylate)

    Energy Technology Data Exchange (ETDEWEB)

    Zubair, Mukarram [Department of Environmental Engineering, University of Dammam, 31982 Dammam (Saudi Arabia); Shehzad, Farrukh [Department of Chemical Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Saudi Arabia, (Saudi Arabia); Al-Harthi, Mamdouh A., E-mail: mamdouh@kfupm.edu.sa [Department of Chemical Engineering, King Fahd University of Petroleum & Minerals, 31261 Dhahran, Saudi Arabia, (Saudi Arabia); Center of Research Excellence in Nanotechnology, King Fahd University of Petroleum & Minerals, 31261 Dhahran (Saudi Arabia)

    2016-06-10

    Highlights: • Modified graphene imparts thermal stability to Poly (styrene-co-methyl methacrylate) [P(st-mma)]. • The thermal stability of P(st-mma) decreased with microwave irradiation. • The thermal stability of P(st-mma)/MG nanocomposites increased with irradiation time up to 10 min and decreased subsequently. • The degradation of P(st-mma) and P(st-mma)/MG is governed by random scission model. - Abstract: Poly (styrene-co-methyl methacrylate) [P(st-mma)] composite containing 0.1 wt% modified graphene (MG) was prepared via melt blending. MG was prepared by oxidation method using nitric acid. The P(st-mma) and P(st-mma)MG composite were irradiated using microwave radiation. The degradation mechanism and thermal stability of the irradiated and un-irradiated samples was analyzed by TGA. P(st-mma)MG showed high thermal stability. The average activation energy of thermal degradation was found to be 200 kJ/mol for P(st-mma), 214 kJ/mol for P(st-mma)MG. The activation energy was highest for 10 min irradiated nanocomposites indicating an improvement in stability. The degradation mechanism was investigated by comparing the master plots constructed using the experimental data with theoretical master plots of various kinetic models. The thermal degradation of P(st-mma) and P(st-mma)MG composite before and after irradiation governs the random scission mechanism. SEM and TEM micrographs showed improved interactions and degradation of composites after 10 min and 20 min irradiation respectively.

  10. Study of Operating Parameters for Accelerated Anode Degradation in SOFCs

    DEFF Research Database (Denmark)

    Ploner, Alexandra; Hagen, Anke; Hauch, Anne

    2017-01-01

    Solid oxide fuel cell (SOFC) applications require lifetimes of several years on the system level. A big challenge is to demonstrate such exceptionally long lifetimes in ongoing R&D projects. Accelerated or compressed testing are alternative methods to obtain this. Activities in this area have been...... carried out without arriving at a generally accepted methodology. This is mainly due to the complexity of degradation mechanisms on the single SOFC components as function of operating parameters. In this study, we present a detailed analysis of approx. 180 durability tests regarding degradation of single...... SOFC components as function of operating conditions. Electrochemical impedance data were collected on the fresh and long-term tested SOFCs and used to de-convolute the individual losses of single SOFC cell components – electrolyte, cathode and anode. The main findings include a time-dependent effect...

  11. Degradation Characterization of Aliphatic POLYESTERS—IN Vitro Study

    Science.gov (United States)

    Vieira, A. C.; Vieira, J. C.; Guedes, R. M.; Marques, A. T.

    2008-08-01

    The most popular and important biodegradable polymers are aliphatic polyesters, such as polylactic acid (PLA), polyglycolic acid (PGA), polycaprolactone (PCL), polyhydoxyalkanoates (PHA's) and polyethylene oxide (PEO). However, each of these has some shortcomings which restrict its applications. Blending techniques are an extremely promising approach which can improve or tune the original properties of the polymers[1]. Aliphatic polyesters are a central class of biodegradable polymers, because hydrolytic and/or enzymatic chain cleavage of these materials leads to α-hydroxyacids, which in most cases are ultimately metabolized in human body. This is particularly useful for controlled release devices and for other biomedical applications like suture fibers and ligaments. For aliphatic polyesters, hydrolysis rates are affected by the temperature, molecular structure, and ester group density as well as by the species of enzyme used. The degree of crystallinity may be a crucial factor, since enzymes attack mainly the amorphous domains of a polymer. Four different aliphatic polyesters were characterized in terms of degradation. Sutures fibers of PGA-PCL, PGA, PLA-PCL and PDO were used in this study. Weight loss, pH, molecular weight, crystallinity and strength were measured after six stages of incubation in distilled water, physiological saline and phosphate buffer solution (PBS). Degradation rate was determined, using a first order kinetic equation for all materials in the three incubation media. A relatively wide range of mechanical properties and degradation rates were observed among the materials studied. PBS was the most aggressive environment for the majority of cases.

  12. Biochemical and genetic studies on degradation of chlorobenzoates by Pseudomonas.

    Science.gov (United States)

    Singh, H; Kahlon, R S

    1989-01-01

    The chlorobenzoates constitute an important class of recalcitrant compounds polluting this biosphere. Two bacterial strains B16 (Pseudomonas aeruginosa) and DT4 (Pseudomonas sp.) isolated by enrichment technique were found to utilize 2-chlorobenzoic acid (2-Cba) and 4-chlorobenzoic acid (4-Cba) respectively as sole source of carbon and energy. 2-Cba and 4-Cba were supplemented in synthetic medium at 1500 micrograms/ml and 1000 micrograms/ml (w/v) respectively. Addition of 100 micrograms/ml (w/v) yeast extract stimulated growth of cultures. Degradation studies revealed that substrates were degraded without release of chloride ion with possible accumulation of respective chlorophenols. Respiration studies revealed inducible nature of enzymes for break down of 2-Cba, 4-Cba benzoic acid, 4-hydroxybenzoic acid and catechol. Extraction of plasmid DNA from parent strains showed presence of plasmid of same size in both strains. Cured strains showed absence of corresponding plasmid DNA bands thus indicating plasmid-borne genes for degradation of chlorobenzoates.

  13. Photocatalytic degradation of rosuvastatin: Analytical studies and toxicity evaluations

    Energy Technology Data Exchange (ETDEWEB)

    Machado, Tiele Caprioli, E-mail: tiele@enq.ufrgs.br [Chemical Engineering Department, Federal University of Rio Grande do Sul, Rua Engenheiro Luiz Englert s/n, CEP: 90040-040 Porto Alegre, RS (Brazil); Pizzolato, Tânia Mara [Chemical Institute, Federal University of Rio Grande do Sul, Avenida Bento Gonçalves, 9500, CEP: 91501-970 Porto Alegre, RS (Brazil); Arenzon, Alexandre [Ecology Center, Federal University of Rio Grande do Sul, Avenida Bento Gonçalves, 9500, CEP: 91501-970 Porto Alegre, RS (Brazil); Segalin, Jeferson [Biotechnology Center, Federal University of Rio Grande do Sul, Avenida Bento Gonçalves, 9500, CEP: 91501-970 Porto Alegre, RS (Brazil); Lansarin, Marla Azário [Chemical Engineering Department, Federal University of Rio Grande do Sul, Rua Engenheiro Luiz Englert s/n, CEP: 90040-040 Porto Alegre, RS (Brazil)

    2015-01-01

    Photocatalytic degradation of rosuvastatin, which is a drug that has been used to reduce blood cholesterol levels, was studied in this work employing ZnO as catalyst. The experiments were carried out in a temperature-controlled batch reactor that was irradiated with UV light. Preliminary the effects of the photocatalyst loading, the initial pH and the initial rosuvastatin concentration were evaluated. The experimental results showed that rosuvastatin degradation is primarily a photocatalytic process, with pseudo-first order kinetics. The byproducts that were generated during the oxidative process were identified using nano-ultra performance liquid chromatography tandem mass spectrometry (nano-UPLC–MS/MS) and acute toxicity tests using Daphnia magna were done to evaluate the toxicity of the untreated rosuvastatin solution and the reactor effluent. - Highlights: • The photocatalytic degradation of rosuvastatin was studied under UV irradiation. • Commercial catalyst ZnO was used. • Initial rosuvastatin concentration, photocatalyst loading and pH were evaluated. • The byproducts generated during the oxidative process were detected and identified. • Acute toxicity tests using Daphnia magna were carried out.

  14. Thermal transpiration: A molecular dynamics study

    Energy Technology Data Exchange (ETDEWEB)

    T, Joe Francis [Computational Nanotechnology Laboratory, School of Nano Science and Technology, National Institute of Technology Calicut, Kozhikode (India); Sathian, Sarith P. [Department of Applied Mechanics, Indian Institute of Technology Madras, Chennai (India)

    2014-12-09

    Thermal transpiration is a phenomenon where fluid molecules move from the cold end towards the hot end of a channel under the influence of longitudinal temperature gradient alone. Although the phenomenon of thermal transpiration is observed at rarefied gas conditions in macro systems, the phenomenon can occur at atmospheric pressure if the characteristic dimensions of the channel is less than 100 nm. The flow through these nanosized channels is characterized by the free molecular flow regimes and continuum theory is inadequate to describe the flow. Thus a non-continuum method like molecular dynamics (MD) is necessary to study such phenomenon. In the present work, MD simulations were carried out to investigate the occurance of thermal transpiration in copper and platinum nanochannels at atmospheric pressure conditions. The mean pressure of argon gas confined inside the nano channels was maintained around 1 bar. The channel height is maintained at 2nm. The argon atoms interact with each other and with the wall atoms through the Lennard-Jones potential. The wall atoms are modelled using an EAM potential. Further, separate simulations were carried out where a Harmonic potential is used for the atom-atom interaction in the platinum channel. A thermally insulating wall was introduced between the low and high temperature regions and those wall atoms interact with fluid atoms through a repulsive potential. A reduced cut off radius were used to achieve this. Thermal creep is induced by applying a temperature gradient along the channel wall. It was found that flow developed in the direction of the increasing temperature gradient of the wall. An increase in the volumetric flux was observed as the length of the cold and the hot regions of the wall were increased. The effect of temperature gradient and the wall-fluid interaction strength on the flow parameters have been studied to understand the phenomenon better.

  15. Isolation and study of Biodegradiation Potential of Phenanthrene degrading bacteria

    Directory of Open Access Journals (Sweden)

    nafise Nourieh

    2009-11-01

    Full Text Available Polycyclic Aromatic Hydrocarbons (PAHs are among of potentially hazardous chemicals for environment and cause health concern. These compounds exhibit carcinogenic and/or mutagenic properties and are listed by the United States Environmental Protection Agency (USEPA as priority pollutants. Polycyclic Aromatic Hydrocarbons are hardly degraded and therefore bioremediation is often considered as a desirable and cost effective remediation technique for soil. contaminated with them. Materials and Methods: In this research Phenanthrene (C14H10, a three-benzene ring PAHs, was selected as a PAH representative compound and two different concentrations of Phenanthrene (100mg/kg and 500mg/kg were studied. First, PAH-degrading microorganisms were separated and after adaptation and enrichment PAH-degrading bacteria were identified. Results: The results showed that removal efficiency of Phenanthrene in the samples containing pseudomonas was more than other specified bacteria. Also the most removal efficiency of Phenanthrene occurred in first 45 days of biotreatment and then decreasing trend slowed down. Other finding was that the bioremediation of the lower concentration of Phenanthrene takes shorter time compared with the higher concentration and also the comparison of Phenanthrene bioremediation by pure bacteria and Consertium indicated that, at the beginning of the process, the pace of eliminating Phenanthrene by Consertium is more than other bacteria. Conclusion: Microbial analysis, based on cinfirmation tests and analytical profile index (api 20E kit tests, showed that Pseudomonas. SPP, Bacillus, Pseudomonas aeruginosa and Acinetobacter were the bacteria, responsible for Phenanthrene degradation. Extraction was conducted by ultra sonic method and Phenanthrene concentration was measured by (HPLC.

  16. Study of distillation and degradation of perfluoro polyether; Estudo da destilacao e degradacao do perfluoropolieter

    Energy Technology Data Exchange (ETDEWEB)

    Lopergolo, Lilian Cristine

    1997-07-01

    Perfluoro-polyethers, PFPE, were first synthesised by Sianesi and collaborators giving rise to a new lubricant oils and greases classes with several applications. Perfluoro polyethers have excellent properties, for instance: high chemical stability and thermal stability, high density, high radiation resistance and excellent lubricating properties. FOMBLIN-Y oil is one of the perfluoro polyethers used as a lubricant in vacuum systems applied in the UF{sub 6} enrichment installations. Due to its excellent properties and for its applications in the nuclear field, IPEN-CNEN/S P had the interest to dominate its production technology with the aim to substitute the commercial FOMBLIN-Y oil used in the national consumption. The FOMBLIN-Y oil synthesis method, adopted in IPEN-CNEN/S P, made by the photooxidation of the hexa fluoro propylene. In this work we study the fraction separation of the national available production with restricted an increased molecular weights which was obtained by fraction distillation in a vacuum according to the ASTM D-1160 norm. We also study the catalytic effect of metals on the thermal stability of perfluoro polyethers. The inertness of perfluoro polyethers at temperatures higher than 300 deg C is strongly affected by presence of some metals. Al and Ti alloys cause fluid degradation at 250 deg C. This degradation is very important because it has a yield increase of the perfluoro polyethers production. (author)

  17. Thermal degradation of M41S-class mesoporous sieves as revealed by small angle X-ray scattering

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, J. E.; Xu, L.; Winans, R. E.; Seifert, S.

    2000-02-16

    The authors have studied the temperature stability of M41S class siliceous mesoporous materials loaded with carbonaceous material by temperature programmed small-angle X-ray scattering (TPSAXS) techniques. Results show the thermal structural instability of large pore pure silica sieve material with carbonaceous material (such as coal extracts) occluded within the pores of mesoporous 31 {angstrom} M41S materials. Unfilled pore M41S materials do not show thermal-related structural instability.

  18. Studies on Thermal Oxidation Stability of Aviation Lubricating Oils

    Directory of Open Access Journals (Sweden)

    Wu Nan

    2017-01-01

    Full Text Available Simulating the operating condition of aviation engine via autoclave experiment of high temperature and pressure, we studied the physic-chemical property of poly-α-olefin base oil samples mixed with antioxidants of 2,6-di-tert-butyl-4-methylphenol and p,p’-diisooctyl diphenylamine at different temperature. The mechanism of degradation of PAO aviation lubricating oil was analyzed according to the oxidized products by modern analytical instruments. The results showed that the aviation lubricating oil produced a large number of low molecule compounds while increasing the temperature, and resulted in the viscosity decreasing and acid value increasing which indicated that the thermal oxidation of the oil sample underwent a radical process.

  19. Electro-thermal Modeling of Modern Power Devices for Studying Abnormal Operating Conditions

    DEFF Research Database (Denmark)

    Wu, Rui

    In modern power electronic systems, there are increasing demands to improve the whole system endurance and safety level while reducing manufacturing and maintenance costs. Insulated Gate Bipolar Transistor (IGBT) power modules are the most widely used as well as most critical power devices...... in industrial power electronic systems in the range above 10 kW. The failure of IGBTs can be generally classified as catastrophic failures and wear out failures. A wear out failure is mainly induced by accumulated degradation with time, while a catastrophic failure is triggered by a single-event abnormal....... It combines a physics-based, device-level, distributed PSpice model with a thermal Finite-Element Method (FEM) simulation, gaining the possibility to take into account the electro-thermal interacting effects and uneven electro-thermal stresses among the chips. Case studies on the new and degraded modules...

  20. Study of variation of thermal diffusivity of advanced composite ...

    Indian Academy of Sciences (India)

    Administrator

    Modified Angstrom method is applied to study the variation of thermal diffusivity of plain woven fabric composite in closed ... Keywords. Thermal diffusivity; composite material; cryogenic temperature; phase difference; modified Ang- strom method. .... where D is the thermal diffusivity, k the heat conductivity and ρ the thermal ...

  1. Activity of nanosized titania synthesized from thermal decomposition of titanium (IV n-butoxide for the photocatalytic degradation of diuron

    Directory of Open Access Journals (Sweden)

    Jitlada Klongdee, Wansiri Petchkroh, Kosin Phuempoonsathaporn, Piyasan Praserthdam, Alisa S. Vangnai and Varong Pavarajarn

    2005-01-01

    Full Text Available Nanoparticles of anatase titania were synthesized by the thermal decomposition of titanium (IV n-butoxide in 1,4-butanediol. The powder obtained was characterized by various characterization techniques, such as XRD, BET, SEM and TEM, to confirm that it was a collection of single crystal anatase with particle size smaller than 15 nm. The synthesized titania was employed as catalyst for the photodegradation of diuron, a herbicide belonging to the phenylurea family, which has been considered as a biologically active pollutant in soil and water. Although diuron is chemically stable, degradation of diuron by photocatalyzed oxidation was found possible. The conversions achieved by titania prepared were in the range of 70–80% within 6 h of reaction, using standard UV lamps, while over 99% conversion was achieved under solar irradiation. The photocatalytic activity was compared with that of the Japanese Reference Catalyst (JRC-TIO-1 titania from the Catalysis Society of Japan. The synthesized titania exhibited higher rate and efficiency in diuron degradation than reference catalyst. The results from the investigations by controlling various reaction parameters, such as oxygen dissolved in the solution, diuron concentration, as well as light source, suggested that the enhanced photocatalytic activity was the result from higher crystallinity of the synthesized titania.

  2. Effect of polyethelene oxide on the thermal degradation of cellulose biofilm - Low cost material for soft tissue repair in dentistry.

    Science.gov (United States)

    Akkus, Anna; Tyler, Rakim; Schiraldi, David; Roperto, Renato; Faddoul, Fady; Teich, Sorin

    2017-07-01

    Bio cellulose is a byproduct of sweet tea fermentation known as kombusha. During the biosynthesis by bacteria cellulose chains are polymerized by enzyme from activated glucose. The single chains are then extruded through the bacterial cell wall. Interestingly, a potential of the Kombucha's byproduct bio cellulose (BC) as biomaterial had come into focus only in the past few decades. The unique physical and mechanical properties such as high purity, an ultrafine and highly crystalline network structure, a superior mechanical strength, flexibility, pronounced permeability to gases and liquids, and an excellent compatibility with living tissue that reinforced by biodegradability, biocompatibility, large swelling ratios. The bio-cellulose film specimens were provided by the R.P Dressel dental materials laboratory, Department of Comprehensive Care, School of Dental Medicine, Case Western Reserve University, Cleveland, US. The films were harvested, washed with water and dried at room temperature overnight. 1wt% of PEG-2000 and 10wt% of NaOH were added into ultrapure water to prepare PEG/NaOH solution. Then bio-cellulose film was added to the mixture and swell for 3 h at room temperature. All bio-cellulose film specimens were all used in the TA Instruments Q500 Thermogravmetric Analyzer to investigate weight percent lost and degradation. The TGA was under ambient air conditions at a heating rate of 10ºC/min. PEG control exhibited one transition with the peak at 380ºC. Cellulose and cellulose/ PEG films showed 3 major transitions. Interestingly, the cellulose/PEG film showed slightly elevated temperatures when compared to the corresponding transitions for cellulose control. The thermal gravimetric analysis (TGA) degradation curves were analyzed. Cellulose control film exhibited two zero order transitions, that indicate the independence of the rate of degradation from the amount on the initial substance. The activation energies for three transitions for cellulose and

  3. Thermal hydraulic parametric investigation of decay heat removal from degraded core of a sodium cooled fast Breeder reactor

    Energy Technology Data Exchange (ETDEWEB)

    Verma, Lokesh [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Kumar Sharma, Anil, E-mail: aksharma@igcar.gov.in [Reactor Design Group, Indira Gandhi Centre for Atomic Research, HBNI, Kalpakkam (India); Velusamy, K. [Reactor Design Group, Indira Gandhi Centre for Atomic Research, HBNI, Kalpakkam (India)

    2017-03-15

    Highlights: • Decay heat removal from degraded core of a typical SFR is highlighted. • Influence of number of DHXs in operation on PAHR is analyzed. • Investigations on structural integrity of the inner vessel and core catcher. • Feasibility study for retention of a part of debris in upper pool of SFR. - Abstract: Ensuring post accident decay heat removal with high degree of reliability following a Core Disruptive Accident (CDA) is very important in the design of sodium cooled fast reactors (SFR). In the recent past, a lot of research has been done towards the design of an in-vessel core catcher below the grid plate to prevent the core debris reaching the main vessel in a pool type SFR. However, during an energetic CDA, the entire core debris is unlikely to reach the core catcher. A significant part of the debris is likely to settle in core periphery between radial shielding subassemblies and the inner vessel. Failure of inner vessel due to the decay heat can lead to core debris reaching the main vessel and threatening its integrity. On the other hand, retention of a part of debris in core periphery can reduce the load on main core catcher. Towards achieving an optimum design of SFR and safety evaluation, it is essential to quantify the amount of heat generating core debris that can be retained safely within the primary vessel. This has been performed by a mathematical simulation comprising solution of 2-D transient form of the governing equations of turbulent sodium flow and heat transfer with Boussinesq approximations. The conjugate conduction-convection model adopted for this purpose is validated against in-house experimental data. Transient evolutions of natural convection in the pools and structural temperatures in critical components have been predicted. It is found that 50% of the core debris can be safely accommodated in the gap between radial shielding subassemblies and inner vessel without exceeding structural temperature limit. It is also

  4. The Assessment of Cement Mortars after Thermal Degradation by Acoustic Non-destructive Methods

    Science.gov (United States)

    Topolář, L.; Štefková, D.; Hoduláková, M.

    2017-10-01

    Thanks, the terrorist attacks on the worldwide interest in the design of structures for fire greatly increased. One of the advantages of concrete over other building materials is its inherent fire-resistive properties. The concrete structural components still must be able to withstand dead and live loads without collapse even though the rise in temperature causes a decrease in the strength and modulus of elasticity for concrete and steel reinforcement. In addition, fully developed fires cause expansion of structural components and the resulting stresses and strains must be resisted. This paper reports the results of measurements by Impact-echo method and measurement by ultrasound. Both methods are based on the acoustic properties of the material which are dependent on its condition. These acoustic methods allow identifying defects and are thus suitable for monitoring the building structure condition. The results are obtained in the laboratory during the degradation of composite materials based on cement by high-temperature.

  5. Module Degradation Mechanisms Studied by a Multi-Scale Approach

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, Steve; Al-Jassim, Mowafak; Hacke, Peter; Harvey, Steven P.; Jiang, Chun-Sheng; Gerber, Andreas; Guthrey, Harvey; Moutinho, Helio; Albin, David; To, Bobby; Tynan, Jerry; Moseley, John; Aguiar, Jeffery; Xiao, Chuanxiao; Waddle, John; Nardone, Marco

    2016-11-21

    A key pathway to meeting the Department of Energy SunShot 2020 goals is to reduce financing costs by improving investor confidence through improved photovoltaic (PV) module reliability. A comprehensive approach to further understand and improve PV reliability includes characterization techniques and modeling from module to atomic scale. Imaging techniques, which include photoluminescence, electroluminescence, and lock-in thermography, are used to locate localized defects responsible for module degradation. Small area samples containing such defects are prepared using coring techniques and are then suitable and available for microscopic study and specific defect modeling and analysis.

  6. Synthesis of new poly(ether-urethane-urea)s based on amino acid cyclopeptide and PEG: study of their environmental degradation.

    Science.gov (United States)

    Rafiemanzelat, Fatemeh; Fathollahi Zonouz, Abolfazl; Emtiazi, Giti

    2013-02-01

    Conventional polyurethanes (PUs) are among biomaterials not intended to degrade but are susceptible to hydrolytic, oxidative and enzymatic degradation in vivo. Biodegradable PUs are typically prepared from polyester polyols, aliphatic diisocyanates and chain extenders. In this work we have developed a degradable monomer based on α-amino acid to accelerate hard segment degradation. Thus a new class of degradable poly(ether-urethane-urea)s (PEUUs) was synthesized via direct reaction of 4,4'-methylene-bis(4-phenylisocyanate) (MDI), L-leucine anhydride (LA) and polyethylene glycol with molecular weight of 1,000 (PEG-1000) as polyether soft segment. The resulting polymers are environmentally biodegradable and thermally stable. Decomposition temperatures for 5 % weight loss occurred above 300 °C by TGA in nitrogen atmospheres. Some structural characterization and physical properties of these polymers before and after degradation in soil, river water and sludge are reported. The environmental degradation of the polymer films was investigated by SEM, FTIR, TGA, DSC, GPC and XRD techniques. A significant rate of degradation occurred in PEUU samples under river water and sludge condition. The polymeric films were not toxic to E. coli (Gram negative), Staphylococcus aureus and Micrococcus (Gram positive) bacteria and showed good biofilm formation on polymer surface. Our results show that hard segment degraded selectively as much as soft segment and these polymers are susceptible to degradation in soil and water. Thus our study shows that new environment-friendly polyurethane, which can degrade in soil, river water and sludge, is synthesized.

  7. FTIR and Thermal Studies on Nylon-66 and 30% Glass Fibre Reinforced Nylon-66

    Directory of Open Access Journals (Sweden)

    Julie Charles

    2009-01-01

    Full Text Available The present study deals with the characterization of the polymeric materials viz., nylon-66 and 30% glass fibre reinforced nylon-66 (GF Nylon-66 by employing FTIR and thermal measurements. The complete vibrational band assignment made available for nylon-66 and GF nylon-66 using FTIR spectra confirm their chemical structure. FTIR spectroscopy provides detailed information on polymer structure through the characteristic vibrational energies of the various groups present in the molecule. The thermal behavior of nylon-66 and GF nylon-66 essential for proper processing and fabrication was studied from TGA and DTA thermograms. The thermal stability of the polymers was studied from TGA and the activation energy for the degradation of the polymeric materials was calculated using Murray-White plot and Coats-Redfern plot. The polymer with high activation energy is more thermally stable. GF nylon-66 is found to be more thermally stable than nylon-66. The major thermal transitions such as crystalline melting temperature (Tm and degradation temperature (Td of the polymers were detected from DTA curves. The melting behaviour of the polymer depends upon the specimen history and in particular upon the temperature of crystallization. The melting behaviour also depends upon the rate at which the specimen is heated. The various factors such as molar mass and degree of chain branching govern the value of Tm in different polymers.

  8. LC, MSn and LC–MS/MS studies for the characterization of degradation products of amlodipine

    Directory of Open Access Journals (Sweden)

    Ravi N. Tiwari

    2015-02-01

    Full Text Available In the present study, comprehensive stress testing of amlodipine (AM was carried out according to International Conference on Harmonization (ICH Q1A(R2 guideline. AM was subjected to acidic, neutral and alkaline hydrolysis, oxidation, photolysis and thermal stress conditions. The drug showed instability in acidic and alkaline conditions, while it remained stable to neutral, oxidative, light and thermal stress. A total of nine degradation products (DPs were formed from AM, which could be separated by the developed gradient LC method on a C18 column. The products formed under various stress conditions were investigated by LC–MS/MS analysis. The previously developed LC method was suitably modified for LC–MS/MS studies by replacing phosphate buffer with ammonium acetate buffer of the same concentration (pH 5.0. A complete fragmentation pathway of the drug was first established to characterize all the degradation products using LC–MS/MS and multi-stage mass (MSn fragmentation studies. The obtained mass values were used to study elemental compositions, and the total information helped with the identification of DPs, along with its degradation pathway. Keywords: Amlodipine, LC–MS/MS, Characterization, Degradation pathway

  9. Investigation the Influence of Different Salts on the Degradation of Organic Dyes Using Non-Thermal Plasma

    Directory of Open Access Journals (Sweden)

    Ahmed El-Tayeb

    2016-10-01

    Full Text Available In dye decolorization tests a non-thermal plasma (NTP corona discharge generated by a high voltage pin-to-ground plate displayed 82% color removal within 11 min. Total color removal was accomplished after 28 min. Different salts such as KCl, NaCl, CaCl2 and AlCl3 were utilized to check the influence of conductivity changes on the dye decolorization process. Higher dye solution conductivity improved the color removal efficiency. The discharge energy and degradation efficiency were computed for diverse concentrations for NaCl, KCl, CaCl2 and AlCl3, whereby it was noticed that the salts generally have a small impact on the level of dye decolorization using corona discharge. In addition, the essential reactive species involved in the oxidation of organic dye compounds such as ozone (O3 generated in treated water and hydrogen peroxide (H2O2 were investigated and the energetic species that produced the non-thermal plasma at the optimum operation time were determined. Energy yields for decolorization and Electrical Energy per Order (EE/O were calculated for different concentrations of NaCl, KCl, CaCl2 and AlCl3. This work may help in designing plasma systems appropriate for treatment of industrial wastewaters polluted by dyes.

  10. Low-temperature thermal pre-treatment of municipal wastewater sludge: Process optimization and effects on solubilization and anaerobic degradation.

    Science.gov (United States)

    Nazari, Laleh; Yuan, Zhongshun; Santoro, Domenico; Sarathy, Siva; Ho, Dang; Batstone, Damien; Xu, Chunbao Charles; Ray, Madhumita B

    2017-04-15

    The present study examines the relationship between the degree of solubilization and biodegradability of wastewater sludge in anaerobic digestion as a result of low-temperature thermal pre-treatment. The main effect of thermal pre-treatment is the disintegration of cell membranes and thus solubilization of organic compounds. There is an established correlation between chemical oxygen demand (COD) solubilization and temperature of thermal pre-treatment, but results of thermal pre-treatment in terms of biodegradability are not well understood. Aiming to determine the impact of low temperature treatments on biogas production, the thermal pre-treatment process was first optimized based on an experimental design study on waste activated sludge in batch mode. The optimum temperature, reaction time and pH of the process were determined to be 80 °C, 5 h and pH 10, respectively. All three factors had a strong individual effect (p effect for temp. pH 2 (p = 0.002). Thermal pre-treatments, carried out on seven different municipal wastewater sludges at the above optimum operating conditions, produced increased COD solubilization of 18.3 ± 7.5% and VSS reduction of 27.7 ± 12.3% compared to the untreated sludges. The solubilization of proteins was significantly higher than carbohydrates. Methane produced in biochemical methane potential (BMP) tests, indicated initial higher rates (p = 0.0013) for the thermally treated samples (k hyd up to 5 times higher), although the ultimate methane yields were not significantly affected by the treatment. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Solar thermal electric power information user study

    Energy Technology Data Exchange (ETDEWEB)

    Belew, W.W.; Wood, B.L.; Marle, T.L.; Reinhardt, C.L.

    1981-02-01

    The results of a series of telephone interviews with groups of users of information on solar thermal electric power are described. These results, part of a larger study on many different solar technologies, identify types of information each group needed and the best ways to get information to each group. The report is 1 of 10 discussing study results. The overall study provides baseline data about information needs in the solar community. An earlier study identified the information user groups in the solar community and the priority (to accelerate solar energy commercialization) of getting information to each group. In the current study only high-priority groups were examined. Results from five solar thermal electric power groups of respondents are analyzed: DOE-Funded Researchers, Non-DOE-Funded Researchers, Representatives of Utilities, Electric Power Engineers, and Educators. The data will be used as input to the determination of information products and services the Solar Energy Research Institute, the Solar Energy Information Data Bank Network, and the entire information outreach community should be preparing and disseminating.

  12. Thermal Stabilization study of polyacrylonitrile fiber obtained by extrusion

    Directory of Open Access Journals (Sweden)

    Robson Fleming Ribeiro

    2015-12-01

    Full Text Available A low cost and environmental friendly extrusion process of the Polyacrylonitrile (PAN polymer was viabilized by using the 1,2,3-propanetriol (glycerol as a plasticizer. The characterization of the fibers obtained by this process was the object of study in the present work. The PAN fibers were heat treated in the range of 200 °C to 300 °C, which is the temperature range related to the stabilization/oxidation step. This is a limiting phase during the carbon fiber processing. The characterization of the fibers was made using infrared spectroscopy, thermal analysis and microscopy. TGA revealed that the degradation of the extruded PAN co-VA fibers between 250 °C and 350 °C, corresponded to a 9% weight loss to samples analyzed under oxidizing atmosphere and 18% when the samples were analyzed under inert atmosphere. DSC showed that the exothermic reactions on the extruded PAN co-VA fibers under oxidizing synthetic air was broader and the cyclization started at a lower temperature compared under inert atmosphere. Furthermore, FT-IR analysis correlated with thermal anlysis showed that the stabilization/oxidation process of the extruded PAN fiber were coherent with other works that used PAN fibers obtained by other spinning processes.

  13. Forced degradation study of racecadotril: Effect of co-solvent, characterization of degradation products by UHPLC-Q-TOF-MS/MS, NMR and cytotoxicity assay.

    Science.gov (United States)

    Chiguru, Vishnuvardhan; Lingesh, Allakonda; R, Srinivas; N, Satheeshkumar

    2016-09-05

    Racecadotril, an enkephalinase inhibitor, was subjected to hydrolysis (acidic and alkaline), oxidation, photolysis and thermal stress, as per ICH specified conditions. The drug showed extensive degradation under acidic, basic hydrolysis and oxidative stress conditions whereas, it was stable under other stress conditions. A total of seven degradation products (DPs) were observed. The chromatographic separation was optimized on Acquity HSS Cyano (100×2.1mm, 1.8μ) column using 0.1% formic acid and acetonitrile as mobile phase in gradient mode. Six DPs were characterised by LC-MS/MS and DP1 by GC-MS. The major DPs (DP 2 and DP 5) were isolated and characterised by NMR. This is a typical case of degradation where co solvent methanol reacts with racecadotril leading to the formation of pseudo DPs, DP 6 and DP 5. Interestingly the MS/MS spectra of protonated drug, DP 4 and DP 7 showed product ions which were formed due to intramolecular benzyl migrations. In vitro cytotoxic activity studies on isolated DP 2 and DP 5 revealed that the former has no cytotoxic nature, whereas the latter has potential pulmonary and hepatic toxicity. Copyright © 2016 Elsevier B.V. All rights reserved.

  14. Cases Studies of Irrigated Soil Degradation and Progradation

    Science.gov (United States)

    Zeyliger, Anatoly; Kust, German; Rozov, Sergey; Stoma, Galina

    2013-04-01

    Waterlogging and salination, along with interaction with other degradation processes, have not only caused the collapse of irrigation-based societies in the past, but are indeed threatening the viability of irrigation at present. The problem is global in scope. Decimation of natural ecosystems, deterioration of soil productivity depletion and pollution of water resources, and conflicts over dwindling supplies have become international problems closely linked with extension of irrigation development to large scale and associated impact to soil fertility and surrounding environment. Practical experience and scientific research done in the frame of FP6 DESIRE project provided an affirmative answer to the question - can irrigated agriculture be sustained for long time. In present contribution two case studies will be discussed and analysed in scope to compare different irrigation practises used for about 35 years and their impact to soil fertility. Investigated areas of both case studies are situated in the same Saratov Region of Russia at the left bank of middle part of Volga River with distance between about 100 km. First case study was developed during 2009-2010 by field trials at irrigated and surrounded areas of agricultural farms situated at Privolghskaya Irrigation System (Marksovsky District). Second case study was developed during summer of 2011 by field trial at experimental farm of research institute called VolgNIIGiM (Enghelsky District). During fields trail soil maps of both case studies were developed and compared with soil maps of the same areas done at 1970th before irrigation projects at both areas were started. Results of soil map comparison are showing that in the territory of first case study considerable soil degradation is taken place, but in the territory of the second case study a substantial soil progradation is taken place. Thus is supported by the time series of ground water monitoring at both irrigated areas. Obtained results will be

  15. Experimentation study of the degradation of polyoxymethylene. Application to the origin of the formaldehyde extended source in comets.

    Science.gov (United States)

    Fray, N.; Bénilan, Y.; Cottin, H.; Gazeau, M.-C.; Raulin, F.

    2003-04-01

    The formaldehyde (H2CO) observed in cometary atmospheres presents a so-called “extended source”. It means that its distribution in comae cannot be explained by a direct sublimation from the nucleus, but rather by a production in the coma. The origin of this extended source is still an unsolved question. The polyoxymethylene [formaldehyde polymers: (-CH2-O-)n] is sometime evoked as a possible parent molecule for this extended source. This polymer in solid state on cometary grains could release gaseous formaldehyde through thermal and photolytic degradation. We have developed an experimental program in order to study the chemical reactions of degradation of solid polymers by UV irradiation and heating. It provides identification of the degradation products and the determination of the photodegradation quantum yields or the thermodegradation kinetics. Those fundamental data are then included into a model of the outer coma in order to interpret observations. It leads to a very good agreement with Giotto observations if we assume that the cometary grains are made of about 4% POM by mass. Moreover the obtained results have also shown that the thermal degradation of POM is the predominant process over photodegradation at 1 au from the sun. So far the thermodegradation kinetics were measured for a small range of temperature and for only one type of POM molecular structure. So the incertitude on the activation barrier and on the frequency factor was large. We will present the improvements of our experimental setup and the new study of the thermal degradation of POM, which permit us to extract more reliable data. The application of this new set of data to the cometary environment will be discussed.

  16. The effect of 4-tert-butylpyridine and Li+ on the thermal degradation of TiO2 - bound ruthenium dye N719

    DEFF Research Database (Denmark)

    Nguyen, Phuong Tuyet; Hansen, Poul Erik; Lund, Torben

    2013-01-01

    Thermal stability experiments were performed at 100 °C of the dye-sensitized solar cell ruthenium dye N719. The experiments were performed as simple test-tube experiments carried out with colloidal solutions of N719-loaded TiO2 particles. The dye degradation was followed by the use of HPLC-couple...

  17. Accelerated Thermal-Aging-Induced Degradation of Organometal Triiodide Perovskite on ZnO Nanostructures and Its Effect on Hybrid Photovoltaic Devices.

    Science.gov (United States)

    Kumar, S; Dhar, A

    2016-07-20

    Organometal halide perovskite materials are presently some of the pacesetters for light harvesting in hybrid photovoltaic devices because of their excellent inherent electrical and optical properties. However, long-term durability of such perovskite materials remains a major bottleneck for their commercialization especially in countries with hot and humid climatic conditions, thus violating the international standards for photovoltaic technology. Albeit, TiO2 as an electron-transport layer has been well investigated for perovskite solar cells; the high-temperature processing makes it unsuitable for low-cost and large-scale roll-to-roll production of flexible photovoltaic devices. Herein, we have chosen low-temperature (<150 °C)-processable nanostructured ZnO as the electron-selective layer and used a two-step method for sensitizing ZnO nanorods with methylammonium lead iodide (MAPbI3) perovskite, which is viable for flexible photovoltaic devices. We have also elaborately addressed the effect of the annealing duration on the conversion of a precursor solution into the required perovskite phase on ZnO nanostructures. The investigations show that the presence of ZnO nanostructures accelerates the rate of degradation of MAPbI3 films under ambient annealing and thus requires proper optimization. The role of ZnO in enhancing the degradation kinetics of the perovskite layer has been investigated by X-ray photoelectron spectroscopy and a buffer layer passivation technique. The effect of the annealing duration of the MAPbI3 perovskite on the optical, morphological, and compositional behavior has been closely studied and correlated with the photovoltaic efficiency. The study captures the degradation behavior of the commercially interesting MAPbI3 perovskite on a ZnO electron-transport layer and thus can provide insight for developing alternative families of perovskite material with better thermal and environmental stability for application in low-cost flexible photovoltaic

  18. Application of non-thermal plasma reactor for degradation and detoxification of high concentrations of dye Reactive Black 5 in water

    Directory of Open Access Journals (Sweden)

    Dojčinović Biljana P.

    2016-01-01

    Full Text Available Degradation and detoxification efficiency of high concentrations of commercially available reactive textile dye Reactive Black 5 solution (40, 80, 200, 500, 1000 mg L-1, were studied. Advanced oxidation processes in water falling film based dielectric barrier discharge as a non-thermal plasma reactor were used. For the first time, this reactor was used for the treatment of high concentrations of organic pollutants such as reactive textile dye Reactive Black 5 in water. Solution of the dye is treated by plasma as thin water solution film that is constantly regenerated. Basically, the reactor works as a continuous flow reactor and the electrical discharge itself takes place at the gas-liquid interphase. The dye solution was recirculated through the reactor with an applied energy density of 0-374 kJ L-1. Decolorization efficiency (% was monitored by UV-VIS spectrophotometric technique. Samples were taken after every recirculation (~ 22 kJ L-1 and decolorization percent was measured after 5 min and 24 h of plasma treatment. The efficiency of degradation (i.e. mineralization and possible degradation products were also tracked by determination of the chemical oxygen demand (COD and by ion chromatography (IC. Initial toxicity and toxicity of solutions after the treatment were studied with Artemia salina test organisms. Efficiency of decolorization decreased with the increase of the dye concentration. Complete decolorization, high mineralization and non-toxicity of the solution (<10 % were acomplished after plasma treatment using energy density of 242 kJ L-1, while the initial concentrations of Reactive Black 5 were 40 and 80 mg L-1. [Projekat Ministarstva nauke Republike Srbije, br. 172030 i br. 171034

  19. Characterization and degradation studies on synthetic polymers for aerospace application

    Science.gov (United States)

    Hsu, M. T. S.

    1982-01-01

    The anti-misting additive for jet fuels known as FM-9 (proprietary polymer) was characterized by elemental analysis, solubility studies and molecular weight determination. Physical properties of surface tension, viscosity, specific gravity and other physical parameters were determined. These results are compared with properties of polyisobutylene and fuels modified with the same; the misting characteristics of polyisobutylene and FM-9 in Jet A fuel are included. Characterization and degradation of phthalocyanine and its derivatives were accomplished by use of a mass spectrometer and a pyroprobe solid pyrolyzer. Metal phthalocyanine tetracarboxylic acids and phthalocyanine-tetraamine cured epoxies were studied. Epoxy/graphite composite panels were exposed to a NASA-Ames radiant panel fire simulator in the flaming and non-flaming modes; toxic gases of HCN and HZS were measured along with oxygen, Co2, Co, and organic gases.

  20. Thermal Conductivity Degradation and Microstructural Damage Characterization in Low-Dose Ion Beam-Irradiated 3C-SiC

    Science.gov (United States)

    Chauhan, Vinay S.; Riyad, M. Faisal; Du, Xinpeng; Wei, Changdong; Tyburska-Püschel, Beata; Zhao, Ji-Cheng; Khafizov, Marat

    2017-12-01

    This study assesses the impact of low-dose and low-temperature irradiation on the properties of cubic silicon carbide (3C-SiC). 3C-SiC was irradiated with Kr ions to different fluences at 420 K (147 °C). Raman spectroscopy was used to investigate the impact of irradiation-induced defects on vibrational modes and time-domain thermoreflectance (TDTR) was used to measure thermal conductivity. We observe a noticeable reduction in thermal conductivity with increasing fluence. Analysis of Raman spectra reveals the longitudinal optical (LO) and transverse optical (TO) modes with noticeable peak broadening of LO mode with increasing dosage. We also notice a decrease of ratio of peak intensities of LO and TO modes in irradiated samples. We observe a correlation between the thermal conductivity reduction and the decrease in the peak intensity ratio and attribute this to the accumulation of charged vacancy defects.

  1. Performance Degradation of Thermal Parameters during Cycle Ageing of High Energy Density Ni-Mn-Co based Lithium-Ion Battery Cells

    DEFF Research Database (Denmark)

    Stanciu, Tiberiu; Stroe, Daniel Loan; Swierczynski, Maciej Jozef

    2016-01-01

    The accelerated demand for electrifying the transportation sector, coupled with the continuous improvement of rechargeable batteries’ characteristics, have made modern high-energy Lithium-ion (Li-ion) batteries the standard choice for hybrid and electric vehicles (EVs). Consequently, Li......-ion batteries’ electrochemical and thermal characteristics are very important topics, putting them at the forefront of the research. Along with the electrical performance of Li-ion battery cells, their thermal behavior needs to be accurately predicted during operation and over the lifespan of the application...... as well, since the thermal management of the battery is crucial for the safety of the EV driver. Moreover, the thermal management system can significantly lower the degradation rate of the battery pack and thus reduce costs. In this paper, the thermal characterization of a commercially available Nickel...

  2. High Temperature Degradation of Advanced Thermal and Environmental Barrier Coatings (TEBCs) by CaO-MgO-Al2O3-SiO2 (CMAS)

    Science.gov (United States)

    Costa, Gustavo; Zhu, Dongming

    2017-01-01

    There is increasing interest in the degradation studies of thermal and environmental barrier coatings (TEBCs) of gas turbines by molten CaO-MgO-Al2O3-SiO2 (CMAS). CMAS minerals are usually referred as silica-containing sand dust and volcano ash materials that are carried by the intake air into gas turbines, e.g. aircraft engines. The low-melting deposits react at high temperatures (1000C) with the coating materials. This causes degradation and accelerated coating failure of the static and rotating components of the turbine engines. We discuss some preliminary results of the reactions between CMAS and Rare-Earth (RE Y, Yb, Dy, Gd, Nd and Sm) oxide stabilized ZrO2 or HfO2 systems, and the stability of the resulting oxides and silicates. Plasma sprayed hollow tube samples (outer diameter 4.7 mm, wall thickness 0.76 mm and 26 mm height) were half filled with CMAS powder, wrapped and sealed with platinum foil, and heat- treated at 1310 C for 5h. Samples were characterized by differential scanning calorimetry, X-ray diffraction and cross section electron microscopy analysis.

  3. Dielectric and thermal studies on gel grown strontium tartrate ...

    Indian Academy of Sciences (India)

    /fulltext/boms/033/04/0377-0382. Keywords. Permittivity; polarization effects; strontium tartrate; thermal properties; dielectric properties. Abstract. Results of dielectric and thermal studies on strontium tartrate pentahydrate crystals are described.

  4. Thermal degradation chemistry of ruthenium complexes in the dye-sensitized solar cell and strategies for reducing the dark current

    DEFF Research Database (Denmark)

    Lund, Torben

    In the last decades dye-sensitized solar cells (DSCs) have extensively been studied. From an economical point of view, DSCs are of high interest because the manufacturing costs of DSCs devices are significantly lower compared with other solar devices such as silicon cells. One of the success...... on the surface of a semiconductor anode (TiO2). In my lecture, I will present and overview of our degradation investigations of the ruthenium dyes N719, Z907 and C106 with the general structure RuLL´(NCS)2 and show how detailed degradation mechanistic knowledge is important in the developing of DSC cells...... transfer from the photo anode to the mediator R+ and the oxidized dye S+ we have applied electrochemical grafting strategies to attach an electrical isolation layer of mono and multilayers of organic molecules on the TiO2 photo anode [3]....

  5. Study of SEY degradation of amorphous carbon coatings

    CERN Document Server

    Bundaleski, N.; Santos, A.; Teodoro, O.M.N.D.; Silva, A.G.

    2013-04-22

    Deposition of low secondary electron yield (SEY) carbon coatings by magnetron sputtering onto the inner walls of the accelerator seems to be the most promising solution for suppressing the electron cloud problem. However, these coatings change their electron emission properties during long term exposure to air. The ageing process of carbon coated samples with initial SEY of about 0.9 received from CERN is studied as a function of exposure to different environments. It is shown that samples having the same initial SEY may age with different rates. The SEY increase can be correlated with the surface concentration of oxygen. Annealing of samples in air at 100-200 {\\deg}C reduces the ageing rate and even recovers previously degraded samples. The result of annealing is reduction of the hydrogen content in the coatings by triggering its surface segregation followed by desorption.

  6. studies of action of heavy metals on caffeine degradation

    African Journals Online (AJOL)

    User

    2015-12-02

    Dec 2, 2015 ... ABSTRACT. Caffeine is an important naturally occurring compound that can be degraded by bacteria. Excessive caffeine consumption is known to have some adverse problems. Previously, Leifsonia sp. strain SIU capable of degrading caffeine was isolated from agricultural soil. The bacterium was tested ...

  7. Studies of action of heavy metals on caffeine degradation by ...

    African Journals Online (AJOL)

    The isolate was encapsulated in gellan gum and its ability to degrade caffeine in the presence of heavy metals was determined. Out of the nine heavy metals tested, Copper (Cu), Mercury (Hg), and Silver (Ag) had significant effects on caffeine degradation at 1mg/L. Therefore, the concentration of these heavy metals was ...

  8. Thermal performance sensitivity studies in support of material modeling for extended storage of used nuclear fuel

    Energy Technology Data Exchange (ETDEWEB)

    Cuta, Judith M. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Suffield, Sarah R. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Fort, James A. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Adkins, Harold E. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2013-08-15

    The work reported here is an investigation of the sensitivity of component temperatures of a storage system, including fuel cladding temperatures, in response to age-related changes that could degrade the design-basis thermal behavior of the system. The purpose of these sensitivity studies is to provide a realistic example of how changes in the physical properties or configuration of the storage system components can affect temperatures and temperature distributions. The magnitudes of these sensitivities can provide guidance for identifying appropriate modeling assumptions for thermal evaluations extending long term storage out beyond 50, 100, 200, and 300 years.

  9. Degradation of Bimetallic Model Electrocatalysts ___ an in situ XAS Study

    Energy Technology Data Exchange (ETDEWEB)

    Friebel, Daniel

    2011-06-22

    One of the major challenges in the development of clean energy fuel cells is the performance degradation of the electrocatalyst, which, apart from poisoning effects, can suffer from corrosion due to its exposure to a harsh environment under high potentials. In this communication, we demonstrate how interactions of Pt with a transition metal support affect not only, as commonly intended, the catalytic activity, but also the reactivity of Pt towards oxide formation or dissolution. We use two well-defined single-crystal model systems, Pt/Rh(111) and Pt/Au(111) and a unique x-ray spectroscopy technique with enhanced energy resolution to monitor the potential-dependent oxidation state of Pt, and find two markedly different oxidation mechanisms on the two different substrates. This information can be of great significance for future design of more active and more stable catalysts. We have studied the potential-induced degradation of Pt monolayer model electrocatalysts on Rh(111) and Au(111) single-crystal substrates. The anodic formation of Pt oxides was monitored using in situ high energy resolution fluorescence detection x-ray absorption spectroscopy (HERFD XAS). Although Pt was deposited on both substrates in a three-dimensional island growth mode, we observed remarkable differences during oxide formation that can only be understood in terms of strong Pt-substrate interactions throughout the Pt islands. Anodic polarization of Pt/Rh(111) up to +1.6 V vs. RHE (reversible hydrogen electrode) leads to formation an incompletely oxidized passive layer, whereas formation of PtO2 and partial Pt dissolution is observed for Pt/Au(111).

  10. Micromechanical Modeling Study of Mechanical Inhibition of Enzymatic Degradation of Collagen Tissues

    Science.gov (United States)

    Tonge, Theresa K.; Ruberti, Jeffrey W.; Nguyen, Thao D.

    2015-01-01

    This study investigates how the collagen fiber structure influences the enzymatic degradation of collagen tissues. We developed a micromechanical model of a fibrous collagen tissue undergoing enzymatic degradation based on two central hypotheses. The collagen fibers are crimped in the undeformed configuration. Enzymatic degradation is an energy activated process and the activation energy is increased by the axial strain energy density of the fiber. We determined the intrinsic degradation rate and characteristic energy for mechanical inhibition from fibril-level degradation experiments and applied the parameters to predict the effect of the crimped fiber structure and fiber properties on the degradation of bovine cornea and pericardium tissues under controlled tension. We then applied the model to examine the effect of the tissue stress state on the rate of tissue degradation and the anisotropic fiber structures that developed from enzymatic degradation. PMID:26682825

  11. Photocatalytic degradation of methyl orange using ZnO nanopowders synthesized via thermal decomposition of oxalate precursor method

    Science.gov (United States)

    Kaur, Japinder; Bansal, S.; Singhal, Sonal

    2013-05-01

    ZnO nanoparticles were synthesized by thermal decomposition of oxalate precursor method. The nanopowders were characterized using powder X-ray diffraction technique and scanning electron microscopy and sample was found to have hexagonal wurtzite structure of ZnO. Average crystallite size of ZnO was found to be ∼27 nm. The photocatalytic activity of ZnO was evaluated by using methyl orange (MO) as probe molecule. It was inferred from control experiments that presence of both ZnO and UV light is necessary for photodegradation. From photocatalytic experiment it was observed that MO is completely degraded in 80 min when the amount of catalyst is 1 g/L and initial concentration of MO is 0.03 mM. The effect of dye concentration, catalyst loading and solution pH on photodegradation rate was also investigated. It was found that optimal conditions for photodegradation of MO are 1 g/L catalyst at a solution pH 9. Photodegradation of MO was found to follow pseudo-first order kinetics. Langmuir-Hinshelwood model was also used to describe the photodegradation process.

  12. In vitro study of proteolytic degradation of rat histidine decarboxylase.

    Science.gov (United States)

    Olmo, M T; Urdiales, J L; Pegg, A E; Medina, M A; Sánchez-Jiménez, F

    2000-03-01

    Mammalian ornithine decarboxylase (ODC) is a very unstable protein which is degraded in an ATP-dependent manner by proteasome 26S, after making contact with the regulatory protein antizyme. PEST regions are sequences described as signals for protein degradation. The C-terminal PEST region of mammalian ODC is essential for its degradation by proteasome 26S. Mammalian histidine decarboxylase (HDC) is also a short-lived protein. The full primary sequence of mammalian HDC contains PEST-regions at both the N- and C-termini. Rat ODC and different truncated and full versions of rat HDC were expressed in vitro. In vitro degradation of rat ODC and rat 1-512 HDC were compared. Like ODC, rat 1-512 HDC is degraded mainly by an ATP-dependent mechanism. However, antizyme has no effect on the degradation of 1-512 HDC. The use of the inhibitors MG-132 and lactacystine significantly inhibited the degradation of 1-512 HDC, suggesting that a ubiquitin-dependent, proteasome 26S proteolytic pathway is involved. Results obtained with the different modifications of rat HDC containing all three PEST regions (full version, 1-656 HDC), only the N-terminal PEST region (1-512 HDC), or no PEST region (69-512 HDC), indicate that the N-terminal (1-69) fragment, but not the C-terminal fragment, determines that the HDC protein is a proteasome substrate in vitro.

  13. SPECTROSCOPIC STUDIES AND THERMAL ANALYSIS OF LEAD ...

    African Journals Online (AJOL)

    a

    KEY WORDS: Lead, Tin, Schiff base, Infrared spectra, Thermal analysis. INTRODUCTION ... elemental analysis, infrared spectra as well as by their thermal analysis (DTA and TG). Analysis results are reported in Table 1. The percentage of lead and tin metals were determined using ..... PbO + 5C + 10C2H2 + N2 + CO.

  14. The comparison of differences in flammability and thermal degradation between cotton fabrics treated with phosphoramidate derivatives

    Science.gov (United States)

    The effectiveness of a phosphoramidate Tetraethyl piperazine-1,4-diyldiphosphoramidate (TEPP) as a flame retardant (FR) on cotton twill fabrics was compared with that of a previously studied Diethyl 4-methylpiperazin-1-ylphosphoramidate (DEPP). TEPP was formed in a reaction between two phosphonates...

  15. Mecanismos de degradação e estabilização térmica do PVC: a review Mechanisms of PVC thermal degradation and stabilization

    Directory of Open Access Journals (Sweden)

    Antonio Rodolfo Jr.

    2007-09-01

    Full Text Available Este artigo apresenta uma revisão sobre o tema degradação térmica e estabilização do PVC. Os principais mecanismos de degradação desta resina são apresentados e correlacionados com os defeitos estruturais presentes no polímero, bem como os princípios de estabilização.This paper presents a review of PVC thermal degradation and stabilization. The main degradation mechanisms for this resin are shown and correlated to structural defects present in the polymer, as well the stabilization principles

  16. Electrochemical degradation, kinetics & performance studies of solid oxide fuel cells

    Science.gov (United States)

    Das, Debanjan

    Linear and Non-linear electrochemical characterization techniques and equivalent circuit modelling were carried out on miniature and sub-commercial Solid Oxide Fuel Cell (SOFC) stacks as an in-situ diagnostic approach to evaluate and analyze their performance under the presence of simulated alternative fuel conditions. The main focus of the study was to track the change in cell behavior and response live, as the cell was generating power. Electrochemical Impedance Spectroscopy (EIS) was the most important linear AC technique used for the study. The distinct effects of inorganic components usually present in hydrocarbon fuel reformates on SOFC behavior have been determined, allowing identification of possible "fingerprint" impedance behavior corresponding to specific fuel conditions and reaction mechanisms. Critical electrochemical processes and degradation mechanisms which might affect cell performance were identified and quantified. Sulfur and siloxane cause the most prominent degradation and the associated electrochemical cell parameters such as Gerisher and Warburg elements are applied respectively for better understanding of the degradation processes. Electrochemical Frequency Modulation (EFM) was applied for kinetic studies in SOFCs for the very first time for estimating the exchange current density and transfer coefficients. EFM is a non-linear in-situ electrochemical technique conceptually different from EIS and is used extensively in corrosion work, but rarely used on fuel cells till now. EFM is based on exploring information obtained from non-linear higher harmonic contributions from potential perturbations of electrochemical systems, otherwise not obtained by EIS. The baseline fuel used was 3 % humidified hydrogen with a 5-cell SOFC sub-commercial planar stack to perform the analysis. Traditional methods such as EIS and Tafel analysis were carried out at similar operating conditions to verify and correlate with the EFM data and ensure the validity of the

  17. Degradation in PV Encapsulation Transmittance: An Interlaboratory Study Toward a Climate-Specific Test

    Energy Technology Data Exchange (ETDEWEB)

    Miller, David C.; Hacke, Peter L.; Kempe, Michael D.; Wohlgemuth, John H.; Annigoni, Eleonora; Sculati-Meillaud, Fanny; Ballion, Amal; Kohl, Michael; Bokria, Jayesh G.; Bruckman, Laura S.; French, Roger H.; Burns, David; Phillips, Nancy H.; Feng; Jiangtao; Elliott, Lamont; Scott, Kurt P.; Fowler, Sean; Gu, Xiaohong; Honeker, Christian C.; Khonkar, Hussam; Perret-Aebi, Laure-Emmanuelle; Shioda, Tsy

    2015-06-14

    Reduced optical transmittance of encapsulation resulting from ultraviolet (UV) degradation has frequently been identified as a cause of decreased PV module performance through the life of installations in the field. The present module safety and qualification standards, however, apply short UV doses only capable of examining design robustness or 'infant mortality' failures. Essential information that might be used to screen encapsulation through product lifetime remains unknown. For example, the relative efficacy of xenon-arc and UVA-340 fluorescent sources or the typical range of activation energy for degradation is not quantified. We have conducted an interlaboratory experiment to provide the understanding that will be used towards developing a climate- and configuration-specific (UV) weathering test. Five representative, known formulations of EVA were studied in addition to one TPU material. Replicate laminated silica/polymer/silica specimens are being examined at 14 institutions using a variety of indoor chambers (including Xe, UVA-340, and metal-halide light sources) or field aging. The solar-weighted transmittance, yellowness index, and the UV cut-off wavelength, determined from the measured hemispherical transmittance, are examined to provide understanding and guidance for the UV light source (lamp type) and temperature used in accelerated UV aging tests. Index Terms -- reliability, durability, thermal activation.

  18. Remote sensing study on geomorphological degradation of Sarda Sagar reservoir.

    Science.gov (United States)

    Kumar, Prem; Saxena, K K; Tyagi, B C; Nayak, Ashok K; Pandey, N N; Haldar, R S; Mahanta, P C

    2013-11-01

    An attempt was made to estimate the geomorphological degradation due to sedimentation of Sarda Sagar reservoir, located in Pilibhit and Udhamsingh Nagar, district of Uttar Pradash and Uttarakhand respectively. The study was conducted using multidated IRS LIISS III remote sensing data for the year 2006-2007. Using satellite images of different seasons during 2006-2007, a total of 45.23 million m3 volume of sedimentation was computed in-between the 183.704 m and 190.504 m elevation. The reservoir has lost 11.72 % of the total capacity of water storage and an average rate of sedimentation was calculated as 0.26 % per year. Due to this sedimentation the new feeder channel of Sarda Sagar is choked with silt and the water flow from this channel has almost stopped. The morphology of the reservoir has been changed due to sedimentation during the period 1962 to 2007. This has altered breeding ground of fishes since important indigenous fish species which need flowing water condition to perform the breeding. This study would be helpful for the planners to manage the reservoir and to assess the biological productivity.

  19. Thermal degradation behaviors of polyethylene and polypropylene. Part I: Pyrolysis kinetics and mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Aboulkas, A.; El Harfi, K. [Laboratoire de Recherche sur la Reactivites des Materiaux et l' Optimisation des Procedes & lt; & lt; REMATOP& gt; & gt; , Departement de chimie, Faculte des Sciences Semlalia, Universite Cadi Ayyad, BP 2390, 40001 Marrakech (Morocco); Laboratoire Interdisciplinaire de Recherche en Sciences et Techniques, Faculte polydisciplinaire de Beni-Mellal, Universite Sultan Moulay Slimane, BP 592, 23000 Beni-Mellal (Morocco); El Bouadili, A. [Laboratoire Interdisciplinaire de Recherche en Sciences et Techniques, Faculte polydisciplinaire de Beni-Mellal, Universite Sultan Moulay Slimane, BP 592, 23000 Beni-Mellal (Morocco)

    2010-07-15

    Study of the decomposition kinetics is an important tool for the development of polymer recycling in industrial scale. In this work, the activation energy and the reaction model of the pyrolysis of high density polyethylene (HDPE), low density polyethylene (LDPE) and polypropylene (PP) have been estimated from non-isothermal kinetic results. Firstly, the activation energy values obtained by Friedman, Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa isoconversional methods, are 238-247 kJ/mol for HDPE, 215-221 kJ/mol for LDPE and 179-188 kJ/mol for PP. Secondly, the appropriate conversion model of the process was determined by Coats-Redfern and Criado methods. The pyrolysis reaction models of HDPE and LDPE are accounted for by ''Contracting Sphere'' model, whereas that of PP by ''Contracting Cylinder'' model. (author)

  20. Thermal Stress Awareness, Self-Study #18649

    Energy Technology Data Exchange (ETDEWEB)

    Chochoms, Michael [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-11-15

    Thermal stresses can expose individuals to a variety of health hazards at work, home, and play. Every year thermal stresses cause severe injuries and death to a large range of people, from elderly people in cities during summer heat waves to young people engaged in winter mountaineering. Awareness is the key to preventing the health hazards associated with thermal stresses. This course is designed for personnel at Los Alamos National Laboratory (LANL). It addresses both heat and cold stresses and discusses their factors, signs and symptoms, treatments, and controls.

  1. Degradation of metallic materials studied by correlative tomography

    Science.gov (United States)

    Burnett, T. L.; Holroyd, N. J. H.; Lewandowski, J. J.; Ogurreck, M.; Rau, C.; Kelley, R.; Pickering, E. J.; Daly, M.; Sherry, A. H.; Pawar, S.; Slater, T. J. A.; Withers, P. J.

    2017-07-01

    There are a huge array of characterization techniques available today and increasingly powerful computing resources allowing for the effective analysis and modelling of large datasets. However, each experimental and modelling tool only spans limited time and length scales. Correlative tomography can be thought of as the extension of correlative microscopy into three dimensions connecting different techniques, each providing different types of information, or covering different time or length scales. Here the focus is on the linking of time lapse X-ray computed tomography (CT) and serial section electron tomography using the focussed ion beam (FIB)-scanning electron microscope to study the degradation of metals. Correlative tomography can provide new levels of detail by delivering a multiscale 3D picture of key regions of interest. Specifically, the Xe+ Plasma FIB is used as an enabling tool for large-volume high-resolution serial sectioning of materials, and also as a tool for preparation of microscale test samples and samples for nanoscale X-ray CT imaging. The exemplars presented illustrate general aspects relating to correlative workflows, as well as to the time-lapse characterisation of metal microstructures during various failure mechanisms, including ductile fracture of steel and the corrosion of aluminium and magnesium alloys. Correlative tomography is already providing significant insights into materials behaviour, linking together information from different instruments across different scales. Multiscale and multifaceted work flows will become increasingly routine, providing a feed into multiscale materials models as well as illuminating other areas, particularly where hierarchical structures are of interest.

  2. Thermal conductivity of penta-graphene from molecular dynamics study.

    Science.gov (United States)

    Xu, Wen; Zhang, Gang; Li, Baowen

    2015-10-21

    Using classical equilibrium molecular dynamics simulations and applying the original Tersoff interatomic potential, we study the thermal transport property of the latest two dimensional carbon allotrope, penta-graphene. It is predicted that its room-temperature thermal conductivity is about 167 W/mK, which is much lower than that of graphene. With normal mode decomposition, the accumulated thermal conductivity with respect to phonon frequency and mean free path is analyzed. It is found that the acoustic phonons make a contribution of about 90% to the thermal conductivity, and phonons with mean free paths larger than 100 nm make a contribution over 50%. We demonstrate that the remarkably lower thermal conductivity of penta-graphene compared with graphene results from the lower phonon group velocities and fewer collective phonon excitations. Our study highlights the importance of structure-property relationship and provides better understanding of thermal transport property and valuable insight into thermal management of penta-graphene.

  3. Study of the influence of combustion parameters on the formation of SO{sub 2}, NO and CO during the thermal degradation of phytosanitary products currently used in West Africa; Etude de l'influence des parametres de combustion sur la formation de SO{sub 2}, de NO et de CO lors de la degradation thermique de produits phytosanitaires d'usage courant en Afrique de l'Ouest

    Energy Technology Data Exchange (ETDEWEB)

    Bouda, M.; Segda, B.G.; Koulidiati, J. [Ouagadougou Univ., Ouagadougou (Burkina Faso). Laboratoire de physique et de chimie de l' environnement; Rogaume, T. [Poitiers a Niort Univ., Chasseneuil-du-Poitou (France). Ecole national superieure de mecanique et d' aerotechnique, Laboratoire de combustion et detonique; Sawadogo, P.W. [Inst. de l' environnement et de recherches agricoles, Ouagadougou (Burkina Faso). Laboratoire sol-eau-plante

    2008-05-15

    The challenge of treating soils in West Africa that have been contaminated with pesticides was discussed. Incineration is considered to be a viable method for the disposal of toxic industrial wastes, including phytosanitary products. The 2 main phytosanitary products currently used in West Africa are Cyperthion D and Cyperthion O. These 2 products were incinerated in a small-scale study in order to determine the influence of combustion parameters on the production of nitrogen monoxide (NO), carbon monoxide (CO), and sulphur dioxide (SO{sub 2}). The incineration process was optimized in order to reduce these emissions and other toxic gases. The study showed that there is a good correlation between the generation of these pollutants during the incineration of phytosanitary wastes and combustion parameters such as oxygen concentration, temperature, and residence time in the reactor core. Emissions of NO and SO{sub 2} decreased with an increase in residence time, but increased with higher local oxygen concentrations and higher combustion temperatures in the reactor core. CO emissions were found to increase with an increase in residence time, but decrease with higher temperatures and higher local oxygen concentrations. The results were used to pursue large-scale assays, in a rotatory incinerator, for the thermal processing of expired phytosanitary products. 22 refs., 2 tabs., 5 figs.

  4. Formation of volatile chemicals from thermal degradation of less volatile coffee components: quinic acid, caffeic acid, and chlorogenic acid.

    Science.gov (United States)

    Moon, Joon-Kwan; Shibamoto, Takayuki

    2010-05-12

    The less volatile constituents of coffee beans (quinic acid, caffeic acid, and chlorogenic acid) were roasted under a stream of nitrogen, air, or helium. The volatile degradation compounds formed were analyzed by gas chromatography and gas chromatography-mass spectrometry. Caffeic acid produced the greatest amount of total volatiles. Quinic acid and chlorogenic acid produced a greater number of volatiles under the nitrogen stream than under the air stream. These results suggest that the presence of oxygen does not play an important role in the formation of volatile compounds by the heat degradation of these chemicals. 2,5-Dimethylfuran formed in relatively large amounts (59.8-2231.0 microg/g) in the samples obtained from quinic acid and chlorogenic acid but was not found in the samples from caffeic acid. Furfuryl alcohol was found in the quinic acid (259.9 microg/g) and caffeic acid (174.4 microg/g) samples roasted under a nitrogen stream but not in the chlorogenic sample. The three acids used in the present study do not contain a nitrogen atom, yet nitrogen-containing heterocyclic compounds, pyridine, pyrrole, and pyrazines, were recovered. Phenol and its derivatives were identified in the largest quantities. The amounts of total phenols ranged from 60.6 microg/g (quinic acid under helium) to 89893.7 microg/g (caffeic acid under helium). It was proposed that phenol was formed mainly from quinic acid and that catechols were formed from caffeic acid. Formation of catechol from caffeic acid under anaerobic condition indicates that the reaction participating in catechol formation was not oxidative degradation.

  5. Hubble Space Telescope Metallized Teflon(registered trademark) FEP Thermal Control Materials: On-Orbit Degradation and Post-Retrieval Analysis

    Science.gov (United States)

    Townsend, Jacqueline A.; Hansen, Patricia A.; Dever, J. A.; deGroh, K. K.; Banks, B.; Wang, L.; He, C.

    1988-01-01

    During the Hubble Space Telescope (HST) Second Servicing Mission (SM2), degradation of unsupported Teflon(Registered Trademark) FEP (fluorinated ethylene propylene), used as the outer layer of the multilayer insulation (MLI) blankets, was evident as large cracks on the telescope light shield. A sample of the degraded outer layer was retrieved during the mission and returned to Earth for ground testing and evaluation. The results of the Teflon(Registered Trademark) FEP sample evaluation and additional testing of pristine Teflon(Registered Trademark) FEP led the investigative team to theorize that the HST damage was caused by thermal cycling with deep-layer damage from electron and proton radiation which allowed the propagation of cracks along stress concentrations , and that the damage increased with the combined total dose of electrons, protons, UV and x-rays along with thermal cycling. This paper discusses the testing and evaluation of the retrieved Teflon(Registered Trademark) FEP.

  6. A study of force extension and force degradation of orthodontic latex elastics: An in vitro study

    Directory of Open Access Journals (Sweden)

    Parag Vishnu Gangurde

    2013-01-01

    Full Text Available Introduction: The purpose of this study was to determine the force values of different orthodontic latex elastics at different extensions when subjected to testing in dry and wet conditions. This study also aims to determine and compare the force degradation of the elastics produced by four manufacturers at different extensions and at regular intervals. Materials and Methods: 5/16 inch lumen medium (Green and ¼ inch lumen medium elastics (blue of 4 companies were used. The elastics were stretched on a correx gauge to two times and three times the inner lumen diameter and at a fixed distance of 25 mm (dry test.The elastics were stretched at the specific distances and then immersed in artificial saliva and checked after 24 and 48 h (wet test. The data was analyzed using Student′s t-test. Results: Force degradation increases with time. Force degradation percentage values vary from 5% to a maximum of 25%. Conclusions: Thus from the study, the clinician can know the force degradation rates of elastics of two different sizes, manufactured by four different companies. This study also shows that though, the force degradation during the 2 nd day was found to be significant in most of the elastics, it is not sufficient to justify daily change of elastics.

  7. Thermal damage study on diamond tools at varying laser heating time and temperature by Raman spectroscopy and SEM

    CSIR Research Space (South Africa)

    Masina, BN

    2011-07-01

    Full Text Available At present it is known that diamond tool degrades with time as it is normally used at high temperatures. One of the question the authors like to answer in this study is whether thermally induced problems in diamond tool arise as a result...

  8. The individual and cumulative effect of brominated flame retardant and polyvinylchloride (PVC) on thermal degradation of acrylonitrile-butadiene-styrene (ABS) copolymer.

    Science.gov (United States)

    Brebu, Mihai; Bhaskar, Thallada; Murai, Kazuya; Muto, Akinori; Sakata, Yusaku; Uddin, Md Azhar

    2004-08-01

    Acrylonitrile-butadiene-styrene (ABS) copolymers without and with a polybrominated epoxy type flame retardant were thermally degraded at 450 degrees C alone (10 g) and mixed with polyvinylchloride (PVC) (8 g/2 g). Gaseous and liquid products of degradation were analysed by various gas chromatographic methods (GC with TCD, FID, AED, MSD) in order to determine the individual and cumulative effect of bromine and chlorine on the quality and quantity of degradation compounds. It was found that nitrogen, chlorine, bromine and oxygen are present as organic compounds in liquid products, their quantity depends on the pyrolysed polymer or polymer mixture. Bromophenol and dibromophenols were the main brominated compounds that come from the flame retardant. 1-Chloroethylbenzene was the main chlorine compound observed in liquid products. It was also determined that interactions appear at high temperatures during decomposition between the flame retardant, PVC and the ABS copolymer.

  9. Identification of volatile butyl rubber thermal-oxidative degradation products by cryofocusing gas chromatography/mass spectrometry (cryo-GC/MS).

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Jonell Nicole; White, Michael Irvin; Bernstein, Robert; Hochrein, James Michael

    2013-02-01

    Chemical structure and physical properties of materials, such as polymers, can be altered as aging progresses, which may result in a material that is ineffective for its envisioned intent. Butyl rubber formulations, starting material, and additives were aged under thermal-oxidative conditions for up to 413 total days at up to 124 ÀC. Samples included: two formulations developed at Kansas City Plant (KCP) (#6 and #10), one commercially available formulation (#21), Laxness bromobutyl 2030 starting material, and two additives (polyethylene AC-617 and Vanax MBM). The low-molecular weight volatile thermal-oxidative degradation products that collected in the headspace over the samples were preconcentrated, separated, and detected using cryofocusing gas chromatography mass spectrometry (cryo-GC/MS). The majority of identified degradation species were alkanes, alkenes, alcohols, ketones, and aldehydes. Observations for Butyl #10 aged in an oxygen-18 enriched atmosphere (18O2) were used to verify when the source of oxygen in the applicable degradation products was from the gaseous environment rather than the polymeric mixture. For comparison purposes, Butyl #10 was also aged under non-oxidative thermal conditions using an argon atmosphere.

  10. Stability studies and degradation kinetics of some commercially ...

    African Journals Online (AJOL)

    The shelf-life of the various brands of the drug was predicted from Arrhenius equation and compared with their manufacturers' label claim. Results confirmed that increase in temperature led to increase in the degradation rate constants for the various brands of the drug. The shelf-life ranged from 35.0 to 80.8 weeks for all ...

  11. Degradation Studies on LiFePO4 cathode

    DEFF Research Database (Denmark)

    Scipioni, Roberto; Jørgensen, Peter Stanley; Hjelm, Johan

    2015-01-01

    In this paper we examine a laboratory LiFePO4 (LFP) cathode and propose a simple model that predicts the electrode capacity as function of C-rate, number of cycles and calendar time. Microcracks were found in Li1-xFePO4 particles in a degraded LFP electrode and low-acceleration voltage (1 kV) FIB...

  12. Forced Oxidative degradation study of Zolpidem tartrate by HPLC ...

    African Journals Online (AJOL)

    indicating assay method developed for the determination of zolpidem in the presence of its degradation products. Zolpidem was refluxed with 6% peroxide at 60°C for 48 hrs with constant stirring. The method was developed and optimized by ...

  13. Preliminary Studies on Microbial Degradation of Plastics Used in ...

    African Journals Online (AJOL)

    The conditions for the pigmentation could not be ascertained. However, the pigment absorbed radiation within UV region and formed a precipitate with ferric chloride. ... DSC measurement further showed ÄH as 89.936 J/g before and 31.945 J/g after microbial degradation. A decrease was also observed in the crystallization ...

  14. studies of action of heavy metals on caffeine degradation

    African Journals Online (AJOL)

    User

    2015-12-02

    Dec 2, 2015 ... This is the first report of effect of heavy metals on caffeine degradation by immobilised Leifsonia sp. strain SIU. Keywords: ... that it may have on the human body. Prolonged caffeine consumption not only ..... influenced by chemical industry, gold mining and Hg mining (Li et al., 2009). In Malaysia, the main ...

  15. An experimental study on thermal stability of biodiesel fuel

    Science.gov (United States)

    Zhu, Yiying

    Biodiesel fuel, as renewable energy, has been used in conventional diesel engines in pure form or as biodiesel/diesel blends for many years. However, thermal stability of biodiesel and biodiesel/diesel blends has been minimally explored. Aimed to shorten this gap, thermal stability of biodiesel is investigated at high temperatures. In this study, batch thermal stressing experiments of biodiesel fuel were performed in stainless steel coils at specific temperature and residence time range from 250 to 425 °C and 3 to 63 minutes, respectively. Evidence of different pathways of biodiesel fuel degradation is demonstrated chromatographically. It was found that biodiesel was stable at 275 °C for a residence time of 8 minutes or below, but the cis-trans isomerization reaction was observed at 28 minutes. Along with isomerization, polymerization also took place at 300 °C at 63 minutes. Small molecular weight products were detected at 350 °C at 33 minutes resulting from pyrolysis reactions and at 360 °C for 33 minutes or above, gaseous products were produced. The formed isomers and dimers were not stable, further decomposition of these compounds was observed at high temperatures. These three main reactions and the temperature ranges in which they occurred are: isomerization, 275--400 °C; polymerization (Diels-Alder reaction), 300--425 °C; pyrolysis reaction, ≥350 °C. The longer residence time and higher temperature resulted in greater decomposition. As the temperature increased to 425 °C, the colorless biodiesel became brownish. After 8 minutes, almost 84% of the original fatty acid methyl esters (FAMEs) disappeared, indicating significant fuel decomposition. A kinetic study was also carried out subsequently to gain better insight into the biodiesel thermal decomposition. A three-lump model was proposed to describe the decomposition mechanism. Based on this mechanism, a reversible first-order reaction kinetic model for the global biodiesel decomposition was shown to

  16. High-temperature degradation of one-dimensional metallodielectric (W/SiO2) photonic crystal as selective thermal emitter for thermophotovoltaic system

    Science.gov (United States)

    Kim, Jin Hwan; Jung, Sang Min; Shin, Moo Whan

    2017-10-01

    In this paper, thermal stability of a one-dimensional metallodielectric photonic crystal (1D MDPhC) structure based on W and SiO2 for thermophotovoltaic systems is reported. The thermal degradation mechanism of the structure, in its operating temperature range, is thoroughly investigated by using energy dispersive spectroscopy (EDS) with transmission electron microscope (TEM) and depth-profiling X-ray photoelectron spectroscopy (XPS). It is found that the structure is entirely destroyed under 1400 K by an inter-diffusion process forming a mixture of W and SiO2 without measurable oxidization of W. But, long-term annealing results in oxidization of W layer even at a lower temperature of 1300 K. During the long-term annealing, oxygen atoms in outside atmosphere are believed to cause oxidation of the upper W layer below the top SiO2 layer. Additionally, delaminated spots are observed over the surface. These thermal behaviors are potential clues to prevent or minimize thermal degradation of the multilayer structure under high temperature operation.

  17. In vitro study on the degradation of lithium-doped hydroxyapatite for bone tissue engineering scaffold

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yaping; Yang, Xu; Gu, Zhipeng; Qin, Huanhuan [College of Polymer Science and Engineering, Sichuan University, Chengdu 610065 (China); Li, Li [Department of Oncology, The 452 Hospital of Chinese PLA, Chengdu, Sichuan Province 610021 (China); Liu, Jingwang [College of Polymer Science and Engineering, Sichuan University, Chengdu 610065 (China); Yu, Xixun, E-mail: yuxixun@163.com [College of Polymer Science and Engineering, Sichuan University, Chengdu 610065 (China)

    2016-09-01

    Li-doped hydroxyapatite (LiHA) which is prepared through introducing low dose of Li into hydroxyapatite (HA) has been increasingly studied as a bone tissue-engineered scaffold. The degradation properties play a crucial role in the success of long-term implantation of a bone tissue-engineered construct. Herein, the in vitro degradation behaviors of LiHA scaffolds via two approaches were investigated in this study: solution-mediated degradation and osteoblast-mediated degradation. In solution-mediated degradation, after being immersed in simulated body fluid (SBF) for some time, some characteristics of these scaffolds (such as release of ionized lithium and phosphate, pH change, mechanical properties, cytocompatibility and SEM surface characterization) were systematically tested. A similar procedure was also employed to research the degradation behaviors of LiHA scaffolds in osteoblast-mediated degradation. The results suggested that the degradation in SBF and degradation in culture medium with cell existed distinguishing mechanisms. LiHA scaffolds were degraded via a hydrolytic mechanism when they were soaked in SBF. Upon degradation, an apatite precipitation (layer) was formed on the surfaces of scaffolds. While a biological mechanism was presented for the degradation of scaffolds in cell-mediated degradation. Compared with pure HA, LiHA scaffolds had a better effect on the growth of osteoblast cells, meanwhile, the release amount of PO{sub 4}{sup 3−} in a degradation medium indicated that osteoblasts could accelerate the degradation of LiHA due to the more physiological activities of osteoblast. According to the results from compressive strength test, doping Li into HA could enhance the strength of HA. Moreover, the results from MTT assay and SEM observation showed that the degradation products of LiHA scaffolds were beneficial to the proliferation of osteoblasts. The results of this research can provide the theoretical basis for the clinical application of Li

  18. Exploring the microbiota dynamics related to vegetable biomasses degradation and study of lignocellulose-degrading bacteria for industrial biotechnological application

    Science.gov (United States)

    Ventorino, Valeria; Aliberti, Alberto; Faraco, Vincenza; Robertiello, Alessandro; Giacobbe, Simona; Ercolini, Danilo; Amore, Antonella; Fagnano, Massimo; Pepe, Olimpia

    2015-02-01

    The aims of this study were to evaluate the microbial diversity of different lignocellulosic biomasses during degradation under natural conditions and to isolate, select, characterise new well-adapted bacterial strains to detect potentially improved enzyme-producing bacteria. The microbiota of biomass piles of Arundo donax, Eucalyptus camaldulensis and Populus nigra were evaluated by high-throughput sequencing. A highly complex bacterial community was found, composed of ubiquitous bacteria, with the highest representation by the Actinobacteria, Proteobacteria, Bacteroidetes and Firmicutes phyla. The abundances of the major and minor taxa retrieved during the process were determined by the selective pressure produced by the lignocellulosic plant species and degradation conditions. Moreover, cellulolytic bacteria were isolated using differential substrates and screened for cellulase, cellobiase, xylanase, pectinase and ligninase activities. Forty strains that showed multienzymatic activity were selected and identified. The highest endo-cellulase activity was seen in Promicromonospora sukumoe CE86 and Isoptericola variabilis CA84, which were able to degrade cellulose, cellobiose and xylan. Sixty-two percent of bacterial strains tested exhibited high extracellular endo-1,4-ß-glucanase activity in liquid media. These approaches show that the microbiota of lignocellulosic biomasses can be considered an important source of bacterial strains to upgrade the feasibility of lignocellulose conversion for the `greener' technology of second-generation biofuels.

  19. Solvent-free preparation of polylactic acid fibers by melt electrospinning using umbrella-like spray head and alleviation of problematic thermal degradation

    Directory of Open Access Journals (Sweden)

    Liu Yong

    2012-01-01

    Full Text Available Melt electrospinning is an even simpler and safer method compared with the solution electrospinning in the production of ultra-fine fibers. Polylactic acid (PLA is a biodegradable and resorbable aliphatic ester that has received significant attention in recent years. PLA is easily degradable at high temperature in the process of melt electrospinning. High efficient fibers were made using our designed umbrella-like spray head spinning facility in this work. To find how to alleviate the problematic degradation and what factors could be relevant to degradation, temperature, relative molecular mass, Differential Scanning Calorimeter and X-ray Diffraction patterns before and after spinning were investigated and compared with each other. Results showed that fibers were facile shorten and fractured when spun at 245°C while the relative molecular mass of PLA fibers decreased markedly as compared with that spun at 210°C. To hinder the degradation, couple of experimental efforts were implemented with adding antioxidants, raising spinning voltage, lowering temperature, and reducing residence time. After such efforts, it was observed that the relative molecular mass of the PLA fibers was higher than those without inputting any efforts. The effect of antioxidant 1010 was found the most promising on the alleviation of PLA problematic thermal degradation.

  20. Thermal Study of Anhydrides Cured Tetrafunctional Cardo Epoxy Resin

    Directory of Open Access Journals (Sweden)

    Jignesh P. Patel

    2013-01-01

    Full Text Available Tetrafunctional cardo epoxy resin (EBCF was cured by using 10 wt% maleic anhydride (MA, pyromellitic dianhydride (PMDA, phthalic anhydride (PA, tetrahydrophthalic anhydride (THPA, tetrabromophthalic anhydride (TBPA, and tetrachlorophthalic anhydride (TCPA as hardeners at 120°C for 40–105 min (gel time and then postcured 1 h at 130°C. Gel time is found to depend on the structure of the anhydrides used. Cured samples were found insoluble in common solvents. Cured and uncured EBCF were characterized by FTIR, DSC, and TGA techniques. Cured and uncured resins followed multistep degradation reactions. Kinetic parameters, namely, order of degradation, energy of activation, frequency factor, and entropy change, were determined according to the Anderson-Freeman method and interpreted in light of the nature of hardeners used for curing purpose. The resins followed integral or fractional order degradation kinetics. Complex degradation reactions are due to different types of linkages in cured resins. Both nature and structure of resin and hardeners affected the curing behavior and the resultant thermal properties of the cured resins.

  1. Laboratory study of oxytetracycline degradation kinetics in animal manure and soil.

    Science.gov (United States)

    Wang, Qiquan; Yates, Scott R

    2008-03-12

    Oxytetracycline (OTC) is a major member of tetracyclines, which are widely administered to animals in confined feeding operations. To diminish the contamination of OTC in the environment, which results from the application of OTC-containing manure as fertilizer in agricultural lands, OTC degradation kinetics in manure and soil under laboratory aerobic conditions was investigated. OTC degradation kinetics was found to be described well by the previously developed availability-adjusted first-order model at all moistures and low temperatures (degradation increased with increasing moisture from 60 to 100%. However, OTC became very persistent in water-saturated manure. Increasing temperature greatly accelerated OTC degradation, and thermal degradation became noticeable at high temperatures (>or=35 degrees C) in manure. At 25 degrees C, OTC half-life was determined to be 8.1 days in manure with moisture at 80%, 33 days in manure-amended soil (amendment ratio at 5%), and 56 days in non-amended soil with both moistures at 20%, demonstrating that OTC may become persistent in the environment once it is released from manure into soil. No pronounced effect of coexistent antibiotics on OTC degradation in manure was observed.

  2. Spectroscopic, thermal and biological studies of coordination ...

    Indian Academy of Sciences (India)

    Administrator

    (Cl)(H2O)3]⋅xH2O (M = Cr(III) and Y(III), x = 5 and 6, respectively) were obtained and characterized by physicochemical and spectroscopic methods. The IR spectra of the complexes suggest that the sulfasalazine behaves as a monoanionic bidentate ligand. The thermal decomposition of the complexes as well as ...

  3. Synthesis, spectroscopy, thermal studies and supramolecular ...

    Indian Academy of Sciences (India)

    The chains thus formed are further cross-linked with the aid of H-donor bonds from both the free as well as the coordinated Im. Both 1 and 2 exhibit - stacking interactions. Complex 1 is thermally more stable as compared to 2, and both complexes can be dehydrated to the corresponding anhydrous complexes by heating ...

  4. Thermally stimulated luminescence studies in combustion ...

    Indian Academy of Sciences (India)

    Wintec

    Photoluminescence; thermoluminescence; gamma irradiation; colour centres. 1. Introduction. Thermally stimulated luminescence (TSL), also called thermoluminescence (TL), is extensively used as a techni- que in dosimetry. The energy absorbed by a phosphor on being exposed to some ionizing radiation is released as.

  5. Synthesis, Photophysical, Electrochemical and Thermal Studies of ...

    Indian Academy of Sciences (India)

    solutions in toluene, CH2Cl2 and CHCl3 in a 1 cm path length quartz cuvette as well as thermally deposited thin solid films, on SHIMADZU UV–2401PC at room temperature. The excitation and emission spec- tra were recorded on a Perkin Elmer LS 55 Fluores- cence spectrophotometer. Fluorescence quantum yield.

  6. Tribological Studies of Dynamic Thermal Seal Materials

    Science.gov (United States)

    DeMange, Jeffrey J.; Taylor, Shawn C.

    2016-01-01

    Thermal seals are required on high-speed vehicles in many dynamic applications such as variable inlets in propulsion systems and control surfaces. These seals, often referred to as dynamic thermal seals, must not only mitigate inboard heat transfer, but must also exhibit sufficient durability when scrubbed against mating surfaces. For high-temperature high-speed vehicle applications, the mating surfaces are often made from thermal protection system (TPS) materials, which are typically rougher and more abrasive than TPS materials used at lower temperatures. The high-temperature TPS materials used can include non-ablative (e.g., lightweight porous oxides, ceramic matrix composites) andor ablative systems (e.g., phenolic systems). Due to the increased need for durable high-temperature dynamic seals, researchers working with the NASA Glenn Research Center embarked on an effort to (a) characterize the tribological performance of state-of-the-art thermal seal materials against a variety of TPS materials and (b) develop approaches for improved wear resistance. Tests were conducted using a recently upgraded high-temperature tribometer to assess wear resistance for a variety of tribopairs under multiple conditions. This data will begin to frame the challenges of using these materials and eventually permit an improved ability to design and implement these critical TPS components.

  7. A Study of Solar Thermal Propulsion System Enhancement via Thermal Storage and Thermal-electric Conversion

    Science.gov (United States)

    2010-03-24

    material. Molybdenum has a thermal conductivity of 138 W/mK, while rheniums is much lower at 39.6 W/mK 2 . Zirconium Boride (ZrB2) and Hafnium Boride ...14,000 Iridium 77 2739 213 147 $42,000 Niobium 41 2750 323 53.7 $170 Molybdenum 42 2896 390 138 $100 The materials listed in Table 1 do not...this paper, several materials with melting points above 3000 K are boride compounds and several of those that are not borides contain elements which

  8. a Study on the Thermal Vibration Analysis of the Graphite Disk Under Thermal Shock

    Science.gov (United States)

    Lee, Young-Shin; Kim, Jae-Hoon; Kim, Hyun-Soo; Kim, Duck-Hoi; Ku, Seong-Hoi; Moon, Soon-Il

    Graphite is applied to structural material of the high temperature reactor and nozzle of high energy rocket engine. The excessive vibration and stress field can be occurred for this material due to the severe thermal condition. In this study, the thermal stress and vibration characteristics of ATJ graphite under high temperature condition are investigated by finite element analysis (FEA). The specimen is designed as a disk shape in order to simulate the rocket nozzle combustion condition. The experiment of thermal heat is also conducted using by CO2 laser.

  9. A thermal study of an encapsulated electrical transformer

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, A. [Unidad Geotermia, Temixco (Mexico). Instituto de Investigaciones Electricas; Espinosa-Paredes, G. [Universidad Autonoma Metropolitana, Vicentina (Mexico). Dpto. de Ingenieria de Procesos e Hidraulica; Hernandez, I. [Centro de Sistemas de Manufactura, Nuevo Leon (Mexico). Instituto Tecnologico y de Estudios Superiores de Monterrey

    2002-11-01

    A thermal study of a 45 KVA-prototype encapsulated transformer is described. Casting resin systems were used as insulating systems for encapsulated electric transformers. Normal transformer operation is at full load and, thus the conductor and insulating system becomes hot owing to current circulation through the winding. To determine the various temperature distributions throughout the transformer, the thermal properties of the insulating system and boundary conditions must be known, so that hot spots are located via numerical modelling and maximum permissible temperatures are not attained. Results presented herein include thermal conductivity, thermal diffusivity, and specific heat capacity. Thermal conductivity was obtained experimentally by means of the line-source technique at various temperatures, between room temperature and 155{sup o}C which is the thermal limit of class F insulators. The thermal diffusivity was obtained by parameter estimation by fitting an approximate analytical model to the temperature-time data of the thermal conductivity experiment. Specific heat capacity was obtained from the definition of thermal diffusivity and the insulating-system density. In order to improve the electrical performance of the transformer criteria, a numerical simulation of the different dielectric structures was made using computer program. The boundary conditions for the thermal simulation stage were also determined experimentally from temperature test runs. Finally, in order to obtain data for thermal design, a numerical simulation of the high tension winding was carried out. The thermal simulation stage was performed at different current densities in the conductor with and without electrostatic shields to determine the temperature field and maximum attainable temperatures. Maximum transformer temperature were found to be 15-20{sup o}C below its thermal limit and a correlation of maximum temperature as function of circulating current was developed for design

  10. Competitive interaction degrades target selection: an ERP study.

    Science.gov (United States)

    Hilimire, Matthew R; Mounts, Jeffrey R W; Parks, Nathan A; Corballis, Paul M

    2009-09-01

    Localized attentional interference (LAI) occurs when attending to a visual object degrades processing of nearby objects. Competitive interaction accounts of LAI explain the phenomenon as the result of competition among objects for representation in extrastriate cortex. Here, we examined the N2pc component of the event-related potential (ERP) as a likely neural correlate of LAI. In Experiment 1, participants responded to the orientation of a target while ignoring a nearby decoy. At small target-decoy separations, N2pc amplitude was attenuated whereas the amplitude of a later, positive component (Ptc) was potentiated. Experiment 2 ruled out sensory explanations of these effects. The N2pc results are consistent with the idea that spatially mediated competition for representation in extrastriate cortex degrades target selection. Moreover, the Ptc may reflect a bias signal needed to resolve the competition at smaller target-decoy separations.

  11. Experimental study of degradable polylactic acid punctal plugs

    Directory of Open Access Journals (Sweden)

    Zhi-Yong Wu

    2013-12-01

    Full Text Available AIM: To develope a type of absorbable punctal plug.METHODS:To produce punctal plugs with polylactic acid. To model the dry eye rabbits by removing of the main lacrimal gland, the third eyelid and Harder's gland; To record the results of Schirmer test and the pyrogen test before and after the implantation of punctal plugs; Schirmer test and pyrogen test were performed before and after punctal plug implantation. The lacrimal plugs histocompatibility and the degradation time were also observed. RESULTS: It can significantly improve the Schirmer test of dry eye rabbits to implant punctual plugs. No pyrogenic reactions had been discovered. Good histocompatibility was achieved and the plugs would degrade within 2 months. CONCLUSION:The plugs produced by polylactic acid biodegradable material, which is widely used in biomedical fields, have no toxic effects on rabbits. It's safe and inexpensive, so it's valuable for further research and clinical application.

  12. Studies of Degradation of Plasticized Polyvinyl Chloride (PPVC)

    OpenAIRE

    Doina Elena Gavrilă

    2016-01-01

    Commercial plasticizers are introduced in Polyvinyl Chloride (PVC) to obtain flexibility, high elongation to break, durability, resistance to heat and chemicals. Very used plasticizers are phthalates, most commonly phthalate being di-2-ethyl hexyl phthalate (DEHP). The phthalates are not chemically bound to PVC and can migrate from different devices and objects due to the influence of temperature, or to other types of degradation. In article are presented the harm effects of phtha...

  13. Liquid-phase non-thermal plasma-prepared N-doped TiO(2) for azo dye degradation with the catalyst separation system by ceramic membranes.

    Science.gov (United States)

    Cheng, Hsu-Hui; Chen, Shiao-Shing; Cheng, Yi-Wen; Tseng, Wei-Lun; Wang, Yi-Hui

    2010-01-01

    This study strived to improve the photocatalytic activity by using liquid-phase non-thermal plasma (LPNTP) technology for preparing N-doping TiO(2) as well as to separate/recover the N-dope TiO(2) particles by using ceramic ultrafiltration membrane process. The yellow color N-doped TiO(2) photocatalysts, obtained through the LPNTP process, were characterized with UV-Vis spectroscopy, X-ray diffraction (XRD), and electron spectroscopy for chemical analysis (ESCA). The UV-Vis spectrum of N-doped TiO(2) showed that the absorption band was shifted to 439 nm and the band gap was reduced to 2.82 eV. The structure analysis of XRD spectra showed that the peak positions and the crystal structure remained unchanged as anatase after plasma-treating at 13.5 W for 40 min. The photocatalytic activity of N-doped TiO(2) was evaluated by azo dyes under visible light, and 63% of them was degraded after 16 hours in a continuous-flow photocatalytic system. For membrane separation/recover system, the recovery efficiency reached 99.5% after the ultrafiltration had been carried out for 90 min, and the result indicated that the photocatalyst was able to be separated/recovered completely.

  14. Thermal conductivity and thermal rectification in graphene nanoribbons: a molecular dynamics study.

    Science.gov (United States)

    Hu, Jiuning; Ruan, Xiulin; Chen, Yong P

    2009-07-01

    We have used molecular dynamics to calculate the thermal conductivity of symmetric and asymmetric graphene nanoribbons (GNRs) of several nanometers in size (up to approximately 4 nm wide and approximately 10 nm long). For symmetric nanoribbons, the calculated thermal conductivity (e.g., approximately 2000 W/m-K at 400 K for a 1.5 nm x 5.7 nm zigzag GNR) is on the similar order of magnitude of the experimentally measured value for graphene. We have investigated the effects of edge chirality and found that nanoribbons with zigzag edges have appreciably larger thermal conductivity than nanoribbons with armchair edges. For asymmetric nanoribbons, we have found significant thermal rectification. Among various triangularly shaped GNRs we investigated, the GNR with armchair bottom edge and a vertex angle of 30 degrees gives the maximal thermal rectification. We also studied the effect of defects and found that vacancies and edge roughness in the nanoribbons can significantly decrease the thermal conductivity. However, substantial thermal rectification is observed even in the presence of edge roughness.

  15. Studies on Post-Irradiation DNA Degradation in Micrococcus Radiodurans, Strain RII51

    DEFF Research Database (Denmark)

    Auda, H.; Emborg, C.

    1973-01-01

    The influence of irradiation condition on post-irradiation DNA degradation was studied in a radiation resistant mutant of M. radiodurans, strain ${\\rm R}_{{\\rm II}}5$. After irradiation with 1 Mrad or higher more DNA is degraded in cells irradiated in wet condition than in cells irradiated...... with the same doses in dry condition. Cells irradiated with 2 Mrad degrade 60% of the DNA after irradiation in wet condition, 45% of the DNA after irradiation in dry condition. In cells irradiated with 1.5 and 2 Mrad in wet condition the rate of degradation is lower than after irradiation in dry condition....

  16. Preparation of Diatomite Supported Nano Zinc Oxide Composite Photocatalytic Material and Study on its Formaldehyde Degradation

    Science.gov (United States)

    Xiao, Liguang; Pang, Bo

    2017-09-01

    This experiment used zinc nitrate as precursor, ethanol as solvent and polyethylene glycol as dispersant, diatomite as carrier, diatomite loaded nano Zinc Oxide was prepared by sol-gel method, in addition, the formaldehyde degradation was studied by two kinds of experimental methods: preparation and loading, preparation and post loading, The samples were characterized by SEM, XRD, BET and IR. Experimental results showed that: Diatomite based nano Zinc Oxide had a continuous adsorption and degradation of formaldehyde, formaldehyde gas with initial concentration was 0.7mg/m3, after 36h degradation, the concentration reached 0.238mg/m3, the degradation rate reached to 66%.

  17. Thermal stability and kinetics of degradation of deoxynivalenol, deoxynivalenol conjugates and ochratoxin A during baking of wheat bakery products.

    Science.gov (United States)

    Vidal, Arnau; Sanchis, Vicente; Ramos, Antonio J; Marín, Sonia

    2015-07-01

    The stability of deoxynivalenol (DON), deoxynivalenol-3-glucoside (DON-3-glucoside), 3-acetyldeoxynivalenol (3-ADON), 15-acetyldeoxynivalenol (15-ADON), de-epoxy-deoxynivalenol (DOM-1) and ochratoxin A (OTA) during thermal processing has been studied. Baking temperature, time and initial mycotoxin concentration in the raw materials were assayed as factors. An improved UPLC-MS/MS method to detect DON, DON-3-glucoside, 3-ADON, 15-ADON and DOM-1 in wheat baked products was developed in the present assay. The results highlighted the importance of temperature and time in mycotoxin stability in heat treatments. OTA is more stable than DON in a baking treatment. Interestingly, the DON-3-glucoside concentrations increased (>300%) under mild baking conditions. On the other hand, it was rapidly reduced under harsh conditions. The 3-ADON decreased during the heat treatment; while DOM-1 increased after the heating process. Finally, the data followed first order kinetics for analysed mycotoxins and thermal constant rates (k) were calculated. This parameter can be a useful tool for prediction of mycotoxin levels. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Study of thermal destruction of lignin

    Energy Technology Data Exchange (ETDEWEB)

    Reti, M.; Hojnos, J.

    1979-01-01

    Using thermofractography, infra- and mass-spectrometry and other techniques thermal destruction of lignin was investigated at a temp. range of 200 to 500/sup 0/C. At temp. from 225 to 330/sup 0/C first of all splitting of ..beta..-aryil- and benzyl-ether binds between principal phenylpropane links of lignin, thus forming derivative phenols, vinyl guaiacol, coinferyl alcohol and aldehyde and respective syringic derivatives. At temp. of 350/sup 0/C splitting of C-C connections occurs in the lateral chain, forming guaiacol, 2,6-dimetoxiphenol and their saturated 4-alkyl derivatives. With a speeded up pyrolysis process, thermal destruction of lignin occurs at temp. of greater than or equal to 400/sup 0/C, with 62% of overall quantity derived at 500-550/sup 0/C with an overall tar release of about 30.

  19. Mechanism and Kinetics Study for Photocatalytic Oxidation Degradation: A Case Study for Phenoxyacetic Acid Organic Pollutant

    Directory of Open Access Journals (Sweden)

    Kian Mun Lee

    2015-01-01

    Full Text Available Photocatalysis is a rapidly expanding technology for wastewater treatment, including a wide range of organic pollutants. Thus, understanding the kinetics and mechanism of the photocatalytic oxidation (PCO for degradation of phenoxyacetic acid (PAA is an indispensable component of risk assessment. In this study, we demonstrated that the central composite design (CCD coupled with response surface methodology (RSM was successfully employed to probe the kinetics and mechanism of PCO degradation for PAA using an efficient zinc oxide (ZnO photocatalyst. In our current case study, four independent factors such as ZnO dosage, initial concentration of PAA, solution pH, and reaction time on the PCO degradation for PAA were examined in detail. Based on our results obtained from RSM analyses, an efficient pathway leading to the high degradation rate (>90% was applying 0.4 g/L of ZnO dosage with 16 mg/L of concentration of PAA at pH 6.73 for 40 minutes. The experimental results were fitted well with the derived response model with R2 = 0.9922. This study offers a cost-effective way for probing our global environmental water pollution issue.

  20. Thermal Oxidation of Polyolefins by Mild Pro-Oxidant Additives Based on Iron Carboxylates and Lipophilic Amines: Degradability in the Absence of Light and Effect on the Adhesion to Paperboard

    Directory of Open Access Journals (Sweden)

    Tuan-Anh Nguyen

    2015-08-01

    Full Text Available Marine and inland pollution by non-degradable plastic bags and other plastic articles is a topic of great concern. Natural degradation processes based on oxidation of plastic pollutants could possibly contribute to limit the extent of pollution. Thermal degradation of polyolefins in the absence of light by non-polluting pro-oxidants has not been presented before. In this study, we show that two amines, stearyl amine and [(3-(11-aminoundecanoyl amino propane-1-] silsesquioxane (amino-POSS in combination with ferric stearate (FeSt3 tremendously accelerate the thermal oxidation of polyolefins compared with reference samples. Both amines and FeSt3 are to a large extent based on renewable resources. Polyethylene and polypropylene samples containing less than 100 ppm of iron and 1% of amine were extremely brittle after 10 days in a circulation oven in the absence of light. No significant degradation could be seen with samples containing iron but no amine. In a different application, the initial oxidation of polyethylene can be used in order to increase its adhesion to cardboard. Excellent adhesion between polyethylene and cardboard is important for liquid packaging based on renewable resources. Amino-POSS has been chosen for food packaging applications due to its expected lower leakage from polyethylene (PE compared with stearyl amine. Film samples of PE/amino-POSS/FeSt3 blends were partly oxidized in a circulation oven. The oxidation was documented by increased carbonyl index (CI and melt flow index (MFI. The limited extent of oxidation has been proved by unchanged tensile strength and only moderate changes in elongation at break when compared to reference polyethylene films containing no FeSt3 or amino-POSS. The PE/amino-POSS/FeSt3 blends were compression moulded to paperboard. The adhesion of non-aged blends to paperboard decreased with increasing amino-POSS content which is in good compliance with an earlier reported lubricant effect of high

  1. Comparative study of thermal insulation boards from leaf and bark ...

    African Journals Online (AJOL)

    The aim of this study was to compare the performance of insulation boards made from leave and bark fibres of Pilios tigma thonningii L.in terms of density, water absorption, apparent thermal conductivity, specific heat and thermal diffusivity. The leave and the bark fibres were prepared in form of squared boards of 200 mm x ...

  2. Thermal Decompositon Studies Of Pre-Irradiated Nickel (II) Azides ...

    African Journals Online (AJOL)

    The effect of pre-irradiation on the thermal decomposition of three samples of nickel (II) azide was studied. It was found that the rates of thermal decomposition of Ni(OH)N3 increased substantially with increase in pre-irradiation dosage. The initial reaction rates change from time-dependant nucleation law for the unirradiated ...

  3. Application of new thermoanalytical methods for the investigation of thermal and thermo-oxidative degradation mechanisms and network formation polymers

    OpenAIRE

    Dümichen, Erik

    2016-01-01

    Due to the macromolecular structure of polymers, the application of thermoanalytical meth-ods is advantageous. Thus two new thermoanalytical techniques were developed. The use of these methods was demonstrated on the basis of real examples and the results were com-pared to established thermoanalytical methods. For the thermal and thermo-oxidative analysis of gaseous thermal decomposition products the thermogravimetry (TGA) was coupled with thermal desorption gas chromatography-mass spectro...

  4. Human resilience in a degrading environment: A case study in China

    NARCIS (Netherlands)

    Haaften, A.J.; Yu, Z.R.; Vijver, van den F.J.R.

    2004-01-01

    Psychological aspects of environmental degradation were studied among 753 Chinese farmers. A good fit was found for a structural equation model postulating a relationship between various input variables (i.e. environmental degradation, socio-economic status, education, coping, and locus of control),

  5. Land degradation in the Sudan Savanna of Ghana: A case study in ...

    African Journals Online (AJOL)

    Land degradation in the area is the result of interaction between the physical and human environments. Physical environmental characteristics influencing land degradation include soil texture, topography and rainfall. The soils in the study area are developed over granite and Birrimian phyllite. In the granitic areas soil ...

  6. Assessing the costs of land degradation: a case study for the Puentes catchment, South East Spain

    NARCIS (Netherlands)

    Hein, L.G.

    2007-01-01

    Whereas many studies point out the economic benefits of controlling land degradation through sustainable land management (SLM) approaches, there is often a lack of local adoption of SLM techniques. Analysis of the local impacts and costs of land degradation is critical for understanding farmers'

  7. Degradation study of pesticides used in Dourados-MS

    Directory of Open Access Journals (Sweden)

    Virgilio Vieira de Olival

    2012-10-01

    Full Text Available The intensive use and irregular disposal of pesticides in agriculture has caused serious environmental and health problems. In this work was evaluated the efficiency of UV and some advanced oxidation processes involving photo-Fenton reaction, O3 and O3/UV for the treatment of aqueous solutions containing commercial and standard pesticides. The results showed that the combination of UV radiation in alkaline means with O3 significantly increased the efficiency of the process of degradation and the photo-Fenton system is a promising alternative for the treatment of effluents containing pesticides.

  8. Prototype of thermal degradation for radioactive wastes of low and intermediate level; Prototipo de degradacion termica para desechos radiactivos de nivel bajo e intermedio

    Energy Technology Data Exchange (ETDEWEB)

    Diaz A, L.V.; Pacheco S, J.O.; Pacheco P, M.; Monroy G, F.; Emeterio H, M. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)]. e-mail: lauradiazarch@yahoo.com.mx

    2005-07-01

    At the present time, the scientific, academic, industrial and technological activities, generate great quantity of radioactive wastes of low and intermediate level (DRNBI). For to assure an appropriate final disposal of these, it is intended their treatment and vitrification by means of thermal plasma. This alternative offers multiple advantages in an only process: elevated energy density (105W/cm{sup 3}), high enthalpy (1400 kJ/mol), elevated chemical reactivity, quick quenching (106K/s) and operation temperatures of 4000 to 15000K; this allows the treatment of a great diversity of waste. Those reactors are compact and they work to atmospheric pressure and reduced thermal inertia. This technology allows to degrade DRNBI and to contain them in a vitreous matrix by means of a system made up of a reactor, canyon of plasma, of monitoring, of washing of gases and of control. Besides the design and general characteristics of the Prototype of Thermal Degradation of DRNBI, they are reported in this work the advances achieved in the selection of the ceramic material for the vitrification. Their characterization was carried out by means of SEM and XRD. With the preliminary results it can discern that the material but appropriate to be used as vitreous matrix is a ceramic clay. With the development of the proposed technology and the material for the vitreous matrix, it will be to treat DRNBI. (Author)

  9. Techniques for Mitigating Thermal Fatigue Degradation, Controlling Efficiency, and Extending Lifetime in a ZnO Thermoelectric Using Grain Size Gradient FGMs

    Science.gov (United States)

    Cramer, Corson L.; Li, Wenjie; Jin, Zhi-He; Wang, Jue; Ma, Kaka; Holland, Troy B.

    2018-01-01

    A functionally graded material (FGM) in terms of grain size gradation is fabricated using zinc oxide (ZnO) with spark plasma sintering and an additive manufacturing technique by diffusion bonding layers of material sintered at different temperatures to achieve a thermoelectric generator (TEG) material that can dissipate heat well and retain high energy conversion efficiency for longer-lasting and comparably efficient TEGs. This FGM is compared to a previously made FGM with continuous grain size gradation. Uniform and graded grain size conditions are modeled for thermoelectric output by using thermoelectric properties of the uniform grain size as well as the varying properties seen in the FGMs. The actual thermoelectric output of the samples is measured and compared to the simulations. The grain size has a large effect on the efficiency and efficiency range. The samples are thermally cycled with a fast heating rate to test the thermal stress robustness and degradation, and the resistance at the highest temperature is measured to indicate degradation from thermal stress. The measured efficiency after cycling shows that the FGMs survive longer lifetime than that with uniform small grains.

  10. A Study on Variation of Thermal Characteristics of Insulation Materials for Buildings According to Actual Long-Term Annual Aging Variation

    Science.gov (United States)

    Choi, Hyun-Jung; Kang, Jae-Sik; Huh, Jung-Ho

    2018-01-01

    Insulation materials used for buildings are broadly classified as organic insulation materials or inorganic insulation materials. Foam gas is used for producing organic insulation materials. The thermal conductivity of foam gas is generally lower than that of air. As a result, foam gas is discharged over time and replaced by outside air that has relatively less thermal resistance. The gas composition ratio in air bubbles inside the insulation materials changes rapidly, causing the performance degradation of insulation materials. Such performance degradation can be classified into different stages. Stage 1 appears to have a duration of 5 years, and Stage 2 takes a period of over 10 years. In this study, two insulation materials that are most frequently used in South Korea were analyzed, focusing on the changes thermal resistance for the period of over 5000 days. The measurement result indicated that the thermal resistance of expanded polystyrene fell below the KS performance standards after about 80-150 days from its production date. After about 5000 days, its thermal resistance decreased by 25.7 % to 42.7 % in comparison with the initial thermal resistance. In the case of rigid polyurethane, a pattern of rapid performance degradation appeared about 100 days post-production, and the thermal resistance fell below the KS performance standards after about 1000 days. The thermal resistance decreased by 22.5 % to 27.4 % in comparison with the initial thermal resistance after about 5000 days.

  11. Thermally-restorable optical degradation and the mechanism of current transport in Cu2S-CdS photovoltaic cells

    Science.gov (United States)

    Fahrenbruch, A. L.; Bube, R. H.

    1974-01-01

    The photovoltaic properties of single-crystal Cu2S-CdS heterojunctions have been investigated as a function of heat treatment by detailed measurements of the dependence of short-circuit current on photon energy, temperature, and the state of optical degradation or enhancement. A coherent picture is formulated for the relationship between enhancement and optical degradation, and their effect on the transport of short-circuit photoexcited current and dark, forward-bias current in the cell. Optical degradation in the Cu2S-CdS cell is shown to be closely identical to optical degradation of lifetime in a homogeneous CdS:Cd:Cu crystal, indicating that the CdS:Cu layer near the junction interface controls carrier transport in the cell. It is proposed that both the photoexcited short-circuit current and the dark, forward-bias current are controlled by a tunneling-recombination process through interface states.

  12. Studies on the atmospheric degradation of chlorpyrifos-methyl.

    Science.gov (United States)

    Muñoz, Amalia; Vera, Teresa; Sidebottom, Howard; Mellouki, Abdelwahid; Borrás, Esther; Ródenas, Milagros; Clemente, Eva; Vázquez, Mónica

    2011-03-01

    The gas-phase atmospheric degradation of chlorpyrifos-methyl (a widely used organophosphate insecticide in Southern European regions) has been investigated at the large outdoor European Photoreactor (EUPHORE) in Valencia, Spain. Photolysis under sunlight conditions and reaction with ozone were shown to be unimportant. The rate constant for reaction of chlorpyrifos-methyl with OH radicals was measured using a conventional relative rate method with cyclohexane and n-octane employed as reference compounds with k = (4.1 ± 0.4) × 10(-11) cm(3) molecule(-1) s(-1) at 300 ± 5 K and atmospheric pressure. The available evidence indicates that tropospheric degradation of chlorpyrifos-methyl is mainly controlled by reaction with OH radicals and that the tropospheric lifetime is estimated to be around 3.5 h. Significant aerosol formation was observed following the reaction of chlorpyrifos-methyl with OH radicals, and the main carbon-containing products detected in the gas phase were chlorpyrifos-methyl oxone and 3,5,6-trichloro-2-pyridinol.

  13. Thermal Degradation and Isomerization of β-Carotene in Oil-in-Water Nanoemulsions Supplemented with Natural Antioxidants.

    Science.gov (United States)

    Yi, Jiang; Fan, Yuting; Yokoyama, Wallace; Zhang, Yuzhu; Zhao, Liqing

    2016-03-09

    The goal of this study was to see the impact on the retention and isomerization of encapsulated β-carotene (BC) in nanoemulsions fortified with natural antioxidants (α-tocopherol (AT) and l-ascorbic acid (AA)). The physical stability of nanoemulsion, oxidative stability, and isomerization of all-trans-β-carotene (BC) in oil-in-water (O/W) nanoemulsions were determined in the presence or absence of natural antioxidants at 25 and 50 °C at certain intervals of time by high-performance liquid chromatography (HPLC). Sodium caseinate was used as the emulsifier, and corn oil (CO) was more protective than medium-chain triglycerides (MCT) and used for isomerization studies. Mean diameters of control (without antioxidants) and AA- and AT-fortified particles were similar. Mean particle diameter of nanoemulsions increased from 10 to 25 nm at 25 °C and from 40 to 50 nm at 50 °C during 30 days of storage. The isomerization from all-trans-BC to cis-BC isomers was inhibited by antioxidants. The isomerization rates were in the following order: 13-cis-BC > 15-cis-BC > 9-cis-BC. AT had better antioxidant activities than AA in inhibiting BC degradation in O/W nanoemulsions. The results indicated that BC encapsulated in nanoemulsions supplemented with antioxidants could significantly improve BC's chemical stability.

  14. Degradation of herbicides in shallow Danish aquifers - an integrated laboratory and field study

    DEFF Research Database (Denmark)

    Albrechtsen, Hans-Jørgen; Mills, M.; Aamand, J.

    2001-01-01

    Degradation of pesticides in aquifers has been evaluated based on a number of co-ordinated field and laboratory studies carried out in Danish aquifers. These studies included investigations of vertical and horizontal variability in degradation rates from the vadose zone to an aquifer, the effects...... of aerobic versus anaerobic conditions, and the importance of concentration on degradation kinetics for a selected range of herbicides. The studies were based on different experimental approaches ranging from simple batch experiments to column studies to field injection experiments and, where appropriate...

  15. Degradation of adhesion molecules of G361 melanoma cells by a non-thermal atmospheric pressure microplasma

    Science.gov (United States)

    Lee, H. J.; Shon, C. H.; Kim, Y. S.; Kim, S.; Kim, G. C.; Kong, M. G.

    2009-11-01

    Increased expression of integrins and focal adhesion kinase (FAK) is important for the survival, growth and metastasis of melanoma cells. Based on this well-established observation in oncology, we propose to use degradation of integrin and FAK proteins as a potential strategy for melanoma cancer therapy. A low-temperature radio-frequency atmospheric microplasma jet is used to study their effects on the adhesion molecules of G361 melanoma cells. Microplasma treatment is shown to (1) cause significant cell detachment from the bottom of microtiter plates coated with collagen, (2) induce the death of human melanoma cells, (3) inhibit the expression of integrin α2, integrin α4 and FAK on the cell surface and finally (4) change well-stretched actin filaments to a diffuse pattern. These results suggest that cold atmospheric pressure plasmas can strongly inhibit the adhesion of melanoma cells by reducing the activities of adhesion proteins such as integrins and FAK, key biomolecules that are known to be important in malignant transformation and acquisition of metastatic phenotypes.

  16. Degradation of adhesion molecules of G361 melanoma cells by a non-thermal atmospheric pressure microplasma

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H J [Department of Electrical Engineering, Pusan National University, Busan 609-735 (Korea, Republic of); Shon, C H [Korea Electrotechnology Research Institute, Changwon 641-120 (Korea, Republic of); Kim, Y S; Kim, S [Department of Pediatric Dentistry, Pusan National University, Busan 602-739 (Korea, Republic of); Kim, G C [Department of Oral Anatomy, Pusan National University, Busan 602-739 (Korea, Republic of); Kong, M G [Department of Electronics and Electrical Engineering, Loughborough University, Leics LE11 3TU (United Kingdom)], E-mail: ki9100m@pusan.ac.kr, E-mail: m.g.kong@lboro.ac.uk

    2009-11-15

    Increased expression of integrins and focal adhesion kinase (FAK) is important for the survival, growth and metastasis of melanoma cells. Based on this well-established observation in oncology, we propose to use degradation of integrin and FAK proteins as a potential strategy for melanoma cancer therapy. A low-temperature radio-frequency atmospheric microplasma jet is used to study their effects on the adhesion molecules of G361 melanoma cells. Microplasma treatment is shown to (1) cause significant cell detachment from the bottom of microtiter plates coated with collagen, (2) induce the death of human melanoma cells, (3) inhibit the expression of integrin {alpha}{sub 2}, integrin {alpha}{sub 4} and FAK on the cell surface and finally (4) change well-stretched actin filaments to a diffuse pattern. These results suggest that cold atmospheric pressure plasmas can strongly inhibit the adhesion of melanoma cells by reducing the activities of adhesion proteins such as integrins and FAK, key biomolecules that are known to be important in malignant transformation and acquisition of metastatic phenotypes.

  17. Feasibility study of D-mannitol as phase change material for thermal storage

    Directory of Open Access Journals (Sweden)

    Rocío Bayón

    2017-05-01

    Full Text Available The feasibility of D-mannitol as PCM for latent heat storage has been studied by keeping it melted at 180 ºC in air for up to 16 days. During this period of time, down to 80% initial mass was lost and sample appearance changed to a dark-brown-sticky paste. The strong mass decrease implies that not only water but also carbon containing volatile species are produced. These results indicate that D-mannitol undergoes thermal degradation which can be associated to caramelization processes similar to the ones occurring in sugars. Such processes involve complex reactions like dehydrations, condensations and polymerizations, which lead to a great variety of volatile and non-volatile products. Various characterization techniques have been applied in order to study both kinetics and reaction products. From the kinetic point of view thermal degradation of D-mannitol proceeds much faster and at lower temperatures than predicted by the models found in the literature. In relation to the degradation products, the analyses with liquid chromatography indicate the formation of three compounds although their stoichiometry could not be fully elucidated with the characterization techniques applied in this work. However it seems that some of the products are polymeric species that contain carbonyl groups and that are the responsible for the sample browning, the strong absorption in the 200 nm–500 nm range, the two bands at 1730 cm–1–1645 cm–1 observed in infrared spectra and also for the occurrence of a glass transition. Therefore this study proves that D-mannitol undergoes strong and fast degradation at temperatures close to its melting point which should be enough reason for avoiding its use as PCM in any latent heat storage application unless it is somehow stabilized.

  18. Study of a radiator degrader CR39 based neutron spectrometer

    Science.gov (United States)

    Caresana, M.; Ferrarini, M.; Pola, A.; Agosteo, S.; Campi, F.; Porta, A.

    2010-08-01

    The paper describes the experimental characterization of a neutron spectrometer based on a CR39 SSNTD coupled to a polyethylene radiator and an aluminium degrader. The response function of the spectrometer is calculated by using two analytical codes: the first one, written in Labview, permits to evaluate the critical angle of a particle (proton, alpha or recoil nucleus) impinging on the detector surface, as a function of the particle energy; the second code, written in Mathcad, calculates the recoil proton distribution generated by a monoenergetic neutron beam impinging on the polyethylene converter. The simulation software also accounts for the self radiator effect due to the recoil protons and to the oxygen and carbon recoil nuclei. The calculated response functions are compared with experimental data showing a fairly good agreement. Also the experimental reproducibility is satisfactory.

  19. Optothermal Raman Studies of Thermal Properties of Graphene Based Films

    Science.gov (United States)

    Malekpour, Hoda

    Efficient thermal management is becoming a critical issue for development of the next generation of electronics. As the size of electronic devices shrinks, the dissipated power density increases, demanding a better heat removal. The discovery of graphene's unique electrical and thermal properties stimulated interest of electronic industry to development of graphene based technologies. In this dissertation, I report the results of my investigation of thermal properties of graphene derivatives and their applications in thermal management. The dissertation consists of three parts. In the first part, I investigated thermal conductivity of graphene laminate films deposited on thermally insulating polyethylene terephthalate substrates. Graphene laminate is made of chemically derived graphene and few layer graphene flakes packed in overlapping structure. Two types of graphene laminate were studied: as deposited and compressed. The thermal conductivity of the laminate was found to be in the range from 40 W/mK to 90 W/mK at room temperature. It was established that the average size and the alignment of graphene flakes are parameters dominating the heat conduction. In the second part of this dissertation, I investigated thermal conductivity of chemically reduced freestanding graphene oxide films. It was found that the in-plane thermal conductivity of graphene oxide can be increased significantly using chemical reduction and temperature treatment. Finally, I studied the effect of defects on thermal conductivity of suspended graphene. The knowledge of the thermal conductivity dependence on the concentration of defects can shed light on the strength of the phonon - point defect scattering in two-dimensional materials. The defects were introduced to graphene in a controllable way using the low-energy electron beam irradiation. It was determined that as the defect density increases the thermal conductivity decreases down to about 400 W/mK, and then reveal saturation type behavior

  20. A study on electrochemical evaluation method of toughness degradation for 12%Cr steel (II)

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Chang Hui; Yoon, Kee Bong [Chungang Univ., Seoul (Korea, Republic of); Seo, Hyun Uk [Hyosung Power and Industrial, Seoul (Korea, Republic of); Park, Ki Sung; Kim, Seoung Tae [Korea Plant Service and Engineering Co., Ltd., Seongnam (Korea, Republic of)

    2001-07-01

    Fossil power plants operated in high temperature condition are composed of components such as turbine, boiler, and piping system. Among these components, turbine blades made with 12%Cr steel operate at a temperature above 500 .deg. C. Due to the long term service, turbine blades experience material degradation manifested by change in mechanical and microstructural properties. The need to make life assessment and to evaluate material degradation of turbine blade is strongly required but in reality, there is a lack of knowledge in defining failure mechanism and fundamental data for this component. Therefore, in making life assessment of turbine blade, evaluation of material degradation must be a priority. For this purpose, evaluation of toughness degradation is very important. The major cause of toughness degradation in 12Cr turbine blade is reported to be critical corrosion pitting induced by segregation of impurity elements(P etc.), coarsening of carbide, and corrosion, but the of materials for in-service application. in this study, the purpose of research is focused on evaluating toughness degradation with respect to operation time for 12%Cr steel turbine blade under high temperature steam environment and quantitatively detecting the degradation properties which is the cause of toughness degradation by means of non-destructive method, electrochemical polarization.

  1. Thermal exposure effects on the in vitro degradation and mechanical properties of Mg–Sr and Mg–Ca–Sr biodegradable implant alloys and the role of the microstructure

    Energy Technology Data Exchange (ETDEWEB)

    Bornapour, M., E-mail: mandana.bornapour@mail.mcgill.ca [McGill University, Materials Engineering, Montreal, QC (Canada); Celikin, M. [INRS, Energy Materials Telecommunications Research Centre, Varennes, QC (Canada); Pekguleryuz, M. [McGill University, Materials Engineering, Montreal, QC (Canada)

    2015-01-01

    Magnesium is an attractive biodegradable material for medical applications due to its non-toxicity, low density and good mechanical properties. The fast degradation rate of magnesium can be tailored using alloy design. The combined addition of Sr and Ca results in a good combination of mechanical and corrosion properties; the alloy compositions with the best performance are Mg–0.5Sr and Mg–0.3Sr–0.3Ca. In this study, we investigated an important effect, namely thermal treatment (at 400 °C), on alloy properties. The bio-corrosion of the alloys was analyzed via in vitro corrosion tests in simulated body fluid (SBF); the mechanical properties were studied through tensile, compression and three-point bending tests in two alloy conditions, as-cast and heat-treated. We showed that 8 h of heat treatment increases the corrosion rate of Mg–0.5Sr very rapidly and decreases its mechanical strength. The same treatment does not significantly change the properties of Mg–0.3Sr–0.3Ca. An in-depth microstructural investigation via transmission electron microscopy, scanning electron microscopy, electron probe micro-analysis and X-ray diffraction elucidated the effects of the thermal exposure. Microstructural characterization revealed that Mg–0.3Sr–0.3Ca has a new intermetallic phase that is stable after 8 h of thermal treatment. Longer thermal exposure (24 h) leads to the dissolution of this phase and to its gradual transformation to the equilibrium phase Mg{sub 17}Sr{sub 2}, as well as to a loss of mechanical and corrosion properties. The ternary alloy shows better thermal stability than the binary alloy, but the manufacturing processes should aim to not exceed exposure to high temperatures (400 °C) for prolonged periods (over 24 h). - Highlights: • Thermal exposure decreases the mechanical properties and increases the biocorrosion rate of Mg–0.5Sr. • Thermally stable globular Ca/Sr-rich phases form in the Mg–0.3Sr–0.3Ca alloy. • Mg–0.3Sr–0.3Ca

  2. Study on durability for thermal cycle of planar SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Ando, Motoo; Nakata, Kei-ichi; Wakayama, Sin-ichi [Tonen Corp., Saitama (Japan)] [and others

    1996-12-31

    TONEN CORPORATION has developed planar type SOFC since 1986. We demonstrated the output of 1.3 kW in 1991 and 5.1 kW in 1995. Simultaneously we have studied how to raise electric efficiency and reliability utilizing hydrogen and propane as fuel. Durability for thermal cycle is one of the most important problems of planar SOFC to make it more practical. The planar type SOFC is made up of separator, zirconia electrolyte and glass sealant. The thermal expansion of these components are expected to be the same value, however, they still possess small differences. In this situation, a thermal cycle causes a thermal stress due to the difference of the cell components and is often followed by a rupture in cell components, therefore, the analysis of the thermal stress should give us much useful information. The thermal cycle process consists of a heating up and cooling down procedure. Zirconia electrolyte is not bonded to the separator under the condition of the initial heating up procedure, and glass sealant becomes soft or melts and glass seals spaces between the zirconia and separator. The glass sealant becomes harder with the cooling down procedure. Moreover, zirconia is tightly bonded with separator below a temperature which is defined as a constraint temperature and thermal stress also occurs. This indicates that the heating up process relaxes the thermal stress and the cooling down increases it. In this paper, we simulated dependence of the stress on the sealing configuration, thermal expansion of sealant and constraint temperature of sealant glass. Furthermore, we presented SOFC electrical properties after a thermal cycle.

  3. Thermal Comfort Studies in Naturally Ventilated Buildings in Jakarta, Indonesia

    OpenAIRE

    Karyono, Tri; Sri, Elita; Sulistiawan, Jevi; Triswanti, Yenny

    2015-01-01

    Many thermal comfort studies have been conducted in offices, classrooms and dwellings, but few in public buildings such as cathedrals, museums and markets. A recent thermal comfort study has been conducted in three naturally ventilated (NV) buildings, a cathedral, a museum and a market, in Jakarta, between March and April 2014. There is a curiosity as to whether people doing slightly different activities with slightly different clothing insulation values, in different building types, might ha...

  4. Soybean peroxidase-mediated degradation of an azo dye– a detailed mechanistic study

    Science.gov (United States)

    2013-01-01

    Background Peroxidases are emerging as an important class of enzymes that can be used for the efficient degradation of organic pollutants. However, detailed studies identifying the various intermediates produced and the mechanisms involved in the enzyme-mediated pollutant degradation are not widely published. Results In the present study, the enzymatic degradation of an azo dye (Crystal Ponceau 6R, CP6R) was studied using commercially available soybean peroxidase (SBP) enzyme. Several operational parameters affecting the enzymatic degradation of dye were evaluated and optimized, such as initial dye concentration, H2O2 dosage, mediator amount and pH of the solution. Under optimized conditions, 40 ppm dye solution could be completely degraded in under one minute by SBP in the presence of H2O2 and a redox mediator. Dye degradation was also confirmed using HPLC and TOC analyses, which showed that most of the dye was being mineralized to CO2 in the process. Conclusions Detailed analysis of metabolites, based on LC/MS results, showed that the enzyme-based degradation of the CP6R dye proceeded in two different reaction pathways- via symmetric azo bond cleavage as well as asymmetric azo bond breakage in the dye molecule. In addition, various critical transformative and oxidative steps such as deamination, desulfonation, keto-oxidation are explained on an electronic level. Furthermore, LC/MS/MS analyses confirmed that the end products in both pathways were small chain aliphatic carboxylic acids. PMID:24308857

  5. Parametric study of closed wet cooling tower thermal performance

    Science.gov (United States)

    Qasim, S. M.; Hayder, M. J.

    2017-08-01

    The present study involves experimental and theoretical analysis to evaluate the thermal performance of modified Closed Wet Cooling Tower (CWCT). The experimental study includes: design, manufacture and testing prototype of a modified counter flow forced draft CWCT. The modification based on addition packing to the conventional CWCT. A series of experiments was carried out at different operational parameters. In view of energy analysis, the thermal performance parameters of the tower are: cooling range, tower approach, cooling capacity, thermal efficiency, heat and mass transfer coefficients. The theoretical study included develops Artificial Neural Network (ANN) models to predicting various thermal performance parameters of the tower. Utilizing experimental data for training and testing, the models simulated by multi-layer back propagation algorithm for varying all operational parameters stated in experimental test.

  6. Degradation and detection of transgenic Bacillus thuringiensis DNA and proteins in flour of three genetically modified rice events submitted to a set of thermal processes.

    Science.gov (United States)

    Wang, Xiaofu; Chen, Xiaoyun; Xu, Junfeng; Dai, Chen; Shen, Wenbiao

    2015-10-01

    This study aimed to investigate the degradation of three transgenic Bacillus thuringiensis (Bt) genes (Cry1Ab, Cry1Ac, and Cry1Ab/Ac) and the corresponding encoded Bt proteins in KMD1, KF6, and TT51-1 rice powder, respectively, following autoclaving, cooking, baking, or microwaving. Exogenous Bt genes were more stable than the endogenous sucrose phosphate synthase (SPS) gene, and short DNA fragments were detected more frequently than long DNA fragments in both the Bt and SPS genes. Autoclaving, cooking (boiling in water, 30 min), and baking (200 °C, 30 min) induced the most severe Bt protein degradation effects, and Cry1Ab protein was more stable than Cry1Ac and Cry1Ab/Ac protein, which was further confirmed by baking samples at 180 °C for different periods of time. Microwaving induced mild degradation of the Bt and SPS genes, and Bt proteins, whereas baking (180 °C, 15 min), cooking and autoclaving led to further degradation, and baking (200 °C, 30 min) induced the most severe degradation. The findings of the study indicated that degradation of the Bt genes and proteins somewhat correlated with the treatment intensity. Polymerase chain reaction, enzyme-linked immunosorbent assay, and lateral flow tests were used to detect the corresponding transgenic components. Strategies for detecting transgenic ingredients in highly processed foods are discussed. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. Study of Thermal Stress Influence on Dimensional Stability of Silicone Molds

    Science.gov (United States)

    Bajčičák, Martin; Šuba, Roland

    2014-06-01

    The paper is focused on the study of temperature influence on dimensional stability of silicone molds used for spin casting of the low melting points alloys. The silicone material denoted as TEKSIL Silicone-GP-S was used to produce samples during experiments. The samples were heated to temperatures in the range from 100 up to 250oC for 30 up to 120 min. Dimensional changes of the samples in the radial and axial directions aa well as their change of weight were evaluated. The results of experiments proved that thermal stress of silicone molds can influence the size and shape of mold cavities. These results can also explain the possible mechanism of degradation process of silicone molds under thermal stress.

  8. Study of Thermal Stress Influence on Dimensional Stability of Silicone Molds

    Directory of Open Access Journals (Sweden)

    Bajčičák Martin

    2014-06-01

    Full Text Available The paper is focused on the study of temperature influence on dimensional stability of silicone molds used for spin casting of the low melting points alloys. The silicone material denoted as TEKSIL Silicone-GP-S was used to produce samples during experiments. The samples were heated to temperatures in the range from 100 up to 250oC for 30 up to 120 min. Dimensional changes of the samples in the radial and axial directions aa well as their change of weight were evaluated. The results of experiments proved that thermal stress of silicone molds can influence the size and shape of mold cavities. These results can also explain the possible mechanism of degradation process of silicone molds under thermal stress.

  9. Reprocessability of PHB in extrusion: ATR-FTIR, tensile tests and thermal studies

    Directory of Open Access Journals (Sweden)

    Leonardo Fábio Rivas

    Full Text Available Abstract Mechanical recycling of biodegradable plastics has to be encouraged, since the consumption of energy and raw materials can be reduced towards a sustainable development in plastics materials. In this study, the evolution of thermal and mechanical properties, as well as structural changes of poly(hydroxybutyrate (PHB up to three extrusion cycles were investigated. Results indicated a significant reduction in mechanical properties already at the second extrusion cycle, with a reduction above 50% in the third cycle. An increase in the crystallinity index was observed due to chemicrystallization process during degradation by chain scission. On the other hand, significant changes in the chemical structure or in thermal stability of PHB cannot be detected by Fourier transform infrared spectroscopy (FTIR and thermogravimetric analyses (TGA, respectively.

  10. Degradation of conductivity and microstructure under thermal and current load in Ni-YSZ cermets for SOFC anodes

    DEFF Research Database (Denmark)

    Thydén, Karl Tor Sune; Barfod, R.; Liu, Yuliang

    2006-01-01

    The degradation of electrical conductivity in porous nickel-yttria stabilized zirconia composite cermets in a H2/H2O atmosphere under high temperature treatments has been investigated. The parameters varied were: temperature, water partial pressure, and electrical current load. The microstructure...

  11. A Study of Thermal Analyses and Fundamental Combustion Characteristics for Thermal Utility with Biomass Volatile Matter

    Science.gov (United States)

    Ida, Tamio; Namba, Kunihiko; Sano, Hiroshi

    Based on un-use biomass utilities, Carbonized technology is noticed as material utilities and solid fuel. Therefore, this technology is tackling by national project as large-scale utilities. But, this technology is dehydrated volatiles matter during carbonized from biomass. Especially, Woody tar into one of volatile matter has vicious handling to get into trouble in carbonized equipment. In this study, we propose to get fundamental knowledge for effective thermal utility through thermal decompositions and fundamental combustion properties on experimental results. Woody tar has high caloric value (approximately 30MJ/kg) and high carbon ration. On the other hand, a woody vinegar liquid has thermal decomposition property close to water property with heat absorption as evaporation latent heat of water. In fundamental combustion experimental result, a woody tar has fl ammable combustion and surface combustion. Especially, a total combustion and ignition time properties has hyperbola relation to environment temperatures in furnace.

  12. Degradation in Mechanical and Thermal Properties of Partially Aligned CNT/Epoxy Composites due to Seawater Absorption

    Science.gov (United States)

    Saha, Sunirmal; Bal, Smrutisikha

    2017-02-01

    This literature gives an overview of the effect of water uptake on the mechanical and thermal performances of partially aligned carbon nanotube (CNT)/ epoxy (having CNTs wt.%: 0.5, 0.75 and 1) along with pure epoxy composites. Weight change behaviour of all the composites immersed in seawater for a period of six months has been recorded. The state of CNT/matrix interface is believed to be influenced due to water absorption. Reduction in flexural modulus, strength, hardness and glass transition temperature (Tg ) of the specimens have been evaluated as compared to their unexposed counterparts due to adverse effect of water absorption. Results demonstrated 35-46% reduction in flexural modulus, 43-56% decrement in flexural strength, 4-7 MPa reduction in hardness and minor deterioration in Tg values for all the composites. However, the specimen having 0.75 wt.% CNT loading, exhibited minimum reduction in properties in all aspects compared to others. Scanning electron microscopy (SEM) has been employed to study the failure mechanism of the specimens after performing the mechanical tests.

  13. Workers exposed to thermal degradation products of TDI- and MDI-based polyurethane: biomonitoring of 2,4-TDA, 2,6-TDA, and 4,4'-MDA in hydrolyzed urine and plasma.

    Science.gov (United States)

    Dalene, M; Skarping, G; Lind, P

    1997-08-01

    The aim of the study was to investigate biomarkers of exposure to thermal degradation products of 2,4- and 2,6-toluene diisocyanate (TDI)- and 4,4'-methylenediphenyl diisocyanate (MDI)-based polyurethane and the toxicokinetics of these products. Blood and urine were collected from 15 factory workers exposed to thermal degradation products of MDI-based polyurethane glue and TDI-based flexible foam. Four of these workers were also studied during an exposure-free period. Urine and plasma were analyzed after acidic hydrolysis and the concentrations of the isocyanates' corresponding amines, 2,4-, 2,6-toluenediamine (TDA), and 4,4'-methylenedianiline (MDA), were determined as derivatives of pentafluoropropionic anhydride by gas chromatography using chemical ionization mass spectrometry monitoring negative ions. Urinary elimination rates were in the range of TDA per hour, TDA per hour, and TDA per mL, TDA per mL, and TDA, 2,6-TDA, and 4,4'-MDA in urine varied during and between workdays. The individual variation in plasma concentrations of 2,4-TDA, 2,6-TDA, and 4,4'-MDA with time was small, but between individuals the variation was great.

  14. Thermal Management Tools for Propulsion System Trade Studies and Analysis

    Science.gov (United States)

    McCarthy, Kevin; Hodge, Ernie

    2011-01-01

    Energy-related subsystems in modern aircraft are more tightly coupled with less design margin. These subsystems include thermal management subsystems, vehicle electric power generation and distribution, aircraft engines, and flight control. Tighter coupling, lower design margins, and higher system complexity all make preliminary trade studies difficult. A suite of thermal management analysis tools has been developed to facilitate trade studies during preliminary design of air-vehicle propulsion systems. Simulink blocksets (from MathWorks) for developing quasi-steady-state and transient system models of aircraft thermal management systems and related energy systems have been developed. These blocksets extend the Simulink modeling environment in the thermal sciences and aircraft systems disciplines. The blocksets include blocks for modeling aircraft system heat loads, heat exchangers, pumps, reservoirs, fuel tanks, and other components at varying levels of model fidelity. The blocksets have been applied in a first-principles, physics-based modeling and simulation architecture for rapid prototyping of aircraft thermal management and related systems. They have been applied in representative modern aircraft thermal management system studies. The modeling and simulation architecture has also been used to conduct trade studies in a vehicle level model that incorporates coupling effects among the aircraft mission, engine cycle, fuel, and multi-phase heat-transfer materials.

  15. Urban area thermal monitoring: Liepaja case study using satellite and aerial thermal data

    Science.gov (United States)

    Gulbe, Linda; Caune, Vairis; Korats, Gundars

    2017-12-01

    The aim of this study is to explore large (60 m/pixel) and small scale (individual building level) temperature distribution patterns from thermal remote sensing data and to conclude what kind of information could be extracted from thermal remote sensing on regular basis. Landsat program provides frequent large scale thermal images useful for analysis of city temperature patterns. During the study correlation between temperature patterns and vegetation content based on NDVI and building coverage based on OpenStreetMap data was studied. Landsat based temperature patterns were independent from the season, negatively correlated with vegetation content and positively correlated with building coverage. Small scale analysis included spatial and raster descriptor analysis for polygons corresponding to roofs of individual buildings for evaluating insulation of roofs. Remote sensing and spatial descriptors are poorly related to heat consumption data, however, thermal aerial data median and entropy can help to identify poorly insulated roofs. Automated quantitative roof analysis has high potential for acquiring city wide information about roof insulation, but quality is limited by reference data quality and information on building types, and roof materials would be crucial for further studies.

  16. Experimental Study of Turbine Fuel Thermal Stability in an Aircraft Fuel System Simulator

    Science.gov (United States)

    Vranos, A.; Marteney, P. J.

    1980-01-01

    The thermal stability of aircraft gas turbines fuels was investigated. The objectives were: (1) to design and build an aircraft fuel system simulator; (2) to establish criteria for quantitative assessment of fuel thermal degradation; and (3) to measure the thermal degradation of Jet A and an alternative fuel. Accordingly, an aircraft fuel system simulator was built and the coking tendencies of Jet A and a model alternative fuel (No. 2 heating oil) were measured over a range of temperatures, pressures, flows, and fuel inlet conditions.

  17. A Thermal Test System for Helmet Cooling Studies

    Directory of Open Access Journals (Sweden)

    Shaun Fitzgerald

    2018-02-01

    Full Text Available One of the primary causes of discomfort to both irregular and elite cyclists is heat entrapment by a helmet resulting in overheating and excessive sweating of the head. To accurately assess the cooling effectiveness of bicycle helmets, a heated plastic thermal headform has been developed. The construction consists of a 3D-printed headform of low thermal conductivity with an internal layer of high thermal mass that is heated to a constant uniform temperature by an electrical heating element. Testing is conducted in a wind tunnel where the heater power remains constant and the resulting surface temperature distribution is directly measured by 36 K-type thermocouples embedded within the surface of the head in conjunction with a thermal imaging camera. Using this new test system, four bicycle helmets were studied in order to measure their cooling abilities and to identify ‘hot spots’ where cooling performance is poor.

  18. Integrated thermal treatment system study -- Phase 2 results. Revision 1

    Energy Technology Data Exchange (ETDEWEB)

    Feizollahi, F.; Quapp, W.J.

    1996-02-01

    This report presents the second phase of a study on thermal treatment technologies. The study consists of a systematic assessment of nineteen thermal treatment alternatives for the contact-handled mixed low-level waste (MLLW) currently stored in the US Department of Energy complex. The treatment alternatives consist of widely varying technologies for safely destroying the hazardous organic components, reducing the volume, and preparing for final disposal of the MLLW. The alternatives considered in Phase 2 were innovative thermal treatments with nine types of primary processing units. Other variations in the study examined the effect of combustion gas, air pollution control system design, and stabilization technology for the treatment residues. The Phase 1 study examined ten initial thermal treatment alternatives. The Phase 2 systems were evaluated in essentially the same manner as the Phase 1 systems. The alternatives evaluated were: rotary kiln, slagging kiln, plasma furnace, plasma gasification, molten salt oxidation, molten metal waste destruction, steam gasification, Joule-heated vitrification, thermal desorption and mediated electrochemical oxidation, and thermal desorption and supercritical water oxidation. The quantities, and physical and chemical compositions, of the input waste used in the Phase 2 systems differ from those in the Phase 1 systems, which were based on a preliminary waste input database developed at the onset of the Integrated Thermal Treatment System study. The inventory database used in the Phase 2 study incorporates the latest US Department of Energy information. All systems, both primary treatment systems and subsystem inputs, have now been evaluated using the same waste input (2,927 lb/hr). 28 refs., 88 figs., 41 tabs.

  19. Thermal loading study for FY 1996. Volume 1

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-11-08

    The primary objective of this study was to provide recommendations for Mined Geologic Disposal System requirements affected by thermal loading that will provide sufficient definition to facilitate development of design concepts and support life cycle cost determinations. The study reevaluated and/or redefined selected thermal goals used for design and are currently contained in the requirements documents or the Controlled Design Assumption Document. The study provided recommendations as to what, if any, actions (such as edge loading and limiting of the heat variability between waste packages) are needed and must be accommodated in the design. Additionally, the study provided recommendations as to what alternative thermal loads should be maintained for continued flexibility. Section 1 provides the study objective, background, scope, and organization of the report. Section 2 documents the requirements and standards to include quality assurance (QA) requirements, any requirements used or evaluated, and the inputs and assumptions considered. Section 3 provides the analysis and recommendations for the thermal goals reevaluation. Section 4 discusses the evaluation of edge loading and provides conclusions. Section 5 provides the analyses done to establish recommendations as to what requirements need to be implemented to either limit or manage the amount of heat output variability that may occur. Section 6 discusses alternate thermal loadings; Section 7 provides the study conclusions and recommendations; Section 8 provides the references, standards, and regulations; and Section 9 contains the acronym list.

  20. Biochemical degradation and physical migration of nutritive compounds in blueberries after PEF and thermal pretreatments and osmotic dehydration

    Science.gov (United States)

    Fresh blueberries were pretreated by pulsed electric fields (PEF) at 3 kV/cm or thermal pretreatment at 90 degrees C for 5 min after which they were subject to osmotic dehydration. The changes in contents of anthocyanins, predominantly phenolic acids and flavonols, total phenolics, polyphenol oxidas...

  1. Thermal exposure effects on the in vitro degradation and mechanical properties of Mg-Sr and Mg-Ca-Sr biodegradable implant alloys and the role of the microstructure.

    Science.gov (United States)

    Bornapour, M; Celikin, M; Pekguleryuz, M

    2015-01-01

    Magnesium is an attractive biodegradable material for medical applications due to its non-toxicity, low density and good mechanical properties. The fast degradation rate of magnesium can be tailored using alloy design. The combined addition of Sr and Ca results in a good combination of mechanical and corrosion properties; the alloy compositions with the best performance are Mg-0.5Sr and Mg-0.3Sr-0.3Ca. In this study, we investigated an important effect, namely thermal treatment (at 400 °C), on alloy properties. The bio-corrosion of the alloys was analyzed via in vitro corrosion tests in simulated body fluid (SBF); the mechanical properties were studied through tensile, compression and three-point bending tests in two alloy conditions, as-cast and heat-treated. We showed that 8h of heat treatment increases the corrosion rate of Mg-0.5Sr very rapidly and decreases its mechanical strength. The same treatment does not significantly change the properties of Mg-0.3Sr-0.3Ca. An in-depth microstructural investigation via transmission electron microscopy, scanning electron microscopy, electron probe micro-analysis and X-ray diffraction elucidated the effects of the thermal exposure. Microstructural characterization revealed that Mg-0.3Sr-0.3Ca has a new intermetallic phase that is stable after 8h of thermal treatment. Longer thermal exposure (24h) leads to the dissolution of this phase and to its gradual transformation to the equilibrium phase Mg17Sr2, as well as to a loss of mechanical and corrosion properties. The ternary alloy shows better thermal stability than the binary alloy, but the manufacturing processes should aim to not exceed exposure to high temperatures (400 °C) for prolonged periods (over 24 h). Copyright © 2014 Elsevier B.V. All rights reserved.

  2. Application of thermal analysis to measure the spatial heterogeneity of organic matter degradation after wildfire: implications for post-fire rehabilitation treatments

    Science.gov (United States)

    Merino, Agustin; Fonturbel, M. Teresa; Vega, Jose A.

    2015-04-01

    Severe wildfires can cause drastic changes in SOM content and quality with important implications for soil conservation and global C balance. Soil heating usually leads to loss of the most labile SOM compounds (e.g. carbohydrates, lipids and peptides) and to generation of aromatic substances. However, these fire-related damages are not uniform over large areas, because of the spatial heterogeneity of different factors such as fire type and environmental conditions. Rapid diagnosis of soil burn severity is required to enable the design of emergency post-fire rehabilitation treatments. The study was conducted in soils from NW Spain, an Atlantic-climate zone that is particularly prone to wildfires. Intact soil cores (forest floor and uppermost mineral soil layer) were taken from a soil developed under granitic rock and subjected to experimental burning (in a bench positioned at the outlet of a wind tunnel). Soil temperature during fire was monitorised and five visual levels of soil burn severity (SBS) were recorded immediately after fire. Solid-state 13C CP-MAS NMR spectroscopy analyses were performed in an Agilent (Varian) VNMRS-500-WB spectrometer. The samples were analyzed by differential scanning calorimetry and thermogravimetry (TGA/DSC, Mettler-Toledo Intl. Inc.). The analyses were performed with 4 mg of samples placed in open aluminium pans under dry air (flow rate, 50 mL-1) and at a scanning rate of 10 °C min-1. The temperature ranged between 50 and 600 °C. In the organic layer, the temperature reached during fire influenced the formation and characteristics of charred material. These materials showed an increasing degree of carbonization/aromatization in relation to the increase of temperature during burning. Burning also led to compounds of higher thermal recalcitrance (increases in T50 values -the temperature at which 50% of the energy stored in SOM is released-). However, values recorded in some samples were lower than those measured in highly

  3. Heat exchange studies on coconut oil cells as thermal energy storage for room thermal conditioning

    Science.gov (United States)

    Sutjahja, I. M.; Putri, Widya A.; Fahmi, Z.; Wonorahardjo, S.; Kurnia, D.

    2017-07-01

    As reported by many thermal environment experts, room air conditioning might be controlled by thermal mass system. In this paper we discuss the performance of coconut oil cells as room thermal energy storage. The heat exchange mechanism of coconut oil (CO) which is one of potential organic Phase Change Material (PCM) is studied based on the results of temperature measurements in the perimeter and core parts of cells. We found that the heat exchange performance, i.e. heat absorption and heat release processes of CO cells are dominated by heat conduction in the sensible solid from the higher temperature perimeter part to the lower temperature core part and heat convection during the solid-liquid phase transition and sensible liquid phase. The capability of heat absorption as measured by the reduction of air temperature is not influenced by CO cell size. Besides that, the application of CO as the thermal mass has to be accompanied by air circulation to get the cool sensation of the room’s occupants.

  4. Study on degrading graphene oxide in wastewater under different conditions for developing an efficient and economical degradation method.

    Science.gov (United States)

    Li, Ting; Zhang, Chao-Zhi; Gu, Chengyue

    2017-12-01

    With popular application of graphene and graphene oxide (GO), they have been discharged into water. Graphene and GO harm organisms. However, an efficient and economical method for removing graphene and GO in wastewater has seldom been reported. Graphene can be oxidized by hydrogen peroxide to give GO; therefore, degradation of graphene oxide is an important step in the procedure of removal of graphene from water. In this paper, GO degradation via photo-Fenton reaction under different conditions was carried out. Experimental results suggested that GO in wastewater can be efficiently and economically degraded into carbon dioxide and H2O when pH value is 3, concentration of H2O2 and FeCl3 are 35 mM and 5 ppm, respectively. Degradation mechanism of GO was suggested based on UV-vis absorption spectra, scanning electron microscopy, X-ray diffraction and liquid chromatography-mass spectra data of degradation intermediates. This paper suggests an efficient and economical degradation way of GO in wastewater.

  5. Integrated thermal treatment systems study. Internal review panel report

    Energy Technology Data Exchange (ETDEWEB)

    Cudahy, J.; Escarda, T.; Gimpel, R. [and others

    1995-04-01

    The U.S. Department of Energy (DOE) Office of Technology Development (OTD) commissioned two studies to evaluate nineteen thermal treatment technologies for treatment of DOE mixed low-level waste. These studies were called the Integrated Thermal Treatment System (ITTS) Phase I and Phase II. With the help of the DOE Office of Environmental Management (EM) Mixed Waste Focus Group, OTD formed an ITTS Internal Review Panel to review and comment on the ITTS studies. This Panel was composed of scientists and engineers from throughout the DOE complex, the U.S. Environmental Protection Agency, the California EPA, and private experts. The Panel met from November 15-18, 1994 to review the ITTS studies and to make recommendations on the most promising thermal treatment systems for DOE mixed low-level wastes and on research and development necessary to prove the performance of the technologies. This report describes the findings and presents the recommendations of the Panel.

  6. Drift Degradation Analysis

    Energy Technology Data Exchange (ETDEWEB)

    D. Kicker

    2004-09-16

    Degradation of underground openings as a function of time is a natural and expected occurrence for any subsurface excavation. Over time, changes occur to both the stress condition and the strength of the rock mass due to several interacting factors. Once the factors contributing to degradation are characterized, the effects of drift degradation can typically be mitigated through appropriate design and maintenance of the ground support system. However, for the emplacement drifts of the geologic repository at Yucca Mountain, it is necessary to characterize drift degradation over a 10,000-year period, which is well beyond the functional period of the ground support system. This document provides an analysis of the amount of drift degradation anticipated in repository emplacement drifts for discrete events and time increments extending throughout the 10,000-year regulatory period for postclosure performance. This revision of the drift degradation analysis was developed to support the license application and fulfill specific agreement items between the U.S. Nuclear Regulatory Commission (NRC) and the U.S. Department of Energy (DOE). The earlier versions of ''Drift Degradation Analysis'' (BSC 2001 [DIRS 156304]) relied primarily on the DRKBA numerical code, which provides for a probabilistic key-block assessment based on realistic fracture patterns determined from field mapping in the Exploratory Studies Facility (ESF) at Yucca Mountain. A key block is defined as a critical block in the surrounding rock mass of an excavation, which is removable and oriented in an unsafe manner such that it is likely to move into an opening unless support is provided. However, the use of the DRKBA code to determine potential rockfall data at the repository horizon during the postclosure period has several limitations: (1) The DRKBA code cannot explicitly apply dynamic loads due to seismic ground motion. (2) The DRKBA code cannot explicitly apply loads due to thermal

  7. [Study on the thermal radiation polarization characteristics of ice].

    Science.gov (United States)

    Wang, Ting-Ting; Zhao, Yun-Sheng; Zhang, Hong-Yan; Zhang, Xia; Zhang, Li-Li

    2014-03-01

    As an important parameter of the global energy balance, climate, hydrological and ecological model, ice directly affects the energy balance of the earth-atmosphere system, weather and climate. It is of great significance to use the thermal infrared polarization technology to study ice thermal radiation. For the ice monitoring and the impact of global climate change on the ice, studies on ice thermal radiation polarization characteristics were conducted based on the wavelength, detection angle and azimuth angle. The results show that the wavelength has an obvious impact on the ice thermal radiation polarization properties. The polarized radiance of four bands shows that L(CH1) > L(CH3) > L(CH4) > L(CH2) while the polarization brightness temperature shows that T(CH4) > T(CH1) > TCH2 > TCH3. It's better to use the brightness temperature of the third channel than the radiance to study the thermal radiation polarization. The detection angle affects the ice thermal radiation polarization characteristics greatly and there are some differences between the polarization angles. The brightness temperature of ice is the lowest in the detection angle of 10 degrees and the polarization angle of 30 degrees, which are non-accidental factors. These was closely related to ice physical and chemical properties. The degree of ice polarization performance shows that P0 thermal radiation polarization characteristics was not significant. And it is affected by the roughness of the surface, organizational structure and other factors which are direct results of ice emitted radiation at different azimuth angles.

  8. Nanoscale studies of thermal transport: R-matrix theory and thermal transport in strained graphene nanoribbons

    Science.gov (United States)

    Gunawardana, K. G. S. H.

    The rapid development of nanotechnology has enabled the fabrication of structures much smaller than the mean free path of electrons and phonons. In modern electronics, miniaturization is desired to increase the transistor density and the clock speed. Electronic transport on the nanoscale has been studied for over three decades and fascinating quantum effects have been observed. Phonon transport on this scale is of significant interest because of the increased power dissipation in nanoelectronics, which undermines the correct functionality of devices and limits their lifetime. Apart from the effort to minimize heat generation, an efficient heat management scheme is necessary. Historically, thermal transport in bulk materials was described by the Fourier's law, in which the thermal conductivity is an intrinsic property of the material. Later a more descriptive model, the Boltzmann approach for thermal transport, was developed and could explain the thermal conductivity down to a 100 nm length scale at high temperatures. At low temperatures and in structures smaller than roughly 100 nm, thermal transport is described by the fully quantum mechanical Landauer- Butticker formalism. In this context, accurate calculation of phonon transmission probabilities is very important. In this dissertation, I develop a continuum model to calculate phonon transmission probabilities between media, which have high contrast in the elastic properties. In this work, we include an interface transition layer between the two media and look for interface properties that improve thermal transport. Secondly, I develop a new theoretical tool based on the R-Matrix theory to calculate phonon transmission probabilities on the atomic scale. R-matrix theory is a well developed theoretical approach commonly used in nuclear and atomic physics to solve scattering problems. Recently, this approach has been successfully developed to calculate electronic scattering in mesoscopic quantum devices. The key

  9. Theoretical and analyzed data related to thermal degradation kinetics of poly (L-lactic acid/chitosan-grafted-oligo L-lactic acid (PLA/CH-g-OLLA bionanocomposite films

    Directory of Open Access Journals (Sweden)

    Akhilesh Kumar Pal

    2017-02-01

    Full Text Available The theoretical and analyzed data incorporated in this article are related to the recently published research article entitled “Thermal degradation behaviour of nanoamphiphilic chitosan dispersed poly (lactic acid bionanocomposite films” (http://dx.doi.org/10.1016/j.ijbiomac.2016.11.024 (A.K. Pal, V. Katiyar, 2016 [1]. Supplementary information and data (both raw and analyzed are related to thermal degradation kinetics and explains various model fitting and is conversional methods, which are used in this research work to enhance the knowledge about degradation behaviour of PLA/CH-g-OLLA bionanocomposite system. Non-isothermal degradation kinetics of such polymeric system was proposed using Kissinger, Kissinger–Akahira–Sunose, Flynn–Wall–Ozawa and Augis and Bennett models to estimate the activation energies (Ea and R2 values.

  10. Study on FPGA-Based Emulator for the Diagnosis of Gradual Degradation in Reciprocating Pump

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Sang Sun; Kim, Wooshik [Sejong Univ., Seoul (Korea, Republic of); Kim, Tae Yun; Chai, Jang Bom [Ajou Univ., Suwon (Korea, Republic of)

    2017-01-15

    The purpose of this study is to develop a method for diagnosing the degree of gradual degradation of a reciprocating pump caused by continuous use as a water supply pump in a nuclear power plant. Normally, the progress of such degradation is too slow to be noticed. Hence, it is difficult to determine the degree of degradation using the existing diagnostic methods. In this paper, we propose a new method by which the normal state and the degraded state of the pump can be differentiated, so that the degree of degradation can be identified. First, an emulator was developed using FPGA by providing the parameters of the pump under normal state, so that the emulator generates the information of the pump in the healthy state. Then, by comparing this information with the parameters received from various output sensors of the emulator during the current state, it is possible to identify and measure the degree of gradual degradation. This paper presents some of the results obtained during the development process, and results that show how the emulator operates, by comparing the data collected from an actual pump.

  11. Review of the integrated thermal and nonthermal treatment system studies

    Energy Technology Data Exchange (ETDEWEB)

    Durrani, H.A.; Schmidt, L.J.; Erickson, T.A.; Sondreal, E.A.; Erjavec, J.; Steadman, E.N.; Fabrycky, W.J.; Wilson, J.S.; Musich, M.A.

    1996-07-01

    This report analyzes three systems engineering (SE) studies performed on integrated thermal treatment systems (ITTSs) and integrated nonthermal treatment systems (INTSs) for the remediation of mixed low-level waste (MLLW) stored throughout the US Department of Energy (DOE) weapons complex. The review was performed by an independent team of nine researchers from the Energy and Environmental Research Center (EERC), Science Applications International Corporation (SAIC), the Waste Policy Institute (WPI), and Virginia Tech (VT). The three studies reviewed were as follows: Integrated Thermal Treatment System Study, Phase 1--issued July 1994; Integrated Thermal Treatment System Study, Phase 2--issued February 1996; and Integrated Nonthermal Treatment System Study--drafted March 1996. The purpose of this review was to (1) determine whether the assumptions taken in the studies might bias the resulting economic evaluations of both thermal and nonthermal systems, (2) identify the critical areas of the studies that would benefit from further investigation, and (3) develop a standard template that could be used in future studies to produce sound SE applications.

  12. Review of the integrated thermal and nonthermal treatment system studies

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-08-01

    This report contains a review and evaluation of three systems analysis studies performed by LITCO on integrated thermal treatment systems and integrated nonthermal treatment systems for the remediation of mixed low-level waste stored throughout the US Department of Energy weapons complex. The review was performed by an independent team of nine researchers from the Energy and Environmental Research Center, Science Applications International Corporation, the Waste Policy Institute, and Virginia Tech. The three studies reviewed were as follows: Integrated Thermal Treatment System Study, Phase 1--issued July 1994; Integrated Thermal Treatment System Study, Phase 2--issued February 1996; and Integrated Nonthermal Treatment System Study--drafted March 1996. The purpose of this review was to (1) determine whether the assumptions of the studies were adequate to produce an unbiased review of both thermal and nonthermal systems, (2) to identify the critical areas of the studies that would benefit from further investigation, and (3) to develop a standard template that could be used in future studies to assure a sound application of systems engineering.

  13. Degradation Studies of b-Cyclodextrin Polyurethane Polymers using ...

    African Journals Online (AJOL)

    NJD

    diisocyanate (TDI) and hexamethylene diisocyanate (HMDI) were carried out by exposing the polymers to different soil types for up to 120 days. The aim of the study was to determine the fate of these novel polymers in the environment.

  14. Degradation Studies of β-Cyclodextrin Polyurethane Polymers using ...

    African Journals Online (AJOL)

    diisocyanate (TDI) and hexamethylene diisocyanate (HMDI) were carried out by exposing the polymers to different soil types for up to 120 days. The aim of the study was to determine the fate of these novel polymers in the environment.

  15. Aluminous porcelain degradation study using mechanoacoustic and microscopic methods

    National Research Council Canada - National Science Library

    Ranachowski, Przemysław; Rejmund, Feliks; Ranachowski, Zbigniew; Pawełek, Andrzej; Piątkowski, Andrzej

    2011-01-01

    .... The objects of study were samples made of C 120 aluminous porcelain. The investigated material has found at present the application in the fabrication of technical elements like overhead power line insulators...

  16. Thermal-decomposition studies of HMX

    Energy Technology Data Exchange (ETDEWEB)

    Kolb, J.R.; Garza, R.G.

    1981-10-20

    We have investigated the rates of decomposition as functions of time and temperature on a combined thermogravimetric analyzer-residual gas analyzer (TGA-RGA). This technique also allows us to identify decomposition products generated as the original HMX begins to decompose. The temperature range studied was 50 to 200/sup 0/C. The decomposition process and the nature of decomposition products as functions of HMX polymorphs and conformations of the organic ring systems and possible reactive intermediates are discussed. 7 figures, 3 tables.

  17. Thermal-structural combined loads design criteria study

    Science.gov (United States)

    Deriugin, V.; Brogren, E. W.; Jaeck, C. L.; Brown, A. L.; Clingan, B. E.

    1972-01-01

    A study was conducted to determine methodology for combining thermal structural loads and assessing the effects of the combined loads on the design of a thermal protection system and a hot structure of a high cross range delta wing space shuttle orbiter vehicle. The study presents guidelines for establishing a basis for predicting thermal and pressure environments and for determining limit and ultimate design loads on the vehicle during reentry. Limit trajectories were determined by using dispersions on a representative nominal mission and system parameters expected during the life of the vehicle. Nine chosen locations on the vehicle surface having TPS or hot structures were examined, and weight sensitivity analyses were performed for each location.

  18. Benzene degradation coupled with chlorate reduction in soil column study

    NARCIS (Netherlands)

    Tan, N.C.G.; Doesburg, van W.C.J.; Langenhoff, A.A.M.; Stams, A.J.M.

    2006-01-01

    Perchlorate and chlorate are electron acceptors that during reduction result in the formation of molecular oxygen. The produced oxygen can be used for activation of anaerobic persistent pollutants, like benzene. In this study chlorate was tested as potential electron acceptor to stimulate benzene

  19. Studies on hydrocarbon degradation by the bacterial isolate ...

    African Journals Online (AJOL)

    The hydrocarbon utilizing capability of Stenotrophomonas rhizophila (PM-1), isolated from oil contaminated soil composts from Western Ghats region of Karnataka was analyzed. In the bioremediation experiment, ONGC heavy crude oil and poly aromatic hydrocarbons (PAHs) utilization by the bacterial isolate was studied.

  20. Environmental/Thermal Barrier Coatings for Ceramic Matrix Composites: Thermal Tradeoff Studies

    Science.gov (United States)

    Murthy, Pappu L. M.; Brewer, David; Shah, Ashwin R.

    2007-01-01

    Recent interest in environmental/thermal barrier coatings (EBC/TBCs) has prompted research to develop life-prediction methodologies for the coating systems of advanced high-temperature ceramic matrix composites (CMCs). Heat-transfer analysis of EBC/TBCs for CMCs is an essential part of the effort. It helps establish the resulting thermal profile through the thickness of the CMC that is protected by the EBC/TBC system. This report documents the results of a one-dimensional analysis of an advanced high-temperature CMC system protected with an EBC/TBC system. The one-dimensional analysis was used for tradeoff studies involving parametric variation of the conductivity; the thickness of the EBC/TBCs, bond coat, and CMC substrate; and the cooling requirements. The insight gained from the results will be used to configure a viable EBC/TBC system for CMC liners that meet the desired hot surface, cold surface, and substrate temperature requirements.

  1. Study on Thermal Insulation Zeolite by Coal Fly Ash

    OpenAIRE

    Huiping Song; Nan Zheng; Fangbin Xue; Fangqin Cheng

    2014-01-01

    This paper takes the coal fly ash as the material and makes zeolite with low thermal conductivity under a two-step synthesis for the purpose of thermal insulation. It studies main factors affecting zeolite such as the different concentration of NaOH, the solid-liquid ratio, the silica-alumina ratio, and the crystallization temperature. The optimal conditions were obtained that the NaOH concentration was 3 mol/L, the solid-liquid ratio was 10 : 1, the silica-alumina ratio was 2, and the crysta...

  2. Positron annihilation studies on reactor irradiated and thermal annealed ferrocene

    Energy Technology Data Exchange (ETDEWEB)

    Marques Netto, A. [Laboratorio de Espectroscopia de Aniquilacao de Positrons-LEAP, Depto. de Quimica, ICEX, Univ. Federal de Minas Gerais-UFMG, Belo Horizonte, MG (Brazil); Carvalho, R.S. [Laboratorio de Espectroscopia de Aniquilacao de Positrons-LEAP, Depto. de Quimica, ICEX, Univ. Federal de Minas Gerais-UFMG, Belo Horizonte, MG (Brazil); Magalhaes, W.F. [Laboratorio de Espectroscopia de Aniquilacao de Positrons-LEAP, Depto. de Quimica, ICEX, Univ. Federal de Minas Gerais-UFMG, Belo Horizonte, MG (Brazil); Sinisterra, R.D. [Laboratorio de Espectroscopia de Aniquilacao de Positrons-LEAP, Depto. de Quimica, ICEX, Univ. Federal de Minas Gerais-UFMG, Belo Horizonte, MG (Brazil)

    1996-10-01

    Retention and thermal annealing following (n, {gamma}) reaction in solid ferrocene, Fe(C{sub 5}H{sub 5}){sub 2}, were studied by positron annihilation lifetime spectroscopy (PAL). Positronium (Ps) formation was observed in the non-irradiated compound with a probability or intensity (I{sub 3}) of 30%. Upon irradiation of the compound with thermal neutrons in a nuclear reactor, I{sub 3} decreases with increasing irradiation time. Thermal treatment again increases I{sub 3} values from 16% to 25%, revealing an important proportion of molecular reformation without variation of the ortho-positronium lifetime ({tau}{sub 3}). These results point out the major influence of the electronic structure as determining the Ps yields in the pure complex. In the irradiated and non irradiated complexes the results are satisfactorily explained on the basis of the spur model. (orig.)

  3. Inverse thermal analysis method to study solidification in cast iron

    DEFF Research Database (Denmark)

    Dioszegi, Atilla; Hattel, Jesper

    2004-01-01

    Solidification modelling of cast metals is widely used to predict final properties in cast components. Accurate models necessitate good knowledge of the solidification behaviour. The present study includes a re-examination of the Fourier thermal analysis method. This involves an inverse numerical...... solution of a 1-dimensional heat transfer problem connected to solidification of cast alloys. In the analysis, the relation between the thermal state and the fraction solid of the metal is evaluated by a numerical method. This method contains an iteration algorithm controlled by an under relaxation term...... was developed in order to investigate the thermal behaviour of the solidifying metal. Three cylindrically shaped cast samples surrounded by different cooling materials were introduced in the same mould allowing a common metallurgical background for samples solidifying at different cooling rates. The proposed...

  4. Variability in microbiological degradation experiments, analysis and case study

    DEFF Research Database (Denmark)

    Sommer, Helle Mølgaard

    1997-01-01

    and describes analysis techniques for testing the reproducibility of a given experiment. The parameter estimation method employed for the experiments in this study is based on an iterative maximum likelihood method and the test statistic is an approximated likelihood ratio test. The estimations were carried out...... of the parameter estimates are depending of the choice of estimation method, this fact has not either received much attention, all though an unsuitable estimation method can lead to estimates which are quite different from the ``true'' values. The present thesis describes various nonlinear estimation techniques...... estimation method. The examination of reproducibility/variability were carried out for two kinds of experiments: A single substrate experiment with toluene and a dual substrate experiment with toluene and benzene. A pure culture, isolated from soil, grew with benzene and/or toluene as the only carbon...

  5. Comparative study of the thermal performance and emission levels ...

    African Journals Online (AJOL)

    Comparative study of the thermal performance and emission levels of an existing and modified coal/biomass burning stove. ... The stove was charged with jive (5) selected wood species and a number of parameters, such as temperature projile amI flue gas composition were measured. Experimental evidence points to an ...

  6. Thermally stimulated discharge conductivity study of zinc oxide ...

    Indian Academy of Sciences (India)

    The present work deals with transmission electron microscopy (TEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermally stimulated discharge current (TSDC) study of inorganic metal oxide (ZnO) nanoparticles and its thermoelectrets. The thermoelectrets were prepared by applying different electric ...

  7. Preparation and studies of some thermal, mechanical and optical ...

    Indian Academy of Sciences (India)

    Unknown

    Preparation and studies of some thermal, mechanical and optical properties of xAl2O3(1 – x)NaPO3 glass system. K V SHAH, V SUDARSAN†, M GOSWAMI, A SARKAR, S MANIKANDAN,. RAKESH KUMAR, B I SHARMA, V K SHRIKHANDE and G P KOTHIYAL*. Technical Physics and Prototype Engineering Division, ...

  8. Crack propagation studies and bond coat properties in thermal ...

    Indian Academy of Sciences (India)

    Ceramic based thermal barrier coatings (TBC) are currently considered as a candidate material for advanced stationary gas turbine components. Crack propagation studies under bending are described that were performed on plasma sprayed ZrO2, bonded by MCrAlY layer to Ni base superalloy. The crack propagation ...

  9. Study of thermally coupled distillation systems for energy-efficient ...

    Indian Academy of Sciences (India)

    Study of thermally coupled distillation systems for energy-efficient distillation. NEHA SAXENA1, NILESH MALI2,* and SATCHIDANAND SATPUTE3. 1 Department of Chemical Engineering, Bharati Vidyapeeth Deemed University College of Engineering,. Pune 411046, India. 2 Chemical Engineering and Process ...

  10. Study of variation of thermal diffusivity of advanced composite ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 32; Issue 1. Study of variation of thermal diffusivity of advanced composite materials of E-glass fibre reinforced plastic (GFRP) in temperature range 5–300 K. Kalobaran Das S M Kamaruzzaman Tapas Ranjan Middya Siddhartha Datta. Ceramics and Glasses Volume 32 ...

  11. A Critical Appraisal of Quantitative Studies of Protein Degradation in the Framework of Cellular Proteostasis

    Directory of Open Access Journals (Sweden)

    Beatriz Alvarez-Castelao

    2012-01-01

    Full Text Available Protein homeostasis, proteostasis, is essential to understand cell function. Protein degradation is a crucial component of the proteostatic mechanisms of the cell. Experiments on protein degradation are nowadays present in many investigations in the field of molecular and cell biology. In the present paper, we focus on the different experimental approaches to study protein degradation and present a critical appraisal of the results derived from steady-state and kinetic experiments using detection of unlabelled and labelled protein methodologies with a proteostatic perspective. This perspective allows pinpointing the limitations in interpretation of results and the need of further experiments and/or controls to establish “definitive evidence” for the role of protein degradation in the proteostasis of a given protein or the entire proteome. We also provide a spreadsheet for simple calculations of mRNA and protein decays for mimicking different experimental conditions and a checklist for the analysis of experiments dealing with protein degradation studies that may be useful for researchers interested in the area of protein turnover.

  12. The Impact of Charcoal Production on Forest Degradation: a Case Study in Tete, Mozambique

    Science.gov (United States)

    Sedano, F.; Silva. J. A.; Machoco, R.; Meque, C. H.; Sitoe, A.; Ribeiro, N.; Anderson, K.; Ombe, Z. A.; Baule, S. H.; Tucker, C. J.

    2016-01-01

    Charcoal production for urban energy consumption is a main driver of forest degradation in sub-Saharan Africa. Urban growth projections for the continent suggest that the relevance of this process will increase in the coming decades. Forest degradation associated to charcoal production is difficult to monitor and commonly overlooked and underrepresented in forest cover change and carbon emission estimates. We use a multi-temporal dataset of very high-resolution remote sensing images to map kiln locations in a representative study area of tropical woodlands in central Mozambique. The resulting maps provided a characterization of the spatial extent and temporal dynamics of charcoal production. Using an indirect approach we combine kiln maps and field information on charcoal making to describe the magnitude and intensity of forest degradation linked to charcoal production, including aboveground biomass and carbon emissions. Our findings reveal that forest degradation associated to charcoal production in the study area is largely independent from deforestation driven by agricultural expansion and that its impact on forest cover change is in the same order of magnitude as deforestation. Our work illustrates the feasibility of using estimates of urban charcoal consumption to establish a link between urban energy demands and forest degradation. This kind of approach has potential to reduce uncertainties in forest cover change and carbon emission assessments in sub-Saharan Africa.

  13. A thin film degradation study of a fluorinated polyether liquid lubricant using an HPLC method

    Science.gov (United States)

    Morales, W.

    1986-01-01

    A High Pressure Liquid Chromatography (HPLC) separation method was developed to study and analyze a fluorinated polyether fluid which is promising liquid lubricant for future applications. This HPLC separation method was used in a preliminary study investigating the catalytic effect of various metal, metal alloy, and ceramic engineering materials on the degradation of this fluid in a dry air atmosphere at 345 C. Using a 440 C stainless steel as a reference catalytic material it was found that a titanium alloy and a chromium plated material degraded the fluorinated polyether fluid substantially more than the reference material.

  14. Theoretical and experimental studies on the atmospheric degradation of 2-bromo-3,3,3-trifluoropropene.

    Science.gov (United States)

    Chen, Weiwang; Zhou, Xiaomeng; Han, Yajun

    2015-08-28

    As a new kind of Halon replacement, 2-bromo-3,3,3-trifluoropropene (2-BTP) is finding application as a fire extinguishing agent in confined spaces. For assessing its environmental impact, it is necessary to perform kinetic and product studies of its degradation in the atmospheric environment. In this sense, five possible reaction pathways between 2-BTP and OH radicals are found by Gaussian 03. Detailed analysis shows that the main product is the CF3CBrCH2OH radical, which may produce a series of compounds by further reaction with O2, NO, etc. In order to further prove the validity of the theoretical calculations and investigate the atmospheric transformation process of 2-BTP, atmospheric degradation of 2-BTP is then studied experimentally under controlled radiation conditions. Based on the theoretical analyses and experimental results, the atmospheric degradation mechanism of 2-BTP is finally proposed and detailed information on the atmospheric chemistry of 2-BTP is provided.

  15. Influence of thermalization on thermal conduction through molecular junctions: Computational study of PEG oligomers

    Science.gov (United States)

    Pandey, Hari Datt; Leitner, David M.

    2017-08-01

    Thermalization in molecular junctions and the extent to which it mediates thermal transport through the junction are explored and illustrated with computational modeling of polyethylene glycol (PEG) oligomer junctions. We calculate rates of thermalization in the PEG oligomers from 100 K to 600 K and thermal conduction through PEG oligomer interfaces between gold and other materials, including water, motivated in part by photothermal applications of gold nanoparticles capped by PEG oligomers in aqueous and cellular environments. Variation of thermalization rates over a range of oligomer lengths and temperatures reveals striking effects of thermalization on thermal conduction through the junction. The calculated thermalization rates help clarify the scope of applicability of approaches that can be used to predict thermal conduction, e.g., where Fourier's law breaks down and where a Landauer approach is suitable. The rates and nature of vibrational energy transport computed for PEG oligomers are compared with available experimental results.

  16. Thermal degradation assessment of canola and olive oil using ultra-fast gas chromatography coupled with chemometrics.

    Science.gov (United States)

    Majchrzak, Tomasz; Lubinska, Martyna; Różańska, Anna; Dymerski, Tomasz; Gębicki, Jacek; Namieśnik, Jacek

    2017-01-01

    Oil blending is often used to enhance the properties of vegetable oils. The admixture of a more thermally stable oil makes the resulting blend more suitable for use in frying. A new method of quality assessment of vegetable oils used in frying is presented in this paper. In this method, ultra-fast gas chromatography coupled with flame ionization detector and chemometrics is employed. Principal component analysis was used for data processing. The results obtained with this method were compared with the results of the Rancimat test and sensory evaluation. It is demonstrated that the addition of olive oil improves the stability of rapeseed oil, and also changes its flavour and aroma profile. In addition, it was found that ultra-fast GC coupled with chemometrics is an effective tool for the assessment of the quality of edible oils. The proposed method does not require sample preparation, and the total time of analysis is less than 2 min.

  17. A stability indicating HPLC method for determination of mebeverine in the presence of its degradation products and kinetic study of its degradation in oxidative condition.

    Science.gov (United States)

    Souri, E; Aghdami, A Negahban; Adib, N

    2014-01-01

    An HPLC method for determination of mebeverine hydrochloride (MH) in the presence of its degradation products was developed. The degradation of MH was studied under hydrolysis, oxidative and photolysis stress conditions. Under alkaline, acidic and oxidative conditions, degradation of MH was observed. The separation was performed using a Symmetry C18 column and a mixture of 50 mM KH2PO4, acetonitrile and tetrahydrfuran (THF) (63:35:2; v/v/v) as the mobile phase. No interference peaks from degradation products in acidic, alkaline and oxidative conditions were observed. The linearity, accuracy and precision of the method were studied. The method was linear over the range of 1-100 μg/ml MH (r(2)>0.999) and the CV values for intra-day and inter-day variations were in the range of 1.0-1.8%. The limit of quantification (LOQ) and the limit of detection (LOD) of the method were 1.0 and 0.2 μg/ml, respectively. Determination of MH in pharmaceutical dosage forms was performed using the developed method. Furthermore the kinetics of the degradation of MH in the presence of hydrogen peroxide was investigated. The proposed method could be a suitable method for routine quality control studies of mebeverine dosage forms.

  18. Comparative IL-TEM study concerning the degradation of carbon supported Pt-based electrocatalysts

    DEFF Research Database (Denmark)

    Hartl, Katrin Gabriele; Hanzlik, Marianne; Arenz, Matthias

    2012-01-01

    responsible for the Pt surface area loss of carbon supported electrocatalysts. It is demonstrated that seemingly similar catalysts can exhibit under identical treatment pronounced differences in their degradation behaviour. As a consequence individual steps in the synthesis of electrocatalysts can have......In the present work the identical location transmission electron microscopy (IL-TEM) approach is used for a comparative study of the degradation of several standard Pt-based electrocatalysts for low temperature proton conducting membrane fuel cells (PEMFCs). The paper discusses the mechanisms...... a distinct effect on the degradation mechanism even if the base chemicals and materials used in their synthesis are identical. This finding sheds new light in the much debated issue if crystallite migration and coalescence or Pt dissolution and re-deposition are mainly responsible for the Pt surface area...

  19. A preliminary study of soft cheese degradation in different packaging conditions by 1H-NMR.

    Science.gov (United States)

    Lamanna, Raffaele; Piscioneri, Ilario; Romanelli, Valeria; Sharma, Neeta

    2008-09-01

    This preliminary work deals with the influence of packaging on the degradation of an Italian soft cheese studied by NMR. The NMR profiles of aqueous cheese extracts were acquired as a function of time during storage of cheese inside and outside the original package. From the NMR spectra 15 metabolites are quantified and used in a kinetic degradation model and in a multivariate algorithm in order to evaluate the changes in the metabolic composition of cheese stored under different conditions. 2008 John Wiley & Sons, Ltd.

  20. Study of the effect of the fibre mass UP2 degradation products on radionuclide mobilisation

    Energy Technology Data Exchange (ETDEWEB)

    Duro, Lara; Grive, Mireia; Gaona, Xavier; Bruno, Jordi [Amphos 21 Consulting S.L., Barcelona (Spain); Andersson, Thomas; Boren, Hans; Dario, Maarten [Linkoeping Univ., Linkoeping (Sweden); Allard, Bert; Hagberg, Jessica [Oerebro Univ., Oerebro (Sweden); Kaellstroem, Klas [Swedish Nuclear Fuel and Waste Management Co., Stockholm (Sweden)

    2012-09-15

    This report presents a literature review and laboratory work of the degradation of the fibre UP2, as well as an assessment of the effects of its degradation products on Europium sorption onto cement, as an example of their effects on radionuclide migration. All laboratory work was performed by the Swedish groups (Linkoeping and Oerebro Universities), who also performed some of the literature review. The data interpretation was performed by the Spanish team (Amphos 21). SKB has combined the reports of these studies into this common document and has added minor editorial changes. All these changes have been accepted by the authors.

  1. Parallelized system for biopolymer degradation studies through automated microresonator measurement in liquid flow

    DEFF Research Database (Denmark)

    Casci Ceccacci, Andrea; Morelli, Lidia; Bosco, Filippo

    2015-01-01

    In this work we present a novel automated system which allows the study of enzymatic degradation of biopolymer films coated on micromechanical resonators. The system combines an optical readout based on Blu-Ray technology with a software-controlled scanning mechanism. Integrated with a microfluidic...... setup unit, the system allows high-throughput measurements of resonance frequency over microresonator arrays under controlled flow conditions. We here demonstrate the acquisition of statistical data on biopolymer films degradation under enzymatic reaction over a large sample of micromechanical...

  2. Review of the integrated thermal and nonthermal treatment system studies

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-10-01

    This report contains a review and evaluation of three systems analysis studies performed by LITCO on integrated thermal treatment systems and integrated nonthermal treatment systems for the remediation of mixed low-level waste stored throughout the US Department of Energy weapons complex. The review was performed by an independent team of nine researchers from the Energy and Environmental Research Center, Science Applications International Corporation, the Waste Policy Institute, and Virginia Tech. The purpose of this review was to (1) determine whether the assumptions of the studies were adequate to produce an unbiased review of both thermal and nonthermal systems, (2) to identify the critical areas of the studies that would benefit from further investigation, and (3) to develop a standard template that could be used in future studies to assure a sound application of systems engineering.

  3. Functional Studies of β-Glucosidases of Cytophaga hutchinsonii and Their Effects on Cellulose Degradation

    Science.gov (United States)

    Bai, Xinfeng; Wang, Xifeng; Wang, Sen; Ji, Xiaofei; Guan, Zhiwei; Zhang, Weican; Lu, Xuemei

    2017-01-01

    Cytophaga hutchinsonii can rapidly digest crystalline cellulose without free cellulases or cellulosomes. Its cell-contact cellulose degradation mechanism is unknown. In this study, the four β-glucosidase (bgl) genes in C. hutchinsonii were singly and multiply deleted, and the functions of these β-glucosidases in cellobiose and cellulose degradation were investigated. We found that the constitutively expressed BglB played a key role in cellobiose utilization, while BglA which was induced by cellobiose could partially make up for the deletion of bglB. The double deletion mutant ΔbglA/bglB lost the ability to digest cellobiose and could not thrive in cellulose medium, indicating that β-glucosidases were important for cellulose degradation. When cultured in cellulose medium, a small amount of glucose accumulated in the medium in the initial stage of growth for the wild type, while almost no glucose accumulated for ΔbglA/bglB. When supplemented with a small amount of glucose, ΔbglA/bglB started to degrade cellulose and grew in cellulose medium. We inferred that glucose might be essential for initiating cellulose degradation, and with additional glucose, C. hutchinsonii could partially utilize cellulose without β-glucosidases. We also found that there were both cellulose binding cells and free cells when cultured in cellulose. Since direct contact between C. hutchinsonii cells and cellulose is necessary for cellulose degradation, we deduced that the free cells which were convenient to explore new territory in the environment might be fed by the adherent cells which could produce cello-oligosaccharide and glucose into the environment. This study enriched our knowledge of the cellulolytic pathway of C. hutchinsonii. PMID:28210251

  4. Study of the degradation of mulch materials in vegetable crops for organic farming

    Science.gov (United States)

    María Moreno, Marta; Mancebo, Ignacio; Moreno, Carmen; Villena, Jaime; Meco, Ramón

    2014-05-01

    Mulching is the most common technique used worldwide by vegetable growers in protected cultivation. For this purpose, several plastic materials have been used, with polyethylene (PE) being the most widespread. However, PE is produced from petroleum derivatives, it is not degradable, and thus pollutes the environment for periods much longer than the crop duration (Martín-Closas and Pelacho, 2011), which are very important negative aspects especially for organic farmers. A large portion of plastic films is left on the field or burnt uncontrollably by the farmers, with the associated negative consequences to the environment (Moreno and Moreno, 2008). Therefore, the best solution is to find a material with a lifetime similar to the crop duration time that can be later incorporated by the agricultural system through a biodegradation process (Martín-Closas and Pelacho, 2011). In this context, various biodegradable materials have been considered as alternatives in the last few years, including oxo-biodegradable films, biopolymer mulches, different types of papers, and crop residues (Kasirajan and Ngouajio, 2012). In this work we evaluate the evolution of different properties related to mulch degradation in both the buried and the superficial (exposed) part of mulch materials of different composition (standard black PE, papers and black biodegradable plastics) in summer vegetable crops under organic management in Castilla-La Mancha (Central Spain). As results, it is remarkable the early deterioration suffered by the buried part of the papers, disappearing completely in the soil at the end of the crop cycles and therefore indicating the total incorporation of these materials to the soil once the crop has finished. In the case of the degradation of the exposed mulch, small differences between crops were observed. In general, all the materials were less degraded under the plants than when receiving directly the solar radiation. As conclusion, biodegradable mulches degrade

  5. Lifetime Performance Assessment of Thermal Systems : Studies on Building, Solar and Disctrict Heating Applications

    OpenAIRE

    Stojanovic, Bojan

    2009-01-01

    The main questions today concerning thermal systems are their economical and environmental impacts. These entities are generally, at present, assessed on the basis of operation performances of newly installed/designed systems, during an assumed lifetime period. While this is the common way of perceiving thermal systems, performance-over-time will change as an effect of degradation, and not solely of different operation scenarios. How and to what extent is the question that needs assessing in ...

  6. A Kinetic Degradation Study of Curcumin in Its Free Form and Loaded in Polymeric Micelles

    NARCIS (Netherlands)

    Naksuriya, Ornchuma; van Steenbergen, Mies J.; Sastre Torano, Javier; Okonogi, Siriporn; Hennink, Wim E.

    Curcumin, a phenolic compound, possesses many pharmacological activities and is under clinical evaluation to treat different diseases. However, conflicting data about its stability have been reported. In this study, the kinetic degradation of curcumin from a natural curcuminoid mixture under various

  7. Identifiability study of the proteins degradation model, based on ADM1, using simultaneous batch experiments

    DEFF Research Database (Denmark)

    Flotats, X.; Palatsi, J.; Ahring, Birgitte Kiær

    2006-01-01

    The objective of the present study is to analyse kinetic and stoichiometric parameter values of gelatine anaerobic degradation at thermophilic range, based on an experiment designed to elucidate if volatile fatty acids (VFA) are inhibitors of the hydrolysis process. Results showed that VFA...

  8. Studies of planetary boundary layer by infrared thermal imagery

    Energy Technology Data Exchange (ETDEWEB)

    Albina, Bogdan; Dimitriu, Dan Gheorghe, E-mail: dimitriu@uaic.ro; Gurlui, Silviu Octavian, E-mail: dimitriu@uaic.ro [Alexandru Ioan Cuza University of Iasi, Faculty of Physics, Atmosphere Optics, Spectroscopy and Lasers Laboratory, 11 Carol I Blvd., 700506 Iasi (Romania); Cazacu, Marius Mihai [Alexandru Ioan Cuza University of Iasi, Faculty of Physics, Atmosphere Optics, Spectroscopy and Lasers Laboratory, 11 Carol I Blvd., 700506 Iasi, Romania and Department of Physics, Gheorghe Asachi Technical University of Iasi, 59A Mangeron Blvd., 700 (Romania); Timofte, Adrian [Alexandru Ioan Cuza University of Iasi, Faculty of Physics, Atmosphere Optics, Spectroscopy and Lasers Laboratory, 11 Carol I Blvd., 700506 Iasi, Romania and National Meteorological Administration, Regional Forecast Center Bacau, 1 Cuza Voda Str., 60 (Romania)

    2014-11-24

    The IR camera is a relatively novel device for remote sensing of atmospheric thermal processes from the Planetary Boundary Layer (PBL) based on measurements of the infrared radiation. Infrared radiation is energy radiated by the motion of atoms and molecules on the surface of aerosols, when their temperature is more than absolute zero. The IR camera measures directly the intensity of radiation emitted by aerosols which is converted by an imaging sensor into an electric signal, resulting a thermal image. Every image pixel that corresponds to a specific radiance is pre-processed to identify the brightness temperature. The thermal infrared imaging radiometer used in this study, NicAir, is a precision radiometer developed by Prata et al. The device was calibrated for the temperature range of 270–320 K and using a calibration table along with image processing software, important information about variations in temperature can be extracted from acquired IR images. The PBL is the lowest layer of the troposphere where the atmosphere interacts with the ground surfaces. The importance of PBL lies in the fact that it provides a finite but varying volume in which pollutants can disperse. The aim of this paper is to analyze the PBL altitude and thickness variations over Iasi region using the IR imaging camera as well as its behavior from day to night and thermal processes occurring in PBL.

  9. Study on Thermal Insulation Zeolite by Coal Fly Ash

    Directory of Open Access Journals (Sweden)

    Huiping Song

    2014-01-01

    Full Text Available This paper takes the coal fly ash as the material and makes zeolite with low thermal conductivity under a two-step synthesis for the purpose of thermal insulation. It studies main factors affecting zeolite such as the different concentration of NaOH, the solid-liquid ratio, the silica-alumina ratio, and the crystallization temperature. The optimal conditions were obtained that the NaOH concentration was 3 mol/L, the solid-liquid ratio was 10 : 1, the silica-alumina ratio was 2, and the crystallization temperature was 12°C. Zeolites have multiple pores and skeletal structures under SEM observation. The mean particle size was 2.78 um of concentrated distribution. The pore volume was 0.148 m3/g measured by BET analysis, the specific surface was 118.6 m2/g, and the thermal conductivity was 0.153 W/(m·K. Zeolite was proved to be a qualified insulation material which can be used in thermal insulation coating as a new material of energy conservation.

  10. Thermal degradation of a synthetic lube oil API SL/CF SAE 5W 40; Degradacao termica do oleo lubrificante sintetico API SL/CF SAE 5W 40

    Energy Technology Data Exchange (ETDEWEB)

    Lopes, Eddy H. de O.; Carvalho, Laura H. de; Silva, Everson de L. [Universidade Federal de Campina Grande (UFCG), PB (Brazil)

    2008-07-01

    This work deals with the thermal degradation to 210 deg C of lubricating oil synthetic API SL/CF SAE 5W 40 as received and on the presence of metallic particles, from engine parts (head and crankshaft). Samples were collected at various intervals of time. The metallic particles were spent in mesh sieve no. 200 (0.074 mm) and used both in the trials of characterization (EDX and SEM) as the thermal degradation of the oil. Changes in rheology, viscosity, density, color and FTIR were monitored over time of heat exposure. The results indicate that thermal exposure caused by thermal oxidation of synthetic oil and that the presence of metallic particles (10 ppm) accelerated this process, so it is suggested that during the exchange of oil are taken care to remove them from to prevent the premature deterioration of the new oil. The behaviour Newtonian was maintained throughout the period degradation and viscosity of the oil has not changed significantly even after long periods (1148 hours) of thermal exposure. Despite the density of oil also has not changed significantly with time of exposure, changes in color indicate that chemical changes occurred, which was detected by FTIR. (author)

  11. Study of silica coatings degradation under laser irradiation and in controlled environment; Etude de la degradation de couches minces de silice sous flux laser et en environnement controle

    Energy Technology Data Exchange (ETDEWEB)

    Becker, S

    2006-11-15

    Performances of optical components submitted to high laser intensities are usually determined by their laser-induced damage threshold. This value represents the highest density of energy (fluence) sustainable by the component before its damage. When submitted to laser fluences far below this threshold, optical performances may also decrease with time. The degradation processes depend on laser characteristics, optical materials, and environment around the component. Silica being the most used material in optics, the aim of this study was to describe and analyse the physical-chemical mechanisms responsible for laser-induced degradation of silica coatings in controlled environment. Experimental results show that degradation is due to the growth of a carbon deposit in the irradiated zone. From these results, a phenomenological model has been proposed and validated with numerical simulations. Then, several technological solutions have been tested in order to reduce the laser-induced contamination of silica coatings. (author)

  12. Degradation characteristics of waste polyurethane by radiation

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jong Seok; Ahn, Sung Jun; Gwon Hui Jeong; Jeong, Sung In; Nho, Young Chang; Lim, Youn Mook [Research Division for Industry and Environment, Korea Atomic Energy Research Institute, Jeongeup (Korea, Republic of)

    2017-06-15

    Polyurethane (PU) is a very popular polymer that is used in a variety of applications due to its good mechanical, thermal, and chemical properties. However, waste PU recycling has received significant attention due to environmental issues. The aim of this work was to investigate the degradation characteristics of waste PU to recycle. Degradation of waste PU was carried out using a radiation techniques. Waste PUs were exposed to a gamma {sup 60}Co sources. To verify degradation, the irradiated PUs were characterized using FT-IR, gel permeation chromatography (GPC), and their thermal/mechanical properties are reported. When the radiation dose was 500 kGy, the molecular weight of the waste PU drastically decreased. Also, the mechanical properties of waste PU were approximately 4 times lower than those of non-irradiated PU. This study has confirmed the possibility of making fine particle of waste PU for recycling through radiation degradation techniques.

  13. The study of 'microsurfaces' using thermal desorption spectroscopy

    Science.gov (United States)

    Thomas, M. E.; Poppa, H.; Pound, G. M.

    1979-01-01

    The use of a newly combined ultrahigh vacuum technique for studying continuous and particulate evaporated thin films using thermal desorption spectroscopy (TDS), transmission electron microscopy (TEM), and transmission electron diffraction (TED) is discussed. It is shown that (1) CO thermal desorption energies of epitaxially deposited (111) Ni and (111) Pd surfaces agree perfectly with previously published data on bulk (111) single crystal, (2) contamination and surface structural differences can be detected using TDS as a surface probe and TEM as a complementary technique, and (3) CO desorption signals from deposited metal coverages of one-thousandth of a monolayer should be detectable. These results indicate that the chemisorption properties of supported 'microsurfaces' of metals can now be investigated with very high sensitivity. The combined use of TDS and TEM-TED experimental methods is a very powerful technique for fundamental studies in basic thin film physics and in catalysis.

  14. Land Sensitivity Analysis of Degradation using MEDALUS model: Case Study of Deliblato Sands, Serbia

    Directory of Open Access Journals (Sweden)

    Kadović Ratko

    2016-12-01

    Full Text Available This paper studies the assessment of sensitivity to land degradation of Deliblato sands (the northern part of Serbia, as a special nature reserve. Sandy soils of Deliblato sands are highly sensitive to degradation (given their fragility, while the system of land use is regulated according to the law, consisting of three zones under protection. Based on the MEDALUS approach and the characteristics of the study area, four main factors were considered for evaluation: soil, climate, vegetation and management. Several indicators affecting the quality of each factor were identified. Each indicator was quantified according to its quality and given a weighting of between 1.0 and 2.0. ArcGIS 9 was utilized to analyze and prepare the layers of quality maps, using the geometric mean to integrate the individual indicator map. In turn, the geometric mean of all four quality indices was used to generate sensitivity of land degradation status map. Results showed that 56.26% of the area is classified as critical; 43.18% as fragile; 0.55% as potentially affected and 0.01% as not affected by degradation. The values of vegetation quality index, expressed as coverage, diversity of vegetation functions and management policy during the protection regime are clearly represented through correlation coefficient (0.87 and 0.47.

  15. Physicochemical properties and radiolytic degradation studies on tri-iso-amyl phosphate (TiAP)

    Energy Technology Data Exchange (ETDEWEB)

    Sreenivasulu, B.; Sivaraman, Nagarajan [Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu (India). Homi Bhabha National Inst.; Suresh, A.; Rajeswari, S.; Ramanathan, N.; Antony, M.P.; Joseph, M. [Indira Gandhi Centre for Atomic Research, Kalpakkam, Tamil Nadu (India). Chemistry Group

    2017-06-01

    The solvent composed of tri-iso-amyl phosphate (TiAP) in n-dodecane (n-DD) is regarded as a promising candidate for reprocessing of spent fuel. In this context, the radiolytic degradation of a solution of TiAP in n-dodecane was investigated by irradiating the solvent to various absorbed dose levels of γ-radiation. The neat extractant or a solution of extractant in n-dodecane was irradiated in the presence of nitric acid. Physicochemical properties such as density, viscosity and interfacial tension (IFT) were measured for unirradiated and irradiated solutions. The extent of degradation was determined by measuring the variation in extraction behavior of U(VI) and Pu(IV) with irradiated solvent systems. Uranium and plutonium retention with irradiated solvents was also measured. The distribution ratio of uranium and plutonium increased with increase in absorbed dose. Effect of alpha degradation was studied by plutonium retention as a function of time using 1.1 M TiAP/n-DD. Laser desorption/ionization mass spectrometric technique was employed to identify the possible radiolytic degradation products. Similar studies were also carried out with tri-n-butyl phosphate (TBP) based solvent system under identical experimental conditions and the results are compared.

  16. Thermodynamic and kinetics study of phenolics degradation and color of yacon (Smallanthus sonchifolius) microparticles under accelerated storage conditions.

    Science.gov (United States)

    Lago, Camila Carvalho; Noreña, Caciano P Zapata

    2017-12-01

    This study aimed to investigate the kinetics and thermodynamic of the phenolics degradation and the kinetics of degradation of the total color difference of yacon juice microcapsules produced by spray drying using Gum Arabic and polydextrose as wall materials. The degradation of the microcapsule was evaluated by accelerated tests under controlled conditions at 35 and 45 °C, and relative humidity of 75 and 90%, for 35 days. Degradation of phenolics followed the first order model and the degradation constant was in the range of 0.0124-0.0209 days-1. The microparticles with gum Arabic were more stable than those with polydextrose for all conditions studied, with longer half-lives. Both wall materials showed similar thermodynamic characteristics, indicating similar mechanism of degradation of phenolics. With respect to the color parameters, the first order model adjusted to data of the total color difference, and no significant differences were observed for the conditions studied.

  17. Experimental and theoretical studies on the OH-initiated degradation of tert-butylamine

    Science.gov (United States)

    Tan, Wen; D'Anna, Barbara; Eichler, Philipp; Mikoviny, Tomas; Müller, Markus; Jørgen Nielsen, Claus; Wisthaler, Armin; Zhu, Liang

    2017-04-01

    Amine-based carbon dioxide (CO2) capture facilities release small amounts of amines into the atmosphere. Once airborne, the amines are photochemically transformed into imines, amides, nitrosamines, nitramines and other breakdown products. As some of these products pose a risk to human health and the environment, we have elucidated photochemical decomposition mechanisms of various types of amines in previous work. Our studies did, however, not include amines in which the primary amino group is attached to a tertiary carbon atom, with 2-amino-2-methyl-1-propanol (AMP, (CH3)2C(NH2)CH2OH) being a prominent candidate used in CO2 capture. Our initial step in elucidating the degradation mechanism of AMP was to study tert-butylamine (tBA, (CH3)3C(NH2)), which is a similar molecule but lacks the OH group. OH-initiated degradation of tBA was studied in chamber experiments at the European Photoreactor (EUPHORE) in Valencia (Spain) using state-of-the-art analytical instrumentation. A Proton-Transfer-Reaction Time-of-Flight Mass Spectrometer (PTR-ToF-MS) was used to measure tBA and tBA degradation products in the gas phase. Propan-2-imine (PI, (CH3)2C(=NH)) and tert-butylnitramine (tBNA, (CH3)3C(NHNO2)) were observed as the two major gas-phase products. An Aerosol Mass Spectrometer (AMS) made quantitative measurements of tert-butylaminium nitrate in the particle phase. A PTR-ToF-MS instrument equipped with a "chemical analysis of aerosol online" (CHARON) inlet detected the two major tBA degradation products (PI, tBNA) in the particle phase. Experimental work was supplemented by quantum chemistry calculations. We will present measured product yields and a complete degradation scheme of tBA. This work was supported by the Norwegian Research Council CLIMIT program under contract 244055.

  18. The potential of isotopically enriched magnesium to study bone implant degradation in vivo.

    Science.gov (United States)

    Draxler, Johannes; Martinelli, Elisabeth; Weinberg, Annelie M; Zitek, Andreas; Irrgeher, Johanna; Meischel, Martin; Stanzl-Tschegg, Stefanie E; Mingler, Bernhard; Prohaska, Thomas

    2017-03-15

    This pilot study highlights the substantial potential of using isotopically enriched (non-radioactive) metals to study the fate of biodegradable metal implants. It was possible to show that magnesium (Mg) release can be observed by combining isotopic mass spectrometry and isotopic pattern deconvolution for data reduction, even at low amounts of Mg released a from slowly degrading (26)Mg enriched (>99%) Mg metal. Following implantation into rats, structural in vivo changes were monitored by μCT. Results showed that the applied Mg had an average degradation rate of 16±5μmyear(-1), which corresponds with the degradation rate of pure Mg. Bone and tissue extraction was performed 4, 24, and 52weeks after implantation. Bone cross sections were analyzed by laser ablation inductively coupled plasma mass spectrometry (ICP-MS) to determine the lateral (26)Mg distribution. The (26)Mg/(24)Mg ratios in digested tissue and excretion samples were analyzed by multi collector ICP-MS. Isotope pattern deconvolution in combination with ICP-MS enabled detection of Mg pin material in amounts as low as 200ppm in bone tissues and 20ppm in tissues up to two fold increased Mg levels with a contribution of pin-derived Mg of up to 75% (4weeks) and 30% (24weeks) were found adjacent to the implant. After complete degradation, no visual bone disturbance or residual pin-Mg could be detected in cortical bone. In organs, increased Δ(26)Mg/(24)Mg values up to 16‰ were determined compared to control samples. Increased Δ(26)Mg/(24)Mg values were detected in serum samples at a constant total Mg level. In contrast to urine, feces did not show a shift in the (26)Mg/(24)Mg ratios. This investigation showed that the organism is capable of handling excess Mg well and that bones fully recover after degradation. Magnesium alloys as bone implants have faced increasing attention over the past years. In vivo degradation and metabolism studies of these implant materials have shown the promising application

  19. Thermal degradation kinetics of anthocyanins extracted from juçara (Euterpe edulis Martius) and "Italia" grapes (Vitis vinifera L.), and the effect of heating on the antioxidant capacity.

    Science.gov (United States)

    Peron, D V; Fraga, S; Antelo, F

    2017-10-01

    The effect of temperature on the degradation of anthocyanins in juçara and "Italia" grape extracts was determined between 50 and 90°C. For both species, thermal degradation followed a first-order kinetic model. The decimal reduction time decreased with increasing temperature, and dependence on the thermodegradable factor was lower at higher temperatures. The anthocyanins from juçara degraded more slowly than those extracted from "Italia" grapes. The activation enthalpy and free energy of inactivation indicated an endothermic reaction, not spontaneous degradation, whereas the activation entropy suggested that the transition state has less structural freedom than that of the reactants. The antioxidant capacity of the extracts was reduced when subjected to 90°C heat treatment, however, significant quantities of this bioactive compound still remained. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Effect of polyethelene oxide on the thermal degradation of cellulose biofilm – Low cost material for soft tissue repair in dentistry

    Science.gov (United States)

    Tyler, Rakim; Schiraldi, David; Roperto, Renato; Faddoul, Fady; Teich, Sorin

    2017-01-01

    Background Bio cellulose is a byproduct of sweet tea fermentation known as kombusha. During the biosynthesis by bacteria cellulose chains are polymerized by enzyme from activated glucose. The single chains are then extruded through the bacterial cell wall. Interestingly, a potential of the Kombucha’s byproduct bio cellulose (BC) as biomaterial had come into focus only in the past few decades. The unique physical and mechanical properties such as high purity, an ultrafine and highly crystalline network structure, a superior mechanical strength, flexibility, pronounced permeability to gases and liquids, and an excellent compatibility with living tissue that reinforced by biodegradability, biocompatibility, large swelling ratios. Material and Methods The bio-cellulose film specimens were provided by the R.P Dressel dental materials laboratory, Department of Comprehensive Care, School of Dental Medicine, Case Western Reserve University, Cleveland, US. The films were harvested, washed with water and dried at room temperature overnight. 1wt% of PEG-2000 and 10wt% of NaOH were added into ultrapure water to prepare PEG/NaOH solution. Then bio-cellulose film was added to the mixture and swell for 3 h at room temperature. All bio-cellulose film specimens were all used in the TA Instruments Q500 Thermogravmetric Analyzer to investigate weight percent lost and degradation. The TGA was under ambient air conditions at a heating rate of 10ºC/min. Results and Conclusions PEG control exhibited one transition with the peak at 380ºC. Cellulose and cellulose/ PEG films showed 3 major transitions. Interestingly, the cellulose/PEG film showed slightly elevated temperatures when compared to the corresponding transitions for cellulose control. The thermal gravimetric analysis (TGA) degradation curves were analyzed. Cellulose control film exhibited two zero order transitions, that indicate the independence of the rate of degradation from the amount on the initial substance. The

  1. Influence of different beverages on the force degradation of intermaxillary elastics: an in vitro study

    Science.gov (United States)

    LEÃO FILHO, Jorge César Borges; GALLO, Daphine Beatriz; SANTANA, Regis Meller; GUARIZA-FILHO, Odilon; CAMARGO, Elisa Souza; TANAKA, Orlando Motohiro

    2013-01-01

    Objective: The aim of this study was to evaluate in vitro the effects of frequently ingested beverages on force degradation of intermaxillary elastics. Material and Methods: One hundred and eighty 1/4-inch intermaxillary elastics (TP Orthodontics) were immersed into six different beverages: (1) Coca-Cola®; (2) Beer; (3) Orange juice; (4) Red wine; (5) Coffee and (6) artificial saliva (control). The period of immersion was 15 min for the first and second cycles and 30 min for the third to fifth cycles. Tensile forces were read in a tensile testing machine before and after the five immersion cycles. One-way repeated measures ANOVA was used to identify significant differences. Results: Force degradation was seen in all evaluated groups and at all observation periods (p<0.05). A greater degree of degradation was present at the initial periods, decreasing gradually over time. However, no statistically significant differences were seen among groups at the same periods, showing that different groups behaved similarly. Conclusion: The chemical nature of the evaluated beverages was not able to influence the degree of force degradation at all observation periods. PMID:23739862

  2. Influence of different beverages on the force degradation of intermaxillary elastics: an in vitro study

    Directory of Open Access Journals (Sweden)

    Jorge César Borges Leão Filho

    2013-04-01

    Full Text Available Objective: The aim of this study was to evaluate in vitro the effects of frequently ingested beverages on force degradation of intermaxillary elastics. Material and Methods: One hundred and eighty 1/4-inch intermaxillary elastics (TP Orthodontics were immersed into six different beverages: (1 Coca-Cola®; (2 Beer; (3 Orange juice; (4 Red wine; (5 Coffee and (6 artificial saliva (control. The period of immersion was 15 min for the first and second cycles and 30 min for the third to fifth cycles. Tensile forces were read in a tensile testing machine before and after the five immersion cycles. One-way repeated measures ANOVA was used to identify significant differences. Results: Force degradation was seen in all evaluated groups and at all observation periods (p<0.05. A greater degree of degradation was present at the initial periods, decreasing gradually over time. However, no statistically significant differences were seen among groups at the same periods, showing that different groups behaved similarly. Conclusions: The chemical nature of the evaluated beverages was not able to influence the degree of force degradation at all observation periods.

  3. Analysis of degradation in UHMWPE a comparative study among the various commercial and laboratory grades UHMWPE

    Science.gov (United States)

    Azam, A. M.; Ali, A.; Khan, H.; Yasin, T.; Mehmood, M. S.

    2016-08-01

    Oxidative degradation of the ultra-high molecular weight polyethylene (UHMWPE) limits the life of implants. This degradation can be monitored to estimate the service life of UHMWPE following the standard protocols as defined by American Standards for Testing Materials (ASTM). In this work, a comparative study has been carried on two commercially available UHMWPE grades i.e. GUR 1020 and GUR 1050 and one laboratory grade UHMWPE which was purchased from Sigma Aldrich. These powder samples were pressed while using hot press with controlled heating and cooling setup in open air under 200 bar of external pressure. These sheets were then subjected to accelerated aging in an oven at 80 °C for three weeks. The degradation of the UHMWPE was monitored by ATR-FTIR techniquefor three weeks. The oxidation index (OI) measurement showed that the commercial grade UHMWPE i.e. GUR-1020 and GUR-1050 degrade more as compared to laboratory grade UHMWPE. The values of OI after three weeks of accelerating aging were found 0.18, 0.14, and 0.09 for GUR-1020, GUR-1050, and Sigma Aldrich, respectively. In addition to this, it was found that commercial grades of UHMWPE suffer more structural alterations as compared to laboratory grade one. We hope that these results will be of particular and fundamental importance for the researchers and orthopaedic industry.

  4. Kinetic study of Mongolian coals by thermal analysis

    Directory of Open Access Journals (Sweden)

    Jargalmaa S

    2018-02-01

    Full Text Available Thermal analysis was used for the thermal characterization of the coal samples. The experiments were performed to study the pyrolysis and gasification kinetics of typical Mongolian brown coals. Low rank coals from Shivee ovoo, Ulaan ovoo, Aduun chuluun and Baganuur deposits have been investigated. Coal samples were heated in the thermogravimetric apparatus under argon at a temperature ranges of 25-1020ºC with heating rates of 10, 20, 30 and 40ºC/min. Thermogravimetry (TG and derivative thermogravimetry (DTG were performed to measure weight changes and rates of weight losses used for calculating the kinetic parameters. The activation energy (Ea was calculated from the experimental results by using an Arrhenius type kinetic model.

  5. Methyl tert-butyl ether (MTBE) degradation by ferrous ion-activated persulfate oxidation: feasibility and kinetics studies.

    Science.gov (United States)

    Chen, K F; Kao, C M; Wu, L C; Surampalli, R Y; Liang, S H

    2009-07-01

    The objective of this study was to evaluate the feasibility of using ferrous ion-activated persulfate oxidation to remediate groundwater contaminated with methyl tert-butyl ether (MTBE). In this study, batch experiments were conducted to evaluate the effects of various factors on the efficiency of MTBE degradation including persulfate concentrations, ferrous ion concentrations, and persulfate coupled with hydrogen peroxide. Results show that ferrous ion-activated persulfate oxidation was capable of degrading MTBE efficiently. Persulfate and ferrous ion concentrations correlated with MTBE degradation rates. However, excess addition of ferrous ion resulted in decreased MTBE degrading rates most likely because of competition for sulfate free radicals between ferrous ion and MTBE. Two main byproducts of MTBE degradation, tert-butyl formate and tert-butyl alcohol, were detected in the experiments; both were, however, subsequently degraded. Results of sulfate analysis show that proper addition of ferrous ion could prevent unnecessary persulfate decomposition.

  6. Thermal comfort study of plastics manufacturing industry in converting process

    Directory of Open Access Journals (Sweden)

    Sugiono Sugiono

    2017-09-01

    Full Text Available Thermal comfort is one of ergonomics factors that can create a significant impact to workers performance. For a better thermal comfort, several environment factors (air temperature, wind speed and relative humidity should be considered in this research. The object of the study is a building for converting process of plastics manufacturing industry located in Malang, Indonesia. The maximum air temperature inside the building can reach as high as 36°C. The result of this study shows that heat stress is dominantly caused by heat source from machine and wall building. The computational fluid dynamics (CFD simulation is used to show the air characteristic through inside the building. By using the CFD simulation, some scenarios of solution are successfully presented. Employees thermal comfort was investigated based on predicted mean vote model (PMV and predicted percentage of dissatisfied model (PPD. Existing condition gives PMV in range from 1.83 to 2.82 and PPD in range from 68.9 to 98%. Meanwhile, modification of ventilation and replacing ceiling material from clear glass into reflective clear glass gave significant impact to reduce PMV into range from 1.63 to 2.18 and PPD into range from 58.2 to 84.2%. In sort, new design converting building process has more comfortable for workers.

  7. Study of land degradation and desertification dynamics in North Africa areas using remote sensing techniques

    OpenAIRE

    Afrasinei, Gabriela Mihaela

    2016-01-01

    In fragile-ecosystem arid and semi-arid land, climatic variations, water scarcity and human pressure accelerate ongoing degradation of natural resources. In order to implement sustainable management, the ecological state of the land must be known and diachronic studies to monitor and assess desertification processes are indispensable in this respect. The present study is developed in the frame of WADIS-MAR (www.wadismar.eu). This is one of the five Demonstration Projects implem...

  8. Barium content study and properties characterization of lead zirconate stannate titanate antiferroelectric ceramics using thermally stimulated depolarization current technique

    Science.gov (United States)

    Li, Ze; Song, Xiaozhen; Zhang, Yong; Chen, Yongzhou; Shen, Ziqin; Baturin, Ivan

    2017-05-01

    Thermally stimulated depolarization current (TSDC) and highly accelerated lifetime testing studies of (Pb0.925-xLa0.05Bax)(Zr0.52Sn0.39Ti0.09)O3 (PLBZST) antiferroelectric ceramics have been performed for three compositions with different barium contents. These studies have revealed that barium substitution increases the failure time and improves the resistance degradation behavior. As a result of the variations of peak current intensity and peak temperature with different polarization temperatures in the TSDC curves, three successive relaxation peaks with different origins have been found to occur: a low-temperature defect dipole peak, an intermediate-temperature in-grain oxygen vacancy migration peak, and a high-temperature transgranular oxygen vacancy migration peak. These results demonstrate that the improved resistance degradation process with the increase of barium substitution is related to the decrease in oxygen vacancy concentration.

  9. Parallel experimental study of a novel super-thin thermal absorber based photovoltaic/thermal (PV/T) system against conventional photovoltaic (PV) system

    OpenAIRE

    Xu, Peng; Zhang, Xingxing; Shen, Jingchun; Zhao, Xudong; He, Wei; Li, Deying

    2015-01-01

    Photovoltaic (PV) semiconductor degrades in performance due to temperature rise. A super thin-conductive thermal absorber is therefore developed to regulate the PV working temperature by retrofitting the existing PV panel into the photovoltaic/thermal (PV/T) panel. This article presented the parallel comparative investigation of the two different systems through both laboratory and field experiments. The laboratory evaluation consisted of one PV panel and one PV/T panel respectively while the...

  10. SYNTHESIS, THERMAL STUDIES AND CONVERSION DEGREE OF DIMETHACRYLATE POLYMERS USING NEW NON-TOXIC COINITIATORS

    Directory of Open Access Journals (Sweden)

    Rafael Turra Alarcon

    Full Text Available The aim of this paper is to replace toxic coinitiators (tertiary amines by non-toxic compounds such as glycerol and inositol (polyalcohol in dimethacrylate resins. For this purpose, mid infrared spectroscopy (MIR was used to calculate the monomers' degree of conversion (%DC; as well as simultaneous Thermogravimetric Analysis – Differential Thermal Analysis (TGA-DTA and Differential Scanning Calorimetry (DSC were conducted to evaluate thermal stability, degradation steps, and thermal events. The use of different initiator systems did not modify the thermal events or the thermal stability of each of the dimethacrylate resins. Results show a substitution of system 2 (toxicity by system 3 (low toxicity, which had a good conversion velocity and total conversion in some monomers, is plausible.

  11. Chemical degradation of proton conducting perflurosulfonic acid ionomer membranes studied by solid-state nuclear magnetic resonance spectroscopy

    Science.gov (United States)

    Ghassemzadeh, L.; Marrony, M.; Barrera, R.; Kreuer, K. D.; Maier, J.; Müller, K.

    The degradation of two different types of perfluorinated polymer membranes, Nafion and Hyflon Ion, has been examined by solid-state 19F and 13C NMR spectroscopy. This spectroscopic technique is demonstrated to be a valuable tool for the study of the membrane structure and its alterations after in situ degradation in a fuel cell. The structural changes in different parts of the polymers are clearly distinguished, which provides unique insight into details of the degradation processes. The experimental NMR spectra prove that degradation mostly takes place within the polymer side chains, as reflected by the intensity losses of NMR signals associated with SO 3H, CF 3, OCF 2 and CF groups. The integral degree of degradation is found to decrease with increasing membrane thickness while for a given thickness, Hyflon Ion appears to degrade less than Nafion.

  12. Literature review of market studies of thermal energy storage

    Energy Technology Data Exchange (ETDEWEB)

    Hattrup, M.P.

    1988-02-01

    This report presents the results of a review of market studies of thermal energy storage (TES). This project was conducted by Pacific Northwest Laboratory (PNL) for the US Department of Energy (DOE). PNL staff reviewed and consolidated the findings of existing TES market studies conducted in the industrial, commercial, and residential sectors. The purpose of this project was to review and assess previous work and to use the information obtained to help provide direction for future technology transfer planning activities and to identify additional economic research needed within those three sectors. 37 refs.

  13. Study The Properties and Weight Loss Degradation of The Blend LDPE/Cellulose in Soil Environment

    Directory of Open Access Journals (Sweden)

    Zuhair Jabbar Abdul Ameer

    2017-05-01

    Full Text Available Wider applications of polyethylene (PE in packaging and agriculture have raised serious issue of waste disposal and pollution. Therefore, it is necessary to raise its biodegradability by additives.In this study, we will add cellulose to low density polyethylene to prepare polymer blend have ability to degradation in soil environment.The samples were prepared by using twin screw extruder.LDPE and CELL have been mixing with different weight proportions, and studied their properties in order to determine its compliance with the required specifications to be able to be used biodegradable polymers. To improve the viability of decomposition PEG has been added to the resulting blend. Several tests were applied to identify those properties such as tensile,hardness, density and creep test. FTIR, digital microscope and SEM test acheved in order to determine the miscibility and blend morphology befor and after degradation.The results show that,the blend weight loss increase with increasing CELL percent.

  14. How to measure thermal effects of personal cooling systems : Human, thermal manikin and human simulator study

    NARCIS (Netherlands)

    Bogerd, N.; Psikuta, A.; Daanen, H.A.M.; Rossi, R.M.

    2010-01-01

    Thermal effects, such as cooling power and thermophysiological responses initiated upon application of a personal cooling system, can be assessed with (i) humans, (ii) a thermal manikin and (iii) a thermophysiological human simulator. In order to compare these methods, a cooling shirt (mild cooling)

  15. Analyzing Thermal Characteristics of Urban Streets Using a Thermal Imaging Camera: A Case Study on Commercial Streets in Seoul, Korea

    Directory of Open Access Journals (Sweden)

    Sugie Lee

    2018-02-01

    Full Text Available Due to continuing city growth and global warming over the past decades, urban heat island (UHI effects, referring to the phenomena wherein the ambient air temperatures in cities are higher than those in rural areas, have become a serious threat to urban populations. Impervious surfaces, buildings with low-albedo materials, and a lack of vegetated areas are the major causes of poor urban thermal environments, particularly during the summer. Previous research has focused primarily on the thermal characteristics of individual building units. Few studies consider the impact of the street-scale thermal environments on the surface temperature, which affects pedestrian thermal comfort. The purpose of this study is to analyze the thermal characteristics of various physical elements on urban streets using thermal imaging cameras, and present policy implications for improving pedestrian thermal comfort. This study examines street-scale thermal environments of three major commercial streets: Garosu road, Serosu road, and Narosu road, in Seoul, Korea. This study conducted field measurements both during the day and the night in June 2017 in order to investigate changes in the urban surface temperatures across time. The results show that street trees are the most effective mitigation element for reducing surface temperatures. With regard to building use types, the highest surface temperatures are typically measured near restaurant buildings. Building façades that are dark-colored or partially covered with a metal contribute to high surface temperatures. Similarly, the temperatures of artificial turf or wooden decks on urban streets are also significantly high during the daytime. The thermal characteristics of various urban street elements should be considered to reduce the surface temperature and mitigate the urban heat island effect.

  16. Chemical Characterization and Thermal Stressing Studies of Perfluorohexane Fluids for Space-Based Applications

    Science.gov (United States)

    Arnold, William A.; Hartman, Thomas G.; McQuillen, John

    2006-01-01

    Perfluorohexane (PFH), C6F14, is a perfluorocarbon fluid. Several PFH fluids with different isomer concentrations were evaluated for use in an upcoming NASA space experiment. Samples tested included two commercially obtained high-purity n-perfluorohexane (n-PFH) fluids and a technical grade mixture of C6F14 branched and linear isomers (FC-72(TradeMark)). These fluids were evaluated for exact chemical composition, impurity purity and high temperature degradation behavior (pyrolysis). Our investigation involved simulated thermal stressing studies of PFH fluids under conditions likely to occur in the event of an atmospheric breach within the International Space Station (ISS) and subsequent exposure of the vapors to the high temperature and catalyst present in its Trace Contaminant Control Subsystem (TCCS). Exposure to temperatures in the temperature range of 200-450 C in an inert or oxidizing atmosphere, with and without the presence of catalyst was investigated. The most aggressive conditions studied were exposure of PFH vapors to 450 C in air and in the presence of TCCS (palladium) catalyst. Gas chromatography-mass spectrometry (GC-MS) and gas chromatography (GC) analyses were conducted on the perfluorohexane samples before and after pyrolysis. The FC-72 and n-PFH samples showed no significant degradation following pyrolysis even under the most aggressive study conditions. Some trace level impurities associated with the PFH samples such as linear perfluorocarbon monohydrides or monoiodides were destroyed by pyrolysis at the upper limit. Other trace level impurities such as olefinic or cycloolefinic perfluorocarbons were converted into oxidation products by pyrolysis. The purity of PFH following pyrolysis actually increased slightly as a consequence since these trace contaminants were effectively scrubbed from the samples. However, since the initial concentrations of the thermally-impacted impurities were so low, the net effect was trivial. A potential byproduct of

  17. Simplified stochastic models with time delay for studying the degradation process of mRNA molecules.

    Science.gov (United States)

    Tian, Tianhai

    2014-01-01

    Message RNA (mRNA) is the template for protein synthesis. It carries information from DNA in the nucleus to the ribosome sites of protein synthesis in the cell. The turnover process of mRNA is a chemical event with multiple small step reactions and the degradation of mRNA molecules is an important step in gene expression. A number of mathematical models have been proposed to study the dynamics of mRNA turnover, ranging from a one-step first order reaction model to the linear multi-component models. Although the linear multi-component models provide detailed dynamics of mRNA degradation, the simple first-order reaction model has been widely used in mathematical modelling of genetic regulatory networks. To illustrate the difference between these models, we first considered a stochastic model based on the multi-component model. Then a simpler stochastic model was proposed to approximate the linear multi-component model. We also discussed the delayed one-step reaction models with different types of time delay, including the constant delay, exponentially distributed delay and Erlang distributed delay. The comparison study suggested that the one-step reaction models failed to realise the dynamics of mRNA turnover accurately. Therefore, more sophisticated one-step reaction models are needed to study the dynamics of mRNA degradation.

  18. A study by non-isothermal thermal methods of spruce wood bark materialss after their application for dye removal

    Directory of Open Access Journals (Sweden)

    VIORICA DULMAN

    2005-11-01

    Full Text Available This paper deals with a study of some materials obtained from spruce bark (Picea abies, Romania, after retention of some dyes frequently used in dyeing processes in the textile industry and waste water treatment. These materials obtained by dye retention exhibit a particular thermal behavior which is different from that of the blank sample (spruce bark. The characteristic temperatures, weight losses, the residue remaining after thermo-oxidative degradation, as well as the activation energies of the significant thermo-destruction stages, estimated from non-isothermal thermogravimetric data, together with the thermal quantities calculated from DTAdata support the conclusion presented in a previous study on dye retention from aqueous solution. The obtained results made evident that, under optimal retention conditions, spruce bark shows the highest retention capacity for the Basic Blue dye, followed by Direct Brown 95 and Direct Brown 2.

  19. Thermal expansion and magnetostriction studies on iron pnictides

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Liran

    2010-09-19

    In this work, a 3-terminal capacitance dilatometer was set up and used for measurements of the thermal expansion and magnetostriction of novel superconducting iron pinictides and related materials. In particular, RFeAsO with R = La, Ce, Pr, Sm, Gd, LaFeASO{sub 1-x}F{sub x} and Ca(F{sub 1-c}Co{sub x}){sub 2}As{sub 2} have been investigated. The data on polycrystalline LaFeAsO{sub 1-x} are the first published thermal expansion data on this material. The lattice effects at the structural and the magnetic phase transition have been investigated and the phase diagram upon F-doping has been studied. A main result is the observation of a previously unknown fluctuation regime for the doping level x ≤ 0.04 over a large T range above the structural transition temperature T{sub S}. The absence of any structural anomalies in the normal state of the superconducting LaFeAlO{sub 1-x}F{sub x} samples with x ≥ 0.05 corroborates the discontinuous character of the phase boundary not only for the magnetism but also for the structural degrees of freedom. Similarly, the presence of high-temperature fluctuations is found for all RFeAsO undoped materials under study. The discussion of the probable origin of the fluctuations as well as the definition of the structural transition temperature T{sub S} are done. The low temperature features shown by the thermal expansion data for RFeAsO are caused by the onset of long range magnetic order of the 4f-moments and their different configurations. In particular, PrFeAsO, which has a very pronounced anomaly associated with Pr-ordering exhibits a large magnetostriction at low temperatures. By discussing this effect along with the magnetization, resistivity and other measurements, it is found that this large magneto-elastic effect may originate from the correlations between the momentum from Fe{sup 3+} and Pr{sup 3+}. Last, the thermal expansion of Ca(Fe{sub 1-x}Co{sub x}){sub 2}As{sub 2} 122 single crystals is investigated. Ca(Fe{sub 1-x}Co{sub x

  20. Thermal Spectroscopy and Kinetic Studies of PEO/PVDF Loaded by Carbon Nanotubes

    Directory of Open Access Journals (Sweden)

    Laila Hussein Gaabour

    2015-01-01

    Full Text Available Nanocomposites of polyethylene oxide (PEO and polyvinylidene fluoride (PVDF without and with low content of single and multiwalled carbon nanotubes (SWCNTs-MWCNTs were prepared and studied by thermogravimetric analysis (TGA using different heating rate. TGA results indicate that the thermal stability of neat PEO/PVDF blend was improved with both heating rate and incorporation of carbon nanotubes (CNTs. The degradation temperature for neat blend was lower than those of the nanocomposites after adding both SWCNTs and MWCNTs. As increase of heating rate, the onset of decomposition is irregularly moved to higher temperatures. This indicates that the thermal stability of the polymeric matrices has been improved after addition of CNTs. The residual weight of the samples left increased steadily with adding of both SWCNTs and MWCNTs. Kinetic thermodynamic parameters such as activation energy, enthalpy, entropy, and Gibbs free energy are evaluated from TGA data using Coats-Redfern model. The values of all parameters irregularly decrease with increasing of heating rate due to increasing of heating rate temperature, the random scission of macromolecule chain in the polymeric matrices predominates and the activation energy has a lower value.

  1. Cross-border cooperation potential in fostering redevelopment of degraded border areas - a case study approach.

    Science.gov (United States)

    Alexandre Castanho, Rui; Ramírez, Beatriz; Loures, Luis; Fernández-Pozo, Luis; Cabezas, José

    2017-04-01

    Border interactions have reached unprecedented levels in recent decades, not only due to their potential for territorial integration but also considering their role in supranational processes, such as landscape reclamation, infrastructure development and land use planning on European territory. In this scenario, successful examples related to the redevelopment of degraded areas have been showing positive impacts at several levels, such as the social, economic, environmental and aesthetic ones which have ultimately related this process, positively, to sustainability issues. However, concerning to border areas, and due to their inherent legislative and bureaucratic conflicts, the intervention in these areas is more complex. Still, and taking into account previously developed projects and strategies of cross-border cooperation (CBC) in European territory it is possible to identified that the definition of common master plans and common objectives are critical issues to achieve the desired territorial success. Additionally, recent studies have put forward some noteworthy ideas highlighting that it is possible to establish a positive correlation between CBC processes and an increasing redevelopment of degraded border areas, with special focus on the reclamation of derelict landscapes fostering soil reuse and redevelopment. The present research, throughout case study analysis at the Mediterranean level - considering case studies from Portugal, Spain, Monaco and Italy - which presents specific data on border landscape redevelopment, enables us to conclude that CBC processes have a positive influence on the potential redevelopment of degraded border areas, considering not only urban but also rural land. Furthermore, this paper presents data obtained through a public participation process which highlights that these areas present a greater potential for landscape reclamation, fostering resource sustainability and sustainable growth. Keywords: Spatial planning; Land

  2. Application of UV spectrophotometric method to study stress degradation behavior of cefprozil

    Directory of Open Access Journals (Sweden)

    Kiran V Jadhav

    2013-01-01

    Full Text Available Background: Cefprozil is a bactericidal drug that is used in the treatment of susceptible infections including upper and lower respiratory tract infections and skin and soft tissue infections. Materials and Methods: The objective of this research work was to develop and validate new, simple ultraviolet (UV spectrophotometric method of Cefprozil in bulk and pharmaceutical dosage form and its application to study its stress degradation behavior. Results: The absorbance maxima peak was found at 280 nm, and linearity was observed in the concentration range of 2-10 μg/ml. The method was validated and found to be precise. Accuracy (percent recovery for Cefprozil was found to be 99.117±1.005. Conclusion: A new method for estimation of Cefprozil by UV spectrophometry was developed and validated and Cefprozil was found to undergo degradation in all stress conditions.

  3. Study of Factors Determinant of Siliceous Electrical Porcelain Resistance to Structural Degradation

    Directory of Open Access Journals (Sweden)

    Ranachowski P.

    2016-09-01

    Full Text Available The subject of this study was investigation of the factors that have a decisive influence on the resistance of siliceous porcelain to degradation processes. There was tested material C 110 type, which is widely used for the production of low-voltage (LV elements such as insulators and bushings. On the basis of mechanical-acoustic and microscopic research of small-sized samples, which were subjected to compression, there were distinguished successive stages of degradation of the material structure. In the authors’ opinion, they have a reference to the ageing process, taking place during many years of work under operating conditions. Thus, it was possible to assess the structural factors that determine the durability and reliability of LV electroinsulating elements. The results were related to electrical aluminous porcelains.

  4. Microstructural studies on degradation of interface between LSM–YSZ cathode and YSZ electrolyte in SOFCs

    DEFF Research Database (Denmark)

    Liu, Yi-Lin; Hagen, Anke; Barfod, Rasmus

    2009-01-01

    The changes in the cathode/electrolyte interface microstructure have been studied on anode-supported technological solid oxide fuel cells (SOFCs) that were subjected to long-term (1500 h) testing at 750 °C under high electrical loading (a current density of 0.75 A/cm2). These cells exhibit...... different cathode degradation rates depending on, among others, the composition of the cathode gas, being significantly smaller in oxygen than in air. FE-SEM and high resolution analytical TEM were applied for characterization of the interface on a submicron- and nano-scale. The interface degradation has...... that in the cell tested in air this mechanism contributes to an estimated overall reduction in the LSM coverage and the TPB length by 50 and 30%, respectively. For the cell tested in oxygen the corresponding values are 10 and 4%. Secondly, in the cell tested in air the LSM coverage and the TPB length appear...

  5. Studies on Enhancing Transverse Thermal Conductivity Carbon/Carbon Composites

    National Research Council Canada - National Science Library

    Manocha, Lalit M; Manocha, Satish M; Roy, Ajit

    2007-01-01

    The structure derived potential properties of Graphite such as high stiffness coupled with high thermal conductivity and low coefficient of thermal expansion have been better achieved in Carbon fibers...

  6. Solar thermal plant impact analysis and requirements definition study

    Science.gov (United States)

    1982-01-01

    The technology and economics of solar thermal electric systems (STES) for electric power production is discussed. The impacts of and requirements for solar thermal electric power systems were evaluated.

  7. Study of the degradation process of polyimide induced by high energetic ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Severin, Daniel

    2008-09-19

    The dissertation focuses on the radiation hardness of Kapton under extreme radiation environment conditions. To study ion-beam induced modifications, Kapton foils were irradiated at the GSI linear accelerator UNILAC using several projectiles (e.g. Ti, Mo, Au, and U) within a large fluence regime (1 x 10{sup 10}-5 x 10{sup 12} ions/cm{sup 2}). The irradiated Kapton foils were analysed by means of infrared and UV/Vis spectroscopy, tensile strength measurement, mass loss analysis, and dielectric relaxation spectroscopy. For testing the radiation stability of Kapton at the cryogenic operation temperature (5-10 K) of the superconducting magnets, additional irradiation experiments were performed at the Grand Accelerateur National d' Ions Lourds (GANIL, France) focusing on the online analysis of the outgassing process of small volatile degradation fragments. The investigations of the electrical properties analysed by dielectric relaxation spectroscopy exhibit a different trend: high fluence irradiations with light ions (e.g. Ti) lead to a slight increase of the conductivity, whereas heavy ions (e.g. Sm, Au) cause a drastic change already in the fluence regime of nonoverlapping tracks (5 x 10{sup 10} ions/cm{sup 2}). Online analysis of the outgassing process during irradiation at cryogenic temperatures shows the release of a variety of small gaseous molecules (e.g. CO, CO{sub 2}, and short hydro carbons). Also a small amount of large polymer fragments is identified. The results allow the following conclusions which are of special interest for the application of Kapton as insulating material in a high-energetic particle radiation environment. a) The material degradation measured with the optical spectroscopy and tensile strength tests are scalable with the dose deposited by the ions. The high correlation of the results allows the prediction of the mechanical degradation with the simple and non-destructive infrared spectroscopy. The degradation curve points to a

  8. Inhibition of dentine collagen degradation by hesperidin: an in situ study.

    Science.gov (United States)

    van Strijp, Augustinus J P; Takatsuka, Tsutomu; Sono, Ryohei; Iijima, Youichi

    2015-12-01

    Dentine caries is a process of demineralization and subsequent degradation of the collagenous matrix. Host-derived proteolytic enzymes, such as matrix metalloproteinases (MMPs), play a role in this process of dentine collagen degradation. Hampering this degradation retards the caries process. Dietary antioxidants, such as the flavonoid hesperidin, can inhibit the proteolytic activity of MMPs and act as natural stabilizers of collagen. The aim of this study was to investigate the anti-collagenolytic activity of hesperidin in an in situ model. A single-blind, split-mouth, in situ experiment was designed. Seventeen participants received two completely demineralized dentine specimens placed contralaterally in the buccal flanges of their partial prosthesis. During the 4-wk experimental period, the participants immersed the dentine specimens in a test solution [1,000 parts per million (p.p.m.) hesperidin] or a control solution (saline), twice daily for 3 min. After the in situ period, the specimens were retrieved and their collagen content was determined. A saliva sample was taken at the start and at the end of the experimental period, to assess collagenolytic activity. A significant protection of collagen, of 24%, was observed in the hesperidin-treated specimens compared with the control-treated specimens. No correlation was found between salivary collagenolytic activity and loss of collagen in the control-treated specimens. The results of this in situ study show that hesperidin could play a role in the preservation of dentine collagen matrix. © 2015 Eur J Oral Sci.

  9. Cement degradation and the alteration of host rocks. Studies within the Grimsel Test Site Project.

    Science.gov (United States)

    Soler, J. M.

    2009-04-01

    Cement is a major component of the engineered barrier system in proposed underground repositories for low- and intermediate-level radioactive waste. Cement grouting of highly-conductive fractures in the vicinity of such repositories is also planned. The interaction between the hyperalkaline solutions derived from the degradation of cement and the rocks hosting such repositories may change the physical and chemical properties of the host rocks. The HPF project (Hyperalkaline Plume in Fractured Rock; ANDRA-FR-, DOE-USA-, JAEA-JP-, NAGRA-CH-, POSIVA-FI-, SKB-SE-) studied the alteration of a fractured granite due to the circulation of a synthetic high-pH solution. A significant decrease in fracture permeability was observed both in the laboratory (core infiltration experiment; decimeter scale) and in the Grimsel Test Site (circulation along a fracture; meter scale), despite the relatively minor mineralogical alteration. Coupling of mineralogical alteration and permeability changes was incorporated into reactive transport modeling of the experiments. The hydration and degradation of cement are being explicitly incorporated into the new LCS (Long-Term Cement Studies; JAEA-JP-, NAGRA-CH-, NDA-GB-, POSIVA-FI-) project at Grimsel. New laboratory and field experiments including a cement source are being designed. Reactive transport modeling of the degradation of cement, causing the formation of hyperalkaline solutions and the alteration of the host rock, will be an essential part of the experiment.

  10. A study on the degradation of endocrine disruptors and dioxins by ozonation and advanced oxidation processes

    Energy Technology Data Exchange (ETDEWEB)

    Nakagawa, S.; Kenmochi, Y.; Tutumi, K.; Tanaka, T. [Ebara Corp., Fujisawa (Japan)

    2003-07-01

    Recently, enhancement and development of treatment technologies related to contaminated water environment by endocrine disruptors such as bisphenol-A(BPA), estradiol(E2) and dioxins have become a focus of attention. In this study, the influence of O{sub 3} dosage and the forms of endocrine disruptors on the degradability during O{sub 3} treatment and AOP treatment were investigated. A reaction kinetic evaluation of these processes was also carried out. In this study, the endocrine disruptors were classified into 2 groups: (1) DXNs: dioxins and (2) EDs: endocrine disruptors other than dioxins. For the case of DXNs decomposition, highly concentrated DXNs from incinerator washwater were degraded by UV/O{sub 3} combined treatment. Influence of O{sub 3} dosage and forms of DXNs on the reaction rate constant were evaluated. For the case of EDs decomposition, the effect of O{sub 3} dosage on the reaction rate constant were investigated during O{sub 3} treatment of secondary treated sewage. Also, a degradability comparison was made for the above 2 groups. (orig.)

  11. Study of Thermal Properties of Cast Metal- Ceramic Composite Foams

    OpenAIRE

    Gawdzińska K.; Chybowski L.; Przetakiewicz W.

    2017-01-01

    Owing to its properties, metallic foams can be used as insulation material. Thermal properties of cast metal-ceramic composite foams have applications in transport vehicles and can act as fire resistant and acoustic insulators of bulkheads. This paper presents basic thermal properties of cast and foamed aluminum, the values of thermal conductivity coefficient of selected gases used in foaming composites and thermal capabilities of composite foams (AlSi11/SiC). A certificate of non-combustibil...

  12. Using Landsat Images for Studying Land Use Dynamics and Soil Degradation - Case Study in Tamduong District, Vinhphuc Province, Vietnam

    NARCIS (Netherlands)

    Trinh, M.V.; Dinh Duong, N.; Keulen, van H.

    2005-01-01

    Tamduong district, Vinhphuc province, is representative for vast areas in the north of Vietnam where soils are strongly degraded and erosion has led to patches of bare soil with exposure of parent material, and crop yields on these soils are strongly reduced. The aims of this study are to apply

  13. Vibrational and thermal study of l-methionine nitrate polycrystals

    Energy Technology Data Exchange (ETDEWEB)

    Victor, F.M.S.; Ribeiro, L.H.L.; Facanha Filho, P.F.; Santos, C.A.S.; Soares, R.A.; Abreu, D.C.; Sousa, J.C.F.; Carvalho, J.O.; Santos, A.O. dos [Universidade Federal do Maranhao (UFMA), MA (Brazil)

    2016-07-01

    Full text: Intensified in studies of nonlinear optical materials has been observed over the past two decades for its wide application in telecommunications, optical modulation and optical signal processing. The goal of this work is the thermal and vibrational study of L-methionine nitrate polycrystalline. The polycrystals were obtained by the method of slow evaporation of solvent at ambient temperature of 25 ° C. The X-ray diffraction was performed to confirm the structure of the material, which has monoclinic structure (space group P21) with four molecules per unit cell structure. Refinement by Rietveld method has been optimized and good quality parameters Rwp = 7.97% , Rp = 5.74 and S = 1.92%. The thermal stability of the material was verified from Thermogravimetric analysis (TGA), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). The measures showed a possible phase transition event at about 107°C before the melting point of the material, which took place at about 127°C. Thermogravimetric analysis showed two mass loss events of 61.5% and 30.4%. The vibrational modes of the L-methionine nitrate molecule were identified by Raman spectroscopy in the spectral range between 35cm-1 and 3500 cm-1, the scattering measurements were made from room temperature up to the melting temperature of the material (140 ° C ) in which the disappearance of bands was found in the region of normal modes at 130 ° C, thus demonstrating a irreversible structural phase transition, because the spectrum obtained after returning the sample to ambient temperature is typical of amorphous material. (author)

  14. Alumina-Forming Austenitics: A New Approach to Thermal and Degradation Resistant Stainless Steels for Industrial Use

    Energy Technology Data Exchange (ETDEWEB)

    David A Helmick; John H Magee; Michael P Brady

    2012-05-31

    A series of developmental AFA alloys was selected for study based on: 25 Ni wt.% (alloys A-F), 20 wt% Ni (alloys G-H), and 12 Ni wt.% (alloys I-L). An emphasis in this work was placed on the lower alloy content direction for AFA alloys to reduce alloy raw material cost, rather than more highly alloyed and costly AFA alloys for higher temperature performance. Alloys A-D explored the effects of Al (3-4 wt.%) and C (0.05-0.2 wt.%) in the Fe-25Ni-14Cr-2Mn-2Mo-1W-1Nb wt.% base range; alloys E and F explored the effects of removing costly Mo and W additions in a Fe-25Ni-14Cr-4Al-2.5Nb-2Mn-0.2C base, alloys G and H examined Nb (1-2.5wt.%) and removal of Mo, W in a Fe-20Ni-14Cr-3Al-2Mn-0.2 C wt.% base; and alloys I-L examined effects of C (0.1-0.2 wt.%) and Mn (5-10 wt.%) on a low cost Fe-14Cr-12Ni-3Cu-2.5Al wt.% base (no Mo, W additions). Creep testing resulted in elemental trends that included the beneficial effect of higher carbon and lower niobium in 20-25%Ni AFA alloys and, the beneficial of lower Mn in 12%Ni AFA alloys. Corrosion tests in steam and sulfidation-oxidation environments showed, in general, these alloys were capable of a ten-fold improvement in performance when compared to conventional austenitic stainless steels. Also, corrosion test results in metal-dusting environments were promising and, warrant further investigation.

  15. Study of Aramid Fiber/Polychloroprene Recycling Process by Thermal Degradation

    OpenAIRE

    Igor Dabkiewicz; Silva, Ítalo Vinícius Soares e; Jossano Saldanha Marcuzzo; Rita de Cassia Mendonça Sales Contini

    2016-01-01

    ABSTRACT Aramid fiber is an important polymer applied as reinforcement in high-performance composites, which, due its exceptional properties, becomes an excellent impact absorption material. It has been broadly utilized in aeronautic industry and ballistic protection. In aircrafts, it is mainly used in secondary structures, such as fairings, floor panels, and bullet proof structures in helicopters, whereas, in ballistic protection industry, it is applied in automotive armor and bullet proof v...

  16. Physics Based Electrolytic Capacitor Degradation Models for Prognostic Studies under Thermal Overstress

    Data.gov (United States)

    National Aeronautics and Space Administration — Electrolytic capacitors are used in several applications rang- ing from power supplies on safety critical avionics equipment to power drivers for electro-mechanical...

  17. STUDY ON THE KINETICS OF BIOMASS BLENDS DEWATERING AS A STAGE OF THERMAL DEGRADATION

    Directory of Open Access Journals (Sweden)

    Yaroslav ZASIADKO

    2017-12-01

    Full Text Available Solid biomass co-combustion with coal in industrial furnaces, including those of power plants, looks promising in terms of fuel base diversification and also presents a way to reduce significantly the emission of air harmful pollutants, particularly carbon dioxide. CO2resultingfrom biomass burning is environmentally neutral, since the same amount of carbon dioxide will be consumed at the next cycle of biomass photosynthesis. In case of the Ukrainian low reactive anthracite schtib used in such technology, the radical differences in the kinetic characteristics of co-fired fuels become critical issues. A significant difference in the attainable degree of fuel milling fineness due to the prohibitively high expense for solid biomass milling makes the problem more complicated. The values of biomass particle fineness are approximately 5…15 mm; whereas the fineness of pulverized coal reaches as low as 30...50mkm. The moisture and volatiles content for the fuel mentioned also differ noticeably. Therefore, the stages of these fuels burn out will be extremely complex in terms of various time scales of subsequent stages and their positioning in the furnace. The case becomes even more aggravated insofar the kinetic characteristic of the stages of biomass combustion arenot known yet in details. The present work is dedicated to the research into the kinetics of biomass blends demoisturizationand aimed at the deriving of the Arrhenius type equations, allowing to develop submodels of the demoisturization as an individual stage of biomass burn out for 3-D models.

  18. Comparative study of hygrothermal properties of five thermal insulation materials

    Directory of Open Access Journals (Sweden)

    Laure Ducoulombier

    2017-09-01

    Full Text Available The objective of this article is to carry out a comparative study of the main hygrothermal properties of five thermal insulation materials for buildings. These properties are necessary for a correct prediction of heat and moisture transfers through the walls and the selection of the most appropriate materials according to the specific buildings. The studied materials were glass wool, rock wool, expanded polystyrene, wood fiberboard and polyester fiberfill. The article is divided into three parts. The first part presents the phenomena of hygrothermal transfers in walls in order to understand the need for determining specific properties of the insulating materials. The second part describes in details the five studied insulating materials and the methods used for the characterization and identification of their main properties. Finally, the last part presents the experimental results and makes comparisons between materials. The differences between the insulating materials are brought out, such as the strong dependence of the thermal conductivity of polystyrene on temperature, or the good permeability of fibrous insulating materials to water vapor. A detailed analysis of the obtained results is presented.

  19. Morphological, structural and thermal studies of gallium nitride ferrite

    Energy Technology Data Exchange (ETDEWEB)

    Indrakanti, Rajani [Department of Physics, VNRVJIET, Hyderabad, Telangana (India); Rao, V. Brahmaji [Department of Nanoscience and Technology, School of Biotechnology, DSRF, Hyderabad, Telangana (India); Kiran, C. Udaya [Department of Mechanical Engineering, JBIET, Hyderabad, Telangana (India)

    2016-05-06

    We report the synthesis and Characterization of III-V doped Nano ferrite Ga{sub (2x+2)}N Fe{sub 2(49-x)}O{sub 3} for x=1 and x=5 by Sol-Gel method. The Morphological, structural and Thermal characterisation studies are done by using Transmission Electron Microscopy, Energy Dispersive X-ray Analysis, Selected Area Electron Diffraction, Thermo-Gravimetric Analysis and Differential Thermal Analysis. Using the Sci-Finder software we could not trace any reports related to GaNFe{sub 2}O{sub 3} in the literature. It has been observed from our studies that the particles are in the Cylindrical and the Globular structure. The particle diameter values from the Histograms are in good agreement with the XRD values that were communicated by us earlier. The SAED and the EDAX studies reveal the confirmation of the composition and also that the synthesized Ferrite exhibits crystalline nature. The TG-DTA results show that the compound indicates constant sample weight.

  20. Organotin persistence in contaminated marine sediments and porewaters: In situ degradation study using species-specific stable isotopic tracers

    Energy Technology Data Exchange (ETDEWEB)

    Furdek, Martina; Mikac, Nevenka [Division for Marine and Environmental Research, Rudjer Boskovic Institute, Bijenicka 54, Zagreb (Croatia); Bueno, Maite; Tessier, Emmanuel; Cavalheiro, Joana [Laboratoire de Chimie Analytique Bio-inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l’Environnement et les Matériaux, CNRS UMR 5254, Université de Pau et des Pays de l’Adour, Hélioparc Pau Pyrénées, 2, Av. P. Angot, 64053 Pau Cedex 9 (France); Monperrus, Mathilde, E-mail: mathilde.monperrus@univ-pau.fr [Laboratoire de Chimie Analytique Bio-inorganique et Environnement, Institut Pluridisciplinaire de Recherche sur l’Environnement et les Matériaux, CNRS UMR 5254, Université de Pau et des Pays de l’Adour, Hélioparc Pau Pyrénées, 2, Av. P. Angot, 64053 Pau Cedex 9 (France)

    2016-04-15

    Highlights: • Limiting step in OTC degradation in sediments is their desorption into porewater. • TBT persistence in contaminated sediments increases in sediments rich in organic matter. • DBT does not accumulate in sediments as degradation product of TBT. • TBT and DBT degradation in porewaters occurs with half-lives from 2.9 to 9.2 days. • PhTs degradation is slower than BuTs degradation in oxic porewaters. - Abstract: This paper provides a comprehensive study of the persistence of butyltins and phenyltins in contaminated marine sediments and presents the first data on their degradation potentials in porewaters. The study’s aim was to explain the different degradation efficiencies of organotin compounds (OTC) in contaminated sediments. The transformation processes of OTC in sediments and porewaters were investigated in a field experiment using species-specific, isotopically enriched organotin tracers. Sediment characteristics (organic carbon content and grain size) were determined to elucidate their influence on the degradation processes. The results of this study strongly suggest that a limiting step in OTC degradation in marine sediments is their desorption into porewaters because their degradation in porewaters occurs notably fast with half-lives of 9.2 days for tributyltin (TBT) in oxic porewaters and 2.9 ± 0.1 and 9.1 ± 0.9 days for dibutyltin (DBT) in oxic and anoxic porewaters, respectively. By controlling the desorption process, organic matter influences the TBT degradation efficiency and consequently defines its persistence in contaminated sediments, which thus increases in sediments rich in organic matter.

  1. Thermal Fluid-Dynamic Study for the thermal control of the new ALICE Central Detectors

    CERN Document Server

    AUTHOR|(CDS)2216237

    The Inner Tracking System Detector of the ALICE Experiment at CERN laboratory will be replaced in 2020 with a new Detector. It will have to provide, among others, higher spatial resolution, higher tracking precision and faster data read-out. These goals will be attained thanks to new pixel sensors chips and new electronic components, which will have a high impact in terms of dissipated heat. Therefore, one of the critical aspects for the success of the Upgrade project is the design of the Detector cooling system. This thesis work has been developed at CERN in Geneva in close contact with the group responsible for the Mechanics and Cooling of the Detector. The aim of the thermal fluid dynamic study devised is to deliver to the group a reliable and accurate description of the air flow inside the New Inner Tracking System Detector. After a first part of problem definition and design study, a Computational Fluid Dynamic (CFD) analysis has been developed with the ANSYS Fluent software. The CFD model built in this ...

  2. Glycolic acid-catalyzed deamidation of asparagine residues in degrading PLGA matrices: a computational study.

    Science.gov (United States)

    Manabe, Noriyoshi; Kirikoshi, Ryota; Takahashi, Ohgi

    2015-03-31

    Poly(lactic-co-glycolic acid) (PLGA) is a strong candidate for being a drug carrier in drug delivery systems because of its biocompatibility and biodegradability. However, in degrading PLGA matrices, the encapsulated peptide and protein drugs can undergo various degradation reactions, including deamidation at asparagine (Asn) residues to give a succinimide species, which may affect their potency and/or safety. Here, we show computationally that glycolic acid (GA) in its undissociated form, which can exist in high concentration in degrading PLGA matrices, can catalyze the succinimide formation from Asn residues by acting as a proton-transfer mediator. A two-step mechanism was studied by quantum-chemical calculations using Ace-Asn-Nme (Ace = acetyl, Nme = NHCH3) as a model compound. The first step is cyclization (intramolecular addition) to form a tetrahedral intermediate, and the second step is elimination of ammonia from the intermediate. Both steps involve an extensive bond reorganization mediated by a GA molecule, and the first step was predicted to be rate-determining. The present findings are expected to be useful in the design of more effective and safe PLGA devices.

  3. A degradation study of cefepime hydrochloride in solutions under various stress conditions by TLC-densitometry.

    Science.gov (United States)

    Dąbrowska, Monika; Starek, Małgorzata; Krzek, Jan; Papp, Elżbieta; Król, Piotr

    2015-03-01

    A rapid, accurate and sensitive thin-layer chromatography (TLC) method with densitometric detection has been developed and validated for the determination of cefepime in pharmaceuticals. Chromatographic separation was achieved on a silica gel TLC F254 plates with a mobile phase consisting of ethanol-2-propanol-glacial acetic acid 99.5%-water (4:4:1:3, v/v). Densitometric detection was carried out at wavelength of 266 nm in reflectance/absorbance mode. The validation of the method was found to be satisfactory with high accuracy (from 99.24 to 101.37%) and precision (RSD from 0.06 to 0.36%). Additionally, the stability of cefepime in solution was investigated, including the effect of pH, temperature and incubation time. Favorable retention parameters (Rf , Rs, α) were obtained under the developed conditions, which guaranteed good separation of the studied components. The degradation process of cefepime hydrochloride was described by kinetic and thermodynamic parameters (k, t0.1 , t0.5 and Ea ). Moreover, the chemical properties of degradation products were characterized by the Rf values, absorption spectra, HPLC-MS/MS and TLC-densitometry analysis. As the method could effectively separate the active substance from its main degradation product (1-methylpyrrolidine), it can be employed as a method to indicate the stability of this drug. Copyright © 2014 John Wiley & Sons, Ltd.

  4. Genome-wide study of mRNA degradation and transcript elongation in Escherichia coli.

    Science.gov (United States)

    Chen, Huiyi; Shiroguchi, Katsuyuki; Ge, Hao; Xie, Xiaoliang Sunney

    2015-01-12

    An essential part of gene expression is the coordination of RNA synthesis and degradation, which occurs in the same cellular compartment in bacteria. Here, we report a genome-wide RNA degradation study in Escherichia coli using RNA-seq, and present evidence that the stereotypical exponential RNA decay curve obtained using initiation inhibitor, rifampicin, consists of two phases: residual RNA synthesis, a delay in the interruption of steady state that is dependent on distance relative to the mRNA's 5' end, and the exponential decay. This gives a more accurate RNA lifetime and RNA polymerase elongation rate simultaneously genome-wide. Transcripts typically have a single RNA decay constant along all positions, which is distinct between different operons, indicating that RNA stability is unlikely determined by local sequences. These measurements allowed us to establish a model for RNA processing involving co-transcriptional degradation, providing quantitative description of the macromolecular coordination in gene expression in bacteria on a system-wide level. © 2015 The Authors. Published under the terms of the CC BY 4.0 license.

  5. Theoretical studies on degradation mechanism for OH-initiated reactions with diuron in water system.

    Science.gov (United States)

    Ren, Xiaohua; Cui, Zhaojie; Sun, Youmin

    2014-07-01

    Diuron, a chlorine-substituted dimethyl herbicide, is widely used in agriculture. Though the degradation of diuron in water has been studied much with experiments, little is known about the detailed degradation mechanism from the molecular level. In this work, the degradation mechanisms for OH-induced reactions of diuron in water phase are investigated at the MPWB1K/6-311+G(3df,2p)//MPWB1K/6-31+G(d,p) level with polarizable continuum model (PCM) calculation. Three reaction types including H-atom abstraction, addition, and substitution are identified. For H-atom abstraction reactions, the calculation results show that the reaction abstracting H atom from the methyl group has the lowest energy barrier; the potential barrier of ortho- H (H1') abstraction is higher than the meta- H abstraction, and the reason is possibly that part of the potential energy is to overcome the side chain torsion for the H1' abstraction reaction. For addition pathways, the ortho- site (C (2) atom) is the most favorable site that OH may first attack; the potential barriers for OH additions to the ortho- sites (pathways R7 and R8) and the chloro-substituted para- site (R10) are lower than other sites, indicating the ortho- and para- sites are more favorable to be attacked, matching well with the -NHCO- group as an ortho-para directing group.

  6. Study of major aromatic compounds in port wines from carotenoid degradation.

    Science.gov (United States)

    Silva Ferreira, António César; Monteiro, Judith; Oliveira, Carla; Guedes de Pinho, Paula

    2008-09-01

    The carotenoids degradation and the formation of volatiles were examined by simulating Port wine aging. A two year old red Port wine was saturated with oxygen, supplemented with lutein and β-carotene and kept at 60°C during 87h. A similar study was performed in a model wine solution. Results showed that the percentage decrease in lutein levels was, respectively, 79% and 95%, in the wine model solution and in the Port wine, and 55% and 10% for β-carotene, indicating that lutein was more sensitive to degradation than β-carotene. Two other unknown degradation carotenoid compounds were identified by HPLC/DAD (reverse phase λmax: 422; 445; 475 and 422; 445; 472) in the lutein supplemented wine. Levels of β-ionone and β-cyclocitral increased (2.5 times) in both, wine and wine model solution, supplemented with β-carotene. Along with these compounds, the same behaviour was observed in β-damascenone in the supplemented lutein wine and wine model solution. New insights were provided into the understanding of aroma modifications occurring during Port wine aging. The relationship between carotenoid molecules (β-carotene and lutein) and some volatiles has also been provided. Copyright © 2008 Elsevier Ltd. All rights reserved.

  7. Effect of impurities and electrolyte thickness on degradation of pure magnesium: A finite element study

    Energy Technology Data Exchange (ETDEWEB)

    Montoya, R., E-mail: rodrigo.montoya@cenim.csic.es [Centro Nacional de Investigaciones Metalurgicas, CENIM, CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain); Departamento de Matematicas, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, UNAM, Ciudad Universitaria, 04510 Mexico D.F. (Mexico); Departamento de Ingenieria Metalurgica, Facultad de Quimica, Universidad Nacional Autonoma de Mexico, UNAM, Ciudad Universitaria, 04510 Mexico D.F. Mexico (Mexico); Escudero, M.L., E-mail: escudero@cenim.csic.es [Centro Nacional de Investigaciones Metalurgicas, CENIM, CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain); Garcia-Alonso, M.C., E-mail: crisga@cenim.csic.es [Centro Nacional de Investigaciones Metalurgicas, CENIM, CSIC, Avda. Gregorio del Amo 8, 28040 Madrid (Spain)

    2011-12-15

    Highlights: Black-Right-Pointing-Pointer Degradation of Mg due to the presence of impurities by finite element method. Black-Right-Pointing-Pointer A thin film of electrolyte causes galvanic corrosion focused only close on impurities. Black-Right-Pointing-Pointer A thick layer of electrolyte provokes galvanic corrosion extended the whole surface. Black-Right-Pointing-Pointer A higher number of impurities causes galvanic corrosion on the Mg surface independently of electrolyte thickness. Black-Right-Pointing-Pointer The electrolyte thickness is an important variable that affects the in vivo degradation. - Abstract: The aim of this work is to study the degradation of magnesium due to the presence of impurities, by finite element method (FEM), when different thickness of physiological medium bathes the surface. The electrochemical experimental data obtained from polarization curves are used to model mathematically the corrosion process by solving the Laplace equation and the proper boundary conditions by means of FEM. The results show that when Mg is covered by a thin film of electrolyte, galvanic corrosion is focused only on the areas located really close to the cathodic sites, and far from the impurities, the Mg matrix remains near to its corrosion potential with a natural corrosion process. However, if the Mg matrix is completely covered by a thick layer of electrolyte the potentials obtained in the Mg surface far from the impurity are higher than its corrosion potential, so the Mg suffers more severe galvanic corrosion. On the other hand, when a higher number of impurities is considered, the Mg matrix is anodically polarized and it suffers severe galvanic corrosion, independently of h. The thickness of the electrolyte h must be considered as an important variable that affects the in vivo degradation.

  8. Biological degradation of EDTA in pulping effluents at higher pH - a laboratory study

    Energy Technology Data Exchange (ETDEWEB)

    Ek, M.; Remberger, M.; Allard, A.S.

    1999-01-01

    The biological degradation of EDTA at different pH, sludge load and sludge age has been investigated in laboratory experiments. The experiments showed that relatively fast degradation of EDTA in the form found in this waste water (from production of TMP) took place at least at pH around 8.5 with moderate COD load and high sludge age. In continuous reactors the degradation of EDTA in a pulp and paper waste water was 2-3 mg EDTA/g SS*day at both pH 7 and 8,5, and at sludge ages from 5 to 21 days. The degradation was dependent on sludge load, and no degradation was seen above 1 g COD/g SS*day. In kinetic experiments with half strength waste water the same degradation rate (1,5-2 mg EDTA/g SS*day) was found at pH 7 and at pH 8,5 with sludge of low age (9 and 5 days SRT). Much faster degradation was found at pH 8,5 with sludge of high age (21 days in the continuous experiment). The mean degradation rate was over 10 mg EDTA/g SS*day from 20 to 5 mg EDTA/l. v{sub max} was determined to be 35 mg EDTA/g SS*day and K{sub M} to 31 mg EDTA/l. COD removal was at least as good at pH 8,5 as at pH 7. Sludge properties were best at pH 8,5 and long sludge retention time (giving low sludge load). Both sludge volume index and residual suspended solids after sedimentation were lower than under normal conditions at pH 7. The direct cost for caustic lime would be about 15 SEK per ton of TMP, with a water like the one investigated here. This can vary a lot depending on starting pH and buffering capacity. Costs for addition of nitrogen source could probably be omitted, but this is normally not more than 1-2 SEK per ton of TMP. The extra need for oxygen in the treatment would not be more than some percent, but may be important if oxygen is limited. A substantial extra cost would be if the aeration volume has to be increased. According to the best results from the kinetic study, this would not be needed in an extended aeration activated plant with 2 days HRT and sludge concentrations of 2

  9. Experimental study of thermal rectification in suspended monolayer graphene

    Science.gov (United States)

    Wang, Haidong; Hu, Shiqian; Takahashi, Koji; Zhang, Xing; Takamatsu, Hiroshi; Chen, Jie

    2017-06-01

    Thermal rectification is a fundamental phenomenon for active heat flow control. Significant thermal rectification is expected to exist in the asymmetric nanostructures, such as nanowires and thin films. As a one-atom-thick membrane, graphene has attracted much attention for realizing thermal rectification as shown by many molecular dynamics simulations. Here, we experimentally demonstrate thermal rectification in various asymmetric monolayer graphene nanostructures. A large thermal rectification factor of 26% is achieved in a defect-engineered monolayer graphene with nanopores on one side. A thermal rectification factor of 10% is achieved in a pristine monolayer graphene with nanoparticles deposited on one side or with a tapered width. The results indicate that the monolayer graphene has great potential to be used for designing high-performance thermal rectifiers for heat flow control and energy harvesting.

  10. Degradation of phytate by the 6-phytase from Hafnia alvei: a combined structural and solution study.

    Directory of Open Access Journals (Sweden)

    Antonio Ariza

    Full Text Available Phytases hydrolyse phytate (myo-inositol hexakisphosphate, the principal form of phosphate stored in plant seeds to produce phosphate and lower phosphorylated myo-inositols. They are used extensively in the feed industry, and have been characterised biochemically and structurally with a number of structures in the PDB. They are divided into four distinct families: histidine acid phosphatases (HAP, β-propeller phytases, cysteine phosphatases and purple acid phosphatases and also split into three enzyme classes, the 3-, 5- and 6-phytases, depending on the position of the first phosphate in the inositol ring to be removed. We report identification, cloning, purification and 3D structures of 6-phytases from two bacteria, Hafnia alvei and Yersinia kristensenii, together with their pH optima, thermal stability, and degradation profiles for phytate. An important result is the structure of the H. alvei enzyme in complex with the substrate analogue myo-inositol hexakissulphate. In contrast to the only previous structure of a ligand-bound 6-phytase, where the 3-phosphate was unexpectedly in the catalytic site, in the H. alvei complex the expected scissile 6-phosphate (sulphate in the inhibitor is placed in the catalytic site.

  11. Studies on UV/NaOCl/TiO2/Sep photocatalysed degradation of Reactive Red 195.

    Science.gov (United States)

    Karaoğlu, M Hamdi; Uğurlu, Mehmet

    2010-02-15

    The photocatalytic degradation of Reactive Red 195 (RR195) has been investigated in aqueous suspensions by using ultraviolet (UV), sodium hypochlorite (NaOCl) and TiO(2)/Sep nanoparticles together. To get the TiO(2)/Sep nanoparticle, the nanocrystalline TiO(2) anatase phase on sepiolite was obtained using a sufficient thermal treatment by gradually increasing the temperature from 300, 400 and 500 degrees C for 3h. Then, TiO(2)/Sep materials were characterized using different spectral and technical structural analyses with scanning electron microscopy (SEM) and X-ray diffraction (XRD). The influence of pH, catalyst amount, oxidant and initial dye concentration was investigated in all the experiments. Maximum colour and chemical oxygen demand (COD) removal were 99.9% and 78% respectively, at a dye concentration of 250 mg L(-1), NaOCl dosage of 50.37 mM, 0.1 g L(-1) weight of TiO(2)/Sep and pH of 5.45 in 3h. In addition, the pseudo-first order model was applied and r(2) values were noted from 0.92 to 0.99.

  12. Mechanical and Thermal Properties of Praseodymium Monopnictides: AN Ultrasonic Study

    Science.gov (United States)

    Bhalla, Vyoma; Kumar, Raj; Tripathy, Chinmayee; Singh, Devraj

    2013-09-01

    We have computed ultrasonic attenuation, acoustic coupling constants and ultrasonic velocities of praseodymium monopnictides PrX(X: N, P, As, Sb and Bi) along the , , in the temperature range 100-500 K using higher order elastic constants. The higher order elastic constants are evaluated using Coulomb and Born-Mayer potential with two basic parameters viz. nearest-neighbor distance and hardness parameter in the temperature range of 0-500 K. Several other mechanical and thermal parameters like bulk modulus, shear modulus, Young's modulus, Poisson ratio, anisotropic ratio, tetragonal moduli, Breazeale's nonlinearity parameter and Debye temperature are also calculated. In the present study, the fracture/toughness (B/G) ratio is less than 1.75 which implies that PrX compounds are brittle in nature at room temperature. The chosen material fulfilled Born criterion of mechanical stability. We also found the deviation of Cauchy's relation at higher temperatures. PrN is most stable material as it has highest valued higher order elastic constants as well as the ultrasonic velocity. Further, the lattice thermal conductivity using modified approach of Slack and Berman is determined at room temperature. The ultrasonic attenuation due to phonon-phonon interaction and thermoelastic relaxation mechanisms have been computed using modified Mason's approach. The results with other well-known physical properties are useful for industrial applications.

  13. Thermal Performance Study of a Prototype Multiport Heat Exchanger

    Science.gov (United States)

    Fotowat, Shahram

    Great efforts have been made to investigate the thermal performance and fluid flow behaviour in Minichannel Heat Exchangers (MICHX), however, the examination of air side in a multiport serpentine slab heat exchanger is rare. In the current investigation, experiments were conducted on air heating via a prototype multiport MICHX. Hot DI-water at different mass flow rates and a constant inlet temperature of 70°C was passed through the channels. The water side Reynolds numbers were varied from 255 to 411. The airside Reynolds numbers were calculated based on the free mean stream velocity and varied from 1750 to 5250, while, the air inlet temperatures were in the range of 22.5°C to 34.5°C. The effects of dimensional parameters, such as Reynolds number, Nusselt number, Prandtl number, Brinkman number, and Dean number on the heat transfer performance were investigated. The effect of the serpentine on the enhancement of DI water thermal performance behaviour was studied. Heat transfer correlations were established and compared to the results in the open literature.

  14. Evolution of the degradation mechanism of pure zinc stent in the one-year study of rabbit abdominal aorta model.

    Science.gov (United States)

    Yang, Hongtao; Wang, Cong; Liu, Chaoqiang; Chen, Houwen; Wu, Yifan; Han, Jintao; Jia, Zichang; Lin, Wenjiao; Zhang, Deyuan; Li, Wenting; Yuan, Wei; Guo, Hui; Li, Huafang; Yang, Guangxin; Kong, Deling; Zhu, Donghui; Takashima, Kazuki; Ruan, Liqun; Nie, Jianfeng; Li, Xuan; Zheng, Yufeng

    2017-11-01

    In the present study, pure zinc stents were implanted into the abdominal aorta of rabbits for 12 months. Multiscale analysis including micro-CT, scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and histological stainings was performed to reveal the fundamental degradation mechanism of the pure zinc stent and its biocompatibility. The pure zinc stent was able to maintain mechanical integrity for 6 months and degraded 41.75 ± 29.72% of stent volume after 12 months implantation. No severe inflammation, platelet aggregation, thrombosis formation or obvious intimal hyperplasia was observed at all time points after implantation. The degradation of the zinc stent played a beneficial role in the artery remodeling and healing process. The evolution of the degradation mechanism of pure zinc stents with time was revealed as follows: Before endothelialization, dynamic blood flow dominated the degradation of pure zinc stent, creating a uniform corrosion mode; After endothelialization, the degradation of pure zinc stent depended on the diffusion of water molecules, hydrophilic solutes and ions which led to localized corrosion. Zinc phosphate generated in blood flow transformed into zinc oxide and small amounts of calcium phosphate during the conversion of degradation microenvironment. The favorable physiological degradation behavior makes zinc a promising candidate for future stent applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Controlled swelling and degradation studies of alginate microbeads in dilute natrium-citrate solutions

    Directory of Open Access Journals (Sweden)

    Mitrović Dragana D.

    2010-01-01

    degree after 3 days of staying in 0.2 mM Na-citrate solution were 136.6 ± 2.8 and 30.8 ± 1.3 kPa, respectively. By day 7 in this solution, the beads still appearing structurally intact, further lost their mechanical strength due to continued polymer chain relaxation so that the compression modulus was 20.7 to 22.6 kPa owed almost solely to undegraded polyguluronate parts. Results of these studies are important from a fundamental standpoint for determination of structure and degradation mechanisms of alginate hydrogels but also from a practical point of view for optimization of hydrogel properties and behavior for potential applications in controlled drug release as well as in tissue engineering.

  16. Insights from the past: incorporating long-term landscape evolution in studies of land degradation

    Science.gov (United States)

    Ferro-Vazquez, Cruz; Lang, Carol; Kabora, Tabitha; Thornton-Barnett, Senna; Richer, Suzi; Gallello, Gianni; Stump, Daryl

    2017-04-01

    Modern approaches for assessing land degradation encompass multidisciplinary studies that have allowed a more realistic understanding of the causes and consequences of land degradation. This incipient perspective includes an increasingly important role of the studies of the past, including human history, to understand modern ecosystems and landscapes. Indeed, the current promotion of indigenous resource-use strategies as models of sustainable development was initially prompted by historical studies. However, systematic studies on whether or not indigenous management practices led to land degradation, and therefore their benefits or constraints for sustained use of natural resources, are not truly known. We argue that a joint approach combining the characterization of current soil properties with the archaeological study of traditional agricultural systems can provide insights on their sustainability. Archaeological excavation enables discerning the order in which sediments are deposited and the sequence in which structures are built. This provides data on coincident cultural and ecological change, and a long-term perspective on how agro-ecological systems operated in pre-modern states and the ways in which they resemble or differ from modern contexts. Simultaneously, these changes would have left a physical, chemical and isotopic imprint in soils that can be detected and interpreted to contribute to the production of a "usable past" (Stump, 2013). The premise is: since ancient agricultural sites may provide information on agronomic conditions after centuries to millennia of use, they can help in understanding the ways in which agroecosystems have survived, failed or adapted in the past. This will contribute to a better holistic understanding of social-ecological systems evolution by including a temporal perspective, and to a more nuanced assessment of land degradation and sustainable use. To illustrate this we present the outcome of our research at two traditional

  17. Predicting urban outdoor thermal comfort by the Universal Thermal Climate Index UTCI--a case study in Southern Brazil.

    Science.gov (United States)

    Bröde, Peter; Krüger, Eduardo L; Rossi, Francine A; Fiala, Dusan

    2012-05-01

    Recognising that modifications to the physical attributes of urban space are able to promote improved thermal outdoor conditions and thus positively influence the use of open spaces, a survey to define optimal thermal comfort ranges for passers-by in pedestrian streets was conducted in Curitiba, Brazil. We applied general additive models to study the impact of temperature, humidity, and wind, as well as long-wave and short-wave radiant heat fluxes as summarised by the recently developed Universal Thermal Climate Index (UTCI) on the choice of clothing insulation by fitting LOESS smoothers to observations from 944 males and 710 females aged from 13 to 91 years. We further analysed votes of thermal sensation compared to predictions of UTCI. The results showed that females chose less insulating clothing in warm conditions compared to males and that observed values of clothing insulation depended on temperature, but also on season and potentially on solar radiation. The overall pattern of clothing choice was well reflected by UTCI, which also provided for good predictions of thermal sensation votes depending on the meteorological conditions. Analysing subgroups indicated that the goodness-of-fit of the UTCI was independent of gender and age, and with only limited influence of season and body composition as assessed by body mass index. This suggests that UTCI can serve as a suitable planning tool for urban thermal comfort in sub-tropical regions.

  18. A study on the thermal conductivity of compacted bentonites

    CERN Document Server

    Tang, Anh-Minh; Le, Trung Tinh; 10.1016/j.clay.2007.11.001

    2008-01-01

    Thermal conductivity of compacted bentonite is one of the most important properties in the design of high-level radioactive waste repositories where this material is proposed for use as a buffer. In the work described here, a thermal probe based on the hot wire method was used to measure the thermal conductivity of compacted bentonite specimens. The experimental results were analyzed to observe the effects of various factors (i.e. dry density, water content, hysteresis, degree of saturation and volumetric fraction of soil constituents) on the thermal conductivity. A linear correlation was proposed to predict the thermal conductivity of compacted bentonite based on experimentally observed relationship between the volumetric fraction of air and the thermal conductivity. The relevance of this correlation was finally analyzed together with others existing methods using experimental data on several compacted bentonites.

  19. The study of thermal change by chemoport in radiofrequency hyperthermia

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Seung Hoon; Lee, Sun Young; Gim, Yang Soo; Kwak, Keun Tak; Yang, Myung Sik; Cha, Seok Yong [Dept. of Radiation Oncology, Chonbuk National University Hospital, Jeonju (Korea, Republic of)

    2015-12-15

    This study evaluate the thermal changes caused by use of the chemoport for drug administration and blood sampling during radiofrequency hyperthermia. 20 cm size of the electrode radio frequency hyperthermia (EHY-2000, Oncotherm KFT, Hungary) was used. The materials of the chemoport in our hospital from currently being used therapy are plastics, metal-containing epoxy and titanium that were made of the diameter 20 cm, height 20 cm insertion of the self-made cylindrical Agar phantom to measure the temperature. Thermoscope(TM-100, Oncotherm Kft, Hungary) and Sim4Life (Ver2.0, Zurich, Switzerland) was compared to the actual measured temperature. Each of the electrode measurement position is the central axis and the central axis side 1.5 cm, 0 cm(surface), 0.5 cm, 1.8 cm, 2.8 cm in depth was respectively measured. The measured temperature is 24.5 - 25.5℃, humidity is 30% - 32%. In five-minute intervals to measure the output power of 100 W, 60 min. In the electrode central axis 2.8 cm depth, the maximum temperature of the case with the unused of the chemoport, plastic, epoxy and titanium were respectively 39.51℃, 39.11℃, 38.81℃, 40.64℃, simulated experimental data were 42.20 ℃, 41.50℃, 40.70℃, 42.50℃. And in the central axis electrode side 1.5 cm depth 2.8 cm, measured data were 39.37℃, 39.32℃, 39.20℃, 39.46℃, the simulated experimental data were 42.00℃, 41.80℃, 41.20℃, 42.30℃. The thermal variations were caused by radiofrequency electromagnetic field surrounding the chemoport showed lower than in the case of unused in non-conductive plastic material and epoxy material, the titanum chemoport that made of conductor materials showed a slight differences. This is due to the metal contents in the chemoport and the geometry of the chemoport. And because it uses a low radio frequency bandwidth of the used equipment. That is, although use of the chemoport in this study do not significantly affect the surrounding tissue. That is, because the

  20. Optothermal Raman Studies of Thermal Properties of Graphene Based Films

    OpenAIRE

    Malekpour, Hoda

    2016-01-01

    Efficient thermal management is becoming a critical issue for development of the next generation of electronics. As the size of electronic devices shrinks, the dissipated power density increases, demanding a better heat removal. The discovery of graphene’s unique electrical and thermal properties stimulated interest of electronic industry to development of graphene based technologies. In this dissertation, I report the results of my investigation of thermal properties of graphene derivatives ...

  1. Extremely High Thermal Conductivity of Graphene: Experimental Study

    OpenAIRE

    Balandin, A. A.; Ghosh, S.; Bao, W.; Calizo, I.; Teweldebrhan, D.; Miao, F.; Lau, C. N.

    2008-01-01

    We report on the first measurement of the thermal conductivity of a suspended single layer graphene. The measurements were performed using a non-contact optical technique. The near room-temperature values of the thermal conductivity in the range ~ 4840 to 5300 W/mK were extracted for a single-layer graphene. The extremely high value of the thermal conductivity suggests that graphene can outperform carbon nanotubes in heat conduction.

  2. Isoconversional Kinetic Study Of The Thermal Decomposition Of Sugarcane Straw For Thermal Conversion Processes.

    OpenAIRE

    Rueda-Ordóñez, Yesid Javier; Tannous, Katia

    2016-01-01

    The aim of this work was investigate the kinetics of the thermal decomposition reaction of sugarcane straw. The thermal decomposition experiments were conducted at four heating rates (1.25, 2.5, 5 and 10 degrees C/min) in a thermogravimetric analyzer using nitrogen as inert atmosphere. The kinetic analysis was carried out applying the isoconversional method of Friedman, and the activation energies obtained varied from 154.1 kJ/mol to 177.8 kJ/mol. The reaction model was determined through mas...

  3. Study on thermal-hydraulics during a PWR reflood phase

    Energy Technology Data Exchange (ETDEWEB)

    Iguchi, Tadashi [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    1998-10-01

    In-core thermal-hydraulics during a PWR reflood phase following a large-break LOCA are quite unique in comparison with two-phase flow which has been studied widely in previous researches, because the geometry of the flow path is complicated (bundle geometry) and water is at extremely low superficial velocity and almost under stagnant condition. Hence, some phenomena realized during a PWR reflood phase are not understood enough and appropriate analytical models have not been developed, although they are important in a viewpoint of reactor safety evaluation. Therefore, author investigated some phenomena specified as important issues for quantitative prediction, i.e. (1) void fraction in a bundle during a PWR reflood phase, (2) effect of radial core power profile on reflood behavior, (3) effect of combined emergency core coolant injection on reflood behavior, and (4) the core separation into two thermal-hydraulically different regions and the in-core flow circulation behavior observed during a combined injection PWR reflood phase. Further, author made analytical models for these specified issues, and succeeded to predict reflood behaviors at representative types of PWRs, i.e.cold leg injection PWRs and Combined injection PWRs, in good accuracy. Above results were incorporated into REFLA code which is developed at JAERI, and they improved accuracy in prediction and enlarged applicability of the code. In the present study, models were intended to be utilized in a practical use, and hence these models are simplified ones. However, physical understanding on the specified issues in the present study is basic and principal for reflood behavior, and then it is considered to be used in a future advanced code development and improvement. (author). 110 refs.

  4. Inhibition of dentin collagen degradation by hesperidin: an in situ study

    NARCIS (Netherlands)

    van Strijp, A.J.P.; Takatsuka, T.; Sono, R.; Iijima, Y.

    2015-01-01

    Dentine caries is a process of demineralization and subsequent degradation of the collagenous matrix. Host-derived proteolytic enzymes, such as matrix metalloproteinases (MMPs), play a role in this process of dentine collagen degradation. Hampering this degradation retards the caries process.

  5. Degradation Studies on LiFePO4 cathode

    DEFF Research Database (Denmark)

    Scipioni, Roberto; Jørgensen, Peter Stanley; Hjelm, Johan

    2014-01-01

    Lithium-ion batteries are a promising technology for automotive application, but limited performance and lifetime is still a big issue. The aim of this work is to study and address degradation processes which affect LiFePO4 (LFP) cathodes - one of the most common cathodes in commercial Li...... in order to observe changes in the pore structure or micro cracks that would affect electronic percolation. Figure 4 displays an example of a fresh LFP cathode after FIB cutting. White particles are LFP grains while the black area contains carbon particles and pores, which are difficult to distinguish from...

  6. Study of starch degradation by yeasts during fermentation for using in animal feed.

    Science.gov (United States)

    Alonso, Santiago; Arévalo-Villena, Maria; Ubeda, Juan; Briones, Ana

    2010-11-01

    Sixteen amylolytic yeasts, drawn from culture collections or isolated from different environments, were used in the present study. Experiments were performed to evaluate the starch degradation due to exocellular activity. The culture media of growth was optimized to find the maximum activity, and some strains produced an extracellular amylolytic enzyme when cultured in presence of starch in the medium. On the other hand, one yeast showed activity in cell extract when cultured under varying conditions in a bench bioreactor; this strain would thus be suitable for use as an animal feed supplement, both as a source of proteins and nucleic acids and in terms of its amylolytic activity.

  7. A Comprehensive Study on the Degradation of Lithium-Ion Batteries during Calendar Ageing

    DEFF Research Database (Denmark)

    Stroe, Daniel Loan; Swierczynski, Maciej Jozef; Kær, Søren Knudsen

    2016-01-01

    their capacity and internal resistance. This paper investigates, based on extended laboratory calendar ageing tests, the degradation of the internal resistance of a Lithium-ion battery. The dependence of the internal resistance increase on the temperature and state-of-charge level have been extensive studied...... and quantified. Based on the obtained laboratory results, an accurate semi-empirical lifetime model, which is able to predict with high accuracy the internal resistance increase of the Lithium-ion battery over a wide temperature range and for all state-of-charge levels was proposed and validated....

  8. Lifetimes of organic photovoltaics: Combining chemical and physical characterisation techniques to study degradation mechanisms

    DEFF Research Database (Denmark)

    Norrman, K.; Larsen, N.B.; Krebs, Frederik C

    2006-01-01

    Degradation mechanisms of a photovoltaic device with an Al/C-60/C-12-PSV/PEDOT:PSS/ITO/glass geometry was studied using a combination of in-plane physical and chemical analysis techniques: TOF-SIMS, AFM, SEM, interference microscopy and fluorescence microscopy. A comparison was made between...... a device being stored in darkness in air and a device that had been subjected to illumination under simulated sunlight (1000 Wm(-2), AM1.5) in air. It was found that oxygen diffuses through pinholes in the aluminium electrode. If stored in air in the dark the oxidation is limited to the C-60 layer...

  9. A DFT study on the thermal cracking of JP-10.

    Science.gov (United States)

    Yue, Lei; Xie, Hu-Jun; Qin, Xiao-Mei; Lu, Xiao-Xing; Fang, Wen-Jun

    2013-12-01

    Density functional theory (DFT) calculations have been carried out to investigate the thermal cracking pathways of JP-10, a high energy density hydrocarbon fuel. Thermal cracking mechanisms are proposed, as supported by our previous experimental results (Xing et al. in Ind Eng Chem Res 47:10034-10040, 2008). Using DFT calculations, the potential energy profiles of the possible thermal cracking pathways for all of the diradicals obtained from homolytic C-C bond cleavage of JP-10 were derived and are presented here. The products of the different thermal cracking pathways are in good agreement with our previous experimental observations.

  10. Effect of Soil Fumigation on Degradation of Pendimethalin and Oxyfluorfen in Laboratory and Ginger Field Studies.

    Science.gov (United States)

    Huang, Bin; Li, Jun; Fang, Wensheng; Liu, Pengfei; Guo, Meixia; Yan, Dongdong; Wang, Qiuxia; Cao, Aocheng

    2016-11-23

    Herbicides are usually applied to agricultural fields following soil fumigation to provide effective weed control in high-value cash crops. However, phytotoxicity has been observed in ginger seedlings following the application of herbicides in fumigated fields. This study tested a mixture of herbicides (pendimethalin and oxyfluorfen) and several fumigant treatments in laboratory and field studies to determine their effect on the growth of ginger. The results showed that soil fumigation significantly (P degradation period of these herbicides in the field and in laboratory studies. The half-life of pendimethalin was extended by an average of approximately 1.29 times in the field and 1.74 times in the laboratory. The half-life of oxyfluorfen was extended by an average of about 1.19 times in the field and 1.32 times in the laboratory. Moreover, the extended period of herbicide degradation in the fumigant and nonfumigant treatments significantly reduced ginger plant height, leaf number, stem diameter, and the chlorophyll content. The study concluded that applying a dose below the recommended rate of these herbicides in chloropicrin (CP) or CP + 1,3-dichloropropene fumigated ginger fields is appropriate, as application of the recommended herbicide dose in fumigated soil may be phytotoxic to ginger.

  11. PEMFC membrane electrode assembly degradation study based on its mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Sridhar, Ranjani Lalitha; Krishnan, Ramya [ARC International, Chennai (India). Centre for Fuel Cell Technology

    2013-09-15

    The membrane electrode assembly determines the performance of the polymer electrolyte membrane fuel cell. Degradation of the membrane electrode assembly has been the subject of recent research with impedance measurements, cyclic voltammetry measurements, scanning electron microscopy, tunneling electron microscopy as the techniques currently in use for characterization. This paper considers the membrane electrode assembly as a laminate and uses the study of mechanical properties as a tool for identification of delamination. An attempt has also been made to compare the changes in the mechanical properties obtained due to delamination with the results obtained from impedance measurement, cyclic voltammetry studies and performance in the fuel cell. In this study mechanical properties such as stress, strain and modulus have been measured and the decrease in modulus as a result of delamination has been characterized. It has been found that study of the mechanical properties of the membrane electrode assembly compliments the other techniques and can be used in the post-mortem analysis of causes for degradation. (orig.)

  12. Electrochemical and thermal studies of lithium ion batteries

    Science.gov (United States)

    Lu, Wenquan

    The structural, electrochemical, and thermal characteristics of carbonaceous anodes and LiNi0.8Co0.2O2 cathode in Li-ion cells were investigated using various electrochemical and calorimetric techniques. The electrode-electrolyte interface was investigated for various carbonaceous materials such as graphite with different shapes, surface modified graphite with copper, and novel carbon material derived from sepiolite template. The structural and morphological properties were determined using XRD, TGA, SEM, BET techniques. The electrochemical characteristics were studied using conventional electrochemical techniques such as galvanostatic charge/discharge cycling, cyclic voltammetry, and impedance (AC and DC) methods. It was observed that the electrochemical active surface area instead of the BET area plays a critical role in the irreversible capacity loss associated with the carbonaceous anodes. It was also found that the exfoliation of carbon anodes especially in PC based electrolyte could be significantly reduced by protective copper coating of the natural graphite. LiNi0.8Co0.2O2 cathode material was found to possess high energy density and excellent cycling characteristics. The structural and electrochemical properties of LiNi0.8Co 0.2O2 synthesized by sol-gel and solid-state methods were studied. Results of the AC impedance spectroscopy carried out on LiNi 0.8Co0.2O2 cathodes revealed that the charge transfer resistance is a function of the state of charge. The solid state Li + diffusion was calculated to be around 10-13 cm2/s in the oxide particle by Warburg impedance method. In addition, the cell fabricated with LiNi0.8Co0.2O 2 cathode showed excellent energy and power performance under static and dynamic load conditions that prevail in Electric and Hybrid Vehicles. Thermal properties of the LiNi0.8Co0.2O2 cathode, carbonaceous anodes, and Li-ion cells fabricated with these electrodes were also investigated using isothermal microcalorimetry (IMC), differential

  13. Die attach dimension and material on thermal conductivity study for high power COB LED

    Science.gov (United States)

    Sarukunaselan, K.; Ong, N. R.; Sauli, Z.; Mahmed, N.; Kirtsaeng, S.; Sakuntasathien, S.; Suppiah, S.; Alcain, J. B.; Retnasamy, V.

    2017-09-01

    High power LED began to gain popularity in the semiconductor market due to its efficiency and luminance. Nonetheless, along with the increased in efficiency, there was an increased in the junction temperature too. The alleviating junction temperature is undesirable since the performances and lifetime will be degraded over time. Therefore, it is crucial to solve this thermal problem by maximizing the heat dissipation to the ambience. Improvising the die attach (DA) layer would be the best option because this layer is sandwiched between the chip (heat source) and the substrate (channel to the ambient). In this paper, the impact of thickness and thermal conductivity onto the junction temperature and Von Mises stress is analyzed. Results obtained showed that the junction temperature is directly proportional to the thickness but the stress was inversely proportional to the thickness of the DA. The thermal conductivity of the materials did affect the junction temperature as there was not much changes once the thermal conductivity reached 20W/mK. However, no significant changes were observed on the Von Mises stress caused by the thermal conductivity. Material with the second highest thermal conductivity had the lowest stress, whereas the highest conductivity material had the highest stress value at 20 µm. Overall, silver sinter provided the best thermal dissipation compared to the other materials.

  14. Experimental and modeling study of forest fire effect on soil thermal conductivity

    Science.gov (United States)

    Kathleen M. Smits; Elizabeth Kirby; William J. Massman; Scott Baggett

    2016-01-01

    An understanding of soil thermal conductivity after a wildfire or controlled burn is important to land management and post-fire recovery efforts. Although soil thermal conductivity has been well studied for non-fire heated soils, comprehensive data that evaluate the long-term effect of extreme heating from a fire on the soil thermal conductivity are limited....

  15. Growth, spectral and thermal studies of ibuprofen crystals

    Energy Technology Data Exchange (ETDEWEB)

    Ramukutty, S.; Ramachandran, E. [Department of Physics, Thiruvalluvar College, Papanasam (India)

    2012-01-15

    RS -Ibuprofen was crystallized for the first time in silica gel under suitable pH conditions by reduction of solubility method. The grown crystals were characterized by single crystal X-ray diffraction and density measurement. The functional groups present in the crystal were identified using Fourier transform infrared spectroscopy. Optical bandgap energy of ibuprofen was estimated as 3.19(3) eV from UV-Vis spectrum. Thermogravimetric analysis revealed that ibuprofen is thermally stable upto 102.9 C and the initial loss of mass was due to evaporation only. Morphological study showed that the growth is prominent along b-axis and the prominent face is {l_brace}100{r_brace}. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Synthesis, Spectral and Thermal Studies of New Rutin Vanadyl Complexes

    Directory of Open Access Journals (Sweden)

    Rodica Olar

    2010-03-01

    Full Text Available Complexes between oxovanadium (IV cation and flavonoid derivatives were developed recently in order to increase the intestinal absorption and to reduce the toxicity of vanadium compounds. For these reasons, is interesting to investigate the complexation process between flavonoid rutin (Rut and vanadyl cation in order to isolate new complexes. Two new complexes [VO(Rut(H2O2](SO40.5×2H2O and [VO(Rut2]×4H2O have been obtained and characterized by elemental and thermal analyses and several spectroscopic techniques (ESI-MS, IR, UV-Vis, fluorescence. The studies concerning complex formation between vanadyl and rutin (Rut performed in different solutions show the formation of mononuclear complexes with 1:1 and 1:2 metal to ligand stoichiometry.

  17. Study of thermal effects of silicate-containing hydroxyapatites

    Science.gov (United States)

    Golovanova, O. A.; Zaits, A. V.; Berdinskaya, N. V.; Mylnikova, T. S.

    2016-02-01

    The possibility of modifications of hydroxyapatite silicate ions, from the extracellular fluid prototype solution under near-physiological conditions has been studied. Formation of silicon-structured hydroxyapatite with different extent of substitution of phosphate groups in the silicate group has been established through chemical and X-ray diffraction analyses, FTIR spectroscopy and optical microscopy. The results obtained are in agreement and suggest the possibility of substitution of phosphate groups for silicate groups in the hydroxyapatite structure when introducing different sources of silica, tetraethoxysilane and sodium silicate, in the reaction mixture. Growth in the amount of silicon in Si-HA results in the increase in the thermal stability of the samples. The greatest mass loss occurs at temperatures in the range of 25-400 0C that is caused by the removal of the crystallization and adsorption water and volatile impurities. It is shown that the modified apatites are of imperfect structure and crystallize in a nanocrystalline state.

  18. Thermal Studies on the SPS Wideband Transverse Feedback Kicker

    CERN Document Server

    Roggen, Toon; Hofle, Wolfgang; Montesinos, Eric; CERN. Geneva. ATS Department

    2016-01-01

    As part of the SPS wideband transverse feedback system in the framework of the LHC Injector Upgrade (LIU) project, a wideband kicker design is being proposed. Vertical beam instabilities due to intensity dependent effects (electron cloud instability (ECI) and transverse mode coupling instability (TMCI)) are potentially suppressed by using a feedback system driving such a kicker system. One of the options for a kicker is a one meter long slotted-coaxial kicker, providing a substantial vertical kick strength (10ˉ5 –10ˉ4 eV.s/m) over a bandwidth ranging from nearly DC to 1 GHz. The necessary kick strength requires a total power of 4 kW. This note describes thermal studies that assisted in the material choice of the feedthroughs of the slotted-coaxial kicker and guided the design choices.

  19. [Study of the types of matrix metalloproteinases involved in dentin bonding interface degradation].

    Science.gov (United States)

    Wang, Danyang; Zhang, Ling; Li, Fang; Xu, Shuai; Chen, Jihua

    2014-08-01

    To study the types of matrix metalloproteinases (MMPs) involved in dentin bonding interface degradation. Dentin slices were prepared and treated with two adhesive systems (Single Bond 2 or Clearfil S3 Bond). The dentin surface was bonded with composite resin. All specimens were immersed in sterile artificial saliva for 0 or 6 months, and their micro-shear bond strength (muSBS) were measured. The fracture modes were observed through field emission scanning electron microscope (FE-SEM). Dentin slices with 4 mm x 3 mm x 1 mm dimensions were prepared. The slices were divided into three groups according to the treatment modes (negative control, Single Bond 2, and Clearfil S3 Bond). All specimens were stored in sterile artificial saliva for 0 or 6 months. The concentrations of MMP-1, -2, -3, -8, and -9 of each group were detected through fluorescent microsphere immunoassay. The muSBS of both adhesive systems significantly decreased after storage aging. Significant differences in failure modes within the four groups tested in this study were observed. Compared with the negative control, the concentrations of MMP-1 and MMP-3 in different adhesive groups showed no significant difference after storage aging. However, the concentrations of MMP-2, -8, and -9 in Single Bond 2 group and the concentrations of MMP-8 and -9 in Clearfil S3 Bond group significantly decreased after 6 months of storage aging. Significant degradation occur in the dentin bonding interface of both adhesive groups under 6 months aging challenge. The concentrations ofdentinal MMP-2, -8, and -9 significantly decrease after treatment with adhesives and aging, indicating that these MMPs have an important function in dentin bonding interface degradation.

  20. Green synthesis, characterization and catalytic degradation studies of gold nanoparticles against congo red and methyl orange.

    Science.gov (United States)

    Umamaheswari, C; Lakshmanan, A; Nagarajan, N S

    2018-01-01

    The present study reports, novel and greener method for synthesis of gold nanoparticles (AuNPs) using 5,7-dihydroxy-6-metoxy-3 ' ,4 ' methylenedioxyisoflavone (Dalspinin), isolated from the roots of Dalbergia coromandeliana was carried out for the first time. The synthesized gold nanoparticles were characterized by UV-Vis spectroscopy, high resolution transmission electron microscopy (HR-TEM), selected area electron diffraction (SAED), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The observed surface plasmon resonance (SPR) at 532nm in the UV-Vis absorption spectrum indicates the formation of gold nanoparticles. The powder XRD and SAED pattern for synthesized gold nanoparticles confirms crystalline nature. The HR-TEM images showed that the AuNPs formed were small in size, highly monodispersed and spherical in shape. The average particle sizes of the AuNPs are found to be ~10.5nm. The prepared AuNPs were found to be stable for more than 5months without any aggregation. The catalytic degradation studies of the synthesized AuNPs towards degradation of congo red and methyl orange, showed good catalytic in the complete degradation of both the dyes. The reduction catalyzed by gold nanoparticles followed the pseudo-first order kinetics, with a rate constant of 4.5×10 -3 s -1 (R 2 =0.9959) and 1.7×10 -3 s -1 (R 2 =0.9918) for congo red (CR) and methyl orange (MO), respectively. Copyright © 2017. Published by Elsevier B.V.