Thermal oxidative degradation kinetics of agricultural residues using distributed activation energy model and global kinetic model.

PubMed

Ren, Xiu'e; Chen, Jianbiao; Li, Gang; Wang, Yanhong; Lang, Xuemei; Fan, Shuanshi

2018-08-01

The study concerned the thermal oxidative degradation kinetics of agricultural residues, peanut shell (PS) and sunflower shell (SS). The thermal behaviors were evaluated via thermogravimetric analysis and the kinetic parameters were determined by using distributed activation energy model (DAEM) and global kinetic model (GKM). Results showed that thermal oxidative decomposition of two samples processed in three zones; the ignition, burnout, and comprehensive combustibility between two agricultural residues were of great difference; and the combustion performance could be improved by boosting heating rate. The activation energy ranges calculated by the DAEM for the thermal oxidative degradation of PS and SS were 88.94-145.30 kJ mol -1 and 94.86-169.18 kJ mol -1 , respectively. The activation energy obtained by the GKM for the oxidative decomposition of hemicellulose and cellulose was obviously lower than that for the lignin oxidation at identical heating rate. To some degree, the determined kinetic parameters could acceptably simulate experimental data. Copyright © 2018 Elsevier Ltd. All rights reserved.

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

PubMed

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.

Degradation kinetics of gamma-oryzanol in antioxidant-stripped rice bran oil during thermal oxidation.

PubMed

Khuwijitjaru, Pramote; Yuenyong, Thippawan; Pongsawatmanit, Rungnaphar; Adachi, Shuji

2009-01-01

Gamma-oryzanol, a group of phytosterol ferulates found in rice bran, possesses antioxidative activity and other bioactivities. The kinetics of thermal degradation of gamma-oryzanol in stripped rice bran oil (SRBO) were investigated under heating at 132, 160, 192 and 222 degrees C for 480, 140, 60 and 50 h, respectively. Losses of the overall gamma-oryzanol and its components (cycloartenyl ferulate, 24-methylene cycloartanyl ferulate, campesteryl ferulate and beta-sitosteryl ferulate) could be expressed by the first-order kinetics model. The rate constant of thermal degradation of gamma-oryzanol increased with increasing heating temperatures. The temperature dependence of the obtained rate constants was found to obey the Arrhenius equation. Campesteryl ferulate showed slightly more thermally resistant than other components at temperature lower than 160 degrees C. However, the change in the absorbance from 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay as a function of heating time exhibited the same pattern for the SRBO with and without gamma-oryzanol for all studied heating temperatures.

CANE FIBERBOARD DEGRADATION WITHIN THE 9975 SHIPPING PACKAGE DURING LONG-TERM STORAGE APPLICATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daugherty, W.; Dunn, K.; Hackney, B.

The 9975 shipping package is used as part of the configuration for long-term storage of special nuclear materials in the K Area Complex at the Savannah River Site. The cane fiberboard overpack in the 9975 package provides thermal insulation, impact absorption and criticality control functions relevant to this application. The Savannah River National Laboratory has conducted physical, mechanical and thermal tests on aged fiberboard samples to identify degradation rates and support the development of aging models and service life predictions in a storage environment. This paper reviews the data generated to date, and preliminary models describing degradation rates of canemore » fiberboard in elevated temperature – elevated humidity environments.« less

Composition-structure-properties relationship of strontium borate glasses for medical applications.

PubMed

Hasan, Muhammad S; Werner-Zwanziger, Ulrike; Boyd, Daniel

2015-07-01

We have synthesized TiO2 doped strontium borate glasses, 70B2O3-(30-x)SrO-xTiO2 and 70B2 O3 -20SrO(10-x)Na2 O-xTiO2 . The composition dependence of glass structure, density, thermal properties, durability, and cytotoxicity of degradation products was studied. Digesting the glass in mineral acid and detecting the concentrations of various ions using an ICP provided the actual compositions that were 5-8% deviated from the theoretical values. The structure was investigated by means of (11)B magic angle spinning (MAS) NMR spectroscopy. DSC analyses provided the thermal properties and the degradation rates were measured by measuring the weight loss of glass disc-samples in phosphate buffered saline at 37°C in vitro. Finally, the MTT assay was used to analyze the cytotoxicity of the degradation products. The structural analysis revealed that replacing TiO2 for SrO or Na2 O increased the BO3/BO4 ratio suggesting the network-forming role of TiO2 . Thermal properties, density, and degradation rates also followed the structural changes. Varying SrO content predominantly controlled the degradation rates, which in turn controlled the ion release kinetics. A reasonable control (2-25% mass loss in 21 days) over mass loss was achieved in current study. Even though, very high concentrations (up to 5500 ppm B, and 1200 ppm Sr) of ions were released from the ternary glass compositions that saturated the degradation media in 7 days, the degradation products from ternary glass system was found noncytotoxic. However, quaternary glasses demonstrated negative affect on cell viability due to very high (7000 ppm) Na ion concentration. All the glasses investigated in current study are deemed fast degrading with further control over degradation rates, release kinetics desirable. © 2014 Wiley Periodicals, Inc.

Crystallization, structural relaxation and thermal degradation in Poly(L-lactide)/cellulose nanocrystal renewable nanocomposites.

PubMed

Lizundia, E; Vilas, J L; León, L M

2015-06-05

In this work, crystallization, structural relaxation and thermal degradation kinetics of neat Poly(L-lactide) (PLLA) and its nanocomposites with cellulose nanocrystals (CNC) and CNC-grafted-PLLA (CNC-g-PLLA) have been studied. Although crystallinity degree of nanocomposites remains similar to that of neat homopolymer, results reveal an increase on the crystallization rate by 1.7-5 times boosted by CNC, which act as nucleating agents during the crystallization process. In addition, structural relaxation kinetics of PLLA chains has been drastically reduced by 53% and 27% with the addition of neat and grafted CNC, respectively. The thermal degradation activation energy (E) has been determined from thermogravimetric analysis in the light of Kissinger's and Ozawa-Flynn-Wall theoretical models. Results reveal a reduction on the thermal stability when in presence of CNC-g-PLLA, while raw CNC slightly increases the thermal stability of PLLA. Fourier transform infrared spectroscopy and energy dispersive X-ray spectroscopy results confirm that the presence of residual catalyst in CNC-g-PLLA plays a pivotal role in the thermal degradation behavior of nanocomposites. Copyright © 2015 Elsevier Ltd. All rights reserved.

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

PubMed

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. Copyright © 2015 Elsevier Ltd. All rights reserved.

Study of temperature and irradiation influence on the physicochemical properties of Aspirin

NASA Astrophysics Data System (ADS)

Al-Maydama, Hussein M.; Abduljabbar, Adlia A.; Al-Maqtari, Maher A.; Naji, Khalid M.

2018-04-01

Pure Aspirin samples were treated with a wide spectrum of light (γ-ray, UV- lamp and sunlight) and 40 °C temperature at various time of exposure. The changes in the thermal degradation parameters, crystalline structure, morphology and purity due to radiation and temperature treatments of Aspirin were pursued by comparing their TGA, XRD, SEM and HPLC results. The non-isothermal thermogravimetric analysis curves (TG, DTG and DSC) at 10 °C min-1 heating rate, under nitrogen flow and overheating range of 25-650 °C showed two degradation steps for the treated and untreated Aspirin samples. Accordingly, their thermal behavior and thermal stability were determined. Aspirin samples treated with 40 °C and UV-12 h were proven to be of the lowest thermal stability as their TDTG values (166.7 and 168.8 °C) were lower than that of the untreated sample (TDTG = 181 °C). The degradation kinetics parameters (i.e. activation energy, pre-exponential factor and order of reaction), life time prediction and thermodynamic parameters (ΔG*, ΔH* and ΔS*) were worked out using the Coats-Redfern (CR) expression and standard equations. The lowest activation energy (104.3 kJ mol-1) associated with the highest degradation rate was observed for the UV-12 h treated Aspirin sample. Crystallinity percentage was estimated from XRD and DSC, whereas, morphology and purity changes due to treatments were detected by scanning electron microscopy (SEM) and HPLC. The significant change in crystallinity from the XRD results of the treated Aspirin samples occurred in the (32.2%-58.7%) range. The photocatalytic degradation of Aspirin samples before and after treatments was carried out using TiO2/sunlight system. The photocatalytic degradation of all samples followed pseudo first order kinetics and the shelf life, rate of reaction and efficiency of degradation were determined and discussed. The highest degradation percentage (∼99%) and the associated lowest shelf life (4.3-5.8 min) were observed in the photocatalytic degradation of the 40 °C, UV-12 h, γ-ray-aqueous and sunlight treated samples.

Role of metal oxides in the thermal degradation of poly(vinyl chloride)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gupta, M.C.; Viswanath, S.G.

Thermal degradation of poly(vinyl chloride) has been studied in the presence of metal oxides by a thermogravimetric method. It follows a two-step mechanism. In the first step chlorine free radical is formed as in the case of pure PVC, and in the second step chlorine free radical replaces oxygen from metal oxide to form metal chloride and oxygen free radical. Subsequently, the oxygen free radical abstracts hydrogen from PVC. Formation of metal chloride is the rate-controlling step. The metal chlorides formed during the thermal degradation either volatilize or decompose simultaneously to lower metallic chlorides depending on the boiling point ormore » the volatilization temperature.« less

Destroying lignocellulosic matters for enhancing methane production from excess sludge.

PubMed

Hao, Xiaodi; Hu, Yuansheng; Cao, Daqi

2016-01-01

A lot of lignocellulosic matters are usually present in excess sludge, which are hardly degraded in anaerobic digestion (AD) and thus remains mostly in digested sludge. This is a reason why the conversion rate of sludge organics into energy (CH4) is often low. Obviously, the hydrolysis of AD cannot destruct the structure of lignocellulosic matters. Structural destruction of lignocellulosic matters has to be performed in AD. In this study, pretreatments with the same principles as cell disintegration of sludge were applied to destruct lignocellulosic matters so that these materials could be converted to CH4 via AD. Acid, alkali, thermal treatment and ultrasonic were used in the experiments to observe the destructed/degraded efficiency of lignocellulosic matters. Thermal treatment was found to be the most effective pretreatment. Under optimized conditions (T = 150 °C and t = 30  min), pretreated sludge had a degraded rate of 52.6% in AD, due to easy destruction and/or degradation of hemicelluloses and celluloses in pretreatment. The sludge pretreated by thermal treatment could enhance the CH4 yield (mL CH4 g(-1) VSS) by 53.6% compared to raw sludge. Economically, the thermal treatment can balance the input energy with the produced energy (steam and electricity).

Outgassing of solid material into vacuum thermal insulation spaces

NASA Technical Reports Server (NTRS)

Wang, Pao-Lien

1994-01-01

Many cryogenic storage tanks use vacuum between inner and outer tank for thermal insulation. These cryogenic tanks also use a radiation shield barrier in the vacuum space to prevent radiation heat transfer. This shield is usually constructed by using multiple wraps of aluminized mylar and glass paper as inserts. For obtaining maximum thermal performance, a good vacuum level must be maintained with the insulation system. It has been found that over a period of time solid insulation materials will vaporize into the vacuum space and the vacuum will degrade. In order to determine the degradation of vacuum, the rate of outgassing of the insulation materials must be determined. Outgassing rate of several insulation materials obtained from literature search were listed in tabular form.

Molecular and Kinetic Models for High-rate Thermal Degradation of Polyethylene

DOE PAGES

Lane, J. Matthew; Moore, Nathan W.

2018-02-01

Thermal degradation of polyethylene is studied under the extremely high rate temperature ramps expected in laser-driven and X-ray ablation experiments—from 10 10 to 10 14 K/s in isochoric, condensed phases. The molecular evolution and macroscopic state variables are extracted as a function of density from reactive molecular dynamics simulations using the ReaxFF potential. The enthalpy, dissociation onset temperature, bond evolution, and observed cross-linking are shown to be rate dependent. These results are used to parametrize a kinetic rate model for the decomposition and coalescence of hydrocarbons as a function of temperature, temperature ramp rate, and density. In conclusion, the resultsmore » are contrasted to first-order random-scission macrokinetic models often assumed for pyrolysis of linear polyethylene under ambient conditions.« less

Molecular and Kinetic Models for High-rate Thermal Degradation of Polyethylene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lane, J. Matthew; Moore, Nathan W.

Thermal degradation of polyethylene is studied under the extremely high rate temperature ramps expected in laser-driven and X-ray ablation experiments—from 10 10 to 10 14 K/s in isochoric, condensed phases. The molecular evolution and macroscopic state variables are extracted as a function of density from reactive molecular dynamics simulations using the ReaxFF potential. The enthalpy, dissociation onset temperature, bond evolution, and observed cross-linking are shown to be rate dependent. These results are used to parametrize a kinetic rate model for the decomposition and coalescence of hydrocarbons as a function of temperature, temperature ramp rate, and density. In conclusion, the resultsmore » are contrasted to first-order random-scission macrokinetic models often assumed for pyrolysis of linear polyethylene under ambient conditions.« less

New insights into the enhanced performance of high solid anaerobic digestion with dewatered sludge by thermal hydrolysis: Organic matter degradation and methanogenic pathways.

PubMed

Chen, Sisi; Li, Ning; Dong, Bin; Zhao, Wentao; Dai, Lingling; Dai, Xiaohu

2018-01-15

Two lab-scale high solid anaerobic digesters fed with untreated sludge (R1) and thermally hydrolyzed sludge (R2) were operated to investigate the influence of thermal hydrolysis pretreatment (THP) on the degradation of individual macromolecular organic components (MOCs), as well as the functional and metabolic responses of microbes during anaerobic digestion (AD). The degradation of MOCs was improved by THP at different rates, in which improved degradation of proteins (by 49.0%) and hemicelluloses (by 25.0%) were the main factors contributing to the increase in volatile solids (VS) reduction. However, no enhancement of final degradation extent of MOCs was observed. With a more densified microbial population, R2 was also enriched in genes involved in amino acid and carbohydrate metabolism, reflected in the enhanced degradation of proteins and carbohydrates. After THP, the methanogenic pathway shifted from strict acetoclastic methanogenesis to acetoclastic/hydrogenotrophic methanogenesis, consistent with the enhanced methane production and the increase of methane content. Copyright © 2017 Elsevier B.V. All rights reserved.

Degradation reaction of Diazo reactive black 5 dye with copper (II) sulfate catalyst in thermolysis treatment.

PubMed

Lau, Yen-Yie; Wong, Yee-Shian; Ang, Tze-Zhang; Ong, Soon-An; Lutpi, Nabilah Aminah; Ho, Li-Ngee

2018-03-01

The theme of present research demonstrates performance of copper (II) sulfate (CuSO 4 ) as catalyst in thermolysis process to treat reactive black 5 (RB 5) dye. During thermolysis without presence of catalyst, heat was converted to thermal energy to break the enthalpy of chemical structure bonding and only 31.62% of color removal. With CuSO 4 support as auxiliary agent, the thermally cleaved molecular structure was further destabilized and reacted with CuSO 4 . Copper ions functioned to delocalize the coordination of π of the lone paired electron in azo bond, C=C bond of the sp 2 carbon to form C-C of the sp 3 amorphous carbon in benzene and naphthalene. Further, the radicals of unpaired electrons were stabilized and RB 5 was thermally decomposed to methyl group. Zeta potential measurement was carried out to analyze the mechanism of RB 5 degradation and measurement at 0 mV verified the critical chemical concentration (CCC) (0.7 g/L copper (II) sulfate), as the maximum 92.30% color removal. The presence of copper (II) sulfate catalyst has remarkably increase the RB 5 dye degradation as the degradation rate constant without catalyst, k 1 is 6.5224 whereas the degradation rate constant with catalyst, k 2 is 25.6810. This revealed the correlation of conversion of thermal energy from heat to break the chemical bond strength, subsequent fragmentation of RB 5 dye molecular mediated by copper (II) sulfate catalyst. The novel framework on thermolysis degradation of molecular structure of RB 5 with respect to the bond enthalpy and interfacial intermediates decomposition with catalyst reaction were determined.

Mechanistic insights into lithium ion battery electrolyte degradation - a quantitative NMR study.

PubMed

Wiemers-Meyer, S; Winter, M; Nowak, S

2016-09-29

The changes in electrolyte composition on the molecular level and the reaction mechanisms of electrolyte degradation upon thermal aging are monitored by quantitative NMR spectroscopy, revealing similar rates of degradation for pristine and already aged electrolytes. The data analysis is not in favor of an autocatalytic reaction mechanism based on OPF 3 but rather indicates that the degradation of LiPF 6 in carbonate based solvents proceeds via a complex sequence of "linear" reactions rather than a cyclic reaction pattern which is determined by the amount of water present in the samples. All investigated electrolytes are reasonably stable at temperatures of up to 60 °C in the presence of minor amounts or absence of water hence indicating that chemical instability of electrolyte components against water is decisive for degradation and an increase in temperature ("thermal aging") just accelerates the degradation impact of water.

Thermal degradation kinetics of all-trans and cis-carotenoids in a light-induced model system.

PubMed

Xiao, Ya-Dong; Huang, Wu-Yang; Li, Da-Jing; Song, Jiang-Feng; Liu, Chun-Quan; Wei, Qiu-Yu; Zhang, Min; Yang, Qiu-Ming

2018-01-15

Thermal degradation kinetics of lutein, zeaxanthin, β-cryptoxanthin, β-carotene was studied at 25, 35, and 45°C in a model system. Qualitative and quantitative analyses of all-trans- and cis-carotenoids were conducted using HPLC-DAD-MS technologies. Kinetic and thermodynamic parameters were calculated by non-linear regression. A total of 29 geometrical isomers and four oxidation products were detected, including all-trans-, keto compounds, mono-cis- and di-cis-isomers. Degradations of all-trans-lutein, zeaxanthin, β-cryptoxanthin, and β-carotene were described by a first-order kinetic model, with the order of rate constants as k β -carotene >k β -cryptoxanthin >k lutein >k zeaxanthin . Activation energies of zeaxanthin, lutein, β-cryptoxanthin, and β-carotene were 65.6, 38.9, 33.9, and 8.6kJ/moL, respectively. cis-carotenoids also followed with the first-order kinetic model, but they did not show a defined sequence of degradation rate constants and activation energies at different temperatures. A possible degradation pathway of four carotenoids was identified to better understand the mechanism of carotenoid degradation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Rheological characterization of thermal, thermo-oxidative and photo-oxidative degradation of LDPE

NASA Astrophysics Data System (ADS)

Rolón-Garrido, Víctor Hugo; Wagner, Manfred Hermann

2015-04-01

Rheology has been used to study thermal degradation (V. H. Rolón-Garrido et al., Rheol. Acta 50, 519-535, 2011), thermo-oxidative degradation (V. H. Rolón-Garrido et al., Rheol. Acta 50, 519-535, 2011; V. H. Rolón-Garrido et al., J. Rheol. 57, 105-129, 2013) and photo-oxidative degradation (V. H. Rolón-Garrido and M. H. Wagner, Polym. Degrad. Stab. 99, 136-145, 2014; V. H. Rolón-Garrido and M. H. Wagner, J. Rheol. 58, 199-22 2, 2014; V. H. Rolón-Garrido et al., Polym. Degrad. Stab. 111, 46-54, 2015) of low-density polyethylene (LDPE). This contribution presents the analogies and differences between these types of degradations of LDPE on the linear (by use of van-Gurp Palmen plots) and non-linear viscoelastic properties (by use of the parameters of the MSF model, fmax2 and β), as well as on the failure mode of the samples (through the maximum strain and stress achieved experimentally). In contrast to thermal and thermo-oxidative degradation, the linear viscoelastic properties of photo-oxidated samples were more affected by degradation. In the non-linear regime, for thermal and thermo-oxidative treated samples, the elongational measurements elucidated the role of chain scission and long-chain branching (LCB) formation, while for photo-oxidated LDPE even the competition between chain scission, LCB formation, and gel formation was demonstrated. The failure behavior was found to be determined by a constant maximum strain in thermo-oxidative degradation, if the LDPE has high content in branching points, or in photo-oxidative degraded LDPE, if a considerable portion of gel structure is present. Otherwise, either the maximum strain or stress measured was found to be strain-rate dependent.

Thermal oxidative degradation reactions of perfluoroalkylethers

NASA Technical Reports Server (NTRS)

Paciorek, K. L.; Ito, T. I.; Kratzer, R. H.

1981-01-01

The mechanisms operative in thermal oxidative degradation of Fomblin Z and hexafluoropropene oxide derived fluids and the effect of alloys and additives upon these processes are investigated. The nature of arrangements responsible for the inherent thermal oxidative instability of the Fomblin Z fluids is not established. It was determined that this behavior is not associated with hydrogen end groups or peroxy linkages. The degradation rate of these fluids at elevated temperatures in oxidizing atmospheres is dependent on the surface/volume ratio. Once a limiting ratio is reached, a steady rate appears to be attained. Based on elemental analysis and oxygen consumption data, CF2OCF2CF2O2, no. CF2CF2O, is one of the major arrangements present. The action of the M-50 and Ti(4 Al, 4 Mn) alloys is much more drastic in the case of Fomblin Z fluids than that observed for the hexafluoropropene derived materials. The effectiveness of antioxidation anticorrosion additives, P-3 and phospha-s-triazine, in the presence of metal alloys is very limited at 316 C; at 288 C the additives arrested almost completely the fluid degradation. The phospha-s-triazine appears to be at least twice as effective as the P-3 compound; it also protected the coupon better. The Ti(4 Al, 4 Mn) alloy degraded the fluid mainly by chain scission processes this takes place to a much lesser degree with M-50.

Processing thermally labile drugs by hot-melt extrusion: The lesson with gliclazide.

PubMed

Huang, Siyuan; O'Donnell, Kevin P; Delpon de Vaux, Sophie M; O'Brien, John; Stutzman, John; Williams, Robert O

2017-10-01

The formation of molecularly dispersed amorphous solid dispersions by the hot-melt extrusion technique relies on the thermal and mechanical energy inputs, which can cause chemical degradation of drugs and polymeric carriers. Additionally, drug degradation may be exacerbated as drugs convert from a more stable crystalline form to a higher energy amorphous form. Therefore, it is imperative to study how drug degrades and evaluate methods to minimize drug degradation during the extrusion process. In this work, gliclazide was used as a model thermally labile drug for the degradation kinetics and process optimization studies. Preformulation studies were conducted using thermal analyses, and liquid chromatography-mass spectroscopy to identify drug degradation pathways and to determine initial extrusion conditions. Formulations containing 10% drug and 90% AFFINISOL™ HPMC HME 100LV were then extruded using a twin screw extruder, and the extrudates were characterized using X-ray powder diffraction, modulated dynamic scanning calorimetry, and potency testing to evaluate physicochemical properties. The energies of activation for both amorphous gliclazide, crystalline gliclazide, and gliclazide solution were calculated using the Arrhenius equation to further guide the extrusion optimization process. Preformulation studies identify two hydrolysis degradation pathways of gliclazide at elevated temperatures. The activation energy study indicates a significantly higher degradation rate for the amorphous gliclazide compared to the crystalline form. After optimization of the hot-melt extrusion process, including improved screw designs, machine setup, and processing conditions, gliclazide amorphous solid dispersion with ∼95% drug recovery was achieved. The ability to process thermally labile drugs and polymers using hot-melt extrusion will significantly expand the possible applications of this manufacturing process. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of solution plasma process with bubbling gas on physicochemical properties of chitosan.

PubMed

Ma, Fengming; Li, Pu; Zhang, Baiqing; Zhao, Xin; Fu, Qun; Wang, Zhenyu; Gu, Cailian

2017-05-01

In the present work, solution plasma process (SPP) with bubbling gas was used to prepare oligochitosan. The effect of SPP irradiation with bubbling gas on the degradation of chitosan was evaluated by the intrinsic viscosity reduction rate and the degradation kinetic. The formation of OH radical was studied. Changes of the physicochemical properties of chitosan were measured by scanning electron microscopy, X-ray diffraction, and thermogravimetric analysis, as well as ultraviolet-visible, Fourier-transform infrared, and 13 C nuclear magnetic resonance spectroscopy. The results indicated an obvious decrease in the intrinsic viscosity reduction rate after SPP irradiation with bubbling gas, and that the rate with bubbling was higher than that without. The main chemical structure of chitosan remained intact after irradiation, but changes in the morphology, crystallinity, and thermal stability of oligochitosan were observed. In particular, the crystallinity and thermal stability tended to decrease. The present study indicated that SPP can be effectively used for the degradation of chitosan. Copyright © 2017. Published by Elsevier B.V.

Non-thermal plasma-induced photocatalytic degradation of 4-chlorophenol in water.

PubMed

Hao, Xiao Long; Zhou, Ming Hua; Lei, Le Cheng

2007-03-22

TiO(2) photocatalyst (P-25) (50mgL(-1)) was tentatively introduced into pulsed high-voltage discharge process for non-thermal plasma-induced photocatalytic degradation of the representative mode organic pollutant parachlorophenol (4-CP), including other compounds phenol and methyl red in water. The experimental results showed that rate constant of 4-CP degradation, energy efficiency for 4-CP removal and TOC removal with TiO(2) were obviously increased. Pulsed high-voltage discharge process with TiO(2) had a promoted effect for the degradation of these pollutants under a broad range of liquid conductivity. Furthermore, the apparent formation rates of chemically active species (e.g., ozone and hydrogen peroxide) were increased, the hydrogen peroxide formation rate from 1.10x10(-6) to 1.50x10(-6)Ms(-1), the ozone formation rate from 1.99x10(-8) to 2.35x10(-8)Ms(-1), respectively. In addition, this process had no influence on the photocatalytic properties of TiO(2). The introduction of TiO(2) photocatalyst into pulsed discharge plasma process in the utilizing of ultraviolet radiation and electric field in pulsed discharge plasma process enhanced the yields of chemically active species, which were available for highly efficient removal and mineralization of organic pollutants.

Differential thermal voltammetry for tracking of degradation in lithium-ion batteries

NASA Astrophysics Data System (ADS)

Wu, Billy; Yufit, Vladimir; Merla, Yu; Martinez-Botas, Ricardo F.; Brandon, Nigel P.; Offer, Gregory J.

2015-01-01

Monitoring of lithium-ion batteries is of critical importance in electric vehicle applications in order to manage the operational condition of the cells. Measurements on a vehicle often involve current, voltage and temperature which enable in-situ diagnostic techniques. This paper presents a novel diagnostic technique, termed differential thermal voltammetry, which is capable of monitoring the state of the battery using voltage and temperature measurements in galvanostatic operating modes. This tracks battery degradation through phase transitions, and the resulting entropic heat, occurring in the electrodes. Experiments to monitor battery degradation using the new technique are compared with a pseudo-2D cell model. Results show that the differential thermal voltammetry technique provides information comparable to that of slow rate cyclic voltammetry at shorter timescale and with load conditions easier to replicate in a vehicle.

Compendium of information on identification and testing of materials for plastic solar thermal collectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

McGinniss, V.D.; Sliemers, F.A.; Landstrom, D.K.

1980-07-31

This report is intended to organize and summarize prior and current literature concerning the weathering, aging, durability, degradation, and testing methodologies as applied to materials for plastic solar thermal collectors. Topics covered include (1) rate of aging of polymeric materials; (2) environmental factors affecting performance; (3) evaluation and prediction of service life; (4) measurement of physical and chemical properties; (5) discussion of evaluation techniques and specific instrumentation; (6) degradation reactions and mechanisms; (7) weathering of specific polymeric materials; and (8) exposure testing methodology. Major emphasis has been placed on defining the current state of the art in plastics degradation andmore » on identifying information that can be utilized in applying appropriate and effective aging tests for use in projecting service life of plastic solar thermal collectors. This information will also be of value where polymeric components are utilized in the construction of conventional solar collectors or any application where plastic degradation and weathering are prime factors in material selection.« less

Effect of thermal treatment and light irradiation on the stability of lycopene with high Z-isomers content.

PubMed

Murakami, Kazuya; Honda, Masaki; Takemura, Ryota; Fukaya, Tetsuya; Wahyudiono; Kanda, Hideki; Goto, Motonobu

2018-06-01

The stability of lycopene with high Z-isomers content during thermal treatment and light irradiation was investigated. Purified (all-E)-lycopene was thermally isomerized to the Z-isomers in dichloromethane (CH 2 Cl 2 ) at 50 °C for 24 h. The total content of the Z-isomers of lycopene reached 56.1%. Then, the mixture of lycopene isomers was stored in the dark at 4, 25, and 40 °C for 30 days, and under light irradiation using a fluorescent light at 4 °C for 336 h. The degradation rate of lycopene during thermal treatment rose with increasing temperature and the activation energy for decomposition of the mixture of lycopene isomers was calculated to be 71.0 kJ mol -1 . The degradation rate of lycopene isomers was almost the same under thermal treatment. On the other hand, during light irradiation, isomerization was promoted rather than decomposition, i.e. (9Z)- and (13Z)-lycopene converted to the (all-E)-isomer. Copyright © 2018 Elsevier Ltd. All rights reserved.

Vacuum and ultraviolet radiation effects on binders and pigments for spacecraft thermal control coatings

NASA Technical Reports Server (NTRS)

Progar, D. J.; Wade, W. R.

1971-01-01

An evaluation of several silicone resin binders and powdered inorganic pigments for potential use in spacecraft thermal-control paint formulations is presented. The pigments were selected on the basis of a hypothesis relating the heat of formation of a compound to the compound's resistance to ultra-radiation-induced degradation. Reflectance measurements were made in situ to determine degradation rates due to ultraviolet radiation. The tested polydimethylsiloxane resins were not significantly affected by long exposures to ultraviolet radiation. All the pigments, which were dispersed in a polydimethylsiloxane resin, were degraded by ultraviolet radiation as determined by an increase of solar absorptance. For the materials evaluated in this study, no evidence was found to indicate that pigments with high heats of formation were resistant to ultraviolet degradation.

Yeast mannoproteins improve thermal stability of anthocyanins at pH 7.0.

PubMed

Wu, Jine; Guan, Yongguang; Zhong, Qixin

2015-04-01

Anthocyanins are food colourants with strong antioxidant activities, but poor thermal stability limits their application in neutral foods. In the present study, impacts of yeast mannoproteins on the thermal stability of anthocyanins were studied at pH 7.0. The degradation of anthocyanins at 80 and 126 °C followed first order kinetics, and the addition of mannoproteins reduced the degradation rate constant and increased the half-life by 4 to 5-fold. After heating at 80 and 126 °C for 30 min, mannoproteins improved the colour stability of anthocyanins by 4 to 5-fold and maintained the antioxidant capacity of anthocyanins. Visible light absorption, fluorescence spectroscopy, and zeta-potential results suggest that anthocyanins bound with the protein moiety of mannoproteins by hydrophobic interactions, and that the inclusion of anthocyanins in complexes effectively reduced the thermal degradation at pH 7.0. Therefore, mannoproteins may expand the application of anthocyanins as natural colours or functional ingredients. Copyright © 2014 Elsevier Ltd. All rights reserved.

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

NASA Astrophysics Data System (ADS)

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

2017-03-01

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

Accelerated aging tests on ENEA-ASE solar coating for receiver tube suitable to operate up to 550 °C

NASA Astrophysics Data System (ADS)

Antonaia, A.; D'Angelo, A.; Esposito, S.; Addonizio, M. L.; Castaldo, A.; Ferrara, M.; Guglielmo, A.; Maccari, A.

2016-05-01

A patented solar coating for evacuated receiver, based on innovative graded WN-AlN cermet layer, has been optically designed and optimized to operate at high temperature with high performance and high thermal stability. This solar coating, being designed to operate in solar field with molten salt as heat transfer fluid, has to be thermally stable up to the maximum temperature of 550 °C. With the aim of determining degradation behaviour and lifetime prediction of the solar coating, we chose to monitor the variation of the solar absorptance αs after each thermal annealing cycle carried out at accelerated temperatures under vacuum. This prediction method was coupled with a preliminary Differential Thermal Analysis (DTA) in order to give evidence for any chemical-physical coating modification in the temperature range of interest before performing accelerated aging tests. In the accelerated aging tests we assumed that the temperature dependence of the degradation processes could be described by Arrhenius behaviour and we hypothesized that a linear correlation occurs between optical parameter variation rate (specifically, Δαs/Δt) and degradation process rate. Starting from Δαs/Δt values evaluated at 650 and 690 °C, Arrhenius plot gave an activation energy of 325 kJ mol-1 for the degradation phenomenon, where the prediction on the coating degradation gave a solar absorptance decrease of only 1.65 % after 25 years at 550 °C. This very low αs decrease gave evidence for an excellent stability of our solar coating, also when employed at the maximum temperature (550 °C) of a solar field operating with molten salt as heat transfer fluid.

Preservation of Thermal Control Specular Gold Baffle Surface on the James Webb Space Telescope (JWST) Integrated Science Instrument Module (ISIM) Electronics Compartment (IEC)

NASA Technical Reports Server (NTRS)

MonteedeGarcia, Kristina; Patel, Jignasha; Perry, Radford, III

2010-01-01

Extremely tight thermal control property degradation allowances on the vapor-deposited, gold-coated IEC baffle surface, made necessary by the cryogenic JWST Observatory operations, dictate tight contamination requirements on adjacent surfaces. Theoretical degradation in emittance with contaminant thickness was calculated. Maximum allowable source outgassing rates were calculated using worst case view factors from source to baffle surface. Tight requirements pushed the team to change the design of the adjacent surfaces to minimize the outgassing sources

Preservation of thermal control specular gold baffle surface on the James Webb Space Telescope (JWST) integrated science instrument module (ISIM) electronics compartment (IEC)

NASA Astrophysics Data System (ADS)

Montt de Garcia, Kristina; Patel, Jignasha; Perry, Radford, III

2010-08-01

Extremely tight thermal control property degradation allowances on the vapor-deposited, gold-coated IEC baffle surface, made necessary by the cryogenic JWST Observatory operations, dictate tight contamination requirements on adjacent surfaces. Theoretical degradation in emittance with contaminant thickness was calculated. Maximum allowable source outgassing rates were calculated using worst case view factors from source to baffle surface. Tight requirements pushed the team to change the design of the adjacent surfaces to minimize the outgassing sources.

Convective drying kinetics of strawberry (Fragaria ananassa): Effects on antioxidant activity, anthocyanins and total phenolic content.

PubMed

Méndez-Lagunas, Lilia; Rodríguez-Ramírez, Juan; Cruz-Gracida, Marlene; Sandoval-Torres, Sadoth; Barriada-Bernal, Gerardo

2017-09-01

The thermal drying effects on strawberries were investigated in terms of the kinetics of antioxidant activity (AA), anthocyanins (A) and total phenolic compound content (TPC), as well as the final colour. The evaluated drying temperatures were 50 and 60°C with an air rate of 1.5m/s. The 2,2-diphenyl-2-picryl-hydrazyl, pH differential and Folin-Ciocalteu methods were used to assess the antioxidant properties. The kinetics of TPC and AA showed an initial and final period of degradation attributed to inhibition of enzymes. A plateau between these two periods suggests that under certain conditions of temperature and water content, no degradation reactions occurred. Final losses of up to 74, 45 and 78% were found for AA, A and TPC, respectively. The total colour change (ΔE) was lesser degree at 60 than 50°C. Thermal degradation of the antioxidant compounds followed a first-order reaction kinetics and the degradation rate constants (k) were calculated. Copyright © 2017 Elsevier Ltd. All rights reserved.

Ultraviolet radiation effects on the infrared damage rate of a thermal control coating

NASA Technical Reports Server (NTRS)

Bass, J. A.

1972-01-01

The effects of ultraviolet radiation on the infrared reflectance of ZnO silicone white thermal coatings were investigated. Narrow band ultraviolet radiation for wavelengths in the 2200A to 3500A range by a monochromator and a high pressure, 150-W Eimac xenon lamp. The sample was irradiated while in a vacuum of at least 0.000001 torr, and infrared reflectance was measured in situ with a spectroreflectometer at 19,500A. Reflectance degradation was studied as a function of wavelength, time, intensity, and dose. Damage was wavelength dependent at constant exposure, but no maximum was evident above the shortest wavelength investigated here. The degradation rate at constant intensity was an exponential function of time and varies with intensity.

Thermal oxidative degradation of ethylene tetrafluoroethylene copolymer systems

NASA Astrophysics Data System (ADS)

Elders, Jonathan Patrick

Thermo-oxidative degradation of ethylene tetrafluoroethylene (ETFE) was investigated to determine how modifications for use in an electrical wire system affected its thermal stability. Modifications included electron irradiation and subsequent cross-linking during manufacture and contact with a metal surface. Samples with irradiation histories between 0 and 48 MRads were investigated. Degradation of ETFE was enhanced by contact with a metal "conductor" surface: silver - coated copper. Polymer degradation was analyzed by weight loss kinetics (thermogravimetric analysis (TGA)), changes in polymer morphology (differential scanning calorimetry (DSC)), optical microscopy, attenuated total reflectance (ATR) infrared spectroscopy, and gas chromatography - mass spectroscopy (GC/MS). Conductor aging (copper permeation through silver with subsequent oxidation) was investigated using scanning Auger Electron Spectroscopy (AES). Conductor aging is enhanced in the presence of the polymer surface. Interactions between conductor and polymer were analyzed by optical microscopy, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The rate of polymer degradation from 220°C to 280°C was independent of time and extent of degradation, and rate was proportional to irradiation dose. The activation energy for degradation of unirradiated ETFE was 227 kJ/mol and decreased from 150 to 138 kJ/mol for ETFE irradiated to doses between 6 and 48 MRads. Rates of degradation at 300°C to 320°C were dependent on the extent of degradation. Rates of degradation at temperatures between 230°C and 310°C were an order of magnitude larger in the presence of a conductor than in its absence, and activation energies for degradation in the presence of conductor were reduced to 120 kJ/mol. Degradation was modeled as the combination of bulk polymer degradation and catalytic degradation at the polymer-metal interface. ETFE aged at 250°C in the presence or absence of a conductor exhibited a double melting endotherm. ATR spectra of aged ETFE indicated polymer oxidation. Based on AES experiments, copper permeation during aging in the presence or absence of ETFE was consistent with Fickian diffusion. The coefficient for copper diffusion through silver was approximately 10 -15 cm2/second, and catalytic ETFE degradation was proportional to conductor aging. The copper oxidized on the surface to yield a material with a stoichiometric composition of Cu3O 2.

Online estimation of internal stack temperatures in solid oxide fuel cell power generating units

NASA Astrophysics Data System (ADS)

Dolenc, B.; Vrečko, D.; Juričić, Ɖ.; Pohjoranta, A.; Pianese, C.

2016-12-01

Thermal stress is one of the main factors affecting the degradation rate of solid oxide fuel cell (SOFC) stacks. In order to mitigate the possibility of fatal thermal stress, stack temperatures and the corresponding thermal gradients need to be continuously controlled during operation. Due to the fact that in future commercial applications the use of temperature sensors embedded within the stack is impractical, the use of estimators appears to be a viable option. In this paper we present an efficient and consistent approach to data-driven design of the estimator for maximum and minimum stack temperatures intended (i) to be of high precision, (ii) to be simple to implement on conventional platforms like programmable logic controllers, and (iii) to maintain reliability in spite of degradation processes. By careful application of subspace identification, supported by physical arguments, we derive a simple estimator structure capable of producing estimates with 3% error irrespective of the evolving stack degradation. The degradation drift is handled without any explicit modelling. The approach is experimentally validated on a 10 kW SOFC system.

Thermal Decoating of Aerospace Aluminum Alloys for Aircraft Recycling

NASA Astrophysics Data System (ADS)

Muñiz Lerma, Jose Alberto; Jung, In-Ho; Brochu, Mathieu

2016-06-01

Recycling of aircraft aluminum alloys can be complex due to the presence of their corrosion protection coating that includes inorganic compounds containing Cr(VI). In this study, the characterization and thermal degradation behavior of the coating on aluminum substrates coming from an aircraft destined for recycling are presented. Elements such as Sr, Cr, Si, Ba, Ti, S, C, and O were found in three different layers by EDS elemental mapping corresponding to SrCrO4, Rutile-TiO2, SiO2, and BaSO4 with an overall particle size D 50 = 1.96 µm. The thermal degradation profile analyzed by TGA showed four different stages. The temperature of complete degradation at the fourth stage occurred at 753.15 K (480 °C) at lower heating rates. At higher heating rates and holding an isotherm at the same temperature, the residence time to fully decompose the aircraft coating has been estimated as 4.0 ± 0.2 minutes. The activation energy calculated by the Flynn-Wall-Ozawa and the modified Coats-Redfern methods for multiple fraction of decomposition showed a non-constant behavior indicating the complexity of the reaction. Finally, the concentration of Cr(VI) released to the environment during thermal decoating was obtained by UV-Vis spectroscopy. It was found that 2.6 ± 0.1 µg of Cr(VI)/mm2 of aluminum substrate could be released unless adequate particle controls are used.

Modeling of thermal degradation kinetics of the C-glucosyl xanthone mangiferin in an aqueous model solution as a function of pH and temperature and protective effect of honeybush extract matrix.

PubMed

Beelders, Theresa; de Beer, Dalene; Kidd, Martin; Joubert, Elizabeth

2018-01-01

Mangiferin, a C-glucosyl xanthone, abundant in mango and honeybush, is increasingly targeted for its bioactive properties and thus to enhance functional properties of food. The thermal degradation kinetics of mangiferin at pH3, 4, 5, 6 and 7 were each modeled at five temperatures ranging between 60 and 140°C. First-order reaction models were fitted to the data using non-linear regression to determine the reaction rate constant at each pH-temperature combination. The reaction rate constant increased with increasing temperature and pH. Comparison of the reaction rate constants at 100°C revealed an exponential relationship between the reaction rate constant and pH. The data for each pH were also modeled with the Arrhenius equation using non-linear and linear regression to determine the activation energy and pre-exponential factor. Activation energies decreased slightly with increasing pH. Finally, a multi-linear model taking into account both temperature and pH was developed for mangiferin degradation. Sterilization (121°C for 4min) of honeybush extracts dissolved at pH4, 5 and 7 did not cause noticeable degradation of mangiferin, although the multi-linear model predicted 34% degradation at pH7. The extract matrix is postulated to exert a protective effect as changes in potential precursor content could not fully explain the stability of mangiferin. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effect of DMMP on the pyrolysis products of polyurethane foam materials in the gaseous phase

NASA Astrophysics Data System (ADS)

Liu, W.; Li, F.; Ge, X. G.; Zhang, Z. J.; He, J.; Gao, N.

2016-07-01

Dimethyl methylphosphonate (DMMP) has been used as a flame retardant containing phosphorus to decrease the flammability of the polyurethane foam material (PUF). Flame retardancy and thermal degradation of PUF samples have been investigated by the LOI tests and thermal analysis. The results show that LOI values of all PUF/DMMP samples are higher than that of the neat PUF sample and the LOI value of the samples increases with both DMMP concentration and the %P value. Thermal analysis indicates that flame retardant PUF shows a dominant condensed flame retardant activity during combustion. Thermogravimetric analysis-infrared spectrometry (TG-FTIR) has been used to study the influence of DMMP on the pyrolysis products in the gaseous phase during the thermal degradation of the PUF sample. Fourier transform infrared spectrometry (FTIR) spectra of the PUF sample at the maximum evolution rates and the generated trends of water and the products containing -NCO have been examined to obtain more information about the pyrolysis product evolutions of the samples at high temperature. These results reveal that although DMMP could improve the thermal stability of PUF samples through the formation of the residual char layer between fire and the decomposed materials, the influence of DMMP on the gaseous phase can be also observed during the thermal degradation process of materials.

Degradability of cross-linked polyurethanes based on synthetic polyhydroxybutyrate and modified with polylactide.

PubMed

Brzeska, Joanna; Morawska, Magda; Sikorska, Wanda; Tercjak, Agnieszka; Kowalczuk, Marek; Rutkowska, Maria

2017-01-01

In many areas of application of conventional non-degradable cross-linked polyurethanes (PUR), there is a need for their degradation under the influence of specific environmental factors. It is practiced by incorporation of sensitive to degradation compounds (usually of natural origin) into the polyurethane structure, or by mixing them with polyurethanes. Cross-linked polyurethanes (with 10 and 30%wt amount of synthetic poly([ R,S ]-3-hydroxybutyrate) (R,S-PHB) in soft segments) and their physical blends with poly([d,l]-lactide) (PDLLA) were investigated and then degraded under hydrolytic (phosphate buffer solution) and oxidative (CoCl 2 /H 2 O 2 ) conditions. The rate of degradation was monitored by changes of samples mass, morphology of surface and their thermal properties. Despite the small weight losses of samples, the changes of thermal properties of polymers and topography of their surface indicated that they were susceptible to gradual degradation under oxidative and hydrolytic conditions. Blends of PDLLA and polyurethane with 30 wt% of R,S -PHB in soft segments and PUR/PDLLA blends absorbed more water and degraded faster than polyurethane with low amount of R,S -PHB.

Comparison of the Thermal Degradation of Heavily Nb-Doped and Normal PZT Thin Films.

PubMed

Yang, Jeong-Suong; Kang, YunSung; Kang, Inyoung; Lim, SeungMo; Shin, Seung-Joo; Lee, JungWon; Hur, Kang Heon

2017-03-01

The degradation of niobium-doped lead zirconate titanate (PZT) and two types of PZT thin films were investigated. Undoped PZT, two-step PZT, and heavily Nb-doped PZT (PNZT) around the morphotropic phase boundary were in situ deposited under optimum condition by RF-magnetron sputtering. All 2- [Formula: see text]-thick films had dense perovskite columnar grain structure and self-polarized (100) dominant orientation. PZT thin films were deposited on Pt/TiO x bottom electrode on Si wafer, and PNZT thin film was on Ir/TiW electrode with the help of orientation control. Sputtered PZT films formed on microelectromechanical system (MEMS) gyroscope and the degradation rates were compared at different temperatures. PNZT showed the best resistance to the thermal degradation, followed by two-step PZT. To clarify the effect of oxygen vacancies on the degradation of the film at high temperature, photoluminescence measurement was conducted, which confirmed that oxygen vacancy rate was the lowest in heavy PNZT. Nb-doping PZT thin films suppressed the oxygen deficit and made high imprint with self-polarization. This defect distribution and high internal field allowed PNZT thin film to make the piezoelectric sensors more stable and reliable at high temperature, such as reflow process of MEMS packaging.

The Effect of the Heat Flux on the Self-Ignition of Oriented Strand Board

NASA Astrophysics Data System (ADS)

Hirle, Siegfried; Balog, Karol

2017-06-01

This article deals with the initiation phase of flaming and smouldering burning of oriented strand board. The influence of heat flux on thermal degradation of OSB boards, time to ignition, heat release rate and mass loss rate using thermal analysis and vertical electrical radiation panel methods were studied. Significant information on the influence of the heat flux density and the thickness of the material on time to ignition was obtained.

Modified ADM1 disintegration/hydrolysis structures for modeling batch thermophilic anaerobic digestion of thermally pretreated waste activated sludge.

PubMed

Ramirez, Ivan; Mottet, Alexis; Carrère, Hélène; Déléris, Stéphane; Vedrenne, Fabien; Steyer, Jean-Philippe

2009-08-01

Anaerobic digestion disintegration and hydrolysis have been traditionally modeled according to first-order kinetics assuming that their rates do not depend on disintegration/hydrolytic biomass concentrations. However, the typical sigmoid-shape increase in time of the disintegration/hydrolysis rates cannot be described with first-order models. For complex substrates, first-order kinetics should thus be modified to account for slowly degradable material. In this study, a slightly modified IWA ADM1 model is presented to simulate thermophilic anaerobic digestion of thermally pretreated waste activated sludge. Contois model is first included for disintegration and hydrolysis steps instead of first-order kinetics and Hill function is then used to model ammonia inhibition of aceticlastic methanogens instead of a non-competitive function. One batch experimental data set of anaerobic degradation of a raw waste activated sludge is used to calibrate the proposed model and three additional data sets from similar sludge thermally pretreated at three different temperatures are used to validate the parameters values.

Wood products : thermal degradation and fire

Treesearch

R.H. White; M.A. Dietenberger

2001-01-01

Wood is a thermally degradable and combustible material. Applications range from a biomass providing useful energy to a building material with unique properties. Wood products can contribute to unwanted fires and be destroyed as well. Minor amounts of thermal degradation adversely affect structural properties. Therefore, knowledge of the thermal degradation and fire...

Phytochemicals content and antioxidant properties of sea buckthorn (Hippophae rhamnoides L.) as affected by heat treatment - Quantitative spectroscopic and kinetic approaches.

PubMed

Ursache, Florentina-Mihaela; Ghinea, Ioana Otilia; Turturică, Mihaela; Aprodu, Iuliana; Râpeanu, Gabriela; Stănciuc, Nicoleta

2017-10-15

The effect of thermal processing (50-100°C) on the degradation of the phytochemicals in sea buckthorn extract was investigated using chromatographic, fluorescence and FT-IR spectroscopy techniques and degradation kinetics. Heating the sea buckthorn extract resulted in structural changes that led to red- or blue-shifts in maximum emission, depending on temperature and excitation wavelengths. The attenuated total reflectance analysis of the sea buckthorn extract revealed a satisfactory thermostability of compounds at high temperatures. A fractional conversion kinetic model was used to describe the mechanism of degradation in terms of rate and activation energy. Activation energies for total carotenoids, polyphenolic, flavonoids, and antioxidant activity were 8.45±0.93kJ/mol, 2.50±0.66kJ/mol, 22.50±7.26kJ/mol and 15.22±2.75kJ/mol, respectively. The kinetic parameters evidence a higher thermal stability of carotenoids and polyphenols, suggesting higher degradation rates for flavonoids and antioxidant activity. Our results demonstrate that industrial process optimization in terms of time-temperature combinations demands product specific kinetic data. Copyright © 2017 Elsevier Ltd. All rights reserved.

Paracetamol degradation in aqueous solution by non-thermal plasma

NASA Astrophysics Data System (ADS)

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

Effect of Boron Addition on the Thermal, Degradation, and Cytocompatibility Properties of Phosphate-Based Glasses

PubMed Central

Hasan, Muhammad S.; Parsons, Andrew J.; Furniss, David; Scotchford, Colin A.; Ahmed, Ifty; Rudd, Chris D.

2013-01-01

In this study eight different phosphate-based glass compositions were prepared by melt-quenching: four in the (P2O5)45-(CaO)16-(Na2O)15-x -(MgO)24-(B2O3)x system and four in the system (P2O5)50-(CaO)16-(Na2O)10-x-(MgO)24-(B2O3)x, where x = 0,1, 5 and 10 mol%. The effect of B2O3 addition on the thermal properties, density, molar volume, dissolution rates, and cytocompatibility were studied for both glass systems. Addition of B2O3 increased the glass transition (T g), crystallisation (T c), melting (T m), Liquidus (T L) and dilatometric softening (T d) temperature and molar volume (V m). The thermal expansion coefficient (α) and density (ρ) were seen to decrease. An assessment of the thermal stability of the glasses was made in terms of their processing window (crystallisation onset, T c,ons minus glass transition temperature, T g), and an increase in the processing window was observed with increasing B2O3 content. Degradation studies of the glasses revealed that the rates decreased with increasing B2O3 content and a decrease in degradation rates was also observed as the P2O5 content reduced from 50 to 45 mol%. MG63 osteoblast-like cells cultured in direct contact with the glass samples for 14 days revealed comparative data to the positive control for the cell metabolic activity, proliferation, ALP activity, and morphology for glasses containing up to 5 mol% of B2O3. PMID:23991425

Chemical evolution of RNA under hydrothermal conditions and the role of thermal copolymers of amino acids for the prebiotic degradation and formation of RNA

NASA Technical Reports Server (NTRS)

Kawamura, K.; Nagahama, M.; Kuranoue, K.

2005-01-01

The roles of thermal copolymers of amino acids (TCAA) were studied for the prebiotic degradation of RNA. A weak catalytic ability of TCAA consisted of Glu, L-Ala, L-Val, L-Glu, L-Asp, and optionally L-His was detected for the cleavage of the ribose phosphodiester bond of a tetranucleotide (5'-dCrCdGdG) in aqueous solution at 80 degees C. The rate constants of the disappearance of 5'-dCrCdGdG were determined in aqueous solutions using different pH buffer and TCAA. The degradation rates were enhanced 1.3-3.0 times in the presence of TCAA at pH 7.5 and 8.0 at 80 degrees C, while the hydrolysis of oligoguanylate (oligo(G)) was accelerated about 1.6 times at pH 8.0. A weak inhibitory activity for the cleavage of oligo(G) was detected in the presence of 0.055 M TCAA-Std. On the other hand, our recent study on the influences of TCAA for the template-directed reaction of oligo(G) on a polycytidylic acid template showed that TCAA has an acceleration activity for the degradation of the activated nucleotide monomer and an acceleration activity for the formation of G5' ppG capped oligo(G). This series of studies suggest that efficient and selective catalytic or inhibitory activities for either the degradation or formation of RNA under hydrothermal conditions could have hardly emerged from the simple thermal condensation products of amino acids. A scenario is going to be deduced on the chemical evolution of enzymatic activities and RNA molecules concerning hydrothermal earth conditions. c2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sabari Arul, N.; Department of Nanoscience and Technology, Bharathiar University, Coimbatore-641 046; Mangalaraj, D.

Hierarchical rose-flower-like CeO{sub 2} nanostructures were formed by using solvothermal and thermal annealing processes. The CeCO{sub 3}OH thin film was transformed into CeO{sub 2} roses due to thermal annealing. CeO{sub 2} nanostructured roses exhibited excellent photocatalytic activity with a degradation rate of 65% for the azo dye acid orange 7 (AO7) under ultraviolet illumination. The fitting of the absorbance maximum versus time showed that the degradation of AO7 obeyed pseudo-first-order reaction kinetics. The enhancement of the photocatalytic activity for the CeO{sub 2} roses was attributed to the high adsorptivity resulting from the surface active sites and special 4f electron configuration.

Degradation of Silicon Carbide Reflective Surfaces in the LEO Environment

NASA Astrophysics Data System (ADS)

Mileti, Sandro; Coluzzi, Plinio; Marchetti, Mario

2009-01-01

Space mirrors in Low Earth Orbit (LEO) encounter a degradation problem caused by the impact of atomic oxygen (ATOX) in the space environment. This paper presents an experiment of the atomic oxygen impact degradation and UV synergic effects on ground simulation. The experiment was carried out in a dedicated ATOX simulation vacuum chamber. As target materials, a polished CVD Beta-silicon carbide (SiC) coating was investigated. The selection of silicon carbide is due to its high potential candidate as a mirror layer substrate material for its good reflectance at UV wavelengths and excellent thermal diffusivity. It has highly desirable mechanical and thermal properties and can achieve an excellent surface finish. The deposition of the coatings were on carbon-based material substrate; i.e., silicon impregnated carbon fiber composite (C/SiC). Mechanical and thermal properties of the coatings such as hardness and Coefficient of Thermal Expansion (CTE) were achieved. Several atomic oxygen impact angles were studied tilting the target samples respect to the flux direction. The various impact angles permitted to analyze the different erosion rates and typologies which the mirrors would encounter in LEO environment. The degradation was analyzed in various aspects. Macroscopic mass loss per unit area, surface roughness and morphology change were basically analyzed. The exposed surfaces of the materials were observed through a Scanning Electron Microscope (SEM). Secondly, optical diagnostic of the surfaces were performed in order to investigate their variation in optical properties as the evaluation of reflectance degradation. The presence of micro-cracks caused by shrinkage, grinding, polishing or thermal cycling and the porosity in the coatings, could have led to the undercutting phenomenon. Observation of uprising of undercutting was also conducted. Remarks are given regarding capabilities in short-term mission exposures to the LEO environment of this coating.

Determination of the thermal, oxidative and photochemical degradation rates of scintillator liquid by fluorescence EEM spectroscopy.

PubMed

Andrews, N L P; Fan, J Z; Forward, R L; Chen, M C; Loock, H-P

2016-12-21

The thermal, oxidative and photochemical stability of the scintillator liquid proposed for the SNO+ experiment has been tested experimentally using accelerated aging methods. The stability of the scintillator constituents was determined through fluorescence excitation emission matrix (EEM) spectroscopy and absorption spectroscopy, using parallel factor analysis (PARAFAC) as an multivariate analysis tool. By exposing the scintillator liquid to a well-known photon flux at 365 nm and by measuring the decay rate of the fluorescence shifters and the formation rate of their photochemical degradation products, we can place an upper limit on the acceptable photon flux as 1.38 ± 0.09 × 10 -11 photon mol L -1 . Similarly, the oxidative stability of the scintillator liquid was determined by exposure to air at several elevated temperatures. Through measurement of the corresponding activation energy it was determined that the average oxygen concentration would have to be kept below 4.3-7.1 ppb w (headspace partial pressure below 24 ppm v ). On the other hand, the thermal stability of the scintillator cocktail in the absence of light and oxygen was remarkable and poses no concern to the SNO+ experiment.

Thermal Degradation Studies of Polyurethane/POSS Nanohybrid Elastomers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewicki, J P; Pielichowski, K; TremblotDeLaCroix, P

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 ofmore » 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.« less

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

PubMed Central

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

Investigation of long term stability in metal hydrides

NASA Technical Reports Server (NTRS)

Marmaro, Roger W.; Lynch, Franklin E.; Chandra, Dhanesh; Lambert, Steve; Sharma, Archana

1991-01-01

It is apparent from the literature and the results of this study that cyclic degradation of AB(5) type metal hydrides varies widely according to the details of how the specimens are cycled. The Rapid Cycle Apparatus (RCA) used produced less degradation in 5000 to 10000 cycles than earlier work with a Slow Cycle Apparatus (SCA) produced in 1500 cycles. Evidence is presented that the 453 K (356 F) Thermal Aging (TA) time spent in the saturated condition causes hydride degradation. But increasing the cooling (saturation) period in the RCA did not greatly increase the rate of degradation. It appears that TA type degradation is secondary at low temperatures to another degradation mechanism. If rapid cycles are less damaging than slow cycles when the saturation time is equal, the rate of hydriding/dehydriding may be an important factor. The peak temperatures in the RCA were about 30 C lower than the SCA. The difference in peak cycle temperatures (125 C in the SCA, 95 C in RCA) cannot explain the differences in degradation. TA type degradation is similar to cyclic degradation in that nickel peaks and line broadening are observed in X ray diffraction patterns after either form of degradation.

Summary Report of Cable Aging and Performance Data for Fiscal Year 2014.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Celina, Mathias C.; Celina, Mathias C.; Redline, Erica Marie

2014-09-01

As part of the Light Water Reactor Sustainability Program, science - based engineering approaches were employed to address cable degradation behavior under a range of exposure environments. Experiments were conducted with the goal to provide best guidance for aged material states, remaining life and expected performance under specific conditions for a range of cable materials. Generic engineering tests , which focus on rapid accelerated aging and tensile elongation , were combined with complementar y methods from polymer degradation science. Sandia's approach, building on previous years' efforts, enabled the generation of some of the necessary data supporting the development of improvedmore » lifetime predictions models, which incorporate known material b ehaviors and feedback from field - returned 'aged' cable materials. Oxidation rate measurements have provided access to material behavior under low dose rate thermal conditions, where slow degradation is not apparent in mechanical property changes. Such da ta have shown aging kinetics consistent with established radiati on - thermal degradation models. ACKNOWLEDGEMENTS We gratefully acknowledge ongoing technical support at the LICA facility and extensive sample handling provided by Maryla Wasiolek and Don Hans on. Sam Durbin and Patrick Mattie are recognized for valuable guidance throughout the year and assistance in the preparation of the final report. Doug Brunson is appreciated for sample analysis, compilation and plotting of experimental data.« less

Thermal Stability of Aqueous Polyurethanes Depending on the Applied Catalysts

PubMed Central

Cakic, Suzana; Nikolic, Goran; Lacnjevac, Caslav; Gligoric, Miladin; Stamenkovic, Jakov; Rajkovic, Milos B.; Barac, Miroljub

2006-01-01

The thermal stability of aqueous polyurethanes has been measured applying the thermogravimetric analysis. The aqueous polyurethanes (aqPUR) with catalysts of different selectivity have been studied by use of the dynamic method. To obtain degradations of 0.025, 0.05, and 0.10, employing the dynamic method, the heating rates of 0.5, 1, 2, 5, and 10 °C min-1 have been used in the range of 30-500 °C. Using the more selective catalysts in the aqueous polyurethanes, the total resulting time of the decompositon has been on the increase at all degrees of the degradation and at the particular starting temperature. This paper shows that the dynamic method based on the thermogravimetric analysis can be used to assess the thermal stability of the aqueous polyurethanes using the catalysts of different selectivity.

Flash-Fire Propensity and Heat-Release Rate Studies of Improved Fire Resistant Materials

NASA Technical Reports Server (NTRS)

Fewell, L. L.

1978-01-01

Twenty-six improved fire resistant materials were tested for flash-fire propensity and heat release rate properties. The tests were conducted to obtain a descriptive index based on the production of ignitable gases during the thermal degradation process and on the response of the materials under a specific heat load.

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

DOE Office of Scientific and Technical Information (OSTI.GOV)

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 leadingmore » 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/thermo-chemical attack mechanisms; (iv) developing a mechanics-based analysis of the driving forces for crack growth and delamination, based on molten phase infiltration, misfit upon cooling, and loss of compliance; (v) understanding changes in TGO growth mechanisms associated with these emerging combustion product streams; and (vi) identifying degradation resistant alternative materials (including new compositions or bi-layer concepts) for use in mitigating the observed degradation modes. To address the materials stability concerns, this program integrated research thrusts aimed at: (1) Conducting tests in simulated syngas and HHC environments to evaluate materials evolution and degradation mechanisms; assessing thermally grown oxide development unique to HHC environmental exposures; carrying out high-resolution imaging and microanalysis to elucidate the evolution of surface deposits (molten phase formation and infiltration); exploring thermo-chemical instabilities; assessing thermo-mechanical drivers and thermal gradient effects on degradation; and quantitatively measuring stress evolution due to enhanced sintering and thermo-chemical instabilities induced in the coating. (2) Executing experiments to study the melting and infiltration of simulated ash deposits, and identifying reaction products and evolving phases associated with molten phase corrosion mechanisms; utilizing thermal spray techniques to fabricate test coupons with controlled microstructures to study mechanisms of instability and degradation; facilitating thermal gradient testing; and developing new materials systems for laboratory testing; (3) Correlating information on the resulting combustion environments to properly assess materials exposure conditions and guide the development of lab-scale simulations of material exposures; specification of representative syngas and high-hydrogen fuels with realistic levels of impurities and contaminants, to explore differences in heat transfer, surface degradation, and deposit formation; and facilitating combustion rig testing of materials test coupons.« less

Thermal degradation kinetics of phycocyanin encapsulation as an antioxidant agent

NASA Astrophysics Data System (ADS)

Nilamsari, A. M.; Yunanda, A.; Hadiyanto, H.

2018-01-01

Phycocyanin is a blue-light pigment that found in Cyanobacteria and two Eukaryotics algae such as Rhodophyta and Crytophyta. Phycocyanin is soluble in water and has a strong fluorescent properties as an antioxidant and normally used in food industry, cosmetic, biotechnology, and drug. However, Phycocyanin is easily damaged by a heating process. The aim of this study is to obtain the optimal condition of phycocyanin encapsulation with different coating materials, Chitosan and Carrageenan, by the calculation of heat resistance of antioxidant activity (D), range of temperature that increase the rate of degradation (Z), rate constant of degradation (k), and activation energy (Ea). The ratio of phycocyanin and the coating material are 2% (w/v) and 2 % (w/v).

Gamma irradiation degradation/modification of 5-ethylidene 2-norbornene (ENB)-based ethylene propylene diene rubber (EPDM) depending on ENB content of EPDM and type/content of peroxides used in vulcanization

NASA Astrophysics Data System (ADS)

Özdemir, Tonguç

2008-06-01

In this study, the radiation degradation/modification of the vulcanized EPDM and the effects of dose rate, peroxide type/content in vulcanization system and ENB content of EPDM were studied to investigate the change in the extend of the modification/degradation of the mechanical properties of vulcanized EPDM via gamma irradiation. In addition, thermal, dynamic mechanical, ATR-FTIR, TGA, TGA-FTIR tests were carried out to understand the change of properties of vulcanized EPDM via irradiation. Samples were irradiated with two different dose rates of 1280 and 64.6 Gy/h. Total dose of irradiation was up to 184 kGy. The FTIR spectral analysis showed structural changes of EPDM via irradiation. It was observed that the dose rate changed the mechanical properties with different extends. The change of ENB content of EPDM and peroxide type and content in vulcanization system affect extend of the modification/degradation of the EPDM's properties.

Passive control of temperature excursion and uniformity in high-energy Li-ion battery packs at high current and ambient temperature

NASA Astrophysics Data System (ADS)

Kizilel, R.; Lateef, A.; Sabbah, R.; Farid, M. M.; Selman, J. R.; Al-Hallaj, S.

A strategy for portable high-power applications with a controlled thermal environment has been developed and has demonstrated the advantage of using the novel phase change material (PCM) thermal management systems over conventional active cooling systems. A passive thermal management system using PCM for Li-ion batteries is tested for extreme conditions, such as ambient temperature of 45 °C and discharge rate of 2.08 C-rate (10 A). Contrary to Li-ion packs without thermal management system, high-energy packs with PCM are discharged safely at high currents and degrading rate of capacity of the Li-ion packs lowered by half. Moreover, the compactness of the packs not only decreases the volume occupied by the packs and its associated complex cooling system, but also decreases the total weight for large power application.

Simultaneous Thermal and Gamma Radiation Aging of Electrical Cable Polymers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fifield, Leonard S.

The polymers used for insulation in nuclear power plant electrical cables are susceptible to aging during long term operation. Elevated temperature is the primary contributor to changes in polymer structure that result loss of mechanical and electrical properties, but gamma radiation is also a significant source of degradation for polymers used within relevant plant locations. Despite many years of polymer degradation research, the combined effects of simultaneous exposure to thermal and radiation stress are not well understood. As nuclear operators contemplate and prepare for extended operations beyond initial license periods, a predictive understanding of exposure-based cable material degradation is becomingmore » an increasingly important input to safety, licensing, operations and economic decisions. We are focusing on carefully-controlled simultaneous thermal and gamma radiation accelerating aging and characterization of the most common nuclear cable polymers to understand the relative contributions of temperature, time, dose and dose rate to changes in cable polymer material structure and properties. Improved understanding of cable performance in long term operation will help support continued sustainable nuclear power generation.« less

Phenomena during thermal removal of binders

NASA Astrophysics Data System (ADS)

Hrdina, Kenneth Edward

The research presented herein has focused on debinding of an ethylene copolymer from a SiC based molded ceramic green body. Examination of the binder burnout process was carried out by breaking down the process into two distinct regions: those events which occur before any weight loss begins, and those events occurring during binder removal. Below the temperature of observed binder loss (175sp°C), both reversible and irreversible displacement was observed to occur. The displacement was accounted for by relaxation of molding stresses, thermal expansion of the system, and melting of the semicrystalline copolymer occurring during heating. Upon further heating the binder undergoes a two stage thermal degradation process. In the first stage, acetic acid is the only degradation product formed, as determined by GC/MS analysis. In this stage, component shrinkage persisted and it was found that one unit volume of shrinkage corresponded with one unit volume of binder removed, indicating that no porosity developed. The escaping acetic acid effluents must diffuse through liquid polymer filled porous regions to escape. The gas pressure of the acetic acid species produced in the first stage of the thermal degradation may exceed the ambient pressure promoting bubble formation. Controlling the heating rate of the specimen maintains the gas pressure below the bubbling threshold and minimizes the degradation time. Experiments have determined the kinetics of the reaction in the presence of the high surface area (10-15msp2/g) ceramic powder and then verified that acetic acid was diffusing through the polymer phase to the specimen surface where evaporation is taking place. The sorption method measured the diffusivity and activity of acetic acid within the filled ceramic system within a TGA. These data were incorporated into a Fickian type model which included the rate of generation of the diffusing species. The modeling process involved prediction of the bloating temperature as a function of the sample size for a given heating rate. The predicted results and experimental results show good correlation. The model was used to optimize the heating schedule which minimized the binder removal time.

Variable anodic thermal control coating on aluminum

NASA Technical Reports Server (NTRS)

Duckett, R. J.; Gilliland, C. S.

1983-01-01

A variable thermal control coating (modified chromic acid anodizing) has been developed to meet the needs for the thermal control of spacecraft. This coating, with controlled variable ranges of 0.10 to 0.72 thermal emittance and 0.2 to 0.4 solar absorptance, allows the user to select any value of thermal emittance and solar absorptance within the range specified and obtain both values within + or - 0.02. Preliminary solar stability has shown less than 15 percent degradation over 2000 hours of vacuum solar exposure. The technique has been determined to be sensitive to the parameters of voltage, rate of voltage application, time, temperature, acid concentration, and material pretreatment.

Effect of pH on the adsorption and photocatalytic degradation of sulfadimidine in Vis/g-C3N4 progress.

PubMed

Yang, Bin; Mao, Xuhui; Pi, Liu; Wu, Yixiao; Ding, Huijun; Zhang, Weihao

2017-03-01

In this study, g-C 3 N 4 was synthesized by thermal polycondensation of melamine and was characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, UV-visible diffuse reflection spectroscopy, and scanning electron microscopy. Results showed that g-C 3 N 4 degraded sulfadimidine (SMD) under visible light, in which the adsorption and photocatalytic degradation was influenced by pH. The maximum adsorption capacity was achieved at approximately pH 5. The highest degradation rate constant was obtained at strong acid and alkali. In addition, the degradation mechanism of g-C 3 N 4 was evaluated with the help of quencher agents. The intermediates, degradation pathways, and mineralization of SMD were also determined to evaluate the degradation and oxidation ability of g-C 3 N 4 .

Finite-element modelling of thermal micracking in fresh and consolidated marbles

NASA Astrophysics Data System (ADS)

Weiss, T.; Fuller, E.; Siegesmund, S.

2003-04-01

The initial stage of marble weathering is supposed to be controlled by thermal microcracking. Due to the anisotropy of the thermal expansion coefficients of calcite, the main rock forming mineral in marble, stresses are caused which lead to thermally-induced microcracking, especially along the grain boundaries. The so-called "granular disintegration" is a frequent weathering phenomenon observed for marbles. The controlling parameters are the grain size, grain shape and grain orientation. We use a finite-element approach to constrain magnitude and directional dependence of thermal degradation. Therefore, different assumptions are validated including the fracture toughness of the grain boundaries, the effects of the grain-to-grain orientation and bulk lattice preferred orientation (here referred to as texture). The resulting thermal microcracking and bulk rock thermal expansion anisotropy are validated. It is evident that thermal degradation depends on the texture. Strongly textured marbles exhibit a clear directional dependence of thermal degradation and a smaller bulk thermal degradation than randomly oriented ones. The effect of different stone consolidants in the pore space of degraded marble is simulated and its influence on mechanical properties such as tensile strength are evaluated.

Study of toluene stability for an Organic Rankine Cycle (ORC) space-based power system

NASA Technical Reports Server (NTRS)

Havens, Vance; Ragaller, Dana

1988-01-01

The design, fabrication, assembly, and endurance operation of a dynamic test loop, built to evaluate the thermal stability of a proposed Organic Rankine Cycle (ORC) working fluid, is discussed. The test fluid, toluene, was circulated through a heater, simulated turbine, regenerator, condenser and pump to duplicate an actual ORC system. The maximum nominal fluid temperature, 750 F, was at the turbine simulator inlet. Samples of noncondensible gases and liquid toluene were taken periodically during the test. The samples were analyzed to identify the degradation products formed and the quantity of these products. From these data it was possible to determine the degradation rate of the working fluid and the generation rate of noncondensible gases. A further goal of this work was to relate the degradation observed in the dynamic operating loop to degradation obtained in isothermal capsule tests. This relationship was the basis for estimating the power loop degradation in the Space Station Organic Rankine Cycle system.

Durability of Cement Composites Reinforced with Sisal Fiber

NASA Astrophysics Data System (ADS)

Wei, Jianqiang

This dissertation focuses mainly on investigating the aging mechanisms and degradation kinetics of sisal fiber, as well as the approaches to mitigate its degradation in the matrix of cement composites. In contrast to previous works reported in the literature, a novel approach is proposed in this study to directly determine the fiber's degradation rate by separately studying the composition changes, mechanical and physical properties of the embedded sisal fibers. Cement hydration is presented to be a crucial factor in understanding fiber degradation behavior. The degradation mechanisms of natural fiber consist of mineralization of cell walls, alkali hydrolysis of lignin and hemicellulose, as well as the cellulose decomposition which includes stripping of cellulose microfibrils and alkaline hydrolysis of amorphous regions in cellulose chains. Two mineralization mechanisms, CH-mineralization and self-mineralization, are proposed. The degradation kinetics of sisal fiber in the cement matrix are also analyzed and a model to predict the degradation rate of cellulose for natural fiber embedded in cement is outlined. The results indicate that the time needed to completely degrade the cellulose in the matrix with cement replacement by 30wt.% metakaolin is 13 times longer than that in pure cement. A novel and scientific method is presented to determine accelerated aging conditions, and to evaluating sisal fiber's degradation rate and durability of natural fiber-reinforced cement composites. Among the static aggressive environments, the most effective approach for accelerating the degradation of natural fiber in cement composites is to soak the samples or change the humidity at 70 °C and higher temperature. However, the dynamic wetting and drying cycling treatment has a more accelerating effect on the alkali hydrolysis of fiber's amorphous components evidenced by the highest crystallinity indices, minimum content of holocellulose, and lowest tensile strength. Based on the understanding of degradation mechanisms, two approaches are proposed to mitigate the degradation of sisal fiber in the cement matrix. In order to relieve the aggressive environment of hydrated cement, cement substitution by a combination of metakaolin and nanoclay, and a combination of rice husk ash and limestone are studied. Both metakaolin and nanoclay significantly optimize the cement hydration, while the combination of these two supplementary cementitious materials validates their complementary and synergistic effect at different stages of aging. The presented approaches effectively reduce the calcium hydroxide content and the alkalinity of the pore solution, thereby mitigating the fiber degradation and improving both the initial mechanical properties and durability of the fiber-cement composites. The role of rice husk ash in cement modification is mainly as the active cementitious supplementary material. In order to improve the degradation resistance of sisal fiber itself, two novel, simple, and economical pretreatments of the fibers (thermal and sodium carbonate treatment) are investigated. Both thermal treatment and Na 2CO3 treatment effectively improve the durability of sisal fiber-reinforced concrete. The thermal treatment achieves improvement of cellulose's crystallization, which ensures the initial strength and improved durability of sisal fiber. A layer consisting of calcium carbonate sediments, which protects the internals of a fiber from the strong alkali pore solution, is formed and filled in pits and cavities on the Na2CO3 treated sisal fiber's surface.

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

PubMed Central

Zhou, Quancheng; Sheng, Guihua

2012-01-01

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

Thermal stability of poly(3-hydroxybutyrate)/vegetable fiber composites

NASA Astrophysics Data System (ADS)

Cipriano, Pâmela Bento; de Sá, Mayelli Dantas; Andrade, André L. Simões; de Carvalho, Laura Hecker; Canedo, Eduardo Luis

2015-05-01

The present work deals with the thermal stability during and after processing of composites of poly(3-hydroxybutyrate) (PHB) - a fully biodegradable semi-crystalline thermoplastic obtained from renewable resources through low-impact biotechnological process, biocompatible and non-toxic - and vegetable fiber from the fruit (coconut) of babassu palm tree. PHB/babassu composites with 0, 5, 10 and 20% w/w load were prepared in a laboratory internal mixer. Two fractions of the mesocarp of babassu with different particle sizes were compounded with PHB and test specimens molded by compression. The effect of loading level and processing conditions on torque, temperature and mechanical energy dissipation were studied using a new engineering model. It was found that PHB degrades during processing at temperatures slightly above the melting point. To minimize thermal degradation stabilizer and chain extender additives were incorporated, with mixed results. These findings were confirmed by the dependence of the melt flow rate on the processing temperature.

Synthesis, characterization and hydrolytic degradation study of polyetheresteramide copolymers based on epsilon-caprolactone, 6-aminocaproic acid, and poly(ethylene glycol).

PubMed

Liu, CaiBing; Qian, ZhiYong; Jia, WenJuan; Huang, MeiJuan; Chao, GuoTao; Gong, ChangYang; Deng, HongXin; Wen, YanJun; Yang, JinLiang; Gou, MaLing; Tu, MingJing

2007-10-01

In this paper, a new kind of biodegradable aliphatic polyetheresteramide copolymers (PEEA) based on epsilon-caprolactone, 6-aminocaproic acid, and poly(ethylene glycol) (PEG) were synthesized by melt polymerization method. The obtained copolymers were characterized by 1H-NMR. The thermal properties of PEEA copolymers were studied by DSC and TGA/DTA under nitrogen atmosphere. The water absorption and hydrolytic degradation behavior was also studied in detail. With the increase in PEG content or the decrease in caprolactone content, the water absorption of the copolymers increased accordingly. For the hydrolytic degradation behavior, with the increase in PEG content or caprolactone content, the degradation rate increased then.

Kinetics of drug decomposition. Part XXXVI. Stability of 10-(1'-methyl-4'-piperazinylpropyl)-phenothiazine derivatives on the grounds of kinetics of thermal degradation and Hammett equation.

PubMed

Pawelczyk, E; Marciniec, B; Matlak, B

1975-01-01

Thermal degradation of aqueous and buffered solutions of perazine, prochlorperazine, trifluoperazine, thioproperazine, thiethylperazine and butaperazine salts was examined by kinetic method using an accelerated testing of pharmaceutical preparations. The order, rate constants and activation parameters (Q100, E, delta H not equal to, delta S not equal to, delta G not equal to ) of the reaction given were discussed. The predicted stability of the examined derivatives was compared on the grounds of a calculated time t10% and K293 kappa. A dependence between the stability and kind of substituent in the C2 positions was discussed in terms of the Hammett equation.

Investigation of Thermophysical Properties of Thermal Degraded Biodiesels

NASA Astrophysics Data System (ADS)

Regatieri, H. R.; Savi, E. L.; Lukasievicz, G. V. B.; Sehn, E.; Herculano, L. S.; Astrath, N. G. C.; Malacarne, L. C.

2018-06-01

Biofuels are an alternative to fossil fuels and can be made from many different raw materials. The use of distinct catalyst and production processes, feedstocks, and types of alcohol results in biofuels with different physical and chemical properties. Even though these diverse options for biodiesel production are considered advantageous, they may pose a setback when quality specifications are considered, since different properties are subject to different reactions during usage, storage and handling. In this work, we present a systematic characterization of biodiesels to investigate how accelerated thermal degradation affects fuel properties. Two different types of biodiesel, commercially obtained from distinct feedstocks, were tested. The thermal degradation process was performed by maintaining the temperature of the sample at 140°C under constant air flux for different times: 0 h, 3 h, 6 h, 9 h, 12 h, 24 h and 36 h. Properties such as density, viscosity, activation energy, volumetric thermal expansion coefficient, gross caloric value, acid value, infrared absorption, and temperature coefficient of the refractive index were used to study the thermal degradation of the biodiesel samples. The results show a significant difference in fuel properties before and after the thermal degradation process suggesting the formation of undesirable compounds. All the properties mentioned above were found to be useful to determine whether a biodiesel sample underwent thermal degradation. Moreover, viscosity and acid value were found to be the most sensitive characteristics to detect the thermal degradation process.

The influence of heat treatment and plastic deformation on the bio-degradation of a Mg-Y-RE alloy.

PubMed

Gunde, Petra; Furrer, Angela; Hänzi, Anja C; Schmutz, Patrik; Uggowitzer, Peter J

2010-02-01

In this study the bio-degradation behavior of a Mg-Y-RE alloy in different heat treatment states with respect to the alloy's potential application as biodegradable implant material was investigated by electrochemical impedance spectroscopy in two body-similar fluids. The heat treatments increase the degradation resistance of the alloy and lead to the formation of a thermal oxide layer on the sample surface and to a change in microstructure such as the distribution of yttrium. The varying Y distribution in the alloy does not significantly influence the degradation behavior, and all samples show a similar low polarization resistance. However, samples with a thermal oxide layer, which consists mainly of Y(2)O(3), degrade much more slowly and feature remarkably high polarization resistance. Nevertheless, in some cases localized corrosion attack occurs and drastically impairs performance. Cracks in the oxide layer, intentionally induced by straining of the samples and which in practice could originate from the implantation process, reduce the corrosion resistance. However, these samples perform still better than polished specimens and show a macroscopically homogeneous degradation behavior without localized corrosion. Microscopically, corrosion attacks start at the cracks and undermining of the oxide layer occurs with time. For all the material conditions a remarkable dependence of the degradation rate on the electrolyte is noted. (c) 2009 Wiley Periodicals, Inc.

Fossilization Processes in Thermal Springs

NASA Technical Reports Server (NTRS)

Farmer, Jack D.; Cady, Sherry; Desmarais, David J.; Chang, Sherwood (Technical Monitor)

1995-01-01

To create a comparative framework for the study of ancient examples, we have been carrying out parallel studies of the microbial biosedimentology, taphonomy and geochemistry of modem and sub-Recent thermal spring deposits. One goal of the research is the development of integrated litho- and taphofacies models for siliceous and travertline sinters. Thermal springs are regarded as important environments for the origin and early evolution of life on Earth, and we seek to utilize information from the fossil record to reconstruct the evolution of high temperature ecosystems. Microbial contributions to the fabric of thermal spring sinters occur when population growth rates keep pace with, or exceed rates of inorganic precipitation, allowing for the development of continuous biofilms or mats. In siliceous thermal springs, microorganisms are typically entombed while viable. Modes of preservation reflect the balance between rates of organic matter degradation, silica precipitation and secondary infilling. Subaerial sinters are initially quite porous and permeable and at temperatures higher than about 20 C, organic materials are usually degraded prior to secondary infilling of sinter frameworks. Thus, organically-preserved microfossils are rare and fossil information consists of characteristic biofabrics formed by the encrustation and underplating of microbial mat surfaces. This probably accounts for the typically low total organic carbon values observed in thermal spring deposits. In mid-temperature, (approx. 35 - 59 C) ponds and outflows, the surface morphology of tufted Phormidium mats is preserved through mat underplating by thin siliceous: crusts. Microbial taxes lead to clumping of ceils and/or preferred filament orientations that together define higher order composite fabrics in thermal spring stromatolites (e.g. network, coniform, and palisade). At lower temperatures (less than 35 C), Calothrix mats cover shallow terracette pools forming flat carpets or pustular surfaces that produce palisade and "shrub" fabrics, respectively. At finer scales, composite fabrics are seen to consist distinctive associations of microstructures formed by the encrustation of individual cells and filaments. Composite fabrics survive the diagenetic transitions from primary opaline silica to quartz and are known from subaerial thermal spring deposits as old as Lower Carboniferous. However, fossil microorganisms tend to be rare in older deposits, and are usually preserved only where cells or sheaths have been stained by iron oxides. In subaqueous mineralizing springs at lower temperatures, early infilling leads to a more rapid and complete reduction in porosity and permeability. This process, along with the slower rates of microbial degradation at lower temperatures, creates a more favorable situation for organic matter preservation. Application of this taphonomic model to the Rhynie Chert, previously interpreted as subaerial, suggest it was probably deposited in a subaqueous spring setting at lower temperatures.

Lifetime Extension Report: Progress on the SAVY-4000 Lifetime Extension Program

DOE Office of Scientific and Technical Information (OSTI.GOV)

Welch, Cynthia F.; Smith, Paul Herrick; Weis, Eric M.

The 3-year accelerated aging study of the SAVY-4000 O-ring shows very little evidence of significant degradation to samples subjected to aggressive elevated temperature and radiation conditions. Whole container thermal aging studies followed by helium leakage testing and compression set measurements were used to establish an estimate for a failure criterion for O-ring compression set of ≥65 %. The whole container aging studies further show that the air flow and efficiency functions of the filter do not degrade significantly after thermal aging. However, the degradation of the water-resistant function leads to water penetration failure after four months at 210°C, but doesmore » not cause failure after 10 months at 120°C (130°C is the maximum operating temperature for the PTFE membrane). The thermal aging data for O-ring compression set do not meet the assumptions of standard time-temperature superposition analysis for accelerated aging studies. Instead, the data suggest that multiple degradation mechanisms are operative, with a reversible mechanism operative at low aging temperatures and an irreversible mechanism dominating at high aging temperatures. To distinguish between these mechanisms, we have measured compression set after allowing the sample to physically relax, thereby minimizing the effect of the reversible mechanism. The resulting data were analyzed using two distinct mathematical methods to obtain a lifetime estimate based on chemical degradation alone. Both methods support a lifetime estimate of greater than 150 years at 80°C. Although the role of the reversible mechanism is not fully understood, it is clear that the contribution to the total compression set is small in comparison to that due to the chemical degradation mechanism. To better understand the chemical degradation mechanism, thermally aged O-ring samples have been characterized by Fourier Transform Infrared (FTIR), Electron Paramagnetic Resonance (EPR), Gel Permeation Chromatography (GPC), and Differential Scanning Calorimetry (DSC). These experiments detect no significant O-ring degradation below 80°C. Furthermore, durometer measurements indicate that there is no significant change in O-ring hardness at all aging conditions examined. Therefore, our current conservative lifetime estimate for the O-ring and the filter is 10 years at 80°C. In FY17, we will continue to probe the chemical degradation mechanism using oxygen consumption measurements under accelerated aging conditions to reveal temperatures at which oxidation occurs, along with any differences in oxidation rate at the low vs. high aging temperatures. We will also refine the failure criteria and finalize the radiation/thermal synergistic studies to determine a final design lifetime.« less

Effect of diisocyanate linkers on the degradation characteristics of copolyester urethanes as potential drug carrier matrices.

PubMed

Mathew, Simi; Baudis, Stefan; Neffe, Axel T; Behl, Marc; Wischke, Christian; Lendlein, Andreas

2015-09-01

In this study, the effect of three aliphatic diisocyanate linkers, L-lysine diisocyanate ethyl ester (LDI), hexamethylene diisocyanate (HDI), and racemic 2,2,4-/2,4,4-trimethyl hexamethylene diisocyanate (TMDI), on the degradation of oligo[(rac-lactide)-co-glycolide] (64:36 mol%) based polyester urethanes (PEU) was examined. Samples were characterized for their molecular weight, mass loss, water uptake, sequence structure, and thermal and mechanical properties. Compared to non-segmented PLGA, the PEU showed higher water uptake and generally degraded faster. Interestingly, the rate of degradation was not directly correlating with the hydrophilicity of the diisocyanate moieties; instead, competing intra-/intermolecular hydrogen bonds in between urethane moieties appear to substantially decrease the rate of degradation for LDI-derived PEU. By comparing microparticles (μm) and films (mm) as matrices of different dimensions, it was shown that autocatalysis remains a contributor to degradation of the larger-sized PEU matrices as it is typical for non-segmented lactide/glycolide copolymers. The shown capacity of lactide/glycolide-based multiblock copolymers to degrade faster than PLGA and exhibit improved elastic properties could be of interest for medical implants and drug release systems. Copyright © 2015 Elsevier B.V. All rights reserved.

Degradation of reactive blue 19 by needle-plate non-thermal plasma in different gas atmospheres: Kinetics and responsible active species study assisted by CFD calculations.

PubMed

Sun, Yu; Liu, Yanan; Li, Rui; Xue, Gang; Ognier, Stéphanie

2016-07-01

This study investigated the degradation of a model organic compound, reactive blue (RB-19), in aqueous solution using a needle-plate non-thermal plasma (NTP) reactor, which was operated using three gas atmospheres (Ar, air, O2) at room temperature and atmospheric pressure. The relative discharge and degradation parameters, including the peak to peak applied voltage, power, ozone generation, pH, decolorization rates, energy density and the total organic carbon (TOC) reduction were analyzed to determine the various dye removal efficiencies. The decolorization rate for Ar, air and O2 were 59.9%, 49.6% and 89.8% respectively at the energy density of 100 kJ/L. The best TOC reduction was displayed by Ar with about 8.8% decrease, and 0% with O2 and air atmospheres. This phenomenon could be explained by the formation of OH• and O3 in the Ar and O2 atmospheres, which are responsible for increased mineralization and efficient decolorization. A one-dimension model was developed using software COMSOL to simulate the RB-19-ozone reaction and verify the experiments by comparing the simulated and experimental results. It was determined that ozone plays the most important role in the dye removal process, and the ozone contribution rate ranged from 0.67 to 0.82. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thermal degradation of aqueous 2-aminoethylethanolamine in CO2 capture; identification of degradation products, reaction mechanisms and computational studies.

PubMed

Saeed, Idris Mohamed; Lee, Vannajan Sanghiran; Mazari, Shaukat Ali; Si Ali, B; Basirun, Wan Jeffrey; Asghar, Anam; Ghalib, Lubna; Jan, Badrul Mohamed

2017-01-01

Amine degradation is the main significant problems in amine-based post-combustion CO 2 capture, causes foaming, increase in viscosity, corrosion, fouling as well as environmental issues. Therefore it is very important to develop the most efficient solvent with high thermal and chemical stability. This study investigated thermal degradation of aqueous 30% 2-aminoethylethanolamine (AEEA) using 316 stainless steel cylinders in the presence and absence of CO 2 for 4 weeks. The degradation products were identified by gas chromatography mass spectrometry (GC/MS) and liquid chromatography-time-of-flight-mass spectrometry (LC-QTOF/MS). The results showed AEEA is stable in the absence of CO 2 , while in the presence of CO 2 AEEA showed to be very unstable and numbers of degradation products were identified. 1-(2-Hydroxyethyl)-2-imidazolidinone (HEIA) was the most abundance degradation product. A possible mechanism for the thermal degradation of AEEA has been developed to explain the formation of degradation products. In addition, the reaction energy of formation of the most abundance degradation product HEIA was calculated using quantum mechanical calculation.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Kandler; Shi, Ying; Santhanagopalan, Shriram

Predictive models of Li-ion battery lifetime must consider a multiplicity of electrochemical, thermal, and mechanical degradation modes experienced by batteries in application environments. To complicate matters, Li-ion batteries can experience different degradation trajectories that depend on storage and cycling history of the application environment. Rates of degradation are controlled by factors such as temperature history, electrochemical operating window, and charge/discharge rate. We present a generalized battery life prognostic model framework for battery systems design and control. The model framework consists of trial functions that are statistically regressed to Li-ion cell life datasets wherein the cells have been aged under differentmore » levels of stress. Degradation mechanisms and rate laws dependent on temperature, storage, and cycling condition are regressed to the data, with multiple model hypotheses evaluated and the best model down-selected based on statistics. The resulting life prognostic model, implemented in state variable form, is extensible to arbitrary real-world scenarios. The model is applicable in real-time control algorithms to maximize battery life and performance. We discuss efforts to reduce lifetime prediction error and accommodate its inevitable impact in controller design.« less

Effect of Modified Red Pottery Clay on the Moisture Absorption Behavior and Weatherability of Polyethylene-Based Wood-Plastic Composites

PubMed Central

Li, Qingde; Gao, Xun; Cheng, Wanli; Han, Guangping

2017-01-01

Red pottery clay (RPC) was modified using a silane coupling agent, and the modified RPC (mRPC) was then used to enhance the performance of high-density polyethylene-based wood-plastic composites. The effect of the mRPC content on the performances of the composites was investigated through Fourier transform infrared spectrometry, differential mechanical analysis (DMA) and ultraviolet (UV)-accelerated aging tests. After adding the mRPC, a moisture adsorption hysteresis was observed. The DMA results indicated that the mRPC effectively enhanced the rigidity and elasticity of the composites. The mRPC affected the thermal gravimetric, leading to a reduction of the thermal degradation rate and a right-shift of the thermal degradation peak; the initial thermal degradation temperature was increased. After 3000 h of UV-accelerated aging, the flexural strength and impact strength both declined. For aging time between 0 and 1000 h, the increase in amplitude of ΔL* (luminescence) and ΔE* (color) reached a maximum; the surface fading did not became obvious. ΔL* and ΔE* increased more significantly between 1000 and 2000 h. These characterization results indicate that the chromophores of the mRPC became briefly active. However, when the aging times were higher than 2000 h, the photo-degradation reaction was effectively prevented by adding the mRPC. The best overall enhancement was observed for an mRPC mass percentage of 5%, with a storage modulus of 3264 MPa and an increase in loss modulus by 16.8%, the best anti-aging performance and the lowest degree of color fading. PMID:28772470

Optimizing Battery Usage and Management for Long Life

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Kandler; Shi, Ying; Wood, Eric

2016-06-16

This presentation discusses the impact of system design factors on battery aging and end of life. Topics include sizing of the SOC operating window, cell balancing and thermal management systems and their value in reducing pack degradation rates and cell imbalance growth over lifetime.

Thermal degradation of Lewis acid complexed LDPE films

NASA Astrophysics Data System (ADS)

Sreelatha, K.; Predeep, P.

2017-06-01

The study highlights the thermal behavior of the semiconducting LDPE films synthesized by SbCl5 doping. The structural peculiarities and the responses of the structure to energetic modifications are studied. TGA and DTG curves are used to determine the thermal stability of the material. Degradation kinetics is elucidated. Activation energy and the entropy of activation for the degradation of the samples are calculated using Coats-Redfern plots and the samples show appreciable thermal stability.

Influence of colorant and film thickness on thermal aging characteristics of oxo-biodegradable plastic bags

NASA Astrophysics Data System (ADS)

Leuterio, Giselle Lou D.; Pajarito, Bryan B.; Domingo, Carla Marie C.; Lim, Anna Patricia G.

2016-05-01

Functional, lightweight, strong and cheap plastic bags incorporated with pro-oxidants undergo accelerated degradation under exposure to heat and oxygen. This work investigated the effect of colorant and film thickness on thermal aging characteristics of commercial oxo-biodegradable plastic bag films at 70 °C. Degradation is monitored through changes in infrared absorption, weight, and tensile properties of thermally aged films. The presence of carbonyl band in infrared spectrum after 672 h of thermal aging supports the degradation behavior of exposed films. Results show that incorporation of colorant and increasing thickness exhibit low maximum weight uptake. Titanium dioxide as white colorant in films lowers the susceptibility of films to oxygen uptake but enhances physical degradation. Higher amount of pro-oxidant loading also contributes to faster degradation. Opaque films are characterized by low tensile strength and high elastic modulus. Decreasing the thickness contributes to lower tensile strength of films. Thermally aged films with colorant and low thickness promote enhanced degradation.

Biodegradation of Aliphatic-Aromatic Copolyesters by Thermomonospora fusca and Other Thermophilic Compost Isolates

PubMed Central

Kleeberg, Ilona; Hetz, Claudia; Kroppenstedt, Reiner Michael; Müller, Rolf-Joachim; Deckwer, Wolf-Dieter

1998-01-01

Random aliphatic-aromatic copolyesters synthesized from 1,4-butanediol, adipic acid, and terephthalic acid (BTA) have excellent thermal and mechanical properties and are biodegradable by mixed cultures (e.g., in compost). Over 20 BTA-degrading strains were isolated by using compost as a microbial source. Among these microorganisms, thermophilic actinomycetes obviously play an outstanding role and appear to dominate the initial degradation step. Two actinomycete strains exhibited about 20-fold higher BTA degradation rates than usually observed in a common compost test. These isolates were identified as Thermomonospora fusca strains. They appeared to be particularly suitable for establishment of rapid degradation tests and were used in comparative studies on the biodegradation of various polyesters. PMID:9572944

Thermal analysis of GFRP-reinforced continuous concrete decks subjected to top fire

NASA Astrophysics Data System (ADS)

Hawileh, Rami A.; Rasheed, Hayder A.

2017-12-01

This paper presents a numerical study that investigates the behavior of continuous concrete decks doubly reinforced with top and bottom glass fiber reinforced polymer (GFRP) bars subjected to top surface fire. A finite element (FE) model is developed and a detailed transient thermal analysis is performed on a continuous concrete bridge deck under the effect of various fire curves. A parametric study is performed to examine the top cover thickness and the critical fire exposure curve needed to fully degrade the top GFRP bars while achieving certain fire ratings for the deck considered. Accordingly, design tables are prepared for each fire curve to guide the engineer to properly size the top concrete cover and maintain the temperature in the GFRP bars below critical design values in order to control the full top GFRP degradation. It is notable to indicate that degradation of top GFRP bars do not pose a collapse hazard but rather a serviceability concern since cracks in the negative moment region widen resulting in simply supported spans.

Optimizing Battery Usage and Management for Long Life

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Kandler; Shi, Ying; Wood, Eric

2016-06-16

This presentation discusses the impact of system design factors on battery aging and end of life. Topics include sizing of the state-of-charge operating window, cell balancing, and thermal management systems and their value in reducing pack degradation rates and cell imbalance growth over lifetime.

Review of thermal properties of graphite composite materials

NASA Technical Reports Server (NTRS)

Kourtides, D. A.

1987-01-01

Flammability, thermal, and selected mechanical properties of composites fabricated with epoxy and other thermally stable resin matrices are described. Properties which were measured included limiting-oxygen index, smoke evolution, thermal degradation products, total-heat release, heat-release rates, mass loss, flame spread, ignition resistance, thermogravimetric analysis, and selected mechanical properties. The properties of 8 different graphite composite panels fabricated using four different resin matrices and two types of graphite reinforcement are described. The resin matrices included: XU71775/H795, a blend of vinyl polystyryl pyridine and bismaleimide; H795, a bismaleimide; Cycom 6162, a phenolic; and PSP 6022M, a polystyryl pyridine. The graphite fiber used was AS-4 in the form of either tape or fabric. The properties of these composites were compared with epoxy composites. It was determined that the blend of vinyl polystyryl pyridine and bismaleimide (XU71775/H795) with the graphite tape was the optimum design giving the lowest heat release rate.

Thermal stability of synthetic thyroid hormone l-thyroxine and l-thyroxine sodium salt hydrate both pure and in pharmaceutical formulations.

PubMed

Ledeţi, Ionuţ; Ledeţi, Adriana; Vlase, Gabriela; Vlase, Titus; Matusz, Petru; Bercean, Vasile; Şuta, Lenuţa-Maria; Piciu, Doina

2016-06-05

In this paper, the thermal stability of pure l-thyroxine (THY) and l-thyroxine sodium salt hydrate (THYSS) vs. two pharmaceutical solid formulations commercialized on both Romanian and European market (with a content of 100μg, respectively 200μg THYSS per tablet) were investigated. In order to determine whether the presence of excipients affects the thermal stability of the active pharmaceutical ingredient (API), the preliminary study of thermal stability in air atmosphere was completed with an in-depth solid-state kinetic study. By kinetic analysis, the non-isothermal degradation of the selected active pharmaceutical ingredients vs. the solid formulation with strength of 200μg THYSS per tablet was investigated. Isoconversional methods (Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa and Friedman) were employed for the estimation of activation energies values, at five different heating rates, β=5, 7, 10, 12 and 15°Cmin(-1). Also, a fourth method was applied in the processing of data, namely NPK, allowing an objective separation in the physical and chemical processes that contribute to the thermal degradation of the selected compounds. A discussion of thermal stability from the kinetic point of view is also presented. Copyright © 2016 Elsevier B.V. All rights reserved.

Quantitative study of bundle size effect on thermal conductivity of single-walled carbon nanotubes

NASA Astrophysics Data System (ADS)

Feng, Ya; Inoue, Taiki; An, Hua; Xiang, Rong; Chiashi, Shohei; Maruyama, Shigeo

2018-05-01

Compared with isolated single-walled carbon nanotubes (SWNTs), thermal conductivity is greatly impeded in SWNT bundles; however, the measurement of the bundle size effect is difficult. In this study, the number of SWNTs in a bundle was determined based on the transferred horizontally aligned SWNTs on a suspended micro-thermometer to quantitatively study the effect of the bundle size on thermal conductivity. Increasing the bundle size significantly degraded the thermal conductivity. For isolated SWNTs, thermal conductivity was approximately 5000 ± 1000 W m-1 K-1 at room temperature, three times larger than that of the four-SWNT bundle. The logarithmical deterioration of thermal conductivity resulting from the increased bundle size can be attributed to the increased scattering rate with neighboring SWNTs based on the kinetic theory.

Thermal mechanisms responsible for the irreversible degradation of superconductivity in commercial superconductors

NASA Astrophysics Data System (ADS)

Romanovskii, V. R.

2017-08-01

Conditions for the irreversible propagation of thermal instabilities in commercial superconductors subjected to intense and soft cooling have been formulated. An analysis has been conducted using two types of the superconductor's I-V characteristics, i.e., an ideal I-V characteristic, which assumes a step superconducting-to-normal transition, and a continuous I-V characteristic, which is described by a power law. The propagation rate of thermal instabilities along the superconducting composite has been determined. Calculations have been made for both subcritical and supercritical values of the current. It has been shown that they propagate along a commercial superconductor in the form of a switching wave. In rapidly cooled commercial superconductors, the steady-state rate of thermal instability propagation in the longitudinal direction can only be positive because there is no region of steady stabilization. It has been proved that, in the case of thermal instability irreversible propagation, the rise in the commercial superconductor temperature is similar to diffusion processes that occur in explosive chain reactions.

Environmental biodegradation of haloarchaea-produced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) in activated sludge.

PubMed

Liu, Xiao-Bin; Wu, Lin-Ping; Hou, Jing; Chen, Jun-Yu; Han, Jing; Xiang, Hua

2016-08-01

Novel poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBHV) copolymers produced by haloarchaea are excellent candidate biomaterials. However, there is no report hitherto focusing on the biodegradation of PHBHV synthesized by haloarchaea. In this study, an environmental biodegradation of haloarchaea-produced PHBHV films, with 10~60 mol% 3-hydroxyvalerate (3HV) composition and different microchemical structures, was studied in nutrition-depleted activated sludge. The changes in mass, molar mass, chemical composition, thermal properties, and surface morphology were monitored. The mass and molar mass of each film decreased significantly, while the PHA monomer composition remained unchanged with time. Interestingly, the sample of random copolymer PHBHV-2 (R-PHBHV-2) (3HV, 30 mol%) had the lowest crystallinity and was degraded faster than R-PHBHV-3 containing the highest 3HV content or the higher-order copolymer PHBHV-1 (O-PHBHV-1) possessing the highest surface roughness. The order of biodegradation rate was in the opposite trend to the degree of crystallizability of the films. Meanwhile, thermal degradation temperature of most films decreased after biodegradation. Additionally, the surface erosion of films was confirmed by scanning electron microscopy. The dominant bacteria probably responsible for the degradation process were identified in the activated sludge. It was inferred that the degradation rate of haloarchaea-produced PHBHV films mainly depended on sample crystallinity, which was determined by monomer composition and microchemical structure and in turn strongly influenced surface morphology.

Chemiluminescence as a condition monitoring method for thermal aging and lifetime prediction of an HTPB elastomer.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gillen, Kenneth Todd; Minier, Leanna M. G.; Celina, Mathias C.

Chemiluminescence (CL) has been applied as a condition monitoring technique to assess aging related changes in a hydroxyl-terminated-polybutadiene based polyurethane elastomer. Initial thermal aging of this polymer was conducted between 110 and 50 C. Two CL methods were applied to examine the degradative changes that had occurred in these aged samples: isothermal 'wear-out' experiments under oxygen yielding initial CL intensity and 'wear-out' time data, and temperature ramp experiments under inert conditions as a measure of previously accumulated hydroperoxides or other reactive species. The sensitivities of these CL features to prior aging exposure of the polymer were evaluated on the basismore » of qualifying this method as a quick screening technique for quantification of degradation levels. Both the techniques yielded data representing the aging trends in this material via correlation with mechanical property changes. Initial CL rates from the isothermal experiments are the most sensitive and suitable approach for documenting material changes during the early part of thermal aging.« less

Ereptiospiration.

PubMed

Woolley, Christine; Garcia, Antonio A; Santello, Marco

2017-04-12

Pure coconut oil, lanolin, and acetaminophen were vaporized at rates of 1-50 mg/min, using a porous network exhibiting a temperature gradient from 5000 to 5500 K/mm, without incurring noticeable chemical changes due to combustion, oxidation, or other thermally-induced chemical structural changes. The newly coined term "ereptiospiration" is used here to describe this combination of thermal transpiration at high temperature gradients since the process can force the creation of thermal aerosols by rapid heating in a localized zone. Experimental data were generated for these materials using two different supports for metering the materials to the battery powered coil: namely, a stainless steel fiber bundle and a 3-D printed steel cartridge. Heating coconut oil, lanolin, or acetaminophen in a beaker to lower temperatures than those achieved at the surface of the coil showed noticeable and rapid degradation in the samples, while visual and olfactory observations for ereptiospiration showed no noticeable degradation in lanolin and coconut oil while HPLC chromatograms along with visual observation confirm that within the limit of detection, acetaminophen remains chemically unaltered by ereptiospiration.

Microwave-assisted synthesis of isosorbide-derived diols for the preparation of thermally stable thermoplastic polyurethane

PubMed Central

Kasmi, Nejib; Roso, Martina; Hammami, Nadia; Majdoub, Mustapha; Boaretti, Carlo; Sgarbossa, Paolo; Vianello, Chiara; Maschio, Giuseppe; Modesti, Michele; Lorenzetti, Alessandra

2017-01-01

Abstract In order to prepare thermally stable isosorbide-derived thermoplastic polyurethane, the synthesis of two new chiral exo–exo configured diols, prepared from isosorbide, and two types of diphenols (bisphenol A and thiodiphenol) was described. The synthesis conditions were optimized under conventional heating and microwave irradiations. To prove their suitability in polymerization, these monomers were successfully polymerized using 4,4′-diphenylmethane diisocyanate (MDI) and hexamethylene diisocyanate (HDI). Both monomers and polymers have been studied by NMR, FT-IR, TGA, DSC; intrinsic viscosity of polymers has also been determined. The results showed the effectiveness of the synthetic strategy proposed; moreover, a dramatic reduction of the reaction time and an important improvement of the monomers yield using microwave irradiation have been demonstrated. The monomers, as well as the polymers, showed excellent thermal stability both in air and nitrogen. It was also shown that the introduction of sulphur in the polyurethane backbone was effective in delaying the onset of degradation as well as the degradation rate. PMID:29491826

Overload characteristics of paper-polypropylene-paper cable

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ernst, A.

1990-09-01

The short-time rating of PPP pipe-type cable may be lower than the equivalent paper cable sized to carry the same normal load. The ratings depend on the relative conductor sizes and the maximum allowable conductor temperatures of the insulation. The insulation thermal resistivity may be a significant parameter for overload times of approximately one hour and should be verified for PPP insulation. The thermal capacitance temperature characteristic of PPP insulation is not known. However, the overload ratings are not very sensitive to this parameter. Overload ratings are given for maximum conductor temperatures from 105 C to 130 C. Use ofmore » ratings based on temperatures greater than 105 C would require testing to determine the extent of degradation of the insulation at these higher temperatures. PPP-insulated cable will be thermally stable over a wider range of operating conditions (voltage and current) compared with paper-insulated cable. The short-circuit ratings of PPP- and paper-insulated cable systems and the positive/negative and zero sequence impedances are compared. 21 refs., 22 figs., 5 tabs.« less

Premelting, Melting, and Degradation Properties of Molten Alkali Nitrates: LiNO3, NaNO3, KNO3, and Binary NaNO3-KNO3

NASA Astrophysics Data System (ADS)

Mohammad, Mehedi Bin; Brooks, Geoffrey Alan; Rhamdhani, Muhammad Akbar

2018-02-01

A simultaneous thermal analyzer (STA) was used to observe the transition and degradation events of LiNO3, NaNO3, KNO3, and binary NaNO3-KNO3 salts for potential use as phase change materials (PCMs) and heat transfer fluid (HTF). Samples were heated from 50 °C to 800 °C at 10 °C/min scanning rate in three atmospheres (argon, air, and oxygen) using an STA to observe decomposition behavior. Thermal stability increased for all salts at high partial pressure of O2 ( P_{{{O}2 }} = 1.0) compared to inert argon ( P_{{{O}2 }} = 0). O2, N2, NO, N2O, and NO2 were main evolved gases during nitrate decomposition. NO and O2 started to evolve at approximately the same temperature after melting, indicating that primary and secondary decomposition reactions were concurrent and overlapping. The solid-solid transition, liquidus and solidus temperatures, heat of transition, heat of melting, and heat of solidification were obtained at various heating-cooling rates (1, 2, 4, 5, 6, 8, 10, and 15 °C/min) using an STA. At all heating-cooling rates, a small gap exists between liquidus and solidus temperatures for all samples due to the salts exhibiting supercooling phenomena. This study showed that the degradation point depends on the blanket atmosphere top of the molten salts and that heating rates have a minor effect on transition events (peaks height, peaks width, and transition enthalpies).

Premelting, Melting, and Degradation Properties of Molten Alkali Nitrates: LiNO3, NaNO3, KNO3, and Binary NaNO3-KNO3

NASA Astrophysics Data System (ADS)

Mohammad, Mehedi Bin; Brooks, Geoffrey Alan; Rhamdhani, Muhammad Akbar

2018-06-01

A simultaneous thermal analyzer (STA) was used to observe the transition and degradation events of LiNO3, NaNO3, KNO3, and binary NaNO3-KNO3 salts for potential use as phase change materials (PCMs) and heat transfer fluid (HTF). Samples were heated from 50 °C to 800 °C at 10 °C/min scanning rate in three atmospheres (argon, air, and oxygen) using an STA to observe decomposition behavior. Thermal stability increased for all salts at high partial pressure of O2 ( P_{{{O}2 }} = 1.0) compared to inert argon ( P_{{{O}2 }} = 0). O2, N2, NO, N2O, and NO2 were main evolved gases during nitrate decomposition. NO and O2 started to evolve at approximately the same temperature after melting, indicating that primary and secondary decomposition reactions were concurrent and overlapping. The solid-solid transition, liquidus and solidus temperatures, heat of transition, heat of melting, and heat of solidification were obtained at various heating-cooling rates (1, 2, 4, 5, 6, 8, 10, and 15 °C/min) using an STA. At all heating-cooling rates, a small gap exists between liquidus and solidus temperatures for all samples due to the salts exhibiting supercooling phenomena. This study showed that the degradation point depends on the blanket atmosphere top of the molten salts and that heating rates have a minor effect on transition events (peaks height, peaks width, and transition enthalpies).

Performance and Reliability of Bonded Interfaces for High-Temperature Packaging (Presentation)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devoto, D.

2014-11-01

The thermal performance and reliability of sintered-silver is being evaluated for power electronics packaging applications. This will be experimentally accomplished by the synthesis of large-area bonded interfaces between metalized substrates that will be subsequently subjected to thermal cycles. A finite element model of crack initiation and propagation in these bonded interfaces will allow for the interpretation of degradation rates by a crack-velocity (V)-stress intensity factor (K) analysis. The experiment is outlined, and the modeling approach is discussed.

Determination of degradation products and process related impurities of asenapine maleate in asenapine sublingual tablets by UPLC

NASA Astrophysics Data System (ADS)

Kumar, Nitin; Sangeetha, D.; Kalyanraman, L.

2017-11-01

For determination of process related impurities and degradation products of asenapine maleate in asenapine sublingual Tablets, a reversed phase, stability indicating UPLC method was developed. Acetonitrile, methanol and potassium dihydrogen phosphate buffer with tetra-n- butyl ammonium hydrogen sulphate as ion pair (pH 2.2; 0.01 M) at flow rate of 0.2 ml/min were used in gradient elution mode. Separation was achieved by using acquity BEH Shield RP18 column (1.7 μm, 2.1 mm×100 mm) at 35 ºC. UV detection was performed at 228 nm. Subsequently the liquid chromatography method was validated as per ICH. The drug product was exposed to the stress conditions of acid hydrolysis, base hydrolysis, water hydrolysis, oxidative, thermal, and photolytic. In oxidative stress and thermal stress significant degradation was observed. All the degradation products were well separated from analyte peak and its impurities. Stability indicating nature of the method was proved by demonstrating the peak purity of Asenapine peak in all the stressed samples. The mass balance was found >95% for all the stress conditions. Based on method validation, the method was found specific, linear, accurate, precise, rugged and robust.

Climate warming over the past half century has led to thermal degradation of permafrost on the Qinghai-Tibet Plateau

NASA Astrophysics Data System (ADS)

Ran, Youhua; Li, Xin; Cheng, Guodong

2018-02-01

Air temperature increases thermally degrade permafrost, which has widespread impacts on engineering design, resource development, and environmental protection in cold regions. This study evaluates the potential thermal degradation of permafrost over the Qinghai-Tibet Plateau (QTP) from the 1960s to the 2000s using estimated decadal mean annual air temperatures (MAATs) by integrating remote-sensing-based estimates of mean annual land surface temperatures (MASTs), leaf area index (LAI) and fractional snow cover values, and decadal mean MAAT date from 152 weather stations with a geographically weighted regression (GWR). The results reflect a continuous rise of approximately 0.04 °C a-1 in the decadal mean MAAT values over the past half century. A thermal-condition classification matrix is used to convert modelled MAATs to permafrost thermal type. Results show that the climate warming has led to a thermal degradation of permafrost in the past half century. The total area of thermally degraded permafrost is approximately 153.76 × 104 km2, which corresponds to 88 % of the permafrost area in the 1960s. The thermal condition of 75.2 % of the very cold permafrost, 89.6 % of the cold permafrost, 90.3 % of the cool permafrost, 92.3 % of the warm permafrost, and 32.8 % of the very warm permafrost has been degraded to lower levels of thermal condition. Approximately 49.4 % of the very warm permafrost and 96 % of the likely thawing permafrost has degraded to seasonally frozen ground. The mean elevations of the very cold, cold, cool, warm, very warm, and likely thawing permafrost areas increased by 88, 97, 155, 185, 161, and 250 m, respectively. The degradation mainly occurred from the 1960s to the 1970s and from the 1990s to the 2000s. This degradation may lead to increased risks to infrastructure, reductions in ecosystem resilience, increased flood risks, and positive climate feedback effects. It therefore affects the well-being of millions of people and sustainable development at the Third Pole.

Degradation mechanisms of cable insulation materials during radiation-thermal ageing in radiation environment

NASA Astrophysics Data System (ADS)

Seguchi, Tadao; Tamura, Kiyotoshi; Ohshima, Takeshi; Shimada, Akihiko; Kudoh, Hisaaki

2011-02-01

Radiation and thermal degradation of ethylene-propylene rubber (EPR) and crosslinked polyethylene (XLPE) as cable insulation materials were investigated by evaluating tensile properties, gel-fraction, and swelling ratio, as well as by the infrared (FTIR) analysis. The activation energy of thermal oxidative degradation changed over the range 100-120 °C for both EPR and XLPE. This may be attributed to the fact that the content of an antioxidant used as the stabilizer for polymers decreases by evaporation during thermal ageing at high temperatures. The analysis of antioxidant content and oxidative products in XLPE as a model sample showed that a small amount of antioxidant significantly reduced the extent of thermal oxidation, but was not effective for radiation induced oxidation. The changes in mechanical properties were well reflected by the degree of oxidation. A new model of polymer degradation mechanisms was proposed where the degradation does not take place by chain reaction via peroxy radical and hydro-peroxide. The role of the antioxidant in the polymer is the reduction of free radical formation in the initiation step in thermal oxidation, and it could not stop radical reactions for either radiation or thermal oxidation.

Investigation of thermal degradation with extrusion-based dispensing modules for 3D bioprinting technology.

PubMed

Lee, Hyungseok; Yoo, James J; Kang, Hyun-Wook; Cho, Dong-Woo

2016-02-04

Recently, numerous three-dimensional (3D) bioprinting systems have been introduced for the artificial regeneration of tissues. Among them, the extrusion-based dispensing module is the most widely used because of the processability it gives various biomaterials. The module uses high forces and temperature to dispense materials through a micro-nozzle. Generally, the harsh conditions induce thermal degradation of the material in the dispensing procedure. The thermal degradation affects the properties of the materials, and the change of the properties should be carefully controlled, because it severely affects the regeneration of tissues. Therefore, in this research, the relationship between the dispensing module and the thermal degradation of material was investigated. Extrusion-based dispensing modules can be divided into the syringe type (ST) and filament type (FT) based on working principles. We prepared a poly lactic-co-glycolic acid (PLGA) scaffold with the two methods at various time points. Then, the characteristics of the printed scaffolds were assessed by measuring molecular weight (M w), glass transition temperature (T g), in vitro degradation, compressive modulus, and cytocompatibility. The results showed that the PLGA scaffold with the FT dispensing module maintained its properties regardless of printing time points. In contrast, severe thermal degradation was observed in the scaffold group prepared by the ST dispensing module. Consequentially, it was obvious that the FT dispensing module was more suitable for producing scaffolds without severe thermal degradation.

Kinetics of thermal decomposition of some biomasses in an inert environment. An investigation of the effect of lead loaded by biosorption.

PubMed

Martín-Lara, María Ángeles; Iáñez-Rodríguez, Irene; Blázquez, Gabriel; Quesada, Lucía; Pérez, Antonio; Calero, Mónica

2017-12-01

The thermal behavior of some types of raw and lead-polluted biomasses typical in south Spain was studied by non-isothermal thermogravimetry. Experiments were carried out in nitrogen atmosphere at three heating rates (5, 10 and 20°C/min). The results of thermogravimetric tests carried out proved that the presence of lead did not change the main degradation pathways of selected biomass (almond shell (AS) and olive pomace (OP)). However, from a point of view of mass loss, lead-polluted samples showed higher decomposition temperatures and decomposition at higher rate. The determination of activation energies was performed by isoconversional methods of Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS) and Friedman (FR). In general, lead-polluted samples showed lower activation energies than raw ones. Then, Coast-Redfern method was applied to determine kinetic function. The kinetic function that seems to determine the mechanism of thermal degradation of main components of all samples was nth order reaction. Finally, a model based on three parallel reactions (for three pseudocomponents) that fit to nth order reactions was evaluated. This model was appropriate to predict the pyrolysis behavior of the raw and lead-polluted samples in all pyrolysis conditions studied. Copyright © 2017 Elsevier Ltd. All rights reserved.

Pigment and color stability of beetroot betalains in cow milk during thermal treatment.

PubMed

Güneşer, Onur

2016-04-01

Thermal stability of beetroot betalains in cow milk was determined during heating at 70-90 °C. Changes in color values of colored milk were also investigated. Degradation of betalains followed first order kinetics while changes of L(∗), Hue angle and Chroma values fitted zero order and first order kinetic, respectively. Reaction rate for degradation of betalains, L(∗), Hue angle and Chroma values ranged between 1.588-30.975 × 10(-3) min(-1), 90.50-379.75 L(∗)min(-1), 0.581-5.008 Hue anglemin(-1) and 3.250-19.750 × 10(-3) min(-1), respectively. Between 70 and 90 °C, activation energy for the degradation of betalains was 42.449 kJ mol(-1). L(∗) values was more stable than Hue angle and Chroma color values in colored milk during heating. 74.150 kJ mol(-1), 111.174 kJ mol(-1) and 93.311 kJ mol(-1) of activation energy values were found for L(∗), Hue angle and Chroma values of milk, respectively. Significant positive and negative linear correlations were determined between betalains and color values. Multiple regression models were also established to predict the content of betalains in milk during thermal process by using color values. Copyright © 2015 Elsevier Ltd. All rights reserved.

Sonochemical degradation of endocrine-disrupting organochlorine pesticide Dicofol: Investigations on the transformation pathways of dechlorination and the influencing operating parameters.

PubMed

Debabrata, Panda; Sivakumar, Manickam

2018-08-01

Dicofol, an extensively used organochlorine pesticide and a recommended Stockholm convention persistent organic pollutant (POP) candidate is well known for its endocrine disruptive properties. The sonochemical degradation of Dicofol in aqueous media has been investigated using a 20-kHz probe type sonicator with power inputs from 150 to 450 W. The degradation rate was determined as a function of concentration of Dicofol, solution pH, bulk phase temperature, ultrasonic power density and H 2 O 2 addition. At optimum operating conditions, the pseudo-first-order degradation rate constant (k) was determined to be 0.032 min -1 and the extent of degradation was found to be 86% within 60 min of ultrasound treatment. High performance liquid chromatography (HPLC) and Gas chromatography coupled with mass spectroscopy (GC-MS) analysis indicated the presence of degraded products. The obtained results of Dicofol degradation and control experiments in the presence of H 2 O 2 and radical scavenger test suggest thermal decomposition along with radical attack at bubble-vapor interface to be the dominant degradation pathway. Sonochemical treatment is effective and promising for successful removal of harmful pesticides such as Dicofol and superior removal efficiency for other POPs is expected in the near future with the successful implementation of ultrasound-based wastewater treatment. Copyright © 2018 Elsevier Ltd. All rights reserved.

Thermal degradation of (6R,S)-5,10-methenyltetrahydrofolate in aqueous solution at pH 8

NASA Astrophysics Data System (ADS)

Tyagi, A.; Penzkofer, A.; Batschauer, A.; Wolf, E.

2009-03-01

The degradation of the folate (6R,S)-5,10-methenyltetrahydrofolate chloride (MTHF-Cl) in aqueous solution at pH 8 at room temperature is studied by absorption spectra measurements. Samples with and without the reducing agent β-mercaptoethanol (β-ME) both under aerobic and anaerobic conditions are investigated. MTHF-Cl hydrolyses to (6R,S)-10-formyltetrahydrofolate (10-HCO-H4folate) in all four cases. 10-HCO-H4folate oxidizes to 10-formyldihydrofolate (10-HCO-H2folate) under aerobic conditions in the absence of β-ME. The degradation dynamics is analysed theoretically and conversion rate constants of hydrolysis and oxidation are determined.

Degradation Characterization of Thermal Interface Greases

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeVoto, Douglas J; Major, Joshua; Paret, Paul P

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 ofmore » 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.« less

Degradation Characterization of Thermal Interface Greases: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeVoto, Douglas J; Major, Joshua; Paret, Paul P

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 ofmore » 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.« less

Degradation Characterization of Thermal Interface Greases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Major, Joshua; Narumanchi, Sreekant V; Paret, Paul P

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 ofmore » 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.« less

Thermal degradation and tensile strength of sansevieria trifasciata-polypropylene composites

NASA Astrophysics Data System (ADS)

Abral, H.; Kenedy, E.

2015-07-01

The paper exhibits thermal degradation and tensile strength of Sansevieria Trifasciata (ST) fibers and polypropylene (PP) composites. Thermal degradation of ST fibers PP composites was conducted by using thermogravimetry (TGA) instrument, meanwhile tensile strength of the composite was done by using tensile equipment. The results show that the thermal resistance of ST fibers PP composites was higher than that of virgin PP only. Increases in volume fraction of fibers in the composites enhance the tensile strength. Scanning Electron Microscope (SEM) observation exhibits good interface bonding between ST fibers and PP matrix.

Photometric and Colorimetric Assessment of LED Chip Scale Packages by Using a Step-Stress Accelerated Degradation Test (SSADT) Method.

PubMed

Qian, Cheng; Fan, Jiajie; Fang, Jiayi; Yu, Chaohua; Ren, Yi; Fan, Xuejun; Zhang, Guoqi

2017-10-16

By solving the problem of very long test time on reliability qualification for Light-emitting Diode (LED) products, the accelerated degradation test with a thermal overstress at a proper range is regarded as a promising and effective approach. For a comprehensive survey of the application of step-stress accelerated degradation test (SSADT) in LEDs, the thermal, photometric, and colorimetric properties of two types of LED chip scale packages (CSPs), i.e., 4000 °K and 5000 °K samples each of which was driven by two different levels of currents (i.e., 120 mA and 350 mA, respectively), were investigated under an increasing temperature from 55 °C to 150 °C and a systemic study of driving current effect on the SSADT results were also reported in this paper. During SSADT, junction temperatures of the test samples have a positive relationship with their driving currents. However, the temperature-voltage curve, which represents the thermal resistance property of the test samples, does not show significant variance as long as the driving current is no more than the sample's rated current. But when the test sample is tested under an overdrive current, its temperature-voltage curve is observed as obviously shifted to the left when compared to that before SSADT. Similar overdrive current affected the degradation scenario is also found in the attenuation of Spectral Power Distributions (SPDs) of the test samples. As used in the reliability qualification, SSADT provides explicit scenes on color shift and correlated color temperature (CCT) depreciation of the test samples, but not on lumen maintenance depreciation. It is also proved that the varying rates of the color shift and CCT depreciation failures can be effectively accelerated with an increase of the driving current, for instance, from 120 mA to 350 mA. For these reasons, SSADT is considered as a suitable accelerated test method for qualifying these two failure modes of LED CSPs.

Photometric and Colorimetric Assessment of LED Chip Scale Packages by Using a Step-Stress Accelerated Degradation Test (SSADT) Method

PubMed Central

Yu, Chaohua; Fan, Xuejun; Zhang, Guoqi

2017-01-01

By solving the problem of very long test time on reliability qualification for Light-emitting Diode (LED) products, the accelerated degradation test with a thermal overstress at a proper range is regarded as a promising and effective approach. For a comprehensive survey of the application of step-stress accelerated degradation test (SSADT) in LEDs, the thermal, photometric, and colorimetric properties of two types of LED chip scale packages (CSPs), i.e., 4000 °K and 5000 °K samples each of which was driven by two different levels of currents (i.e., 120 mA and 350 mA, respectively), were investigated under an increasing temperature from 55 °C to 150 °C and a systemic study of driving current effect on the SSADT results were also reported in this paper. During SSADT, junction temperatures of the test samples have a positive relationship with their driving currents. However, the temperature-voltage curve, which represents the thermal resistance property of the test samples, does not show significant variance as long as the driving current is no more than the sample’s rated current. But when the test sample is tested under an overdrive current, its temperature-voltage curve is observed as obviously shifted to the left when compared to that before SSADT. Similar overdrive current affected the degradation scenario is also found in the attenuation of Spectral Power Distributions (SPDs) of the test samples. As used in the reliability qualification, SSADT provides explicit scenes on color shift and correlated color temperature (CCT) depreciation of the test samples, but not on lumen maintenance depreciation. It is also proved that the varying rates of the color shift and CCT depreciation failures can be effectively accelerated with an increase of the driving current, for instance, from 120 mA to 350 mA. For these reasons, SSADT is considered as a suitable accelerated test method for qualifying these two failure modes of LED CSPs. PMID:29035300

Pathway for recovery of photo-degraded polymer solar cells by post degradation thermal anneal

DOE PAGES

Bhattacharya, J.; Joshi, P. H.; Biswas, Rana; ...

2017-02-16

The photo-degradation of polymer solar cells is a critical challenge preventing its commercial deployment. We experimentally fabricate organic solar cells and characterize their degradation under solar simulators in an environmental chamber under nitrogen flow, without exposure to oxygen and moisture. We have developed a thermally stable inverted organic solar cell architecture in which light induced degradation of device characteristics can be reversibly annealed to the pristine values. The stable inverted cells utilized MoO x layers that are thermally treated immediately after their deposition on the organic layer, and before metal cathode deposition. Organic solar cells that are photo-degraded in themore » presence of oxygen, however show irreversible degradation that cannot be thermally recovered. The decrease of organic solar cell characteristics correlates with increases in mid-gap electronic states, measured using capacitance spectroscopy and dark current. It is likely the photo-induced defect states caused by local H motion from the alkyl chains to the aromatic backbone, can be reversibly annealed at elevated temperatures after photo-degradation. Finally, our results provide a pathway for improving the stability of organic photovoltaics.« less

Pathway for recovery of photo-degraded polymer solar cells by post degradation thermal anneal

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharya, J.; Joshi, P. H.; Biswas, Rana

The photo-degradation of polymer solar cells is a critical challenge preventing its commercial deployment. We experimentally fabricate organic solar cells and characterize their degradation under solar simulators in an environmental chamber under nitrogen flow, without exposure to oxygen and moisture. We have developed a thermally stable inverted organic solar cell architecture in which light induced degradation of device characteristics can be reversibly annealed to the pristine values. The stable inverted cells utilized MoO x layers that are thermally treated immediately after their deposition on the organic layer, and before metal cathode deposition. Organic solar cells that are photo-degraded in themore » presence of oxygen, however show irreversible degradation that cannot be thermally recovered. The decrease of organic solar cell characteristics correlates with increases in mid-gap electronic states, measured using capacitance spectroscopy and dark current. It is likely the photo-induced defect states caused by local H motion from the alkyl chains to the aromatic backbone, can be reversibly annealed at elevated temperatures after photo-degradation. Finally, our results provide a pathway for improving the stability of organic photovoltaics.« less

Status Report - Cane Fiberboard Properties And Degradation Rates For Storage Of The 9975 Shipping Package In KAC

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daugherty, W.

Thermal, mechanical and physical properties have been measured on cane fiberboard samples following accelerated aging for up to approximately 10 years. The aging environments have included elevated temperature < 250 ºF (the maximum allowed service temperature for fiberboard in 9975 packages) and elevated humidity. The results from this testing have been analyzed, and aging models fit to the data. Correlations relating several properties (thermal conductivity, energy absorption, weight, dimensions and density) to their rate of change in potential storage environments have been developed. Combined with an estimate of the actual conditions the fiberboard experiences in KAC, these models allow developmentmore » of service life predictions.« less

Thermal Characterization and Flammability of Structural Epoxy Adhesive and Carbon/Epoxy Composite with Environmental and Chemical Degradation (Postprint)

DTIC Science & Technology

2012-01-01

this study). TGA scans show the thermal degradation of carbon/ epoxy composite by fuel additive at room temperature. Through Microscale Combustion...concerns regarding the durability of structural epoxy adhesive contaminated by hydraulic fluid or fuel additive , under simplified test conditions (no...higher than room tem- perature) or fuel additive (at all temperatures of this study). TGA scans show the thermal degradation of carbon/ epoxy composite

Recycling of poly (lactic acid)/silk based bionanocomposites films and its influence on thermal stability, crystallization kinetics, solution and melt rheology.

PubMed

Tesfaye, Melakuu; Patwa, Rahul; Gupta, Arvind; Kashyap, Manash Jyoti; Katiyar, Vimal

2017-08-01

In this study, the effect of silk nanocrystals (SNCs) on the thermal and rheological properties of poly (lactic acid) (PLA) under repetitive extrusion process is investigated. The presence of SNCs facilitates the crystallization process and delaying the thermal degradation of PLA matrix. This leads to the reduction in cold crystallization peak temperature with lower crystallization half-time and higher growth rate. The substantial improvement in nucleation density observed through Polarized Optical Microscope (POM) proves the nucleating effect of SNC in all processing cycles. Moreover, the rheological investigation (complex viscosity, storage and loss modules values) revealed the stabilizing effect of SNC and the drastic degradation of neat PLA (NPLA) in third and fourth cycle is observed to be fortified by the presence of SNC. Cole-Cole plot and cross over frequencies have been correlated with the molar mass distribution of PLA and PLA-Silk composite during processing, which is further supported by the intrinsic viscosity measurement and acid value analysis. This investigation suggests that the melt viscosity and thermal properties of PLA can be stabilized by addition of silk nanocrystals. Copyright © 2017 Elsevier B.V. All rights reserved.

Beating the Heat: Fast Scanning Melts Beta Sheet Crystals

NASA Astrophysics Data System (ADS)

Cebe, Peggy; Hu, Xiao; Kaplan, David; Zhuravlev, Evgeny; Wurm, Andreas; Arbeiter, Daniella; Schick, Christoph

2014-03-01

Beta-pleated-sheet crystals are among the most stable of protein secondary structures, and are responsible for the remarkable physical properties of many fibrous proteins, such as silk. Previous thinking was that beta-pleated-sheet crystals in the dry solid state would not melt upon input of heat energy alone. Indeed, at conventional heating rates (~1-50 °C/min), silk exhibits its glass transition (~175 °C), followed by cold crystallization, and then by immediate thermal degradation beginning at about 225 °C. Here we demonstrate that beta-pleated-sheet crystals can melt directly from the solid state to become random coils, helices, and turns. We use fast scanning chip calorimetry at 2,000 K/s to avoid thermal degradation, and report the first reversible thermal melting of protein beta-pleated-sheet crystals, exemplified by silk fibroin. The similarity between thermal melting behavior of lamellar crystals of synthetic polymers and beta-pleated-sheet crystals is confirmed. The authors acknowledge support from the National Science Foundation and German Academic Exchange Service DAAD; EZ acknowledges a European Union funded Marie Curie EST fellowship (ADVATEC); XH and DK acknowledge NIH P41 Tissue Engineering Resource Center.

Gradient RP-HPLC method for the determination of potential impurities in atazanavir sulfate.

PubMed

Chitturi, Sreenivasa Rao; Somannavar, Yallappa Somappa; Peruri, Badarinadh Gupta; Nallapati, Sreenivas; Sharma, Hemant Kumar; Budidet, Shankar Reddy; Handa, Vijay Kumar; Vurimindi, Hima Bindu

2011-04-28

This paper proposes a simple and selective RP-HPLC method for the determination of process impurities and degradation products (degradants) of atazanavir sulfate (ATV) drug substance. Chromatographic separation was achieved on Ascentis(®) Express C8, (150mm×4.6mm, 2.7μm) column thermostated at 30°C under gradient elution by a binary mixture of potassium dihydrogen phosphate (pH 3.5, 0.02M) and ACN at a flow rate of 1.0ml/min. A photodiode array (PDA) detector set at 250nm was used for detection. Stress testing (forced degradation) of ATV was carried out under acidic, alkaline, oxidative, photolytic, thermal and humidity conditions. In presence of alkali, ATV transformed into cyclized products and the order of degradation reaction is determined by the method of initial rates. The unknown process impurities and alkaline degradants are isolated by preparative LC and characterized by ESI-MS/MS, (1)H NMR, and FT-IR spectral data. The developed method is validated with respect to sensitivity (lod and loq), linearity, precision, accuracy and robustness and can be implemented for routine quality control analysis and stability testing of ATV. Copyright © 2011 Elsevier B.V. All rights reserved.

IR window design for hypersonic missile seekers: thermal shock and cooling systems

NASA Astrophysics Data System (ADS)

Hingst, Uwe; Koerber, Stefan

2001-10-01

Infra-red (IR) seekers on missiles at high Mach-numbers in the lower tier air defence often suffer from degradation in performance due to aerothermodynamic effects. The kind and rate of degradation depends on the geometric design (shape) and location of the IR-window. Optimal design may reduce those effects but still misses to totally withstand the imposed thermal stresses (thermal shock). Proper thermal protection systems and/or window cooling systems will be needed. The first part of this paper deals particularly with passive IR- window design features to reduce the thermal stresses. A series of wind-tunnel testings focused on the thermal shock behavior of different IR-window shapes under critical flight conditions. The variation of typical design parameters demonstrates the available features to reduce thermal shock by passive ways. The second part presents active thermal stress reduction devices, e.g. an active cooling system. Among others the most efficient reduction of thermal heating is based on three components: A partial coverage of the IR-dome to protect most parts against heating effects, a rotating system bearing the IR-dome and a liquid spray-cooling system in the gap between the cover and the IR-dome. The hemispherical or pyramidal dome can be located either midways in the missile nose section or sideways on the structure. The liquid spray cooling system combines both, a heat exchange by fluid evaporation and a heat transfer by fluid and gas cross flow (convection), causing a low fluid consumption. Such a cooling system along with their driving parameters and the resulting analytical performance will be presented.

Controls on dissolved organic matter (DOM) degradation in a headwater stream: the influence of photochemical and hydrological conditions in determining light-limitation or substrate-limitation of photo-degradation

NASA Astrophysics Data System (ADS)

Cory, R. M.; Harrold, K. H.; Neilson, B. T.; Kling, G. W.

2015-11-01

We investigated how absorption of sunlight by chromophoric dissolved organic matter (CDOM) controls the degradation and export of DOM from Imnavait Creek, a beaded stream in the Alaskan Arctic. We measured concentrations of dissolved organic carbon (DOC), as well as concentrations and characteristics of CDOM and fluorescent dissolved organic matter (FDOM), during ice-free periods of 2011-2012 in the pools of Imnavait Creek and in soil waters draining to the creek. Spatial and temporal patterns in CDOM and FDOM in Imnavait Creek were analyzed in conjunction with measures of DOM degradation by sunlight and bacteria and assessments of hydrologic residence times and in situ UV exposure. CDOM was the dominant light attenuating constituent in the UV and visible portion of the solar spectrum, with high attenuation coefficients ranging from 86 ± 12 m-1 at 305 nm to 3 ± 1 m-1 in the photosynthetically active region (PAR). High rates of light absorption and thus light attenuation by CDOM contributed to thermal stratification in the majority of pools in Imnavait Creek under low-flow conditions. In turn, thermal stratification increased the residence time of water and DOM, and resulted in a separation of water masses distinguished by contrasting UV exposure (i.e., UV attenuation by CDOM with depth resulted in bottom waters receiving less UV than surface waters). When the pools in Imnavait Creek were stratified, DOM in the pool bottom water closely resembled soil water DOM in character, while the concentration and character of DOM in surface water was reproduced by experimental photo-degradation of bottom water. These results, in combination with water column rates of DOM degradation by sunlight and bacteria, suggest that photo-degradation is the dominant process controlling DOM fate and export in Imnavait Creek. A conceptual model is presented showing how CDOM amount and lability interact with incident UV light and water residence time to determine whether photo-degradation is "light-limited" or "substrate-limited". We suggest that degradation of DOM in CDOM-rich streams or ponds similar to Imnavait is typically light-limited under most flow conditions. Thus, export of DOM from this stream will be less under conditions that increase the light available for DOM photo-degradation (i.e., low flows, sunny days).

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

PubMed

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.

Degradation of chitosan hydrogel dispersed in dilute carboxylic acids by solution plasma and evaluation of anticancer activity of degraded products

NASA Astrophysics Data System (ADS)

Chokradjaroen, Chayanaphat; Rujiravanit, Ratana; Theeramunkong, Sewan; Saito, Nagahiro

2018-01-01

Chitosan is a polysaccharide that has been extensively studied in the field of biomedicine, especially its water-soluble degraded products called chitooligosaccharides (COS). In this study, COS were produced by the degradation of chitosan hydrogel dispersed in a dilute solution (i.e., 1.55 mM) of various kinds of carboxylic acids using a non-thermal plasma technology called solution plasma (SP). The degradation rates of chitosan were influenced by the type of carboxylic acids, depending on the interaction between chitosan and each carboxylic acid. After SP treatment, the water-soluble degraded products containing COS could be easily separated from the water-insoluble residue of chitosan hydrogel by centrifugation. The production yields of the COS were mostly higher than 55%. Furthermore, the obtained COS products were evaluated for their inhibitory effect as well as their selectivity against human lung cancer cells (H460) and human lung normal cells (MRC-5).

ABIOTIC DEGRADATION OF TRICHLOROETHYLENE UNDER THERMAL REMEDIATION CONDITIONS

EPA Science Inventory

The degradation of TCE (C₂HCl₃) to carbon dioxide (CO₂) and chloride (Cl^-) has been reported to occur during thermal remediation of subsurface environments. The overall goal of this study was to evaluate abiotic degradation of TCE at el...

Plasticity of Performance Curves Can Buffer Reaction Rates from Body Temperature Variation in Active Endotherms.

PubMed

Seebacher, Frank; Little, Alexander G

2017-01-01

Endotherms regulate their core body temperature by adjusting metabolic heat production and insulation. Endothermic body temperatures are therefore relatively stable compared to external temperatures. The thermal sensitivity of biochemical reaction rates is thought to have co-evolved with body temperature regulation so that optimal reaction rates occur at the regulated body temperature. However, recent data show that core body temperatures even of non-torpid endotherms fluctuate considerably. Additionally, peripheral temperatures can be considerably lower and more variable than core body temperatures. Here we discuss whether published data support the hypothesis that thermal performance curves of physiological reaction rates are plastic so that performance is maintained despite variable body temperatures within active (non-torpid) endotherms, and we explore mechanisms that confer plasticity. There is evidence that thermal performance curves in tissues that experience thermal fluctuations can be plastic, although this question remains relatively unexplored for endotherms. Mechanisms that alter thermal responses locally at the tissue level include transient potential receptor ion channels (TRPV and TRPM) and the AMP-activated protein kinase (AMPK) both of which can influence metabolism and energy expenditure. Additionally, the thermal sensitivity of processes that cause post-transcriptional RNA degradation can promote the relative expression of cold-responsive genes. Endotherms can respond to environmental fluctuations similarly to ectotherms, and thermal plasticity complements core body temperature regulation to increase whole-organism performance. Thermal plasticity is ancestral to endothermic thermoregulation, but it has not lost its selective advantage so that modern endotherms are a physiological composite of ancestral ectothermic and derived endothermic traits.

Plasticity of Performance Curves Can Buffer Reaction Rates from Body Temperature Variation in Active Endotherms

PubMed Central

Seebacher, Frank; Little, Alexander G.

2017-01-01

Endotherms regulate their core body temperature by adjusting metabolic heat production and insulation. Endothermic body temperatures are therefore relatively stable compared to external temperatures. The thermal sensitivity of biochemical reaction rates is thought to have co-evolved with body temperature regulation so that optimal reaction rates occur at the regulated body temperature. However, recent data show that core body temperatures even of non-torpid endotherms fluctuate considerably. Additionally, peripheral temperatures can be considerably lower and more variable than core body temperatures. Here we discuss whether published data support the hypothesis that thermal performance curves of physiological reaction rates are plastic so that performance is maintained despite variable body temperatures within active (non-torpid) endotherms, and we explore mechanisms that confer plasticity. There is evidence that thermal performance curves in tissues that experience thermal fluctuations can be plastic, although this question remains relatively unexplored for endotherms. Mechanisms that alter thermal responses locally at the tissue level include transient potential receptor ion channels (TRPV and TRPM) and the AMP-activated protein kinase (AMPK) both of which can influence metabolism and energy expenditure. Additionally, the thermal sensitivity of processes that cause post-transcriptional RNA degradation can promote the relative expression of cold-responsive genes. Endotherms can respond to environmental fluctuations similarly to ectotherms, and thermal plasticity complements core body temperature regulation to increase whole-organism performance. Thermal plasticity is ancestral to endothermic thermoregulation, but it has not lost its selective advantage so that modern endotherms are a physiological composite of ancestral ectothermic and derived endothermic traits. PMID:28824463

Identifying thermal breakdown products of thermoplastics.

PubMed

Guillemot, Marianne; Oury, Benoît; Melin, Sandrine

2017-07-01

Polymers processed to produce plastic articles are subjected to temperatures between 150°C and 450°C or more during overheated processing and breakdowns. Heat-based processing of this nature can lead to emission of volatile organic compounds (VOCs) into the thermoplastic processing shop. In this study, laboratory experiments, qualitative and quantitative emissions measurement in thermoplastic factories were carried out. The first step was to identify the compounds released depending on the thermoplastic nature, the temperature and the type of process. Then a thermal degradation protocol that can extrapolate the laboratory results to industry scenarios was developed. The influence of three parameters on released thermal breakdown products was studied: the sample preparation methods-manual cutting, ambient, or cold grinding-the heating rate during thermal degradation-5, 10 20, and 50°C/min-and the decomposition method-thermogravimetric analysis and pyrolysis. Laboratory results were compared to atmospheric measurements taken at 13 companies to validate the protocol and thereby ensure its representativeness of industrial thermal processing. This protocol was applied to most commonly used thermoplastics to determine their thermal breakdown products and their thermal behaviour. Emissions data collected by personal exposure monitoring and sampling at the process emission area show airborne concentrations of detected compounds to be in the range of 0-3 mg/m 3 under normal operating conditions. Laser cutting or purging operations generate higher pollution levels in particular formaldehyde which was found in some cases at a concentration above the workplace exposure limit.

Determination of Kinetic Parameters for the Thermal Decomposition of Parthenium hysterophorus

NASA Astrophysics Data System (ADS)

Dhaundiyal, Alok; Singh, Suraj B.; Hanon, Muammel M.; Rawat, Rekha

2018-02-01

A kinetic study of pyrolysis process of Parthenium hysterophorous is carried out by using thermogravimetric analysis (TGA) equipment. The present study investigates the thermal degradation and determination of the kinetic parameters such as activation E and the frequency factor A using model-free methods given by Flynn Wall and Ozawa (FWO), Kissinger-Akahira-Sonuse (KAS) and Kissinger, and model-fitting (Coats Redfern). The results derived from thermal decomposition process demarcate decomposition of Parthenium hysterophorous among the three main stages, such as dehydration, active and passive pyrolysis. It is shown through DTG thermograms that the increase in the heating rate caused temperature peaks at maximum weight loss rate to shift towards higher temperature regime. The results are compared with Coats Redfern (Integral method) and experimental results have shown that values of kinetic parameters obtained from model-free methods are in good agreement. Whereas the results obtained through Coats Redfern model at different heating rates are not promising, however, the diffusion models provided the good fitting with the experimental data.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Petty, C. C., E-mail: petty@fusion.gat.com; Van Zeeland, M. A.; Pace, D. C.

“Steady-state” hybrid plasmas in DIII-D with zero surface loop voltage have been maintained for up to two current relaxation times using 3.4 MW of central electron cyclotron current drive (ECCD). In addition to driving ≈0.2 MA of plasma current, central ECCD leads to significant changes in Alfvén eigenmode (AE) activity and thermal transport. For neutral-beam-only heating, strong AE activity is observed that causes a ∼35% degradation in the neutron rate. With central ECCD this AE activity is suppressed, replaced by a bursty energetic particle mode that appears more benign as the neutron rate is closer to the classical value. Themore » electron thermal diffusivity increases by ≈50% for 2.4 MW of ECCD compared to neutral-beam-only cases. Fortunately, the global thermal confinement factor remains the same (H{sub 98y2}=1.4) as the higher thermal transport for P{sub EC}=2.4 MW hybrids is offset by the decreased fast ion transport resulting from AE suppression.« less

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

PubMed

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.

Failure analysis of InGaN/GaN high power light-emitting diodes fabricated with ITO transparent p-type electrode during accelerated electro-thermal stress.

PubMed

Moon, Seong Min; Kim, Y D; Oh, S K; Park, M J; Kwak, Joon Seop

2012-05-01

We have investigated the high-temperature degradation of optical power as well as electrical properties of InGaN/GaN light-emitting diodes (LEDs) fabricated with ITO transparent p-electrode during accelerated electro-thermal stress. As the thermal stress increased from 150 degrees C to 250 degrees C at a electrical stress of 200 mA, the optical power of the LEDs was significantly reduced. Degradation of the optical power was thermally activated, with the activation of 0.9 eV. In addition, the activation energy of the degradation of optical power was fairly similar to that of the degradation of series resistance of the LEDs, 1.0 eV, which implies that the increase in the series resistance may result in the severe degradation of optical power. We also showed that the increase in the series resistance of the LEDs during the accelerated electro-thermal stress can be attributed to reduction of the active acceptor concentration in the p-type semiconductor layers and local joule heating due to the current crowding.

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.

PubMed

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 <6 ng kg -1 and the detoxification rate was ⩾97% after treatment for 1 h at 400 °C under oxygen-deficient conditions. About 8.49% of the polychlorinated dibenzo- p-dioxins and dibenzofurans in toxic equivalent quantity (TEQ) of the original fly ash were desorbed or regenerated. The extreme high polychlorinated dibenzo- p-dioxin and dibenzofuran levels and dibenzo- p-dioxin and dibenzofuran congener profiles in the dust of the flue gas showed that desorption was the main reason, rather than de novo synthesis of polychlorinated dibenzo- p-dioxins and dibenzofurans in the exhaust pipe. Degradation furnace flue gas was introduced to the municipal 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.

Skylab parasol material evaluation

NASA Technical Reports Server (NTRS)

Jacobs, S.

1975-01-01

Results of experimental work to evaluate the degradation rate of a parasol that was used as a means of alleviating thermal problems encountered soon after the launch of the Skylab 1 space vehicle are presented. Material selection criteria are discussed; the material chosen is described, and results of tests performed after environmental exposure at five facilities are given. The facilities used for exposure to ultraviolet radiation/thermal-vacuum environments and the equipment used for testing physical properties before and after exposure are described. Comparisons of ground test and flight test data are included.

Linking Initial Microstructure to ORR Related Property Degradation in SOFC Cathode: A Phase Field Simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lei, Y.; Cheng, T. -L.; Wen, Y. H.

Microstructure evolution driven by thermal coarsening is an important factor for the loss of oxygen reduction reaction rates in SOFC cathode. In this work, the effect of an initial microstructure on the microstructure evolution in SOFC cathode is investigated using a recently developed phase field model. Specifically, we tune the phase fraction, the average grain size, the standard deviation of the grain size and the grain shape in the initial microstructure, and explore their effect on the evolution of the grain size, the density of triple phase boundary, the specific surface area and the effective conductivity in LSM-YSZ cathodes. Itmore » is found that the degradation rate of TPB density and SSA of LSM is lower with less LSM phase fraction (with constant porosity assumed) and greater average grain size, while the degradation rate of effective conductivity can also be tuned by adjusting the standard deviation of grain size distribution and grain aspect ratio. The implication of this study on the designing of an optimal initial microstructure of SOFC cathodes is discussed.« less

Linking Initial Microstructure to ORR Related Property Degradation in SOFC Cathode: A Phase Field Simulation

DOE PAGES

Lei, Y.; Cheng, T. -L.; Wen, Y. H.

2017-07-05

Microstructure evolution driven by thermal coarsening is an important factor for the loss of oxygen reduction reaction rates in SOFC cathode. In this work, the effect of an initial microstructure on the microstructure evolution in SOFC cathode is investigated using a recently developed phase field model. Specifically, we tune the phase fraction, the average grain size, the standard deviation of the grain size and the grain shape in the initial microstructure, and explore their effect on the evolution of the grain size, the density of triple phase boundary, the specific surface area and the effective conductivity in LSM-YSZ cathodes. Itmore » is found that the degradation rate of TPB density and SSA of LSM is lower with less LSM phase fraction (with constant porosity assumed) and greater average grain size, while the degradation rate of effective conductivity can also be tuned by adjusting the standard deviation of grain size distribution and grain aspect ratio. The implication of this study on the designing of an optimal initial microstructure of SOFC cathodes is discussed.« less

Space simulation test for thermal control materials

NASA Technical Reports Server (NTRS)

Hardgrove, W. R.

1990-01-01

Tests were run in TRW's Combined Environment Facility to examine the degradation of thermal control materials in a simulated space environment. Thermal control materials selected for the test were those presently being used on spacecraft or predicted to be used within the next few years. The geosynchronous orbit environment was selected as the most interesting. One of the goals was to match degradation of those materials with available flight data. Another aim was to determine if degradation can adequately be determined with accelerated or short term ground tests.

Abiotic degradation of plastic films

NASA Astrophysics Data System (ADS)

Ángeles-López, Y. G.; Gutiérrez-Mayen, A. M.; Velasco-Pérez, M.; Beltrán-Villavicencio, M.; Vázquez-Morillas, A.; Cano-Blanco, M.

2017-01-01

Degradable plastics have been promoted as an option to mitigate the environmental impacts of plastic waste. However, there is no certainty about its degradability under different environmental conditions. The effect of accelerated weathering (AW), natural weathering (NW) and thermal oxidation (TO) on different plastics (high density polyethylene, HDPE; oxodegradable high density polyethylene, HDPE-oxo; compostable plastic, Ecovio ® metalized polypropylene, PP; and oxodegradable metalized polypropylene, PP-oxo) was studied. Plastics films were exposed to AW per 110 hours; to NW per 90 days; and to TO per 30 days. Plastic films exposed to AW and NW showed a general loss on mechanical properties. The highest reduction in elongation at break on AW occurred to HDPE-oxo (from 400.4% to 20.9%) and was higher than 90% for HDPE, HDPE-oxo, Ecovio ® and PP-oxo in NW. No substantial evidence of degradation was found on plastics exposed to TO. Oxo-plastics showed higher degradation rates than their conventional counterparts, and the compostable plastic was resistant to degradation in the studied abiotic conditions. This study shows that degradation of plastics in real life conditions will vary depending in both, their composition and the environment.

Prevention of thermal- and moisture-induced degradation of the photoluminescence properties of the Sr2Si5N8:Eu(2+) red phosphor by thermal post-treatment in N2-H2.

PubMed

Zhang, Chenning; Uchikoshi, Tetsuo; Xie, Rong-Jun; Liu, Lihong; Cho, Yujin; Sakka, Yoshio; Hirosaki, Naoto; Sekiguchi, Takashi

2016-05-14

A red phosphor of Sr2Si5N8:Eu(2+) powder was synthesized by a solid state reaction. The synthesized phosphor was thermally post-treated in an inert and reductive N2-H2 mixed-gas atmosphere at 300-1200 °C. The main phase of the resultant phosphor was identified as Sr2Si5N8. A passivation layer of ∼0.2 μm thickness was formed around the phosphor surface via thermal treatment. Moreover, two different luminescence centers of Eu(SrI) and Eu(SrII) in the synthesized Sr2Si5N8:Eu(2+) phosphor were proposed to be responsible for 620 nm and 670 nm emissions, respectively. More interestingly, thermal- and moisture-induced degradation of PL intensity was effectively reduced by the formation of a passivation layer around the phosphor surface, that is, the relative PL intensity recovered 99.8% of the initial intensity even after encountering thermal degradation; both moisture-induced degraded external and internal QEs were merely 1% of the initial QEs. The formed surface layer was concluded to primarily prevent the Eu(2+) activator from being oxidized, based on the systemic analysis of the mechanisms of thermal- and moisture-induced degradation.

Pressure and temperature effects on degradation kinetics and storage stability of total anthocyanins in blueberry juice.

PubMed

Buckow, Roman; Kastell, Anja; Terefe, Netsanet Shiferaw; Versteeg, Cornelis

2010-09-22

The degradation kinetics of total anthocyanins in blueberry (Vaccinium myrtillus) juice were studied during thermal processing by treatment at selected temperatures (60-121 °C) and combined high pressure-temperature processing (100-700 MPa, 40-121 °C). Anthocyanin stability was also studied for several of these treatments during storage at 4, 25, and 40 °C. Both pressure and temperature increased d, the degradation rate of total anthocyanins in blueberry juice, meaning that at constant temperature, anthocyanins were more rapidly degraded with increasing pressure. For example, 32% degradation of anthocyanins was observed after 20 min heating at 100 °C and atmospheric pressure, whereas at 100 °C and 600 MPa, approximately 50% of total anthocyanins were lost. Degradation of anthocyanins was significantly accelerated with increasing storage temperatures. Combined pressure-temperature treatment of pasteurized juice led to a slightly faster degradation of total anthocyanins during storage compared to heat treatments at ambient pressure. Degradation of anthocyanins was best described by a 1.4th-order reaction at all conditions investigated. A mathematical model describing the degradation of blueberry anthocyanins in juice as a function of pressure, temperature, and treatment time is presented.

Toluene stability Space Station Rankine power system

NASA Technical Reports Server (NTRS)

Havens, V. N.; Ragaller, D. R.; Sibert, L.; Miller, D.

1987-01-01

A dynamic test loop is designed to evaluate the thermal stability of an organic Rankine cycle working fluid, toluene, for potential application to the Space Station power conversion unit. Samples of the noncondensible gases and the liquid toluene were taken periodically during the 3410 hour test at 750 F peak temperature. The results obtained from the toluene stability loop verify that toluene degradation will not lead to a loss of performance over the 30-year Space Station mission life requirement. The identity of the degradation products and the low rates of formation were as expected from toluene capsule test data.

Controls on dissolved organic matter (DOM) degradation in a headwater stream: the influence of photochemical and hydrological conditions in determining light-limitation or substrate-limitation of photo-degradation

NASA Astrophysics Data System (ADS)

Cory, R. M.; Harrold, K. H.; Neilson, B. T.; Kling, G. W.

2015-07-01

We investigated how absorption of sunlight by chromophoric dissolved organic matter (CDOM) controls the degradation and export of DOM from Imnavait Creek, a beaded stream in the Alaskan Arctic. We measured concentrations of dissolved organic carbon (DOC), as well as concentrations and characteristics of CDOM and fluorescent dissolved organic matter (FDOM), during ice-free periods of 2011-2012 in the pools of Imnavait Creek and in soil waters draining to the creek. Spatial and temporal patterns in CDOM and FDOM in Imnavait Creek were analyzed in conjunction with measures of DOM degradation by sunlight and bacteria and assessments of hydrologic residence times and in situ UV exposure. CDOM was the dominant light attenuating constituent in the UV and visible portion of the solar spectrum, with high attenuation coefficients ranging from 86 ± 12 m-1 at 305 nm to 3 ± 1 m-1 in the photosynthetically active region (PAR). High rates of light absorption and thus light attenuation by CDOM contributed to thermal stratification in the majority of pools in Imnavait Creek under low-flow conditions. In turn, thermal stratification increased the residence time of water and DOM, and resulted in a separation of water masses distinguished by contrasting UV exposure (i.e., UV attenuation by CDOM with depth resulted in bottom waters receiving less UV than surface waters). When the pools in Imnavait Creek were stratified, DOM in the pool bottom water closely resembled soil water DOM in character, while the concentration and character of DOM in surface water was reproduced by experimental photo-degradation of bottom water. These results, in combination with water column rates of DOM degradation by sunlight and bacteria, suggest that photo-degradation is the dominant process controlling DOM fate and export in Imnavait Creek. A conceptual model is presented showing how CDOM amount and lability interact with incident UV light and water residence time to determine whether photo-degradation is "light-limited" or "substrate-limited". We suggest that degradation, and thus export, of DOM in CDOM-rich streams or ponds similar to Imnavait is typically light-limited under most flow conditions.

4D Imaging in Thermally Damaged Polymer-bonded Explosives

NASA Astrophysics Data System (ADS)

Parker, Gary; Bourne, Neil; Eastwood, David; Jacques, Simon; Dickson, Peter; Lopez-Pulliam, Ian; Heatwole, Eric; Holmes, Matt; Smilowitz, Laura; Rau, Christoph

2017-06-01

PBXs are composites in which explosive crystallites are bound by compliant polymers. There are safety benefits derived from compliant binders; e.g. they mitigate some effects of mechanical insult. However, during elevated thermal insult, degradation of binder and HE crystallites can modify the morphology in ways that can reduce safety margins by increasing post-ignition reaction violence. The response of thermally damaged PBXs, before and following self-ignition has safety implications and it is desirable to understand the fundamental physics controlling the rate of pre-ignition thermal runaway and the post-ignition flame propagation in thermal accident scenarios. Coupled with this there is an ongoing effort to make in situ, time-resolved, measurements of the size, nature and extent of micro-porosity in PBX 9501 during thermal decomposition. We report on PBX heating experiments conducted at the Diamond synchrotron with both PBX 9501 and an inert mock. During heating, CT radiography was conducted in order to observe void production and interconnectivity of gas flow pathways, as well as to monitor phase changes within the crystals. We explore the variation of behavior as a function of heating rate, soak temperature, soak time and confinement.

Thermal decomposition of wood: influence of wood components and cellulose crystallite size.

PubMed

Poletto, Matheus; Zattera, Ademir J; Forte, Maria M C; Santana, Ruth M C

2012-04-01

The influence of wood components and cellulose crystallinity on the thermal degradation behavior of different wood species has been investigated using thermogravimetry, chemical analysis and X-ray diffraction. Four wood samples, Pinus elliottii (PIE), Eucalyptus grandis (EUG), Mezilaurus itauba (ITA) and Dipteryx odorata (DIP) were used in this study. The results showed that higher extractives contents associated with lower crystallinity and lower cellulose crystallite size can accelerate the degradation process and reduce the wood thermal stability. On the other hand, the thermal decomposition of wood shifted to higher temperatures with increasing wood cellulose crystallinity and crystallite size. These results indicated that the cellulose crystallite size affects the thermal degradation temperature of wood species. Copyright © 2012. Published by Elsevier Ltd.

Thermal degradation of the tensile strength of unidirectional boron/aluminum composites

NASA Technical Reports Server (NTRS)

Grimes, H. H.; Lad, R. A.; Maisel, J. E.

1977-01-01

The variation of ultimate tensile strength with thermal treatment of B-Al composite materials and of boron fibers chemically removed from these composites in an attempt to determine the mechanism of the resulting strength degradation was studied. Findings indicate that thermally cycling B-Al represents a more severe condition than equivalent time at temperature. Degradation of composite tensile strength from about 1.3 GN/m squared to as low as 0.34 GN/m squared was observed after 3,000 cycles to 420 C for 203 micrometers B-1100 Al composite. In general, the 1100 Al matrix composites degraded somewhat more than the 6061 matrix material studied. Measurement of fiber strengths confirmed a composite strength loss due to the degradation of fiber strength. Microscopy indicated a highly flawed fiber surface.

Impacts of microalgae pre-treatments for improved anaerobic digestion: thermal treatment, thermal hydrolysis, ultrasound and enzymatic hydrolysis.

PubMed

Ometto, Francesco; Quiroga, Gerardo; Pšenička, Pavel; Whitton, Rachel; Jefferson, Bruce; Villa, Raffaella

2014-11-15

Anaerobic digestion (AD) of microalgae is primarily inhibited by the chemical composition of their cell walls containing biopolymers able to resist bacterial degradation. Adoption of pre-treatments such as thermal, thermal hydrolysis, ultrasound and enzymatic hydrolysis have the potential to remove these inhibitory compounds and enhance biogas yields by degrading the cell wall, and releasing the intracellular algogenic organic matter (AOM). This work investigated the effect of four pre-treatments on three microalgae species, and their impact on the quantity of soluble biomass released in the media and thus on the digestion process yields. The analysis of the composition of the soluble COD released and of the TEM images of the cells showed two main degradation actions associated with the processes: (1) cell wall damage with the release of intracellular AOM (thermal, thermal hydrolysis and ultrasound) and (2) degradation of the cell wall constituents with the release of intracellular AOM and the solubilisation of the cell wall biopolymers (enzymatic hydrolysis). As a result of this, enzymatic hydrolysis showed the greatest biogas yield increments (>270%) followed by thermal hydrolysis (60-100%) and ultrasounds (30-60%). Copyright © 2014 Elsevier Ltd. All rights reserved.

Multifunctional Composites for Improved Polyimide Thermal Stability

NASA Technical Reports Server (NTRS)

Miller, Sandi G.

2007-01-01

The layered morphology of silicate clay provides an effective barrier to oxidative degradation of the matrix resin. However, as resin thermal stability continues to reach higher limits, development of an organic modification with comparable temperature capabilities becomes a challenge. Typically, phyllosilicates used in polymer nanocomposites are modified with an alkyl ammonium ion. Such organic modifiers are not suited for incorporation into high temperature polymers as they commonly degrade below 200oC. Therefore, the development of nanoparticle specifically suited for high temperature applications is necessary. Several nanoparticles were investigated in this study, including pre-exfoliated synthetic clay, an organically modified clay, and carbon nanofiber. Dispersion of the layered silicate increases the onset temperature of matrix degradation as well as slows oxidative degradation. The thermally stable carbon nanofibers are also observed to significantly increase the resin thermal stability.

Thermal degradation and plasticizing mechanism of poly(vinyl chloride) plasticized with a novel cardanol derived plasticizer

NASA Astrophysics Data System (ADS)

Chen, J.; Nie, X. A.; Jiang, J. C.; Zhou, Y. H.

2018-01-01

A natural plasticizer cardanol derivatives glycidyl ether (CGE) was synthesized and employed as a plasticizer for the poly(vinyl chloride). The effect of CGE on thermal degradation of PVC films and its plasticizing mechanism were firstly reported. The molecular structure of CGE was characterized with Fourier transform infrared spectroscopy (FTIR). Thermal properties, degradation properties and compatibility of the PVC films were investigated by Differential scanning calorimeter analysis (DSC), Thermogravimetric analysis (TGA) and FTIR, respectively. Compared with the commercial plasticizers dioctylphthalate (DOP), CGE can endow PVC film with a decrease of 4.31 °C in glass transition temperature (Tg), an increase of 24.01 °C and 25.53 °C in 10% weight loss (T 10) and 50% weight loss (T 50) respectively, and a higher activetion energy of thermal degradation (Ea ).

Partially degradable fibers and microvascular materials formed from the fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, Hefei; Pety, Stephen J.; Sottos, Nancy R.

A partially degradable polymeric fiber includes a thermally degradable polymeric core and a coating surrounding at least a portion of the core. The thermally degradable polymeric core includes a polymeric matrix including a poly(hydroxyalkanoate), and a metal selected from the group consisting of an alkali earth metal and a transition metal, in the core polymeric matrix. The concentration of the metal in the polymeric matrix is at least 0.1 wt %. The partially degradable polymeric fiber may be used to form a microvascular system containing one or more microfluidic channels.

Degradation of thermal control materials under a simulated radiative space environment

NASA Astrophysics Data System (ADS)

Sharma, A. K.; Sridhara, N.

2012-11-01

A spacecraft with a passive thermal control system utilizes various thermal control materials to maintain temperatures within safe operating limits. Materials used for spacecraft applications are exposed to harsh space environments such as ultraviolet (UV) and particle (electron, proton) irradiation and atomic oxygen (AO), undergo physical damage and thermal degradation, which must be considered for spacecraft thermal design optimization and cost effectiveness. This paper describes the effect of synergistic radiation on some of the important thermal control materials to verify the assumptions of beginning-of-life (BOL) and end-of-life (EOL) properties. Studies on the degradation in the optical properties (solar absorptance and infrared emittance) of some important thermal control materials exposed to simulated radiative geostationary space environment are discussed. The current studies are purely related to the influence of radiation on the degradation of the materials; other environmental aspects (e.g., thermal cycling) are not discussed. The thermal control materials investigated herein include different kind of second-surface mirrors, white anodizing, white paints, black paints, multilayer insulation materials, varnish coated aluminized polyimide, germanium coated polyimide, polyether ether ketone (PEEK) and poly tetra fluoro ethylene (PTFE). For this purpose, a test in the constant vacuum was performed reproducing a three year radiative space environment exposure, including ultraviolet and charged particle effects on North/South panels of a geostationary three-axis stabilized spacecraft. Reflectance spectra were measured in situ in the solar range (250-2500 nm) and the corresponding solar absorptance values were calculated. The test methodology and the degradations of the materials are discussed. The most important degradations among the low solar absorptance materials were found in the white paints whereas the rigid optical solar reflectors remained quite stable. Among the high solar absorptance elements, as such the change in the solar absorptance was very low, in particular the germanium coated polyimide was found highly stable.

Degradation of Leakage Currents in Solid Tantalum Capacitors Under Steady-State Bias Conditions

NASA Technical Reports Server (NTRS)

Teverovsky, Alexander A.

2010-01-01

Degradation of leakage currents in various types of solid tantalum capacitors under steady-state bias conditions was investigated at temperatures from 105 oC to 170 oC and voltages up to two times the rated voltage. Variations of leakage currents with time under highly accelerated life testing (HALT) and annealing, thermally stimulated depolarization currents, and I-V characteristics were measured to understand the conduction mechanism and the reason for current degradation. During HALT the currents increase gradually up to three orders of magnitude in some cases, and then stabilize with time. This degradation is reversible and annealing can restore the initial levels of leakage currents. The results are attributed to migration of positively charged oxygen vacancies in tantalum pentoxide films that diminish the Schottky barrier at the MnO2/Ta2O5 interface and increase electron injection. A simple model allows for estimation of concentration and mobility of oxygen vacancies based on the level of current degradation.

Development and Validation of a Stability-Indicating Assay of Etofenamate by RP-HPLC and Characterization of Degradation Products

PubMed Central

Peraman, Ramalingam; Nayakanti, Devanna; Dugga, Hari Hara Theja; Kodikonda, Sudhakara

2013-01-01

A validated stability-indicating RP-HPLC method for etofenamate (ETF) was developed by separating its degradation products on a C18 (250 mm × 4.6 mm 5 μm) Qualisil BDS column using a phosphate buffer (pH-adjusted to 6.0 with orthophosphoric acid) and methanol in the ratio of 20:80 % v/v as the mobile phase at a flow rate of 1.0 mL/min. The column effluents were monitored by a photodiode array detector set at 286 nm. The method was validated in terms of specificity, linearity, accuracy, precision, detection limit, quantification limit, and robustness. Forced degradation of etofenamate was carried out under acidic, basic, thermal, photo, and peroxide conditions and the major degradation products of acidic and basic degradation were isolated and characterized by 1H-NMR, 13C-NMR, and mass spectral studies. The mass balance of the method varied between 92–99%. PMID:24482770

Mission Life Thermal Analysis and Environment Correlation for the Lunar Reconnaissance Orbiter

NASA Technical Reports Server (NTRS)

Garrison, Matthew B.; Peabody, Hume

2012-01-01

Standard thermal analysis practices include stacking worst-case conditions including environmental heat loads, thermo-optical properties and orbital beta angles. This results in the design being driven by a few bounding thermal cases, although those cases may only represent a very small portion of the actual mission life. The NASA Goddard Space Flight Center Thermal Branch developed a procedure to predict the flight temperatures over the entire mission life, assuming a known beta angle progression, variation in the thermal environment, and a degradation rate in the coatings. This was applied to the Global Precipitation Measurement core spacecraft. In order to assess the validity of this process, this work applies the similar process to the Lunar Reconnaissance Orbiter. A flight-correlated thermal model was exercised to give predictions of the thermal performance over the mission life. These results were then compared against flight data from the first two years of the spacecraft s use. This is used to validate the process and to suggest possible improvements for future analyses.

Metabolism Dealing with Thermal Degradation of NAD+ in the Hyperthermophilic Archaeon Thermococcus kodakarensis.

PubMed

Hachisuka, Shin-Ichi; Sato, Takaaki; Atomi, Haruyuki

2017-10-01

NAD + is an important cofactor for enzymatic oxidation reactions in all living organisms, including (hyper)thermophiles. However, NAD + is susceptible to thermal degradation at high temperatures. It can thus be expected that (hyper)thermophiles harbor mechanisms that maintain in vivo NAD + concentrations and possibly remove and/or reuse undesirable degradation products of NAD + Here we confirmed that at 85°C, thermal degradation of NAD + results mostly in the generation of nicotinamide and ADP-ribose, the latter known to display toxicity by spontaneously linking to proteins. The hyperthermophilic archaeon Thermococcus kodakarensis possesses a putative ADP-ribose pyrophosphatase (ADPR-PPase) encoded by the TK2284 gene. ADPR-PPase hydrolyzes ADP-ribose to ribose 5-phosphate (R5P) and AMP. The purified recombinant TK2284 protein exhibited activity toward ADP-ribose as well as ADP-glucose. Kinetic analyses revealed a much higher catalytic efficiency toward ADP-ribose, suggesting that ADP-ribose was the physiological substrate. To gain insight into the physiological function of TK2284, a TK2284 gene disruption strain was constructed and examined. Incubation of NAD + in the cell extract of the mutant strain at 85°C resulted in higher ADP-ribose accumulation and lower AMP production compared with those in experiments with the host strain cell extract. The mutant strain also exhibited lower cell yield and specific growth rates in a synthetic amino acid medium compared with those of the host strain. The results obtained here suggest that the ADPR-PPase in T. kodakarensis is responsible for the cleavage of ADP-ribose to R5P and AMP, providing a means to utilize the otherwise dead-end product of NAD + breakdown. IMPORTANCE Hyperthermophilic microorganisms living under high temperature conditions should have mechanisms that deal with the degradation of thermolabile molecules. NAD + is an important cofactor for enzymatic oxidation reactions and is susceptible to thermal degradation to ADP-ribose and nicotinamide. Here we show that an ADP-ribose pyrophosphatase homolog from the hyperthermophilic archaeon Thermococcus kodakarensis converts the detrimental ADP-ribose to ribose 5-phosphate and AMP, compounds that can be directed to central carbon metabolism. This physiological role for ADP-ribose pyrophosphatases might be universal in hyperthermophiles, as their homologs are widely distributed among both hyperthermophilic bacteria and archaea. Copyright © 2017 American Society for Microbiology.

A review of liquid lubricant thermal/oxidative degradation

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.

1983-01-01

The fundamental processes occurring during the thermal and oxidative degradation of hydrocarbons are reviewed. Particular emphasis is given to various classes of liquid lubricants such as mineral oils, esters, polyphenyl ethers, C-ethers, and fluorinated polyethers. Experimental techniques for determining thermal and oxidative stabilities of lubricants are discussed. The role of inhibitors and catalysis is also covered.

Thermal and catalytic degradation of high and low density polyethylene into fuel oil

DOE Office of Scientific and Technical Information (OSTI.GOV)

Uddin, Azhar; Koizumi, Kazuo; Sakata, Yusaku

1996-12-31

The degradation of four different types of polyethylene (PE) namely high density PE (HDPE), low density PE (LDPE), linear low density PE (LLDPE), and cross-linked PE (XLPE) was carried out at 430 {degrees}C by batch operation using silica-alumina as a solid acid catalyst and thermally without any catalyst. For thermal degradation, both HDPE and XLPE produced significant amount of wax-like compounds and the yield of liquid products were lower than that of LDPE and LLDPE. LDPE and LLDPE also produced small amount of wax-like compounds. Thus the structure of the degrading polymers influenced the product yields. The liquid products frommore » thermal degradation were broadly distributed in the carbon fraction of n-C{sub 5} to n-C{sub 25} (boiling point range, 36-405 C). With silica-alumina, the polyethylenes were converted to liquid products with high yields (77-83 wt%) and without any wax production. The liquid products were distributed in the range of n-C{sub 5} to n-C{sub 20} (Mostly C{sub 5}-C{sub 12}). Solid acid catalyst indiscriminately degraded the various types of polyethylene into light fuel oil. 5 refs., 4 figs., 1 tab.« less

Thermal degradation of TiO2 nanotubes on titanium

NASA Astrophysics Data System (ADS)

Shivaram, Anish; Bose, Susmita; Bandyopadhyay, Amit

2014-10-01

The objective of this research was to study thermal degradation behavior of TiO2 nanotubes on titanium (Ti). TiO2 nanotubes were grown via anodization method on commercially pure Ti (Cp-Ti) discs using two different electrolytes, 1 vol. % HF in deionized (DI) water and 1 vol. % HF + 0.5 wt. % NH4F + 10 vol. % DI water in ethylene glycol, to obtain nanotubes with two different lengths, 300 nm and 950 nm keeping the nanotube diameter constant at 100 ± 20 nm. As grown TiO2 nanotubes were subjected to heat treatment to understand thermal degradation as a function of both temperature and hold time. The signs of degradation were observed mainly when amorphous nanotubes started to crystallize, however the crystallization temperature varied based on TiO2 nanotubes length and anodizing condition. Overall, 300 nm nanotubes were thermally stable at least up to 400 °C for 12 h, while the 950 nm long nanotubes show signs of degradation from 400 °C for 6 h only. Clearly, length of nanotubes, heat treatment temperature as well as hold times show influence toward degradation kinetics of TiO2 nanotubes on titanium.

SEM method for direct visual tracking of nanoscale morphological changes of platinum based electrocatalysts on fixed locations upon electrochemical or thermal treatments.

PubMed

Zorko, Milena; Jozinović, Barbara; Bele, Marjan; Hodnik, Nejc; Gaberšček, Miran

2014-05-01

A general method for tracking morphological surface changes on a nanometer scale with scanning electron microscopy (SEM) is introduced. We exemplify the usefulness of the method by showing consecutive SEM images of an identical location before and after the electrochemical and thermal treatments of platinum-based nanoparticles deposited on a high surface area carbon. Observations reveal an insight into platinum based catalyst degradation occurring during potential cycling treatment. The presence of chloride clearly increases the rate of degradation. At these conditions the dominant degradation mechanism seems to be the platinum dissolution with some subsequent redeposition on the top of the catalyst film. By contrast, at the temperature of 60°C, under potentiostatic conditions some carbon corrosion and particle aggregation was observed. Temperature treatment simulating the annealing step of the synthesis reveals sintering of small platinum based composite aggregates into uniform spherical particles. The method provides a direct proof of induced surface phenomena occurring on a chosen location without the usual statistical uncertainty in usual, random SEM observations across relatively large surface areas. Copyright © 2014 Elsevier B.V. All rights reserved.

Cubesat in-situ degradation detector (CIDD)

NASA Astrophysics Data System (ADS)

Rievers, Benny; Milke, Alexander; Salden, Daniel

2015-07-01

The design of the thermal control and management system (TCS) is a central task in satellite design. In order to evaluate and dimensionize the properties of the TCS, material parameters specifying the conductive and radiative properties of the different TCS components have to be known including their respective variations within the mission lifetime. In particular the thermo-optical properties of the outer surfaces including critical TCS components such as radiators and thermal insulation are subject to degradation caused by interaction with the space environment. The evaluation of these material parameters by means of ground testing is a time-consuming and expensive endeavor. Long-term in-situ measurements on board the ISS or large satellites not only realize a better implementation of the influence of the space environment but also imply high costs. Motivated by this we propose the utilization of low-cost nano-satellite systems to realize material tests within space at a considerably reduced cost. We present a nanosat-scale degradation sensor concept which realizes low power consumption and data rates compatible with nanosat boundaries at UHF radio. By means of a predefined measurement and messaging cycle temperature curves are measured and evaluated on ground to extract the change of absorptivity and emissivity over mission lifetime.

Moderate Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically Damaged Zooxanthellae (Symbiodinium) from Corals.

PubMed

Fujise, Lisa; Yamashita, Hiroshi; Suzuki, Go; Sasaki, Kengo; Liao, Lawrence M; Koike, Kazuhiko

2014-01-01

The foundation of coral reef biology is the symbiosis between corals and zooxanthellae (dinoflagellate genus Symbiodinium). Recently, coral bleaching, which often results in mass mortality of corals and the collapse of coral reef ecosystems, has become an important issue around the world as coral reefs decrease in number year after year. To understand the mechanisms underlying coral bleaching, we maintained two species of scleractinian corals (Acroporidae) in aquaria under non-thermal stress (27°C) and moderate thermal stress conditions (30°C), and we compared the numbers and conditions of the expelled Symbiodinium from these corals. Under non-thermal stress conditions corals actively expel a degraded form of Symbiodinium, which are thought to be digested by their host coral. This response was also observed at 30°C. However, while the expulsion rates of Symbiodinium cells remained constant, the proportion of degraded cells significantly increased at 30°C. This result indicates that corals more actively digest and expel damaged Symbiodinium under thermal stress conditions, likely as a mechanism for coping with environmental change. However, the increase in digested Symbiodinium expulsion under thermal stress may not fully keep up with accumulation of the damaged cells. There are more photosynthetically damaged Symbiodinium upon prolonged exposure to thermal stress, and corals release them without digestion to prevent their accumulation. This response may be an adaptive strategy to moderate stress to ensure survival, but the accumulation of damaged Symbiodinium, which causes subsequent coral deterioration, may occur when the response cannot cope with the magnitude or duration of environmental stress, and this might be a possible mechanism underlying coral bleaching during prolonged moderate thermal stress.

Moderate Thermal Stress Causes Active and Immediate Expulsion of Photosynthetically Damaged Zooxanthellae (Symbiodinium) from Corals

PubMed Central

Fujise, Lisa; Yamashita, Hiroshi; Suzuki, Go; Sasaki, Kengo; Liao, Lawrence M.; Koike, Kazuhiko

2014-01-01

The foundation of coral reef biology is the symbiosis between corals and zooxanthellae (dinoflagellate genus Symbiodinium). Recently, coral bleaching, which often results in mass mortality of corals and the collapse of coral reef ecosystems, has become an important issue around the world as coral reefs decrease in number year after year. To understand the mechanisms underlying coral bleaching, we maintained two species of scleractinian corals (Acroporidae) in aquaria under non-thermal stress (27°C) and moderate thermal stress conditions (30°C), and we compared the numbers and conditions of the expelled Symbiodinium from these corals. Under non-thermal stress conditions corals actively expel a degraded form of Symbiodinium, which are thought to be digested by their host coral. This response was also observed at 30°C. However, while the expulsion rates of Symbiodinium cells remained constant, the proportion of degraded cells significantly increased at 30°C. This result indicates that corals more actively digest and expel damaged Symbiodinium under thermal stress conditions, likely as a mechanism for coping with environmental change. However, the increase in digested Symbiodinium expulsion under thermal stress may not fully keep up with accumulation of the damaged cells. There are more photosynthetically damaged Symbiodinium upon prolonged exposure to thermal stress, and corals release them without digestion to prevent their accumulation. This response may be an adaptive strategy to moderate stress to ensure survival, but the accumulation of damaged Symbiodinium, which causes subsequent coral deterioration, may occur when the response cannot cope with the magnitude or duration of environmental stress, and this might be a possible mechanism underlying coral bleaching during prolonged moderate thermal stress. PMID:25493938

In situ degradation studies of two-dimensional WSe₂-graphene heterostructures.

PubMed

Wang, B; Eichfield, S M; Wang, D; Robinson, J A; Haque, M A

2015-09-14

Heterostructures of two-dimensional materials can be vulnerable to thermal degradation due to structural and interfacial defects as well as thermal expansion mismatch, yet a systematic study does not exist in the literature. In this study, we investigate the degradation of freestanding WSe2-graphene heterostructures due to heat and charge flow by performing in situ experiments inside a transmission electron microscope. Experimental results show that purely thermal loading requires higher temperatures (>850 °C), about 150 °C higher than that under combined electrical and thermal loading. In both cases, selenium is the first element to decompose and migration of silicon atoms from the test structure to the freestanding specimen initiates rapid degradation through the formation of tungsten disilicide and silicon carbide. The role of the current flow is to enhance the migration of silicon from the sample holder and to knock-out the selenium atoms. The findings of this study provide fundamental insights into the degradation of WSe2-graphene heterostructures and inspire their application in electronics for use in harsh environments.

Effect of in-pile degradation of the meat thermal conductivity on the maximum temperature of the plate-type U-Mo dispersion fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pavel G. Medvedev

2009-11-01

Effect of in-pile degradation of thermal conductivity on the maximum temperature of the plate-type research reactor fuels has been assessed using the steady-state heat conduction equation and assuming convection cooling. It was found that due to very low meat thickness, characteristic for this type of fuel, the effect of thermal conductivity degradation on the maximum fuel temperature is minor. For example, the fuel plate featuring 0.635 mm thick meat operating at heat flux of 600 W/cm2 would experience only a 20oC temperature rise if the meat thermal conductivity degrades from 0.8 W/cm-s to 0.3 W/cm-s. While degradation of meat thermalmore » conductivity in dispersion-type U-Mo fuel can be very substantial due to formation of interaction layer between the particles and the matrix, and development of fission gas filled porosity, this simple analysis demonstrates that this phenomenon is unlikely to significantly affect the temperature-based safety margin of the fuel during normal operation.« less

Effect of thermal processing practices on the properties of superplastic Al-Li alloys

NASA Technical Reports Server (NTRS)

Hales, Stephen J.; Lippard, Henry E.

1993-01-01

The effect of thermal processing on the mechanical properties of superplastically formed structural components fabricated from three aluminum-lithium alloys was evaluated. The starting materials consisted of 8090, 2090, and X2095 (Weldalite(TM) 049), in the form of commercial-grade superplastic sheet. The experimental test matrix was designed to assess the impact on mechanical properties of eliminating solution heat treatment and/or cold water quenching from post-forming thermal processing. The extensive hardness and tensile property data compiled are presented as a function of aging temperature, superplastic strain and temper/quench rate for each alloy. The tensile properties of the materials following superplastic forming in two T5-type tempers are compared with the baseline T6 temper. The implications for simplifying thermal processing without degradation in properties are discussed on the basis of the results.

Fractography evolution in accelerated aging of UHMWPE after gamma irradiation in air.

PubMed

Medel, F; Gómez-Barrena, E; García-Alvarez, F; Ríos, R; Gracia-Villa, L; Puértolas, J A

2004-01-01

We studied the fracture surface evolution of ultra high molecular weight polyethylene (UHMWPE) specimens, manufactured from GUR 1050 compression moulded sheets, after gamma sterilisation in air followed by different aging times after thermal treatment at 120 degrees C. Degradation profiles were obtained by FTIR and DSC measurements after 0, 7, 14, 24 and 36h aging. We observed by SEM the morphology patterns at these aging times, in surface fractographies after uniaxial tensile test of standardised samples. The results pointed out clear differences between short and long aging times. At shorter times, 7h, the behaviour was similar to non-degraded UHMWPE, exhibiting ductile behaviour. At longer times, 24-36h, this thermal protocol provided a highly degraded zone in the subsurface, similar to the white band found after gamma irradiation in air followed by natural aging, although closer to the surface, at 150-200mum. The microstructure of this oxidation zone, similarly found in gamma irradiated samples shelf-aged for 6-7 years, although with different distribution of microvoids, was formed by fibrils, associated with embrittlement of the oxidised UHMWPE. In addition, the evolution of the oxidation index, the enthalpy content, the mechanical parameters, and the depth of the oxidation front deduced from the fractographies versus aging time showed that a changing behaviour in the degradation rate appeared at intermediate aging times.

Heat treatment versus properties studies associated with the Inconel 718 PBF acoustic filters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smolik, G.R.; Reuter, W.G.

PBF acoustic filter Unit No. 1 cracked when heat treatment was attempted. The effects of prior thermal cycling, solution anneal temperature, and cooling rate from solution anneals were investigated. The investigations concerned influences of the above variables upon both 1400$sup 0$F stress rupture solution- annealed properties and room temperature age-hardened properties. 1400$sup 0$F stress rupture properties were of interest to assist the prevention of cracking during heat treatments. Room temperature age-hardened properties were needed to ensure that design requirement would be provided. Prior thermal cycling was investigated to determine if extra thermal cycles would be detrimental to the repaired filter.more » Slow furnace cools were considered as a means of reducing thermal stresses. Effects of solution annealing at 2000 and 1900$sup 0$F were also determined. Test results showed that slow cooling rates would not only reduce thermal stresses but also improve 1400$sup 0$F ductility. A modified aging treatment was established which provided the required 145 ksi room temperature yield strength for the slowly cooled material. Prior cooling did not degrade final age-hardened room temperature tensile or impact properties. (auth)« less

Reduced temperature hydrolysis at 134 °C before thermophilic anaerobic digestion of waste activated sludge at increasing organic load.

PubMed

Gianico, A; Braguglia, C M; Cesarini, R; Mininni, G

2013-09-01

The performance of thermophilic digestion of waste activated sludge, either untreated or thermal pretreated, was evaluated through semi-continuous tests carried out at organic loading rates in the range of 1-3.7 kg VS/m(3)d. Although the thermal pretreatment at T=134 °C proved to be effective in solubilizing organic matter, no significant gain in organics degradation was observed. However, the digestion of pretreated sludge showed significant soluble COD removal (more than 55%) whereas no removal occurred in control reactors. The lower the initial sludge biodegradability, the higher the efficiency of thermal pretreated digestion was observed, in particular as regards higher biogas and methane production rates with respect to the parallel untreated sludge digestion. Heat balance of the combined thermal hydrolysis/thermophilic digestion process, applied on full-scale scenarios, showed positive values for direct combustion of methane. In case of combined heat and power generation, attractive electric energy recoveries were obtained, with a positive heat balance at high load. Copyright © 2013. Published by Elsevier Ltd.

Investigation of thermal fatigue in fiber composite materials. [(thermal cycling tests)

NASA Technical Reports Server (NTRS)

Fahmy, A. A.; Cunningham, T. G.

1976-01-01

Graphite-epoxy laminates were thermally cycled to determine the effects of thermal cycles on tensile properties and thermal expansion coefficients of the laminates. Three 12-ply laminate configurations were subjected to up to 5,000 thermal cycles. The cumulative effect of the thermal cycles was determined by destructive inspection (electron micrographs and tensile tests) of samples after progressively larger numbers of cycles. After thermal cycling, the materials' tensile strengths, moduli, and thermal expansion coefficients were significantly lower than for the materials as fabricated. Most of the degradation of properties occurred after only a few cycles. The property degradation was attributed primarily to the progressive development of matrix cracks whose locations depended upon the layup orientation of the laminate.

Long-term performance of the passive thermal control systems of the IRAS spacecraft

NASA Technical Reports Server (NTRS)

Mason, P. V.

1988-01-01

Degradation of passive thermal control systems in space is a matter of serious concern and has been observed in many missions. The performance of the passive thermal control systems of the Infrared Astronomical Satellite (IRAS) over a period of three years is reported here. An exterior temperature of 200 K and a sunshade temperature of approximately 100 K were maintained over this period without significant degradation. The temperature of the telescope contained in the IRAS cryostat was also observed for two years after expenditure of the helium cryogen. It remained at 100 K with no degradation.

Trend analysis of GIMMS and MODIS NDVI time series for establishing a land degradation neutrality national baseline

NASA Astrophysics Data System (ADS)

Gichenje, Helene; Godinho, Sergio

2017-04-01

Land degradation is a key global environment and development problem that is recognized as a priority by the international development community. The Sustainable Development Goals (SDGs) were adopted by the global community in 2015, and include a goal related to land degradation and the accompanying target to achieve a land degradation-neutral (LDN) world by 2030. The LDN concept encompasses two joint actions of reducing the rate of degradation and increasing the rate of restoration. Using Kenya as the study area, this study aims to develop and test a spatially explicit methodology for assessing and monitoring the operationalization of a land degradation neutrality scheme at the national level. Time series analysis is applied to Normalized Difference Vegetation Index (NDVI) satellite data records, based on the hypothesis that the resulting NDVI residual trend would enable successful detection of changes in vegetation photosynthetic capacity and thus serve as a proxy for land degradation and regeneration processes. Two NDVI data sets are used to identify the spatial and temporal distribution of degraded and regenerated areas: the long term coarse resolution (8km, 1982-2015) third generation Global Inventory Modeling and Mapping Studies (GIMMS) NDVI3g data record; and the shorter-term finer resolution (250m, 2001-2015) Moderate Resolution Imaging Spectroradiometer (MODIS) derived NDVI data record. Climate data (rainfall, temperature and soil moisture) are used to separate areas of human-induced vegetation productivity decline from those driven by climate dynamics. Further, weekly vegetation health (VH) indexes (4km, 1982-2015) developed by National Oceanic and Atmospheric Administration (NOAA), are assessed as indicators for early detection and monitoring of land degradation by estimating vegetation stress (moisture, thermal and combined conditions).

Stress Intensity of Delamination in a Sintered-Silver Interconnection: Preprint

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeVoto, D. J.; Paret, P. P.; Wereszczak, A. A.

2014-08-01

In automotive power electronics packages, conventional thermal interface materials such as greases, gels, and phase-change materials pose bottlenecks to heat removal and are also associated with reliability concerns. The industry trend is toward high thermal performance bonded interfaces for large-area attachments. However, because of coefficient of thermal expansion mismatches between materials/layers and resultant thermomechanical stresses, adhesive and cohesive fractures could occur, posing a reliability problem. These defects manifest themselves in increased thermal resistance. This research aims to investigate and improve the thermal performance and reliability of sintered-silver for power electronics packaging applications. This has been experimentally accomplished by the synthesismore » of large-area bonded interfaces between metalized substrates and copper base plates that have subsequently been subjected to thermal cycles. A finite element model of crack initiation and propagation in these bonded interfaces will allow for the interpretation of degradation rates by a crack-velocity (V)-stress intensity factor (K) analysis. A description of the experiment and the modeling approach are discussed.« less

Evaluation of a 2.5 kWel automotive low temperature PEM fuel cell stack with extended operating temperature range up to 120 °C

NASA Astrophysics Data System (ADS)

Ruiu, Tiziana; Dreizler, Andreas M.; Mitzel, Jens; Gülzow, Erich

2016-01-01

Nowadays, the operating temperature of polymer electrolyte membrane fuel cell stacks is typically limited to 80 °C due to water management issues of membrane materials. In the present work, short-term operation at elevated temperatures up to 120 °C and long-term steady-state operation under automotive relevant conditions at 80 °C are examined using a 30-cell stack developed at DLR. The high temperature behavior is investigated by using temperature cycles between 90 and 120 °C without adjustment of the gases dew points, to simulate a short-period temperature increase, possibly caused by an extended power demand and/or limited heat removal. This galvanostatic test demonstrates a fully reversible performance decrease of 21 ± 1% during each thermal cycle. The irreversible degradation rate is about a factor of 6 higher compared to the one determined by the long-term test. The 1200-h test at 80 °C demonstrates linear stack voltage decay with acceptable degradation rate, apart from a malfunction of the air compressor, which results in increased catalyst degradation effects on individual cells. This interpretation is based on an end-of-life characterization, aimed to investigate catalyst, electrode and membrane degradation, by determining hydrogen crossover rates, high frequency resistances, electrochemically active surface areas and catalyst particle sizes.

Thermal Degradation and Identification of Heat-Sensitive Polymers

ERIC Educational Resources Information Center

Clough, Stuart C.; Goldman, Emma W.

2005-01-01

A study demonstrates the thermal degradation of two heat-sensitive polymers, namely, polystyrene and poly (methyl methacrylate). The experiment described in the study introduces undergraduate students to polymer structure as well as the application of spectroscopic techniques to the solution of structural problems.

SOM quality and phosphorus fractionation to evaluate degradation organic matter: implications for the restoration of soils after fire

NASA Astrophysics Data System (ADS)

Merino, Agustin; Fonturbel, Maria T.; Omil, Beatriz; Chávez-Vergara, Bruno; Fernandez, Cristina; Garcia-Oliva, Felipe; Vega, Jose A.

2016-04-01

The design of emergency treatment for the rehabilitation of fire-affected soils requires a quick diagnosis to assess the degree of degradation. For its implication in the erosion and subsequent evolution, the quality of soil organic matter (OM) plays a particularly important role. This paper presents a methodology that combines the visual recognition of the severity of soil burning with the use of simple analytical techniques to assess the degree of degradation of OM. The content and quality of the OM was evaluated in litter and mineral soils using thermogravimetry-differential scanning calorimetry (DSC-TG) spectroscopy, and the results were contrasted with 13C CP-MAS NMR. The types of methodologies were texted to assess the thermal analysis: a) the direct calculation of the Q areas related to three degrees of thermal stabilities: Q1 (200-375 °C; labil OM); Q2 (375-475 °C, recalcitrant OM); and Q3 (475-550 °C). b) deconvolution of DSC curves and calculation of each peak was expressed as a fraction of the total DSC curve area. Additionally, a P fractionation was done following the Hedley sequential extraction method. The severity levels visually showed different degrees of SOM degradation. Although the fire caused important SOM losses in moderate severities, changes in the quality of OM only occurred at higher severities. Besides, the labile organic P fraction decreased and the occluded inorganic P fraction increased in the high severity soils. These changes affect the OM processes such as hydrophobicity and erosion largely responsible for soil degradation post-fire. The strong correlations between the thermal parameters and NMR regions and derived measurements such as hydrophobicity and aromaticity show the usefulness of this technique as rapid diagnosis to assess the soil degradation.The marked loss of polysaccharide and transition to highly thermic-resistant compounds, visible in deconvoluted thermograms, which would explain the changes in microbial activity and soil nutrients availability (basal respiration, microbial biomass, qCO2, and enzymatic activity). And also it would have implications in hydrophobicity and stability of soil aggregates, leading to the extreme erosion rates that occur usually are found in soils affected by higher severities.

Long-term thermal degradation and alloying constituent effects on five boron/aluminum composites

NASA Technical Reports Server (NTRS)

Olsen, G. C.

1982-01-01

Thermal exposure effects on the properties of five boron/aluminum composite systems were experimentally investigated. The composite systems were 49 volume percent boron fibers (203 micron diameter) in aluminum-alloy matrices 1100 Al, 2024 Al, 3003 Al, 5052 Al, and 6061 Al. Specimens were thermally exposed up to 10,000 hours at 500 K and 590 K, up to 500 hours at 730 K, and up to 10,000 hours at 500 K and 590 K, up to 500 hours at 730 K, and up to 2000 thermal cycles between 200 K and 590 K. Composite longitudinal and transverse tensile strengths, longitudinal compression strength, and in-plane shear strength were determined. None of the systems was severely degraded by exposure at 590 K. The best performing system was B-2024 Al. Effects of matrix alloys on degradation mechanisms were experimentally investigated. Composite specimens and individual fibers were metallurgically analyzed with a scanning electron microscope and an electron microprobe to determine failure characteristics, chemical element distribution, and reaction layer morphology. Alloying constituents were found to be affect the composite degradation mechanisms as follows: alloys containing iron, but without manganese as a stabilizer, caused increased low-temperature degradation; alloys containing magnesium, iron, or manganese caused increased degradation; and alloys containing copper caused increased fiber strength.

Results from the IMP-J violet solar cell experiment and violet cell balloon flights

NASA Technical Reports Server (NTRS)

Gaddy, E. M.

1976-01-01

The Interplanetary Monitoring Platform-J violet solar cell experiment was flown in an orbit with mild thermal cycling and low hard-particle radiation. The results of the experiment show that violet cells degrade at about the same rate as conventional cells in such an orbit. Balloon flight measurements show that violet solar cells produce approximately 20% more power than conventional cells.

Results from the IMP-J violet solar cell experiment and violet cell balloon flights

NASA Technical Reports Server (NTRS)

Gaddy, E. M.

1976-01-01

The IMP-J violet solar cell experiment was flown in an orbit with mild thermal cycling and low hard particle radiation. The results of the experiment show that violet cells degrade at about the same rate as conventional cells in such an orbit. Balloon flight measurements show that violet solar cells produce approximately 20% more power than conventional cells.

Bacterial secondary production on vascular plant detritus: relationships to detritus composition and degradation rate.

PubMed Central

Moran, M A; Hodson, R E

1989-01-01

Bacterial production at the expense of vascular plant detritus was measured for three emergent plant species (Juncus effusus, Panicum hemitomon, and Typha latifolia) degrading in the littoral zone of a thermally impacted lake. Bacterial secondary production, measured as tritiated thymidine incorporation into DNA, ranged from 0.01 to 0.81 microgram of bacterial C mg of detritus-1 day-1. The three plant species differed with respect to the amount of bacterial productivity they supported per milligram of detritus, in accordance with the predicted biodegradability of the plant material based on initial nitrogen content, lignin content, and C/N ratio. Bacterial production also varied throughout the 22 weeks of in situ decomposition and was positively related to the nitrogen content and lignin content of the remaining detritus, as well as to the temperature of the lake water. Over time, production was negatively related to the C/N ratio and cellulose content of the degrading plant material. Bacterial production on degrading plant material was also calculated on the basis of plant surface area and ranged from 0.17 to 1.98 micrograms of bacterial C cm-2 day-1. Surface area-based calculations did not correlate well with either initial plant composition or changing composition of the remaining detritus during decomposition. The rate of bacterial detritus degradation, calculated from measured production of surface-attached bacteria, was much lower than the actual rate of weight loss of plant material. This discrepancy may be attributable to the importance of nonbacterial organisms in the degradation and loss of plant material from litterbags or to the microbially mediated solubilization of particulate material prior to bacterial utilization, or both. PMID:2802603

Isothermal and hygrothermal agings of hybrid glass fiber/carbon fiber composite

NASA Astrophysics Data System (ADS)

Barjasteh, Ehsan

New applications of fiber-reinforced polymer composites (FRPCs) are arising in non-traditional sectors of industry, such as civil infrastructure, automotive, and power distribution. For example, composites are being used in place of steel to support high-voltage overhead conductors. In this application, conductive strands of aluminum are wrapped around a solid composite rod comprised of unidirectional carbon and glass fibers in an epoxy matrix, which is commercially called ACCC conductor. Composite-core conductors such as these are expected to eventually replace conventional steel-reinforced conductors because of the reduced sag at high temperatures, lower weight, higher ampacity, and reduced line losses. Despite the considerable advantages in mechanical performance, long-term durability of composite conductors is a major concern, as overhead conductors are expected to retain properties (with minimal maintenance) over a service life that spans multiple decades. These concerns stem from the uncertain effects of long-term environmental exposure, which includes temperature, moisture, radiation, and aggressive chemicals, all of which can be exacerbated by cyclic loads. In general, the mechanical and physical properties of polymer composites are adversely affected by such environmental factors. Consequently, the ability to forecast changes in material properties as a function of environmental exposure, particularly bulk mechanical properties, which are affected by the integrity of fiber-matrix interfaces, is required to design for extended service lives. Polymer composites are susceptible to oxidative degradation at high temperatures approaching but not quite reaching the glass transition temperature ( Tg). Although the fibers are stable at such temperatures, the matrix and especially the fiber-matrix interface can undergo degradation that affects the physical and mechanical properties of the structure over time. Therefore, as a first step, the thermal aging of an anhydride/epoxy network used in composite-reinforced conductor cables was investigated to determine the extent of thermal oxidative (surface effect) and non-oxidative (bulk effect) degradation. Thermal oxidation tests were performed in air-circulating and vacuum ovens at 180°C and 200ºC (the maximum emergency temperature for ACCC conductors). The extent of oxidation during aging was determined by monitoring the thickness of the oxidized layer. Results showed that the oxidized layer thickness did not increase monotonically as a function of exposure time, and even decreased for a limited period of time. A phenomenological reaction-diffusion model was implemented to predict the thickness of oxidized layer, and the calculated results were compared with measurements for aging times up to 10,000 hours. The accuracy of the reaction-diffusion-based thickness values for the isothermally aged epoxy specimen was affected by the permeability properties of the oxidized material, and to a lesser extent by the degree of oxidation. The diffusivity varied because of changes in the density of the oxidized layer, the macro-void content, crack formation, and the molecular structures. To investigate the effects on diffusivity, the morphology of the oxidized layer and the void content was monitored over time. In addition, the density of the oxidized specimens was calculated by direct measurements of volume and weight during exposure. An empirically based volume-loss model was developed to predict the changes in volume of the specimen as a function of aging times and hence to predict the effects on the oxidized layer thickness. Volume-loss measurements provide an indication of material degradation by demonstrating a direct measurement of shrinkage rates and insight into crack initiation, as opposed to typical weight-loss measurements that provide no insight into material failure. Thermal oxidation of a unidirectional carbon-fiber/glass-fiber hybrid composite was also investigated in this study. The aim was to determine oxidation kinetics, degradation mechanisms, oxidation thickness growth (a damage indicator), and oxidation effects on mechanical property. The epoxy composite rods were comprised of a carbon-fiber core and a glass-fiber shell. The thickness of the oxidized layer (TOL) was measured experimentally for samples exposed to 180ºC and 200ºC for up to 8,736 hours. A reaction-diffusion model was developed for each of the two hybrid sections to obtain the oxygen-concentration profile and the TOL within the composite rods. The TOL values measured experimentally were similar to the modeling predictions. The glass-fiber shell functioned as a protective layer, limiting the oxidation of the carbon-fiber core. The domain validity for the reaction-diffusion model was determined from gravimetric experiments by measuring the weight-loss of hybrid composite samples exposed isothermally in air and in vacuum at 200°C for up to 13,104 hours (1.5 years). The results showed that after prolonged thermal exposure, the degradation mechanism changed from thermal oxidation to thermal degradation. Thermogravimetric analysis (TGA) was performed to determine the thermal degradation and stability of the aged composite. The results indicated that the onset temperature of matrix degradation increased by increasing exposure time. Inorganic fillers are widely used in pultruded parts to facilitate pultrusion, especially for long production runs. Therefore, another scope of this study was to investigate the effects of filler on oxidation kinetics and degradation mechanisms during thermal aging of prultruded composite rods. Similar aging tests and oxidation modeling to those for the unfilled composites were performed. The predicted and measured TOL values for filled composites were slightly less than those for unfilled composites. The addition of kaolin fillers did not affect the oxidation mechanism or the reaction rate of the epoxy matrix, although it did cause a slight decrease in the oxygen-transport properties (diffusivity and solubility of oxygen). The effect of thermal aging on mechanical properties of the aged composites was investigated. A relationship was derived relating TOL to tensile strength of the hybrid composite. The tensile strength remained essentially unchanged by thermal oxidation after 52 weeks of exposure. On the contrary, the oxidation resulted in a decrease in short-beam-shear (SBS) strength (a matrix-dominated property) due to degradation of matrix and fiber/matrix interface strength. However, the filled composites showed a lower reduction in SBS strength than that of the unfilled one for an identical duration of exposure. In addition, the effect of thermal aging on glass transition temperature (T g) was determined for isothermal exposures at 180ºC and 200ºC. The simultaneous effects of post-curing and thermal degradation resulted in the change in Tg during exposure. Another study on the composite rod was performed to investigate the sorption kinetics and the effects of moisture on mechanical and physical properties. Sorption curves were obtained for both hybrid and non-hybrid composite rods to determine characteristic parameters, including the diffusion coefficient (D) and the maximum moisture uptake (Minfinity ). The moisture uptake for the hybrid composites generally exhibited Fickian behavior (no hybridization effects), behaving much like non-hybrid composites. A two-dimensional diffusion model was employed to calculate moisture diffusivities in the longitudinal direction. Interfaces and thermally-induced residual stresses affected the moisture diffusion. In addition, the effect of hygrothermal aging on glass transition temperature (Tg), short beam shear strength (SBS), and tensile strength was determined for hygrothermal exposure at 60°C and 85% relative humidity (RH). Property retention and reversibility of property degradation was also measured. Microscopic inspection revealed no evidence of damage. Prediction of the lifetime of carbon-fiber/fiberglass (GF/CF) hybrid composites under various loads and service life conditions requires fundamental knowledge about the degradation mechanisms associated with overhead conductors with the hybrid GF/CF composite cores. This study provides adequate information on mechanical and thermal behaviors of the composite core under prolong isothermal and hygrothermal exposure, which is necessary for defining a lifetime model.

Kinetic analyses and pyrolytic behavior of Para grass (Urochloa mutica) for its bioenergy potential.

PubMed

Ahmad, Muhammad Sajjad; Mehmood, Muhammad Aamer; Al Ayed, Omar S; Ye, Guangbin; Luo, Huibo; Ibrahim, Muhammad; Rashid, Umer; Arbi Nehdi, Imededdine; Qadir, Ghulam

2017-01-01

The biomass of Urochloa mutica was subjected to thermal degradation analyses to understand its pyrolytic behavior for bioenergy production. Thermal degradation experiments were performed at three different heating rates, 10, 30 and 50°Cmin -1 using simultaneous thermogravimetric-differential scanning calorimetric analyzer, under an inert environment. The kinetic analyses were performed using isoconversional models of Kissenger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO). The high heating value was calculated as 15.04MJmol -1 . The activation energy (E) values were shown to be ranging from 103 through 233 kJmol -1 . Pre-exponential factors (A) indicated the reaction to follow first order kinetics. Gibbs free energy (ΔG) was measured to be ranging from 169 to 173kJmol -1 and 168 to 172kJmol -1 , calculated by KAS and FWO methods, respectively. We have shown that Para grass biomass has considerable bioenergy potential comparable to established bioenergy crops such as switchgrass and miscanthus. Copyright © 2016 Elsevier Ltd. All rights reserved.

Enhancement of Fracture Toughness of Epoxy Nanocomposites by Combining Nanotubes and Nanosheets as Fillers

PubMed Central

Domun, Nadiim; Paton, Keith R.; Sainsbury, Toby; Zhang, Tao; Mohamud, Hibaaq

2017-01-01

In this work the fracture toughness of epoxy resin has been improved through the addition of low loading of single part and hybrid nanofiller materials. Functionalised multi-walled carbon nanotubes (f-MWCNTs) was used as single filler, increased the critical strain energy release rate, GIC, by 57% compared to the neat epoxy, at only 0.1 wt% filler content. Importantly, no degradation in the tensile or thermal properties of the nanocomposite was observed compared to the neat epoxy. When two-dimensional boron nitride nanosheets (BNNS) were added along with the one-dimensional f-MWCNTs, the fracture toughness increased further to 71.6% higher than that of the neat epoxy. Interestingly, when functionalised graphene nanoplatelets (f-GNPs) and boron nitride nanotubes (BNNTs) were used as hybrid filler, the fracture toughness of neat epoxy is improved by 91.9%. In neither of these hybrid filler systems the tensile properties were degraded, but the thermal properties of the nanocomposites containing boron nitride materials deteriorated slightly. PMID:29048345

The mechanisms of hydrothermal deconstruction of lignocellulose: New insights from thermal–analytical and complementary studies

PubMed Central

Ibbett, Roger; Gaddipati, Sanyasi; Davies, Scott; Hill, Sandra; Tucker, Greg

2011-01-01

Differential Scanning Calorimetry, Dynamic Mechanical Thermal Analysis, gravimetric and chemical techniques have been used to study hydrothermal reactions of straw biomass. Exothermic degradation initiates above 195 °C, due to breakdown of the xylose ring from hemicellulose, which may be similar to reactions occurring during the early stage pyrolysis of dry biomass, though activated at lower temperature through water mediation. The temperature and magnitude of the exotherm reduce with increasing acid concentration, suggesting a reduction in activation energy and a change in the balance of reaction pathways. The presence of xylan oligomers in auto-catalytic hydrolysates is believed to be due to a low rate constant rather than a specific reaction mechanism. The loss of the lignin glass transition indicates that the lignin phase is reorganised under high temperature auto-catalytic conditions, but remains partially intact under lower temperature acid-catalytic conditions. This shows that lignin degradation reactions are activated thermally but are not effectively catalysed by aqueous acid. PMID:21763128

Enhancement of Fracture Toughness of Epoxy Nanocomposites by Combining Nanotubes and Nanosheets as Fillers.

PubMed

Domun, Nadiim; Paton, Keith R; Hadavinia, Homayoun; Sainsbury, Toby; Zhang, Tao; Mohamud, Hibaaq

2017-10-19

In this work the fracture toughness of epoxy resin has been improved through the addition of low loading of single part and hybrid nanofiller materials. Functionalised multi-walled carbon nanotubes (f-MWCNTs) was used as single filler, increased the critical strain energy release rate, G IC , by 57% compared to the neat epoxy, at only 0.1 wt% filler content. Importantly, no degradation in the tensile or thermal properties of the nanocomposite was observed compared to the neat epoxy. When two-dimensional boron nitride nanosheets (BNNS) were added along with the one-dimensional f-MWCNTs, the fracture toughness increased further to 71.6% higher than that of the neat epoxy. Interestingly, when functionalised graphene nanoplatelets (f-GNPs) and boron nitride nanotubes (BNNTs) were used as hybrid filler, the fracture toughness of neat epoxy is improved by 91.9%. In neither of these hybrid filler systems the tensile properties were degraded, but the thermal properties of the nanocomposites containing boron nitride materials deteriorated slightly.

Pollutant content in marine debris and characterization by thermal decomposition.

PubMed

Iñiguez, M E; Conesa, J A; Fullana, A

2017-04-15

Marine debris (MDs) produces a wide variety of negative environmental, economic, safety, health and cultural impacts. Most marine litter has a very low decomposition rate (plastics), leading to a gradual accumulation in the coastal and marine environment. Characterization of the MDs has been done in terms of their pollutant content: PAHs, ClBzs, ClPhs, BrPhs, PCDD/Fs and PCBs. The results show that MDs is not a very contaminated waste. Also, thermal decomposition of MDs materials has been studied in a thermobalance at different atmospheres and heating rates. Below 400-500K, the atmosphere does not affect the thermal degradation of the mentioned waste. However, at temperatures between 500 and 800K the presence of oxygen accelerates the decomposition. Also, a kinetic model is proposed for the combustion of the MDs, and the decomposition is compared with that of their main constituents, i.e., polyethylene (PE), polystyrene (PS), polypropylene (PP), nylon and polyethylene-terephthalate (PET). Copyright © 2017 Elsevier Ltd. All rights reserved.

Thermal Degradation and Combustion Behavior of Polypropylene/MWCNT Composites

NASA Astrophysics Data System (ADS)

Zaikov, G. E.; Rakhimkulov, A. D.; Lomakin, S. M.; Dubnikova, I. L.; Shchegolikhin, A. N.; Davidov, E. Ya.

2010-06-01

Studies of thermal and fire-resistant properties of the polypropylene/multi-walled carbon nanotube composites (PP/MWCNT) prepared by means of melt intercalation are discussed. The sets of the data acquired with the aid of non-isothermal TG experiments have been treated by the model kinetic analysis. The thermal-oxidative degradation behavior of PP/MWCNT and stabilizing effect caused by addition of MWCNT has been investigated by means of TGA and EPR spectroscopy. The results of cone calorimetric tests lead to the conclusion that char formation plays a key role in the mechanism of flame retardation for nanocomposites. This could be explained by the specific antioxidant properties and high thermal conductivity of MWCNT which determine high-performance carbonization during thermal degradation process. Comparative analysis of the flammability characteristics for PP-clay/MWCNT nanocomposites was provided in order to emphasize the specific behavior of the nanocomposites under high-temperature tests.

Thermal dephasing in second-harmonic generation of an amplified copper-vapor laser beam in beta barium borate.

PubMed

Prakash, Om; Dixit, Sudhir Kumar; Bhatnagar, Rajiva

2005-03-20

The conversion efficiency in second-harmonic generation of an amplified beam in a master-oscillator power amplifier copper-vapor laser (CVL) is lower than that of the oscillator beam alone. This lower efficiency is often vaguely attributed to wave-front degradation in the amplifier. We investigate the role of wave-front degradation and thermal dephasing in the second-harmonic generation of a CVL from a beta-barium borate crystal. Choosing two beams with constant intrapulse divergence, one from a generalized diffraction filtered resonator master oscillator alone and other obtained by amplifying oscillator by use of a power amplifier, we show that at low flux levels the decrease in efficiency is due to wave-front degradation. At a fundamental power above the critical power for thermal dephasing, the decrease is due to increased UV absorption and consequent thermal dephasing. Thermal dephasing is higher for the beam with the lower coherence width.

Protective and Heat Retention Effects of Thermo-sensitive Basement Membrane Extract (Matrigel) in Hepatic Radiofrequency Ablation in an Experimental Animal Study.

PubMed

Fu, Jing-Jing; Wang, Song; Yang, Wei; Gong, Wei; Jiang, An-Na; Yan, Kun; Chen, Min-Hua

2017-07-01

To evaluate the protective effect of using thermo-sensitive basement membrane extract (Matrigel) for hydrodissection to minimize thermal injury to nearby structures and to evaluate its heat sink effect on the ablation zone in radiofrequency ablation (RFA) of the liver. First, the viscosity profile and heat sink effect of Matrigel were assessed during RFA in vitro and ex vivo. Fresh pig liver tissue was used, and the temperature changes in Matrigel and in 5% dextrose in water (D5W) during RFA were recorded. Then, the size of the ablation zone in the peripheral liver after RFA was measured. Second, in an in vivo study, 45 Sprague-Dawley rats were divided into three groups of 15 rats each (Matrigel, D5W and control). In the experimental groups, artificial ascites with 10 ml of Matrigel or D5W were injected using ultrasound guidance prior to RFA. The frequency of thermal injury to the nearby organs was compared among the three groups, with assessments of several locations: near the diaphragm, the abdominal wall and the gastrointestinal (GI) tract. Finally, the biological degradation of Matrigel by ultrasound was evaluated over 60 days. First, Matrigel produced a greater heat retention (less heat sink) effect than D5W during ex vivo ablation (63 ± 9 vs. 26 ± 6 °C at 1 min on the surface of the liver, P < 0.001). Hepatic ablation zone volume did not differ between the two groups. Second, thermal injury to the nearby structures was found in 14 of 15 cases (93.3%) in the control group, 8 of 15 cases (53.3%) in the D5W group, and 1 of 15 cases (6.7%) in the Matrigel group. Significant differences in the thermal injury rates for nearby structures were detected among the three groups (P < 0.001). The most significant difference in the thermal injury rate was found in locations near the GI tract (P = 0.003). Finally, Matrigel that was injected in vivo was gradually degraded during the following 60 days. Using thermo-sensitive Matrigel as a hydrodissection material might help reduce the frequency of collateral thermal injury to nearby structures, especially in locations close to the GI tract, compared to conventional D5W. Additionally, Matrigel did not increase the heat sink effect on the ablation zone during ablation and was degraded over time in vivo.

Minimizing thermal degradation in gas chromatographic quantitation of pentaerythritol tetranitrate.

PubMed

Lubrano, Adam L; Field, Christopher R; Newsome, G Asher; Rogers, Duane A; Giordano, Braden C; Johnson, Kevin J

2015-05-15

An analytical method for establishing calibration curves for the quantitation of pentaerythriol tetranitrate (PETN) from sorbent-filled thermal desorption tubes by gas chromatography with electron capture detection (TDS-GC-ECD) was developed. As PETN has been demonstrated to thermally degrade under typical GC instrument conditions, peaks corresponding to both PETN degradants and molecular PETN are observed. The retention time corresponding to intact PETN was verified by high-resolution mass spectrometry with a flowing atmospheric pressure afterglow (FAPA) ionization source, which enabled soft ionization of intact PETN eluting the GC and subsequent accurate-mass identification. The GC separation parameters were transferred to a conventional GC-ECD instrument where analytical method-induced PETN degradation was further characterized and minimized. A method calibration curve was established by direct liquid deposition of PETN standard solutions onto the glass frit at the head of sorbent-filled thermal desorption tubes. Two local, linear relationships between detector response and PETN concentration were observed, with a total dynamic range of 0.25-25ng. Published by Elsevier B.V.

Improving methane production from digested manure biofibers by mechanical and thermal alkaline pretreatment.

PubMed

Tsapekos, P; Kougias, Panagiotis G; Frison, A; Raga, R; Angelidaki, I

2016-09-01

Animal manure digestion is associated with limited methane production, due to the high content in fibers, which are hardly degradable lignocellulosic compounds. In this study, different mechanical and thermal alkaline pretreatment methods were applied to partially degradable fibers, separated from the effluent stream of biogas reactors. Batch and continuous experiments were conducted to evaluate the efficiency of these pretreatments. In batch experiments, the mechanical pretreatment improved the degradability up to 45%. Even higher efficiency was shown by applying thermal alkaline pretreatments, enhancing fibers degradability by more than 4-fold. In continuous experiments, the thermal alkaline pretreatment, using 6% NaOH at 55°C was proven to be the most efficient pretreatment method as the methane production was increased by 26%. The findings demonstrated that the methane production of the biogas plants can be increased by further exploiting the fraction of the digested manure fibers which are discarded in the post-storage tank. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

NASA Technical Reports Server (NTRS)

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.

Crosslinking of agarose bioplastic using citric acid.

PubMed

Awadhiya, Ankur; Kumar, David; Verma, Vivek

2016-10-20

We report chemical crosslinking of agarose bioplastic using citric acid. Crosslinking was confirmed using Fourier transform infrared (FTIR) spectroscopy. The effects of crosslinking on the tensile strength, swelling, thermal stability, and degradability of the bioplastic were studied in detail. The tensile strength of the bioplastic films increased from 25.1MPa for control films up to a maximum of 52.7MPa for citric acid crosslinked films. At 37°C, the amount of water absorbed by crosslinked agarose bioplastic was only 11.5% of the amount absorbed by non-crosslinked controls. Thermogravimetric results showed that the crosslinked samples retain greater mass at high temperature (>450°C) than control samples. Moreover, while the crosslinked films were completely degradable, the rate of degradation was lower compared to non-crosslinked controls. Copyright © 2016 Elsevier Ltd. All rights reserved.

Temperature sensitivity and enzymatic mechanisms of soil organic matter decomposition along an altitudinal gradient on Mount Kilimanjaro

NASA Astrophysics Data System (ADS)

Blagodatskaya, Evgenia; Blagodatsky, Sergey; Khomyakov, Nikita; Myachina, Olga; Kuzyakov, Yakov

2016-02-01

Short-term acceleration of soil organic matter decomposition by increasing temperature conflicts with the thermal adaptation observed in long-term studies. Here we used the altitudinal gradient on Mt. Kilimanjaro to demonstrate the mechanisms of thermal adaptation of extra- and intracellular enzymes that hydrolyze cellulose, chitin and phytate and oxidize monomers (14C-glucose) in warm- and cold-climate soils. We revealed that no response of decomposition rate to temperature occurs because of a cancelling effect consisting in an increase in half-saturation constants (Km), which counteracts the increase in maximal reaction rates (Vmax with temperature). We used the parameters of enzyme kinetics to predict thresholds of substrate concentration (Scrit) below which decomposition rates will be insensitive to global warming. Increasing values of Scrit, and hence stronger canceling effects with increasing altitude on Mt. Kilimanjaro, explained the thermal adaptation of polymer decomposition. The reduction of the temperature sensitivity of Vmax along the altitudinal gradient contributed to thermal adaptation of both polymer and monomer degradation. Extrapolating the altitudinal gradient to the large-scale latitudinal gradient, these results show that the soils of cold climates with stronger and more frequent temperature variation are less sensitive to global warming than soils adapted to high temperatures.

Preparation and characterization of two new forced degradation products of letrozole and development of a stability-indicating RP-LC method for its determination.

PubMed

Elkady, Ehab Farouk; Fouad, Marwa Ahmed

2015-11-01

Two new hydrolytic products of letrozole were identified and proved to be true degradation products obtained by alkaline and acidic degradation of the drug. The acid and amide forms of the nitrile groups of letrozole were prepared and identified by IR and mass spectroscopic techniques. Subsequently, a simple, precise and selective stability-indicating RPLC method was developed and validated for the determination of letrozole in the presence of its degradation products. Letrozole was subjected to alkali and acid hydrolysis, oxidation, thermal degradation and photo-degradation. The degradation products were well isolated from letrozole. The chromatographic method was achieved using gradient elution of the drug and its degradation products on a reversed phase Zorbax Eclipse C18 column (100mm x 4.6mm, 3.5 μm) using a mobile phase consisting of 0.01M KH₂PO₄and methanol at a flow rate of 1 mL min⁻¹. Quantitation was achieved with UV detection at 230 nm. Linearity, accuracy and precision were found to be acceptable over the concentration range of 0.01-80 μgmL⁻¹. The proposed method was successfully applied to the determination of letrozole in bulk, plasma and in its pharmaceutical preparation.

Investigating lithium-ion battery materials during overcharge-induced thermal runaway: an operando and multi-scale X-ray CT study.

PubMed

Finegan, Donal P; Scheel, Mario; Robinson, James B; Tjaden, Bernhard; Di Michiel, Marco; Hinds, Gareth; Brett, Dan J L; Shearing, Paul R

2016-11-16

Catastrophic failure of lithium-ion batteries occurs across multiple length scales and over very short time periods. A combination of high-speed operando tomography, thermal imaging and electrochemical measurements is used to probe the degradation mechanisms leading up to overcharge-induced thermal runaway of a LiCoO 2 pouch cell, through its interrelated dynamic structural, thermal and electrical responses. Failure mechanisms across multiple length scales are explored using a post-mortem multi-scale tomography approach, revealing significant morphological and phase changes in the LiCoO 2 electrode microstructure and location dependent degradation. This combined operando and multi-scale X-ray computed tomography (CT) technique is demonstrated as a comprehensive approach to understanding battery degradation and failure.

Fate of sulfur mustard on soil: Evaporation, degradation, and vapor emission.

PubMed

Jung, Hyunsook; Kah, Dongha; Chan Lim, Kyoung; Lee, Jin Young

2017-01-01

After application of sulfur mustard to the soil surface, its possible fate via evaporation, degradation following absorption, and vapor emission after decontamination was studied. We used a laboratory-sized wind tunnel, thermal desorber, gas chromatograph-mass spectrometry (GC-MS), and 13 C nuclear magnetic resonance ( 13 C NMR) for systematic analysis. When a drop of neat HD was deposited on the soil surface, it evaporated slowly while being absorbed immediately into the matrix. The initial evaporation or drying rates of the HD drop were found to be power-dependent on temperature and initial drop volume. Moreover, drops of neat HD, ranging in size from 1 to 6 μL, applied to soil, evaporated at different rates, with the smaller drops evaporating relatively quicker. HD absorbed into soil remained for a month, degrading eventually to nontoxic thiodiglycol via hydrolysis through the formation of sulfonium ions. Finally, a vapor emission test was performed for HD contaminant after a decontamination process, the results of which suggest potential risk from the release of trace chemical quantities of HD into the environment. Copyright © 2016 Elsevier Ltd. All rights reserved.

Gamma Irradiation and Oxidative Degradation of a Silica-Filled Silicone Elastomer

DOE PAGES

Labouriau, Andrea; Cady, Carl Mcelhinney; Gill, John T.; ...

2015-03-21

The radiation oxidative degradation of a commonly used silica-filled silicone elastomer DC745 was investigated by a series of experimental techniques. This elastomer is known to be chemically and thermally stable, but insufficient data exist on the radiation resistance. In the present work, gamma doses up to 200 kGy were applied under air at RT and 1Gy/s. Radiation chemical changes were investigated by NMR, FT-IR, Raman, and mass spectroscopy. DSC and TGA experiments probed thermal transitions and thermal stability changes with exposure dose. SEM probed variations on the surface of the elastomer, and solvent swelling methods were used to investigate changesmore » in the polymer network properties. Electron paramagnetic resonance was employed to detect and identify free radicals. Uniaxial compression load tests at variable temperatures were performed to assess changes in the material’s mechanical response as a function of radiation dose. Results demonstrate that, with increasing exposure, DC745 undergoes changes in chemistry that lead to an increase in thermal stability and cross-link density, formation of free radical species, decrease in heat of fusion and increase in stiffness at low temperatures. Taken together, these results indicate that oxidative cross-linking is the dominant radiolysis mechanism that occurs when this material is exposed to gamma irradiation in air at high dose rates.« less

Gamma Irradiation and Oxidative Degradation of a Silica-Filled Silicone Elastomer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Labouriau, Andrea; Cady, Carl Mcelhinney; Gill, John T.

The radiation oxidative degradation of a commonly used silica-filled silicone elastomer DC745 was investigated by a series of experimental techniques. This elastomer is known to be chemically and thermally stable, but insufficient data exist on the radiation resistance. In the present work, gamma doses up to 200 kGy were applied under air at RT and 1Gy/s. Radiation chemical changes were investigated by NMR, FT-IR, Raman, and mass spectroscopy. DSC and TGA experiments probed thermal transitions and thermal stability changes with exposure dose. SEM probed variations on the surface of the elastomer, and solvent swelling methods were used to investigate changesmore » in the polymer network properties. Electron paramagnetic resonance was employed to detect and identify free radicals. Uniaxial compression load tests at variable temperatures were performed to assess changes in the material’s mechanical response as a function of radiation dose. Results demonstrate that, with increasing exposure, DC745 undergoes changes in chemistry that lead to an increase in thermal stability and cross-link density, formation of free radical species, decrease in heat of fusion and increase in stiffness at low temperatures. Taken together, these results indicate that oxidative cross-linking is the dominant radiolysis mechanism that occurs when this material is exposed to gamma irradiation in air at high dose rates.« less

THERMAL DEGRADATION OF POLY (ALPHA-METHYLSTYRENE) IN SOLUTION

EPA Science Inventory

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 exami...

Efficiency degradation behaviors of current/thermal co-stressed GaN-based blue light emitting diodes with vertical-structure

NASA Astrophysics Data System (ADS)

Liu, Lilin; Ling, Minjie; Yang, Jianfu; Xiong, Wang; Jia, Weiqing; Wang, Gang

2012-05-01

With this work, we demonstrate a three-stage degradation behavior of GaN based LED chips under current/thermal co-stressing. The three stages in sequence are the initial improvement stage, the platform stage, and the rapid degradation stage, indicating that current/thermal co-stressing activates positive effects and negative ones simultaneously, and the dominant degradation mechanisms evolve with aging time. Degradation mechanisms are discussed. Electric current stress has dual characters: damaging the active layers by generating defects and at the same time improving the p-type conductivity by activating the Mg-dopant. High temperature stresses will promote the effects from electric current stresses. The activation of the Mg-dopant will saturate, whereas the generation of defects is carried on in a progressive way. Other mechanisms, such as deterioration of ohmic contacts, also operate. These mechanisms compete/cooperate with each other and evolve with aging time, resulting in the observed three-stage degradation behavior. There exist risks to predict the lifetime of LEDs by a model with a constant accelerated factor.

Forced Degradation Studies of Aloe Emodin and Emodin by HPTLC.

PubMed

Narayanan, Sindhu; Jadhav, Aruna P; Kadam, V J

2015-01-01

Anthraquinones are natural phenolic compounds, which are reported to act as anti-aging, anti-inflammatory, antioxidant, anti-cancer, laxative and antitumor agents. They are abudant in plants like candle bush, aloes, cascara bark and rhubarb. The present work was to observe the effect of different forced degradation conditions by high-performance thin layer chromatography on potential markers i.e. aloe emodin and emodin. Both aloe emodin and emodin were subjected to various forced degradation studies such as oxidation, acid and alkaline hydrolysis, photolysis, hydrolytic and thermal degradation. Aloe emodin, was more susceptible to acid hydrolysis and degradation was found to a lesser extent under thermal degradation whereas significant degradation was observed under acid hydrolysis, lesser extent was observed under alkali hydrolysis for emodin. Forced degradation studies on aloe emodin and emodin gives information about its storage and intrinsic stability conditions considering the advanced pharmaceutical aspects of formulation.

Carbon fiber content measurement in composite

NASA Astrophysics Data System (ADS)

Wang, Qiushi

Carbon fiber reinforced polymers (CFRPs) have been widely used in various structural applications in industries such as aerospace and automotive because of their high specific stiffness and specific strength. Their mechanical properties are strongly influenced by the carbon fiber content in the composites. Measurement of the carbon fiber content in CFRPs is essential for product quality control and process optimization. In this work, a novel carbonization-in-nitrogen method (CIN) is developed to characterize the fiber content in carbon fiber reinforced thermoset and thermoplastic composites. In this method, a carbon fiber composite sample is carbonized in a nitrogen environment at elevated temperatures, alongside a neat resin sample. The carbon fibers are protected from oxidization while the resin (the neat resin and the resin matrix in the composite sample) is carbonized under the nitrogen environment. The residue of the carbonized neat resin sample is used to calibrate the resin carbonization rate and calculate the amount of the resin matrix in the composite sample. The new method has been validated on several thermoset and thermoplastic resin systems and found to yield an accurate measurement of fiber content in carbon fiber polymer composites. In order to further understand the thermal degradation behavior of the high temperature thermoplastic polymer during the carbonization process, the mechanism and the kinetic model of thermal degradation behavior of carbon fiber reinforced poly (phenylene sulfide) (CPPS) are studied using thermogravimetry analysis (TGA). The CPPS is subjected to TGA in an air and nitrogen atmosphere at heating rates from 5 to 40°C min--1. The TGA curves obtained in air are different from those in nitrogen. This demonstrates that weight loss occurs in a single stage in nitrogen but in two stages in air. To elucidate this difference, thermal decomposition kinetics is analyzed by applying the Kissinger, Flynn-Wall-Ozawa, Coat-Redfern and Malek methods. The activation energy (Ea) of the solid-state process is determined to be 202 kJ mol--1 in an oxidative atmosphere using Kissinger's method, which is 10-15 kJ mol--1 more than the results calculated in a nitrogen atmosphere. The value of the activation energy obtained using Ozawa-Flynn methods is in agreement with that using the Kissinger method. Different degradation mechanisms are used to compare with this value. Based on the analytical result, the actual thermal degradation mechanism of the CPPS is a Dn deceleration type. The carbonization temperature range of the CPPS is the same as pure PPS resin.

Reliability analysis of InGaN/GaN multi-quantum-well solar cells under thermal stress

NASA Astrophysics Data System (ADS)

Huang, Xuanqi; Fu, Houqiang; Chen, Hong; Lu, Zhijian; Baranowski, Izak; Montes, Jossue; Yang, Tsung-Han; Gunning, Brendan P.; Koleske, Dan; Zhao, Yuji

2017-12-01

We investigate the thermal stability of InGaN solar cells under thermal stress at elevated temperatures from 400 °C to 500 °C. High Resolution X-Ray Diffraction analysis reveals that material quality of InGaN/GaN did not degrade after thermal stress. The external quantum efficiency characteristics of solar cells were well-maintained at all temperatures, which demonstrates the thermal robustness of InGaN materials. Analysis of current density-voltage (J-V) curves shows that the degradation of conversion efficiency of solar cells is mainly caused by the decrease in open-circuit voltage (Voc), while short-circuit current (Jsc) and fill factor remain almost constant. The decrease in Voc after thermal stress is attributed to the compromised metal contacts. Transmission line method results further confirmed that p-type contacts became Schottky-like after thermal stress. The Arrhenius model was employed to estimate the failure lifetime of InGaN solar cells at different temperatures. These results suggest that while InGaN solar cells have high thermal stability, the degradation in the metal contact could be the major limiting factor for these devices under high temperature operation.

Accelerated Aging Experiments for Capacitor Health Monitoring and Prognostics

NASA Technical Reports Server (NTRS)

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

2012-01-01

This paper discusses experimental setups for health monitoring and prognostics of electrolytic capacitors under nominal operation and accelerated aging conditions. Electrolytic capacitors have higher failure rates than other components in electronic systems like power drives, power converters etc. Our current work focuses on developing first-principles-based degradation models for electrolytic capacitors under varying electrical and thermal stress conditions. Prognostics and health management for electronic systems aims to predict the onset of faults, study causes for system degradation, and accurately compute remaining useful life. Accelerated life test methods are often used in prognostics research as a way to model multiple causes and assess the effects of the degradation process through time. It also allows for the identification and study of different failure mechanisms and their relationships under different operating conditions. Experiments are designed for aging of the capacitors such that the degradation pattern induced by the aging can be monitored and analyzed. Experimental setups and data collection methods are presented to demonstrate this approach.

Thermal decomposition of wood: kinetics and degradation mechanisms.

PubMed

Poletto, Matheus; Zattera, Ademir J; Santana, Ruth M C

2012-12-01

The influence of wood components and cellulose crystallinity on the kinetic degradation of different wood species has been investigated using thermogravimetry. Four wood species were studied: Pinus elliottii (PIE), Eucalyptus grandis (EUG), Mezilaurus itauba (ITA) and Dipteryx odorata (DIP). Thermogravimetric results showed that higher extractive contents in the wood accelerate the degradation process and promote an increase in the conversion values at low temperatures. Alternatively, the results indicated that the cellulose crystallinity inhibits wood degradation; organized cellulose regions slow the degradation process because the well-packed cellulose chains impede heat diffusion, which improves the wood's thermal stability. The wood degradation mechanism occurs by diffusion processes when the conversion values are below 0.4. When the conversion values are above 0.5, the degradation is a result of random nucleation with one nucleus in each particle. Copyright © 2012 Elsevier Ltd. All rights reserved.

Experimental Study of Turbine Fuel Thermal Stability in an Aircraft Fuel System Simulator

NASA Technical Reports Server (NTRS)

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.

Thermal degradation events as health hazards - Particle vs gas phase effects, mechanistic studies with particles

NASA Technical Reports Server (NTRS)

Oberdoerster, G.; Ferin, J.; Finkelstein, J.; Soderholm, S.

1992-01-01

Experiments on animal subjects are performed to demonstrate that significant lung injury can result from the inhalation of ultrafine TiO2 or Al2O3 particles. The methods include intratracheal instillation of particles, long-term inhalation of particles, and in vitro studies of alveolar macrophages (AMs) to study the production of fibroplast growth factors. The ultrafine TiO2 particles are shown to induce more acute inflammatory reactions than larger particles and lead to persistent chronic effects in the AM-mediated clearance function of particles. The ultrafine particles also induce cytokines more readily, and the data generally suggests that the occurrence of such particles in thermal degradation events makes the fumes highly toxic. The exposure to thermal degradation products is therefore a critical concern for manned space missions with potentially degradable plastic products.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Pankaj, E-mail: pankaj@mail.nplindia.ernet.in; Centre for Organic Electronics, Physics, University of Newcastle, Callaghan NSW-2308; Bilen, Chhinder

The degradation and thermal regeneration of poly(3-hexylethiophene) (P3HT):[6,6]-phenyl-C{sub 61}-butyric acid methyl ester (PCBM) and P3HT:indene-C{sub 60} bisadduct (ICBA) polymer solar cells, with Ca/Al and Ca/Ag cathodes and indium tin oxide/poly(ethylene-dioxythiophene):polystyrene sulfonate anode have been investigated. Degradation occurs via a combination of three primary pathways: (1) cathodic oxidation, (2) active layer phase segregation, and (3) anodic diffusion. Fully degraded devices were subjected to thermal annealing under inert atmosphere. Degraded solar cells possessing Ca/Ag electrodes were observed to regenerate their performance, whereas solar cells having Ca/Al electrodes exhibited no significant regeneration of device characteristics after thermal annealing. Moreover, the solar cells withmore » a P3HT:ICBA active layer exhibited enhanced regeneration compared to P3HT:PCBM active layer devices as a result of reduced changes to the active layer morphology. Devices combining a Ca/Ag cathode and P3HT:ICBA active layer demonstrated ∼50% performance restoration over several degradation/regeneration cycles.« less

Crew Launch Vehicle Mobile Launcher Solid Rocket Motor Plume Induced Environment

NASA Technical Reports Server (NTRS)

Vu, Bruce T.; Sulyma, Peter

2008-01-01

The plume-induced environment created by the Ares 1 first stage, five-segment reusable solid rocket motor (RSRMV) will impose high heating rates and impact pressures on Launch Complex 39. The extremes of these environments pose a potential threat to weaken or even cause structural components to fail if insufficiently designed. Therefore the ability to accurately predict these environments is critical to assist in specifying structural design requirements to insure overall structural integrity and flight safety. This paper presents the predicted thermal and pressure environments induced by the launch of the Crew Launch Vehicle (CLV) from Launch Complex (LC) 39. Once the environments are predicted, a follow-on thermal analysis is required to determine the surface temperature response and the degradation rate of the materials. An example of structures responding to the plume-induced environment will be provided.

Thermal degradation of wood fibers during hot-pressing of MDF composites. Part I, Relative effects and benefits of thermal exposure

Treesearch

Jerrold E. Winandy; Andrzej M. Krzysik

2007-01-01

This research evaluated the potential of wood fiber to chemically decompose during hot-pressing. We evaluated changes in carbohydrate composition and structure as a function of multiple press temperatures (180°, 200°, and 220°C) and an array of hot-pressing durations from 180 to 2500 s. Results show how this thermal degradation in chemical composition directly results...

Guidance and Control of an Autonomous Soaring Vehicle with Flight Test Results

NASA Technical Reports Server (NTRS)

Allen, Michael J.

2007-01-01

A guidance and control method was developed to detect and exploit thermals for energy gain. Latency in energy rate estimation degraded performance. The concept of a UAV harvesting energy from the atmosphere has been shown to be feasible with existing technology. Many UAVs have similar mission constraints to birds and sailplanes. a) Surveillance; b) Point to point flight with minimal energy; and c) Increased ground speed.

Experimental investigation of a packed bed thermal energy storage system

NASA Astrophysics Data System (ADS)

Cascetta, Mario; Cau, Giorgio; Puddu, Pierpaolo; Serra, Fabio

2015-11-01

In this work experimental investigations on a thermal energy storage system with a solid material as storage media and air as heat transfer fluid will be presented. The experimental test rig, installed at the DIMCM of the University of Cagliari, consists of a carbon steel tank filled with freely poured alumina beads that allows investigations of heat transfer phenomena in packed beds. The aim of this work is to show the influence of the operating conditions and physical parameters on thermocline formation and, in particular, the thermal behaviour of the thermal energy storage for repeated charging and discharging cycles. Better charging efficiency is obtained for lower values of mass flow rate and maximum air temperature and for increasing aspect ratio. A decreasing influence of the metal wall with continuous operation is also highlighted. In conclusion, the analysis focuses on the thermal hysteresis phenomenon, which causes degradation of the thermocline and the reduction of the energy that can be stored by the accumulator as the repeated number of cycles increases.

Geospatial tools for assessing land degradation in Budgam district, Kashmir Himalaya, India

NASA Astrophysics Data System (ADS)

Rashid, Mehnaz; Lone, Mahjoor Ahmad; Romshoo, Shakil Ahmad

2011-06-01

Land degradation reduces the ability of the land to perform many biophysical and chemical functions. The main aim of this study was to determine the status of land degradation in the Budgam area of Kashmir Himalaya using remote sensing and geographic information system. The satellite data together with other geospatial datasets were used to quantify different categories of land degradation. The results were validated in the field and an accuracy of 85% was observed. Land use/land cover of the study area was determined in order to know the effect of land use on the rate of land degradation. Normalized differential vegetation index (NDVI) and slope of the area were determined using LANDSAT-enhanced thematic mapper plus (ETM+) data, advanced space borne thermal emission and reflection radiometer, and digital elevation model along with other secondary data were analysed to create various thematic maps, viz., land use/land cover, geology, NDVI and slopes used in modelling land degradation in the Kashmir Himalayan region. The vegetation condition, elevation and land use/land cover information of the area were integrated to assess the land degradation scenario in the area using the ArcGIS `Spatial Analyst Module'. The results reveal that about 13.19% of the study area has undergone moderate to high degradation, whereas about 44.12% of the area has undergone slight degradation.

Monitoring the degradation of physical properties and fire hazards of high-impact polystyrene composite with different ageing time in natural environments.

PubMed

Wang, Bibo; Zhang, Yan; Tao, Youji; Zhou, Xia; Song, Lei; Jie, Ganxin; Hu, Yuan

2018-06-15

The current study aims at monitoring the role of the different natural environments on the physical properties and fire hazards of HIPS composites ageing in Turpan and Qionghai. The results indicated that the chromatic aberration and degradation of surface appearance intensified with the increasing ageing time. More flame retardants migrated and were eroded for HIPS composites ageing in Qionghai than those ageing in Turpan, which was caused by the combination of sunlight, high temperature and rainwater in Qionghai. After degradation in the natural environments, the HIPS composites possessed the lower thermal stability and char residues, more toxic gases release, higher peak heat release rate and fire hazard. For example, the peak heat release rate in Qionghai increased by 88.9%, which is much higher than that of in Turpan (55.6%). Moreover, the tensile strength and elongation at break decreased by 46% and 59% for HIPS composites ageing in Turpan and reduced by 53% and 67% for HIPS composites aged in Qionghai, respectively. The results demonstrate that more serious degradation of physical properties and higher fire hazard for HIPS composites ageing in Qionghai than those in Turpan due to the different natural ageing environments. Copyright © 2018 Elsevier B.V. All rights reserved.

Thermal and oxidative degradation studies of formulated C-ethers by gel-permeation chromatography

NASA Technical Reports Server (NTRS)

Jones, W. R., Jr.; Morales, W.

1982-01-01

Gel-permeation chromatography was used to analyze C-ether lubricant formulations from high-temperature bearing tests and from micro-oxidation tests. Three mu-styragel columns (one 500 and two 100 A) and a tetrahydrofuran mobile phase were found to adequately separate the C-ether degradation products. The micro-oxidation tests yielded degradation results qualitatively similar to those observed from the bearing tests. Micro-oxidation tests conducted in air yielded more degradation than did tests in nitrogen. No great differences were observed between the thermal-oxidative stabilities of the two C-ether formulations or between the catalytic degradation activities of silver and M-50 steel. C-ether formulation I did yield more degradation than did formulation II in 111- and 25-hour bearing tests, respectively.

Identification and differentiation of methcathinone analogs by gas chromatography-mass spectrometry.

PubMed

Tsujikawa, Kenji; Mikuma, Toshiyasu; Kuwayama, Kenji; Miyaguchi, Hajime; Kanamori, Tatsuyuki; Iwata, Yuko T; Inoue, Hiroyuki

2013-08-01

To overcome a number of challenges involved in analyzing methcathinone (MC) analogues, we performed gas chromatography-mass spectrometry (GC-MS) analysis, including sample preparation, of nine MC analogues - 4-methylmethcathinone, three positional isomers of fluoromethcathinones, 4-methoxymethcathinone, N-ethylcathinone, N,N-dimethylcathinone, buphedrone, and pentedrone. The MC analogues underwent dehydrogenation when the free bases were analyzed using splitless injection. Most of this thermal degradation was prevented using split injection. This indicated that a shorter residence time in the hot injector prevented decomposition. Uniquely, 2-fluoromethcathinone degraded to another product in a process that could not be prevented by the split injection. Replacing the liner with a new, clean one was also effective in preventing thermal degradation. Most of the analytes showed a substantial loss (>30%) when the free base solution in ethyl acetate was evaporated under a nitrogen stream. Adding a small amount of dimethylformamide as a solvent keeper had a noticeable effect, but it did not completely prevent the loss. Three positional isomers of fluoromethcathinones were separated with baseline resolution by heptafluorobutyrylation with a slow column heating rate (8 °C/min) using a non-polar DB-5 ms capillary column. These results will be useful for the forensic analysis of MC analogues in confiscated materials. Copyright © 2012 John Wiley & Sons, Ltd.

Native Cellulose: Structure, Characterization and Thermal Properties

PubMed Central

Poletto, Matheus; Ornaghi Júnior, Heitor L.; Zattera, Ademir J.

2014-01-01

In this work, the relationship between cellulose crystallinity, the influence of extractive content on lignocellulosic fiber degradation, the correlation between chemical composition and the physical properties of ten types of natural fibers were investigated by FTIR spectroscopy, X-ray diffraction and thermogravimetry techniques. The results showed that higher extractive contents associated with lower crystallinity and lower cellulose crystallite size can accelerate the degradation process and reduce the thermal stability of the lignocellulosic fibers studied. On the other hand, the thermal decomposition of natural fibers is shifted to higher temperatures with increasing the cellulose crystallinity and crystallite size. These results indicated that the cellulose crystallite size affects the thermal degradation temperature of natural fibers. This study showed that through the methods used, previous information about the structure and properties of lignocellulosic fibers can be obtained before use in composite formulations. PMID:28788179

Sonochemical degradation of perfluorooctanesulfonate in aqueous film-forming foams.

PubMed

Vecitis, Chad D; Wang, Yajuan; Cheng, Jie; Park, Hyunwoong; Mader, Brian T; Hoffmann, Michael R

2010-01-01

Aqueous film-forming foams (AFFFs) are fire extinguishing agents developed by the Navy to quickly and effectively combat fires occurring close to explosive materials and are utilized today at car races, airports, oil refineries, and military locations. Fluorochemical (FC) surfactants represent 1-5% of the AFFF composition, which impart properties such as high spreadability, negligible fuel diffusion, and thermal stability to the foam. FC's are oxidatively recalcitrant, persistent in the environment, and have been detected in groundwater at AFFF training sites. Ultrasonic irradiation of aqueous FCs has been reported to degrade and subsequently mineralize the FC surfactants perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS). Here we present results of the sonochemical degradation of aqueous dilutions of FC-600, a mixture of hydrocarbon (HC) and fluorochemical components including cosolvents, anionic hydrocarbon surfactants, fluorinated amphiphilic surfactants, anionic fluorinated surfactants, and thickeners such as starch. The primary FC surfactant in FC-600, PFOS, was sonolytically degraded over a range of FC-600 aqueous dilutions, 65 ppb < [PFOS]i < 13100 ppb. Sonochemical PFOS-AFFF decomposition rates, RAFFF-PFOS, are similar to PFOS-Milli-Q rates, RMQ-PFOS, indicating that the AFFF matrix only had a minor effect on the sonochemical degradation rate, 0.5 < RAFFF-PFOS/RMQ-PFOS < 2.0, even though the total organic concentration was 50 times the PFOS concentration, [Org]tot/[PFOS] 50, consistent with the superior FC surfactant properties. Sonochemical sulfate production is quantitative, delta[SO42-]/delta[PFOS] > or = 1, indicating that bubble-water interfacial pyrolytic cleavage of the C-S bond in PFOS is the initial degradation step, in agreement with previous studies done in Milli-Q water. Sonochemical fluoride production is significantly below quantitative expectations, delta[F-]/delta[PFOS] 4 vs 17, suggesting that in the AFFF matrix, PFOS' fluorochemical tail is not completely degraded, whereas Milli-Q studies yielded quantitative F- production. Measurements of time-dependent methylene blue active substances and total organic carbon indicate that the other FC-600 components were also sonolytically decomposed.

Degradation of a Multilayer Insulation Due to a Seam and a Penetration

NASA Technical Reports Server (NTRS)

Sumner, I. E.

1976-01-01

The degradation of the thermal performance of a multilayer insulation due to the presence of a seam and a penetration was studied. The multilayer insulation had 30 aluminized Mylar radiation shields with silk net spacers. The seam, an offset butt joint, caused a heat input of 0.169 watt per meter in addition to the basic insulation thermal performance of 0.388 watt per square meter obtained before the installation of the butt joint. The penetration, a fiberglass tank support strut, provided a heat input (including the degradation of the insulation) of 0.543 watt in addition to the basic insulation thermal performance of 0.452 watt per square meter obtained before the penetration.

Thermal degradation kinetics of anthocyanins from blood orange, blackberry, and roselle using the arrhenius, eyring, and ball models.

PubMed

Cisse, Mady; Vaillant, Fabrice; Acosta, Oscar; Dhuique-Mayer, Claudie; Dornier, Manuel

2009-07-22

Anthocyanin stability was assessed over temperatures ranging from 30 to 90 degrees C for seven products: blood orange juice [Citrus sinensis (L.) Osbeck]; two tropical highland blackberry juices (Rubus adenotrichus Schlech.), one with high content and the other with low content of suspended insoluble solids (SIS); and four roselle extracts (Hibiscus sabdariffa L.). The blackberry juice showed the highest content of anthocyanins with 1.2 g/L (two times less in the roselle extracts and 12 times less in the blood orange juice). The rate constant for anthocyanin degradation and isothermal kinetic parameters were calculated according to three models: Arrhenius, Eyring, and Ball. Anthocyanins in blood orange juice presented the highest rate constant for degradation, followed by the blackberry juices and roselle extracts. Values of activation energies were 66 and 37 kJ/mol, respectively, for blood orange and blackberry and 47-61 kJ/mol for roselle extracts. For the blackberry juices, a high SIS content provided only slight protection for the anthocyanins. The increasing content of dissolved oxygen, from 0.5 to 8.5 g/L, did not significantly increase the rate constant. For both isothermal and nonisothermal treatments, all three models accurately predicted anthocyanin losses from different food matrices.

Heavy Ion Induced Degradation in SiC Schottky Diodes: Bias and Energy Deposition Dependence

NASA Technical Reports Server (NTRS)

Javanainen, Arto; Galloway, Kenneth F.; Nicklaw, Christopher; Bosser, Alexandre L.; Ferlet-Cavrois, Veronique; Lauenstein, Jean-Marie; Pintacuda, Francesco; Reed, Robert A.; Schrimpf, Ronald D.; Weller, Robert A.;

Thermally Altered Silurian Cyanobacterial Mats: A Key to Earth's Oldest Fossils

NASA Astrophysics Data System (ADS)

Kazmierczak, Józef; Kremer, Barbara

2009-10-01

Diagenetic changes in thermally altered cyanobacterial mats from early Silurian black radiolarian cherts of southwestern Poland (Bardzkie Montains, Sudetes) have been studied. These early diagenetically silicified mats are composed of variously degraded remains of benthic microbes that resemble some modern chroococcalean and pleurocapsalean cyanobacteria. Two modes of degradational processes have been recognized in the studied mats: (i) early postmortem biodegradation and (ii) late diagenetic thermal or thermobaric degradation. The latter led to partial transformation of the fossilized organic remnants of cyanobacterial sheaths and capsules, which resulted in the formation of objects morphologically distant from the original microbiota but preserved features that allow for their identification as bona fide biogenic structures. Some of these thermally generated Silurian fossils are highly similar to the controversial microfossil-like carbonaceous structures described from the Early Archean Apex Chert of Australia. This similarity opens a promising way for credible recognition of remnants of cyanobacteria and similar microbiota in other thermally metamorphosed Archean sedimentary rocks

Wood Products Thermal Degradation and Fire

Treesearch

Mark Dietenberger; Laura Hasburgh

2016-01-01

As wood reaches elevated temperatures, the different chemical components undergo thermal degradation that affect the performance of wood. The extent of these changes depends on the temperature level and length of time under exposure conditions. Permanent reductions in strength and modulus of elasticity can occur at temperatures >65 °C, with the amount depending...

Study of the thermal degradation mechanism of a composite propellant. [using electron microscopes

NASA Technical Reports Server (NTRS)

Schmidt, W. G.

1975-01-01

The current experimental program was designed to systematically investigate the role of the oxidizer in the thermal degradation process of composite propellants. The scanning electron microscope (SEM) was used to examine the failure sites in thermally degraded propellant samples. The formulation variables tested were oxidizer purity, oxidizer particle size, and oxidizer to binder bonding agent. The binder, a saturated hydrocarbon, was kept constant throughout the experiments. The oxidizers were: AP, chlorate-doped AP, arsenate-doped AP, and phosphate-doped AP. The oxidizer particle size distribution was 60% of the large fraction and 40% of the small fraction. The bonding agent, when present, was used at the 0.15% level. The data showed that both the oxidizer purity and particle size had an important affect on the thermal degradation process. The affect of the oxidizer particle size was more noticeable at the higher temperature and stress levels. An examination of the failure site, by SEM, of propellants subject to these latter conditions indicated that the fracturing of the large oxidizer particles led to the propellant cracking.

High temperature degradation mechanism of a red phosphor, CaAlSiN3:Eu for solid-state lighting

NASA Astrophysics Data System (ADS)

Oishi, Masatsugu; Shiomi, Shohei; Yamamoto, Takashi; Ueki, Tomoyuki; Kai, Yoichiro; Chichibu, Shigefusa F.; Takatori, Aiko; Kojima, Kazunobu

2017-09-01

Thermal properties of a red phosphor CaAlSiN3:Eu (CASN) at elevated temperatures were evaluated. A heat treatment at 800 °C degraded the photoluminescence property of CASN and caused irreversible changes in both the excitation and emission intensities. The heat treatment in air simultaneously decreased the N elements and increased the O elements. Consequently, the Eu2+ luminescence center was oxidized and CASN lost its photoluminescence property. Although the crystal structure of CASN host was stable even after the heat treatments, the local structure change around the Eu2+ ions is the origin of the thermal degradation of CASN. We found that the heat treatment in N2 atmosphere suppresses the thermal degradation. This is due to the suppression of N evolutions and the incorporation of O elements, which sustains the optically active Eu2+ state.

Effect of Solar Exposure on the Atomic Oxygen Erosion of Hubble Space Telescope Aluminized-Teflon Thermal Shields

NASA Astrophysics Data System (ADS)

Guo, Aobo; Ashmead, Claire C.; de Groh, Kim K.; Sechkar, Edward A.

When exposed to low Earth orbit (LEO) environment, external spacecraft materials degrade due to radiation, thermal cycling, micrometeoroid and debris impacts, and interaction with atomic oxygen (AO). Collisions between AO and spacecraft can result in oxidation of external spacecraft surface materials, which can lead to erosion and severe structural and/or optical properties deterioration. It is therefore essential to understand the AO erosion yield (Ey), the volume loss per incident oxygen atom (cm3/atom) of polymers to assure durability of spacecraft materials. The objective of this study was to determine whether solar radiation exposure can increase the rate of AO erosion of polymers in LEO. The material studied was a section of aluminized-Teflon® fluorinated ethylene propylene (Al-FEP) thermal shield exposed to space on the Hubble Space Telescope (HST) for 8.25 years. Retrieved samples were sectioned from the circular thermal shield and exposed to ground laboratory thermal energy AO. The results indicate that the average Ey of the solar facing HST Al-FEP was 1.9 × 10-24 cm3/atom, while the average Ey of the anti-solar HST Al-FEP was 1.5 × 10-24 cm3/atom. The Ey of the pristine samples was 1.6 to 1.7 × 10-24 cm3/atom. These results indicate that solar exposure affects the post-flight erosion rate of FEP in a plasma asher. Therefore, it likely affects the erosion rate while in LEO.

Effect of Solar Exposure on the Atomic Oxygen Erosion of Hubble Space Telescope Aluminized-Teflon Thermal Shields

NASA Technical Reports Server (NTRS)

Guo, Aobo; Ashmead, Claire C.; deGroh, Kim K.

2012-01-01

When exposed to low Earth orbital (LEO) environment, external spacecraft materials degrade due to radiation, thermal cycling, micrometeoroid and debris impacts, and atomic oxygen (AO) interaction. Collisions between AO and spacecraft can result in oxidation of external spacecraft surface materials, which can lead to erosion and severe structural and/or optical property deterioration. It is therefore essential to understand the AO erosion yield (Ey), the volume loss per incident oxygen atom (cu cm/atom), of polymers to assure durability of spacecraft materials. The objective of this study was to determine whether solar radiation exposure can increase the rate of AO erosion of polymers in LEO. The material studied was a section of aluminized-Teflon (DuPont) fluorinated ethylene propylene (Al-FEP) thermal shield exposed to space on the Hubble Space Telescope (HST) for 8.25 years. Retrieved samples were sectioned from the circular thermal shield and exposed to ground laboratory thermal energy AO. The results indicate that the average Ey of the solar facing HST Al-FEP was 1.9 10(exp -24)cu cm/atom, while the average Ey of the anti-solar HST Al-FEP was 1.5 10(exp -24)cu cm/atom. The Ey of the pristine samples was 1.6- 1.7 10(exp -24)cu cm/atom. These results indicate that solar exposure affects the post-flight erosion rate of FEP in a plasma asher. Therefore, it likely affects the erosion rate while in LEO.

Interplay of Interfacial Layers and Blend Composition To Reduce Thermal Degradation of Polymer Solar Cells at High Temperature.

PubMed

Ben Dkhil, Sadok; Pfannmöller, Martin; Schröder, Rasmus R; Alkarsifi, Riva; Gaceur, Meriem; Köntges, Wolfgang; Heidari, Hamed; Bals, Sara; Margeat, Olivier; Ackermann, Jörg; Videlot-Ackermann, Christine

2018-01-31

The thermal stability of printed polymer solar cells at elevated temperatures needs to be improved to achieve high-throughput fabrication including annealing steps as well as long-term stability. During device processing, thermal annealing impacts both the organic photoactive layer, and the two interfacial layers make detailed studies of degradation mechanism delicate. A recently identified thermally stable poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl

Self-Healable Electrical Insulation for High Voltage Applications

NASA Technical Reports Server (NTRS)

Williams, Tiffany S.

2017-01-01

Polymeric aircraft electrical insulation normally degrades by partial discharge with increasing voltage, which causes excessive localized Joule heating in the material and ultimately leads to dielectric failure of the insulator through thermal breakdown. Developing self-healing insulation could be a viable option to mitigate permanent mechanical degradation, thus increasing the longevity of the insulation. Instead of relying on catalyst and monomer-filled microcapsules to crack, flow, and cure at the damaged sites described in well-published mechanisms, establishment of ionic crosslinks could allow for multiple healing events to occur with the added benefit of achieving full recovery strength under certain thermal environments. This could be possible if the operating temperature of the insulator is the same as or close to the temperature where ionic crosslinks are formed. Surlyn, a commercial material with ionic crosslinks, was investigated as a candidate self-healing insulator based off prior demonstrations of self-healing behavior. Thin films of varying thicknesses were investigated and the effects of thickness on the dielectric strength were evaluated and compared to representative polymer insulators. The effects of thermal conditioning on the recovery strength and healing were observed as a function of time following dielectric breakdown. Moisture absorption was also studied to determine if moisture absorption rates in Surlyn were lower than that of common polyimides.

Reduced graphene oxide enwrapped phosphors for long-term thermally stable phosphor converted white light emitting diodes

NASA Astrophysics Data System (ADS)

Anoop, Gopinathan; Rani, Janardhanan R.; Lim, Juhwan; Jang, Myoung Soo; Suh, Dong Wook; Kang, Shinill; Jun, Seong Chan; Yoo, Jae Soo

2016-09-01

The long-term instability of the presently available best commercial phosphor-converted light-emitting diodes (pcLEDs) is the most serious obstacle for the realization of low-cost and energy-saving lighting applications. Emission from pcLEDs starts to degrade after approximately 200 h of operation because of thermal degradation of the phosphors. We propose a new strategy to overcome this thermal degradation problem of phosphors by wrapping the phosphor particles with reduced graphene oxide (rGO). Through the rGO wrapping, we have succeeded in controlling the thermal degradation of phosphors and improving the stability of fabricated pcLEDs. We have fabricated pcLEDs with long-term stability that maintain nearly 98% of their initial luminescence emission intensity even after 800 h of continuous operation at 85 °C and 85% relative humidity. The pcLEDs fabricated using SrBaSi2O2N2:Eu2+ phosphor particles wrapped with reduced graphene oxide are thermally stable because of enhanced heat dissipation that prevents the ionization of Eu2+ to Eu3+. We believe that this technique can be applied to other rare-earth doped phosphors for the realization of highly efficient and stable white LEDs.

Investigation of Thermally Induced Degradation in CH3NH3PbI3 Perovskite Solar Cells using In-situ Synchrotron Radiation Analysis.

PubMed

Kim, Nam-Koo; Min, Young Hwan; Noh, Seokhwan; Cho, Eunkyung; Jeong, Gitaeg; Joo, Minho; Ahn, Seh-Won; Lee, Jeong Soo; Kim, Seongtak; Ihm, Kyuwook; Ahn, Hyungju; Kang, Yoonmook; Lee, Hae-Seok; Kim, Donghwan

2017-07-05

In this study, we employ a combination of various in-situ surface analysis techniques to investigate the thermally induced degradation processes in MAPbI 3 perovskite solar cells (PeSCs) as a function of temperature under air-free conditions (no moisture and oxygen). Through a comprehensive approach that combines in-situ grazing-incidence wide-angle X-ray diffraction (GIWAXD) and high-resolution X-ray photoelectron spectroscopy (HR-XPS) measurements, we confirm that the surface structure of MAPbI 3 perovskite film changes to an intermediate phase and decomposes to CH 3 I, NH 3 , and PbI 2 after both a short (20 min) exposure to heat stress at 100 °C and a long exposure (>1 hour) at 80 °C. Moreover, we observe clearly the changes in the orientation of CH 3 NH 3 + organic cations with respect to the substrate in the intermediate phase, which might be linked directly to the thermal degradation processes in MAPbI 3 perovskites. These results provide important progress towards improved understanding of the thermal degradation mechanisms in perovskite materials and will facilitate improvements in the design and fabrication of perovskite solar cells with better thermal stability.

Thermal degradation of cloudy apple juice phenolic constituents.

PubMed

De Paepe, D; Valkenborg, D; Coudijzer, K; Noten, B; Servaes, K; De Loose, M; Voorspoels, S; Diels, L; Van Droogenbroeck, B

2014-11-01

Although conventional thermal processing is still the most commonly used preservation technique in cloudy apple juice production, detailed knowledge on phenolic compound degradation during thermal treatment is still limited. To evaluate the extent of thermal degradation as a function of time and temperature, apple juice samples were isothermally treated during 7,200s over a temperature range of 80-145 °C. An untargeted metabolomics approach based on liquid chromatography-high resolution mass spectrometry was developed and applied with the aim to find out the most heat labile phenolic constituents in cloudy apple juice. By the use of a high resolution mass spectrometer, the high degree of in-source fragmentation, the quality of deconvolution and the employed custom-made database, it was possible to achieve a high degree of structural elucidation for the thermolabile phenolic constituents. Procyanidin subclass representatives were discovered as the most heat labile phenolic compounds of cloudy apple juice. Copyright © 2014. Published by Elsevier Ltd.

Challenges in GC-MS analysis: Case studies on phenibut and ethylphenidate.

PubMed

Lee, Hui Zhi Shirley; Ong, Mei Ching; Lim, Jong Lee Wendy; Yap, Tiong Whei Angeline

2017-08-01

The challenges associated with drug analysis using GC-MS such as thermal degradation, cyclisation or unwanted side reactions causing potential erroneous identification have become evident in view of the high surge in new drugs available in the market. Two case studies illustrated how alternative methods or modifications to existing techniques can help to circumvent the limitations. In the first case study, phenibut which is a GABA analogue, cyclises to 4-phenyl-2-pyrrolidinone under thermal conditions. The identification of phenibut was achieved through derivatisation and identification of its TMS derivative. The second case study, thermal degradation was minimised on drugs of interest methylphenidate and ethylphenidate by reducing the injector port temperature to 200°C and maintaining the GC oven temperature at below 190°C in order to prevent thermal degradation of the drugs of interest. Copyright © 2017 Elsevier B.V. All rights reserved.

α-Amino acid containing degradable polymers as functional biomaterials: rational design, synthetic pathway, and biomedical applications.

PubMed

Sun, Huanli; Meng, Fenghua; Dias, Aylvin A; Hendriks, Marc; Feijen, Jan; Zhong, Zhiyuan

2011-06-13

Currently, biomedical engineering is rapidly expanding, especially in the areas of drug delivery, gene transfer, tissue engineering, and regenerative medicine. A prerequisite for further development is the design and synthesis of novel multifunctional biomaterials that are biocompatible and biologically active, are biodegradable with a controlled degradation rate, and have tunable mechanical properties. In the past decades, different types of α-amino acid-containing degradable polymers have been actively developed with the aim to obtain biomimicking functional biomaterials. The use of α-amino acids as building units for degradable polymers may offer several advantages: (i) imparting chemical functionality, such as hydroxyl, amine, carboxyl, and thiol groups, which not only results in improved hydrophilicity and possible interactions with proteins and genes, but also facilitates further modification with bioactive molecules (e.g., drugs or biological cues); (ii) possibly improving materials biological properties, including cell-materials interactions (e.g., cell adhesion, migration) and degradability; (iii) enhancing thermal and mechanical properties; and (iv) providing metabolizable building units/blocks. In this paper, recent developments in the field of α-amino acid-containing degradable polymers are reviewed. First, synthetic approaches to prepare α-amino acid-containing degradable polymers will be discussed. Subsequently, the biomedical applications of these polymers in areas such as drug delivery, gene delivery and tissue engineering will be reviewed. Finally, the future perspectives of α-amino acid-containing degradable polymers will be evaluated.

Degradation Kinetics Study of Alogliptin Benzoate in Alkaline Medium by Validated Stability-Indicating HPTLC Method.

PubMed

Bodiwala, Kunjan Bharatkumar; Shah, Shailesh; Thakor, Jeenal; Marolia, Bhavin; Prajapati, Pintu

2016-11-01

A rapid, sensitive, and stability-indicating high-performance thin-layer chromatographic method was developed and validated to study degradation kinetics of Alogliptin benzoate (ALG) in an alkaline medium. ALG was degraded under acidic, alkaline, oxidative, and thermal stress conditions. The degraded samples were chromatographed on silica gel 60F254-TLC plates, developed using a quaternary-solvent system (chloroform-methanol-ethyl acetate-triethyl amine, 9+1+1+0.5, v/v/v/v), and scanned at 278 nm. The developed method was validated per International Conference on Harmonization guidelines using validation parameters such as specificity, linearity and range, precision, accuracy, LOD, and LOQ. The linearity range for ALG was 100-500 ng/band (correlation coefficient = 0.9997) with an average recovery of 99.47%. The LOD and LOQ for ALG were 9.8 and 32.7 ng/band, respectively. The developed method was successfully applied for the quantitative estimation of ALG in its synthetic mixture with common excipients. Degradation kinetics of ALG in an alkaline medium was studied by degrading it under three different temperatures and three different concentrations of alkali. Degradation of ALG in the alkaline medium was found to follow first-order kinetics. Contour plots have been generated to predict degradation rate constant, half-life, and shelf life of ALG in various combinations of temperature and concentration of alkali using Design Expert software.

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

NASA Technical Reports Server (NTRS)

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.

Active Pattern Factor Control for Gas Turbine Engines

NASA Technical Reports Server (NTRS)

May, James E.

1998-01-01

Small variations in fuel/air mixture ratios within gas turbine combustors can result in measurable, and potentially detrimental, exit thermal gradients. Thermal gradients can increase emissions, as well as shorten the design life of downstream turbomachinery, particularly stator vanes. Uniform temperature profiles are usually sought through careful design and manufacturing of related combustor components. However, small componentto-component variations as well as numerous aging effects degrade system performance. To compensate for degraded thermal performance, researchers are investigating active, closed-loop control schemes.

Dual degradation of gaseous 1,2-dichlorobenzene and PCDD/Fs using Ce doped VxOy/TiO2 immobilized on cordierite.

PubMed

Chen, Yan; Wu, Qiong; Liu, Kuiren

2016-07-01

The photocatalytic film Ce doped VxOy/TiO2 was loaded on cordierite honeycomb (CHC), and this composite was prepared by sol-gel and dipping method, with Ce, oxides of V and TiO2 as dopant and key substances, respectively. Using gaseous 1,2-dichlorobenzene to replace dioxin as target pollutant, dual degradation experiments at 140-280 °C were carried out (thermal decomposition and photodegradation), and the effects of preparation conditions on catalytic activity were investigated: doping amount of Ce, dipping time in the gel, the concentration of ammonium metavanadate (NH4VO3) solution, dipping time in NH4VO3 solution, sintering temperature. The gaseous samples were taken before and after the reactor and analyzed by gas chromatography. According to the results, the optimal preparation conditions were determined, and the corresponding removal rate was above 95% after 90 min of degradation at 280 °C. The composite was examined by ultrasonic to analyze the adhesive strength between the film and CHC, and further characterized by XRD and SEM. Furthermore, flue gas from waste incinerator was chosen as target pollutant, which contained PCDD/Fs, the industrial sidestream degradation experiment was carried out and showed excellent removal efficiency of the composite, the removal rate of PCDD/Fs reached ca. 90% after 90 min of degradation. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

Treesearch

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...

Shuttle Orbiter Active Thermal Control Subsystem design and flight experience

NASA Technical Reports Server (NTRS)

Bond, Timothy A.; Metcalf, Jordan L.; Asuncion, Carmelo

1991-01-01

The paper examines the design of the Space Shuttle Orbiter Active Thermal Control Subsystem (ATCS) constructed for providing the vehicle and payload cooling during all phases of a mission and during ground turnaround operations. The operation of the Shuttle ATCS and some of the problems encountered during the first 39 flights of the Shuttle program are described, with special attention given to the major problems encountered with the degradation of the Freon flow rate on the Orbiter Columbia, the Flash Evaporator Subsystem mission anomalies which occurred on STS-26 and STS-34, and problems encountered with the Ammonia Boiler Subsystem. The causes and the resolutions of these problems are discussed.

Ground Laboratory Soft X-Ray Durability Evaluation of Aluminized Teflon FEP Thermal Control Insulation

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; deGroh, Kim K.; Stueber, Thomas J.; Sechkar, Edward A.

1998-01-01

Metallized Teflon fluorinated ethylene propylene (FEP) thermal control insulation is mechanically degraded if exposed to a sufficient fluence of soft x-ray radiation. Soft x-ray photons (4-8 A in wavelength or 1.55 - 3.2 keV) emitted during solar flares have been proposed as a cause of mechanical properties degradation of aluminized Teflon FEP thermal control insulation on the Hubble Space Telescope (HST). Such degradation can be characterized by a reduction in elongation-to-failure of the Teflon FER Ground laboratory soft x-ray exposure tests of aluminized Teflon FEP were conducted to assess the degree of elongation degradation which would occur as a result of exposure to soft x-rays in the range of 3-10 keV. Tests results indicate that soft x-ray exposure in the 3-10 keV range, at mission fluence levels, does not alone cause the observed reduction in elongation of flight retrieved samples. The soft x-ray exposure facility design, mechanical properties degradation results and implications will be presented.

Ground Laboratory Soft X-Ray Durability Evaluation of Aluminized Teflon FEP Thermal Control Insulation. Revised

NASA Technical Reports Server (NTRS)

Banks, Bruce A.; deGroh, Kim K.; Stueber, Thomas J.; Sechkar, Edward A.; Hall, Rachelle L.

1998-01-01

Metallized Teflon fluorinated ethylene propylene (FEP) thermal control insulation is mechanically degraded if exposed to a sufficient fluence of soft x-ray radiation. Soft x-ray photons (4-8 A in wavelength or 1.55 - 3.2 keV) emitted during solar flares have been proposed as a cause of mechanical properties degradation of aluminized Teflon FEP thermal control insulation on the Hubble Space Telescope (HST). Such degradation can be characterized by a reduction in elongation-to-failure of the Teflon FEP. Ground laboratory soft x-ray exposure tests of aluminized Teflon FEP were conducted to assess the degree of elongation degradation which would occur as a result of exposure to soft x-rays in the range of 3-10 keV. Tests results indicate that soft x-ray exposure in the 3-10 keV range, at mission fluence levels, does not alone cause the observed reduction in elongation of flight retrieved samples. The soft x-ray exposure facility design, mechanical properties degradation results and implications will be presented.

EV space suit gloves (passive)

NASA Technical Reports Server (NTRS)

Fletcher, E. G.; Dodson, J. D.; Elkins, W.; Tickner, E. G.

1975-01-01

A pair of pressure and thermal insulating overgloves to be used with an Extravehicular (EV) suit assembly was designed, developed, fabricated, and tested. The design features extensive use of Nomex felt materials in lieu of the multiple layer insulation formerly used with the Apollo thermal glove. The glove theoretically satisfies all of the thermal requirements. The presence of the thermal glove does not degrade pressure glove tactility by more than the acceptable 10% value. On the other hand, the thermal glove generally degrades pressure glove mobility by more than the acceptable 10% value, primarily in the area of the fingers. Life cycling tests were completed with minimal problems. The thermal glove/pressure glove ensemble was also tested for comfort; the test subjects found no problems with the thermal glove although they did report difficulties with pressure points on the pressure glove which were independent of the thermal glove.

Thermal performance of gaseous-helium-purged tank-mounted multilayer insulation system during ground-hold and space-hold thermal cycling and exposure to water vapor

NASA Technical Reports Server (NTRS)

Sumner, I. E.

1978-01-01

An experimental investigation was conducted to determine (1) the ground-hold and space-hold thermal performance of a multilayer insulation (MLI) system mounted on a spherical, liquid-hydrogen propellant tank and (2) the degradation to the space-hold thermal performance of the insulation system that resulted from both thermal cycling and exposure to moisture. The propellant tank had a diameter of 1.39 meters (4.57ft). The MLI consisted of two blankets of insulation; each blanket contained 15 double-aluminized Mylar radiation shields separated by double silk net spacers. Nineteen tests simulating basic cryogenic spacecraft thermal (environmental) conditions were conducted. These tests typically included initial helium purge, liquid-hydrogen fill and ground-hold, ascent, space-hold, and repressurization. No significant degradation of the space-hold thermal performance due to thermal cycling was noted.

Thermal barrier coating life prediction model development, phase 1

NASA Technical Reports Server (NTRS)

Demasi, Jeanine T.; Ortiz, Milton

1989-01-01

The objective of this program was to establish a methodology to predict thermal barrier coating (TBC) life on gas turbine engine components. The approach involved experimental life measurement coupled with analytical modeling of relevant degradation modes. Evaluation of experimental and flight service components indicate the predominant failure mode to be thermomechanical spallation of the ceramic coating layer resulting from propagation of a dominant near interface crack. Examination of fractionally exposed specimens indicated that dominant crack formation results from progressive structural damage in the form of subcritical microcrack link-up. Tests conducted to isolate important life drivers have shown MCrAlY oxidation to significantly affect the rate of damage accumulation. Mechanical property testing has shown the plasma deposited ceramic to exhibit a non-linear stress-strain response, creep and fatigue. The fatigue based life prediction model developed accounts for the unusual ceramic behavior and also incorporates an experimentally determined oxide rate model. The model predicts the growth of this oxide scale to influence the intensity of the mechanic driving force, resulting from cyclic strains and stresses caused by thermally induced and externally imposed mechanical loads.

The Degradation Behavior of SiCf/SiO2 Composites in High-Temperature Environment

NASA Astrophysics Data System (ADS)

Yang, Xiang; Cao, Feng; Qing, Wang; Peng, Zhi-hang; Wang, Yi

2018-04-01

SiCf/SiO2 composites had been fabricated efficiently by Sol-Gel method. The oxidation behavior, thermal shock property and ablation behavior of SiCf/SiO2 composites was investigated. SiCf/SiO2 composites showed higher oxidation resistance in oxidation atmosphere, the flexural strength retention ratio was larger than 90.00%. After 1300 °C thermal shock, the mass retention ratio was 97.00%, and the flexural strength retention ratio was 92.60%, while after 1500 °C thermal shock, the mass retention ratio was 95.37%, and the flexural strength retention ratio was 83.34%. After 15 s ablation, the mass loss rate was 0.049 g/s and recession loss rate was 0.067 mm/s. The SiO2 matrix was melted in priority and becomes loosen and porous. With the ablation going on, the oxides were washed away by the shearing action of the oxyacetylene flame. The evaporation of SiO2 took away large amount of heat, which is also beneficial to the protection for SiCf/SiO2 composites.

Integration and software for thermal test of heat rate sensors. [space shuttle external tank

NASA Technical Reports Server (NTRS)

Wojciechowski, C. J.; Shrider, K. R.

1982-01-01

A minicomputer controlled radiant test facility is described which was developed and calibrated in an effort to verify analytical thermal models of instrumentation islands installed aboard the space shuttle external tank to measure thermal flight parameters during ascent. Software was provided for the facility as well as for development tests on the SRB actuator tail stock. Additional testing was conducted with the test facility to determine the temperature and heat flux rate and loads required to effect a change of color in the ET tank external paint. This requirement resulted from the review of photographs taken of the ET at separation from the orbiter which showed that 75% of the external tank paint coating had not changed color from its original white color. The paint on the remaining 25% of the tank was either brown or black, indicating that it had degraded due to heating or that the spray on form insulation had receded in these areas. The operational capability of the facility as well as the various tests which were conducted and their results are discussed.

Thermal degradation behaviors and reaction mechanism of carbon fibre-epoxy composite from hydrogen tank by TG-FTIR.

PubMed

Zhang, Zhi; Wang, Changjian; Huang, Gai; Liu, Haoran; Yang, Shenlin; Zhang, Aifeng

2018-05-28

Thermal degradation behaviors and reaction mechanism of Carbon fibre-epoxy composite, obtained from Chinese widely applied hydrogen storage tank, were studied by thermogravimetry combined with Fourier transform infrared spectrometry at varying heating rates. The pyrolysis of carbon fibre-epoxy composite mainly occurs at 550-750 K. The average value of final residue is 72.42%. The calculated activation energies increase exponentially from 206.27 KJ/mol to 412.98 KJ/mol with the average value of 276.6 KJ/mol. The fourth reaction order model is responsible for the pyrolysis of carbon fibre-epoxy composite. The absorption spectra of the evolved gases provided the information that the main evolved products are H 2 O, CO 2 , CO (acid anhydride, ketone or aldehyde), ε- caprolactam, alcohols and phenol. Moreover, CO group > alcohols > phenol > ε- caprolactam > CO 2  > H 2 O. Epoxy is the main pyrolysis crude material in carbon fibre-epoxy composite. Copyright © 2018 Elsevier B.V. All rights reserved.

A modified commercial gas chromatograph for the continuous monitoring of the thermal degradation of sunflower oil and off-line solid phase extraction gas-chromatography-mass spectrometry characterization of released volatiles.

PubMed

Ontañon, I; Sanz, J; Escudero, A; de Marcos, S; Ferreira, V; Galbán, J

2015-04-03

A homemade flow cell attached to a commercial Gas Chromatograph equipped with a Flame Ionization Detector (FID) has been designed for the continuous monitoring of volatile compounds released during heating edible oils. Analytical parameters such as mass of sample, temperature and flow rates have been optimized and the obtained results have been compared with the corresponding thermographs from standard TG systems. Results show that under optimum conditions, the profiles of volatiles released upon heating are comparable to the profiles of TG curves, suggesting that the FID based system could be an alternative to TGA. Additionally, volatiles have been retained in a Lichrolut EN(®) resin, eluted and analyzed by Gas Chromatography-Mass Spectrometry. In this case, forty five compounds have been identified (acids, alcohols, alkanes, aldehydes, ketones and furans) and compared with the FID signals, working both in air or nitrogen atmosphere. It has been concluded that the oxidative thermal degradation is prevented in the presence of a nitrogen atmosphere. Copyright © 2015 Elsevier B.V. All rights reserved.

Plasma effects on the passive external thermal control coating of Space Station Freedom

NASA Technical Reports Server (NTRS)

Carruth, Ralph, Jr.; Vaughn, Jason A.; Holt, James M.; Werp, Richard; Sudduth, Richard D.

1992-01-01

The current baseline chromic acid anodized thermal control coating on 6061-T6 aluminum meteoroid debris (M/D) shields for SSF has been evaluated. The degradation of the solar absorptance, alpha, and the thermal emittance, epsilon, of chromic acid anodized aluminum due to dielectric breakdown in plasma was measured to predict the on-orbit lifetime of the SSF M/D shields. The lifetime of the thermal control coating was based on the surface temperatures achieved with degradation of the thermal control properties, alpha and epsilon. The temperatures of each M/D shield from first element launch (FEL) through FEL+15 years were analyzed. It is shown that the baseline thermal control coating cannot withstand the -140 V potential between the conductive structure of the SSF and the current plasma environment.

Long-life mission reliability for outer planet atmospheric entry probes

NASA Technical Reports Server (NTRS)

Mccall, M. T.; Rouch, L.; Maycock, J. N.

1976-01-01

The results of a literature analysis on the effects of prolonged exposure to deep space environment on the properties of outer planet atmospheric entry probe components are presented. Materials considered included elastomers and plastics, pyrotechnic devices, thermal control components, metal springs and electronic components. The rates of degradation of each component were determined and extrapolation techniques were used to predict the effects of exposure for up to eight years to deep space. Pyrotechnic devices were aged under accelerated conditions to an equivalent of eight years in space and functionally tested. Results of the literature analysis of the selected components and testing of the devices indicated that no severe degradation should be expected during an eight year space mission.

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

NASA Astrophysics Data System (ADS)

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.

Molecular Design and Evaluation of Biodegradable Polymers Using a Statistical Approach

PubMed Central

Lewitus, Dan; Rios, Fabian; Rojas, Ramiro; Kohn, Joachim

2013-01-01

The challenging paradigm of bioresorbable polymers, whether in drug delivery or tissue engineering, states that a fine-tuning of the interplay between polymer properties (e.g., thermal, degradation), and the degree of cell/tissue replacement and remodeling is required. In this paper we describe how changes in the molecular architecture of a series of terpolymers allow for the design of polymers with varying glass transition temperatures and degradation rates. The effect of each component in the terpolymers is quantified via design of experiment (DoE) analysis. A linear relationship between terpolymer components and resulting Tg (ranging from 34 to 86 °C) was demonstrated. These findings were further supported with mass-per-flexible-bond (MPFB) analysis. The effect of terpolymer composition on the in vitro degradation of these polymers revealed molecular weight loss ranging from 20 to 60% within the first 24 hours. DoE modeling further illustrated the linear (but reciprocal) relationship between structure elements and degradation for these polymers. Thus, we describe a simple technique to provide insight into the structure property relationship of degradable polymers, specifically applied using a new family of tyrosine-derived polycarbonates, allowing for optimal design of materials for specific applications. PMID:23888354

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

NASA Technical Reports Server (NTRS)

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.

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

PubMed Central

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

2015-01-01

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. PMID:28793512

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

PubMed

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.

Final report for SERDP WP-2209 Replacement melt-castable formulations for Composition B

DTIC Science & Technology

2017-05-19

Chemical reaction of the materials in the melt ............................................................... 5 Thermal degradation of materials...reasons other than the hazard of explosion, these include: • Chemical reaction of the materials in the melt • Thermal degradation at low...temperature • Sublimation and condensation of explosive material on equipment and exposure to workers Chemical reaction of the materials in the melt

Cyanide toxicity from the thermal degradation of rigid polyurethane foam.

PubMed

Bell, R H; Stemmer, K L; Barkley, W; Hollingsworth, L D

1979-09-01

Thermal degradation products (tdp) from a model, rigid polyurethane foam were collected in such a manner as to eliminate carbon monoxide and other gases with low boiling points. The effects in rats resulting from intratracheal intubation (I.T.) of the tdp are discussed. Cyanide was found to be a major factor associated with severe toxic responses of the experimental rats.

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

NASA Astrophysics Data System (ADS)

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.

Effects of different culture media on biodegradation of triclosan by Rhodotorula mucilaginosa and Penicillium sp.

PubMed

Ertit Taştan, Burcu; Özdemir, Caner; Tekinay, Turgay

Triclosan is an antimicrobial agent and a persistent pollutant. The biodegradation of triclosan is dependent on many variables including the biodegradation organism and the environmental conditions. Here, we evaluated the triclosan degradation potential of two fungi strains, Rhodotorula mucilaginosa and Penicillium sp., and the rate of its turnover to 2,4-dichlorophenol (2,4-DCP). Both of these strains showed less susceptibility to triclosan when grown in minimal salt medium. In order to further evaluate the effects of environmental conditions on triclosan degradation, three different culture conditions including original thermal power plant wastewater, T6 nutrimedia and ammonium mineral salts medium were used. The maximum triclosan degradation yield was 48% for R. mucilaginosa and 82% for Penicillium sp. at 2.7 mg/L triclosan concentration. Biodegradation experiments revealed that Penicillium sp. was more tolerant to triclosan. Scanning electron microscopy micrographs also showed the morphological changes of fungus when cells were treated with triclosan. Overall, these fungi strains could be used as effective microorganisms in active uptake (degradation) and passive uptake (sorption) of triclosan and their efficiency can be increased by optimizing the culture conditions.

A study of the effects of solid phase reactions on the thermal degradation and ballistic properties of solid propellants

NASA Technical Reports Server (NTRS)

Schmidt, W. G.

1974-01-01

The thermal stability of perchlorate composite propellants was studied at 135 and 170 C. The experimental efforts were concentrated on determining the importance of heterogeneous oxidizer-fuel reactions in the thermal degradation process. The experimental approach used to elucidate the mechanisms by which the oxidizer fuel composites thermally degrade was divided into two parts: (1) keeping the fuel constant and varying the nature of the oxidizers, and (2) holding the oxidizer constant and varying the fuel components. The fuel component primarily utilized in the first phase was polyethylene. Oxidizers included KClO4, KClO3, NH4ClO4 and NH4ClO4 doped with materials such as chlorate, phosphate and arsenate. In the second phase the oxidizer used was primarily NH4ClO4 while the fuels included saturated and unsaturated polybutadiene prepolymers and a series of bonding agents. Techniques employed in the current study include thermogravimetric measurements, differential thermal analysis, infrared, mass spectrometry, electron microscopy, and appropriate wet chemical analysis.

The Effect of Simulated Lunar Dust on the Absorptivity, Emissivity, and Operating Temperature on AZ-93 and Ag/FEP Thermal Control Surfaces

NASA Technical Reports Server (NTRS)

Gaier, James R.; Siamidis, John; Panko, Scott R.; Rogers, Kerry J.; Larkin, Elizabeth M. G.

2008-01-01

JSC-1AF lunar simulant has been applied to AZ-93 and AgFEP thermal control surfaces on aluminum or composite substrates in a simulated lunar environment. The temperature of these surfaces was monitored as they were heated with a solar simulator and cooled in a 30 K coldbox. Thermal modeling was used to determine the absorptivity ( ) and emissivity ( ) of the thermal control surfaces in both their clean and dusted states. Then, a known amount of power was applied to the samples while in the coldbox and the steady state temperatures measured. It was found that even a submonolayer of simulated lunar dust can significantly degrade the performance of both white paint and second-surface mirror type thermal control surfaces under these conditions. Contrary to earlier studies, dust was found to affect as well as . Dust lowered the emissivity by as much as 16 percent in the case of AZ-93, and raised it by as much as 11 percent in the case of AgFEP. The degradation of thermal control surface by dust as measured by / rose linearly regardless of the thermal control coating or substrate, and extrapolated to degradation by a factor 3 at full coverage by dust. Submonolayer coatings of dust were found to not significantly change the steady state temperature at which a shadowed thermal control surface will radiate.

Aquifer thermal energy storage - A feasibility study for large scale demonstration

NASA Astrophysics Data System (ADS)

Skinner, W. V.; Supkow, D. J.

Engineering procedures necessary for aquifer thermal energy storage (ATES), based on studies of the Magothy Aquifer on Long Island, NY, are presented, with chilled winter water pumped into the aquifer and reclaimed in summer months for air conditioning. The choice of aquifer involves necessary volume, flow rate, efficiency of thermal recovery, and avoidance of conflict with other users; utilization depends on choice of appropriate piping, heat exchangers, and well construction to prevent degradation of the aquifer. The methods employed to probe the Magothy for suitability are described, including drilling an asymmetric well cluster for observation, and 48 hr pumping and 8 hr recovery. Transmissivity was found to vary from 8,000 to 29,000 sq ft/day. A doublet well was then drilled and water withdrawn, chilled, and returned. Later withdrawal indicated a 46% thermal recovery, with computer models projecting 80% with additional cycling. The study verified the feasibility of ATES, which can be expanded with additional demand.

On-orbit checkout of satellites, volume 2. Part 3 of on-orbit checkout study. [space maintenance

NASA Technical Reports Server (NTRS)

Pritchard, E. I.

1978-01-01

Early satellite failures significantly degrading satellite operations are reviewed with emphasis on LANDSAT D, the Technology Demonstration Satellite, the ATREX/AEM spacecraft, STORMSAT 2, and the synchronous meteorological satellite. Candidates for correction with on-orbit checkout and appropriate actions are analyzed. On-orbit checkout subsystem level studies are summarized for electrical power, attitude control, thermal control, reaction control and propulsion, instruments, and angular rate matching for alignment of satellite IRU.

Degradation of a two-layer thermal barrier coating under thermal cycling. [for superalloys of aircraft turbine engine blades

NASA Technical Reports Server (NTRS)

Maier, R. D.; Scheuermann, C. M.; Andrews, C. W.

1981-01-01

A two-layer plasma-sprayed thermal barrier coating on a directionally solidified nickel-base eutectic alloy substrate was characterized prior to and after thermal cycling to 1095 C in an accelerated furnace test. The coating was comprised of an inner layer of Ni-16.4Cr-5.1Al-0.15Y (wt%) bond coat and an outer layer of ZrO2-7.9Y2O3 (wt%) thermal barrier. Characterization of the bond coat revealed that substantial amounts of yttrium and aluminum were oxidized during plasma-spraying in air. The oxidation of these elements reduced the protective capacity of the bond coat so that, on thermal exposure, severe degradation of the bond coat resulted and large amounts of nickel oxide formed. This nickel oxide was demonstrated to grow outward into the thermal barrier, which appears to have increased the stresses in the thermal barrier and contributed to its failure near the thermal barrier-bond coat interface.

Finding of 13(2) , 17(3) -cyclopheophorbide a enol as a degradation product of chlorophyll in shrunk zooxanthellae of the coral Montipora digitata.

PubMed

Suzuki, Toshiyuki; Casareto, Beatriz Estela; Shioi, Yuzo; Ishikawa, Yoshio; Suzuki, Yoshimi

2015-02-01

We examined the morphology and pigment composition of zooxanthellae in corals subjected to normal temperature (27°C) and thermal stress (32°C). We observed several normal and abnormal morphological types of zooxanthellar cells. Normal cells were intact and their chloroplasts were unbroken (healthy); abnormal cells were shrunken and had partially degraded or broken chloroplasts, or they were bleached and without chloroplasts. At 27°C, most healthy zooxanthellar cells were retained in the coral tissue, whereas shrunken zooxanthellae were expelled. Under thermal stress, the abundance of healthy zooxanthellae declined and the proportion of shrunken/abnormal cells increased in coral tissues. The rate of algal cell expulsion was reduced under thermal stress. Within the shrunken cells, we detected the presence of a chl-like pigment that is not ordinarily found in healthy zooxanthellae. Analysis of the absorption spectrum, absorption maxima, and retention time (by HPLC) indicated that this pigment was 13(2) , 17(3) -cyclopheophorbide a enol (cPPB-aE), which is frequently found in marine and lacustrine sediments, and in protozoans that graze on phytoplankton. The production of cPPB-aE in shrunken zooxanthellae suggests that the chls have been degraded to cPPB-aE, a compound that is not fluorescent. The lack of a fluorescence function precludes the formation of reactive oxygen species. We therefore consider the formation of cPPB-aE in shrunken zooxanthellae to be a mechanism for avoiding oxidative stress. © 2014 The Authors. Journal of Phycology published by Wiley Periodicals, Inc. on behalf of Phycological Society of America.

Scaling behavior of moisture-induced grain degradation in polycrystalline hybrid perovskite thin films

DOE PAGES

Wang, Qi; Chen, Bo; Liu, Ye; ...

2017-01-01

The stability of perovskite solar cells has shown a huge variation with respect to the film process and film morphology, while the underlining mechanism for the morphology-dependent degradation of the perovskite film has remained elusive. Herein, we report a scaling behavior of moisture-induced grain degradation in polycrystalline CH 3NH 3PbI 3 films. The degradation rates of CH 3NH 3PbI 3 films in moisture were shown to be sensitive to the grain sizes. The duration that was needed for different films to degrade by the same percent showed a linear relationship with the grain size, despite the fact that the filmsmore » were formed by five different deposition methods. This scaling behavior can be explained by the degradation along the in-plane direction, which is initiated at the grain boundary (GB). The GBs of CH 3NH 3PbI 3 films consist of an amorphous intergranular layer, which allows quick diffusion of moisture into the perovskite films. It was found that thermal annealing induced surface self-passivation plays a critical role in stabilizing the surfaces of thin films and single crystals by reducing the moisture-sensitive methylammonium ions at the surface. Finally, the determination of the scaling behavior of grain degradation highlights the importance of stabilizing the GBs to improve the stability of perovskite solar cells.« less

Scaling behavior of moisture-induced grain degradation in polycrystalline hybrid perovskite thin films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Qi; Chen, Bo; Liu, Ye

The stability of perovskite solar cells has shown a huge variation with respect to the film process and film morphology, while the underlining mechanism for the morphology-dependent degradation of the perovskite film has remained elusive. Herein, we report a scaling behavior of moisture-induced grain degradation in polycrystalline CH 3NH 3PbI 3 films. The degradation rates of CH 3NH 3PbI 3 films in moisture were shown to be sensitive to the grain sizes. The duration that was needed for different films to degrade by the same percent showed a linear relationship with the grain size, despite the fact that the filmsmore » were formed by five different deposition methods. This scaling behavior can be explained by the degradation along the in-plane direction, which is initiated at the grain boundary (GB). The GBs of CH 3NH 3PbI 3 films consist of an amorphous intergranular layer, which allows quick diffusion of moisture into the perovskite films. It was found that thermal annealing induced surface self-passivation plays a critical role in stabilizing the surfaces of thin films and single crystals by reducing the moisture-sensitive methylammonium ions at the surface. Finally, the determination of the scaling behavior of grain degradation highlights the importance of stabilizing the GBs to improve the stability of perovskite solar cells.« less

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

NASA Astrophysics Data System (ADS)

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.

Photo, thermal and chemical degradation of riboflavin

PubMed Central

Kazi, Sadia Hafeez; Ahmed, Sofia; Anwar, Zubair; Ahmad, Iqbal

2014-01-01

Summary 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. PMID:25246959

Thermal stress cycling of GaAs solar cells

NASA Technical Reports Server (NTRS)

Francis, Robert W.

1987-01-01

Thermal stress cycling was performed on gallium arsenide solar cells to investigate their electrical, mechanical, and structural integrity. Cells were cycled under low Earth orbit (LEO) simulated temperature conditions in vacuum. Cell evaluations consisted of power output values, spectral response, optical microscopy and ion microprobe mass analysis, and depth profiles on both front surface inter-grid areas and metallization contact grid lines. Cells were examined for degradation after 500, 5,000, 10,000 and 15,245 thermal cycles. No indication of performance degradation was found for any vendor's cell lot.

Melting, glass transition, and apparent heat capacity of α-D-glucose by thermal analysis.

PubMed

Magoń, A; Pyda, M

2011-11-29

The thermal behaviors of α-D-glucose in the melting and glass transition regions were examined utilizing the calorimetric methods of standard differential scanning calorimetry (DSC), standard temperature-modulated differential scanning calorimetry (TMDSC), quasi-isothermal temperature-modulated differential scanning calorimetry (quasi-TMDSC), and thermogravimetric analysis (TGA). The quantitative thermal analyses of experimental data of crystalline and amorphous α-D-glucose were performed based on heat capacities. The total, apparent and reversingheat capacities, and phase transitions were evaluated on heating and cooling. The melting temperature (T(m)) of a crystalline carbohydrate such as α-D-glucose, shows a heating rate dependence, with the melting peak shifted to lower temperature for a lower heating rate, and with superheating of around 25K. The superheating of crystalline α-D-glucose is observed as shifting the melting peak for higher heating rates, above the equilibrium melting temperature due to of the slow melting process. The equilibrium melting temperature and heat of fusion of crystalline α-D-glucose were estimated. Changes of reversing heat capacity evaluated by TMDSC at glass transition (T(g)) of amorphous and melting process at T(m) of fully crystalline α-D-glucose are similar. In both, the amorphous and crystalline phases, the same origin of heat capacity changes, in the T(g) and T(m) area, are attributable to molecular rotational motion. Degradation occurs simultaneously with the melting process of the crystalline phase. The stability of crystalline α-D-glucose was examined by TGA and TMDSC in the melting region, with the degradation shown to be resulting from changes of mass with temperature and time. The experimental heat capacities of fully crystalline and amorphous α-D-glucose were analyzed in reference to the solid, vibrational, and liquid heat capacities, which were approximated based on the ATHAS scheme and Data Bank. Copyright © 2011 Elsevier Ltd. All rights reserved.

Thermal Performance of Cryogenic Piping Multilayer Insulation in Actual Field Installations

NASA Technical Reports Server (NTRS)

Fesmire, J.; Augustnynowicz, S.; Thompson, K. (Technical Monitor)

2002-01-01

A standardized way of comparing the thermal performance of different pipelines in different sizes is needed. Vendor data for vacuum-insulated piping are typically given in heat leak rate per unit length (W/m) for a specific diameter pipeline. An overall k-value for actual field installations (k(sub oafi)) is therefore proposed as a more generalized measure for thermal performance comparison and design calculation. The k(sub oafi) provides a direct correspondence to the k-values reported for insulation materials and illustrates the large difference between ideal multilayer insulation (MLI) and actual MLI performance. In this experimental research study, a section of insulated piping was tested under cryogenic vacuum conditions, including simulated spacers and bending. Several different insulation systems were tested using a 1-meter-long cylindrical cryostat test apparatus. The simulated spacers tests showed significant degradation in the thermal performance of a given insulation system. An 18-meter-long pipeline test apparatus is now in operation at the Cryogenics Test Laboratory, NASA Kennedy Space Center, for conducting liquid nitrogen thermal performance tests.

Aerothermal performance and structural integrity of a Rene 41 thermal protection system at Mach 6.6

NASA Technical Reports Server (NTRS)

Deveikis, W. D.; Miserentino, R.; Weinstein, I.; Shideler, J. L.

1975-01-01

A flightweight panel based on a metallic thermal-protection-system concept for hypersonic and reentry vehicles was subjected repeatedly to thermal cycling by quartz-lamp radiant heating using a thermal history representative of a reentry heat pulse and to aerodynamic heating at heating rates required to sustain a surface temperature of 1089 K (1960 R). The panel consisted of a corrugated heat shield and support members of 0.05-cm (0.02-in.) thick Rene 41 of riveted construction and 5.08-cm (2-in.) thick silica fibrous insulation packages covered by Rene 41 foil and inconel screening. All tests were conducted in the Langley 8-foot high-temperature structures tunnel with the heat shield corrugations alined in the stream direction. The panel sustained 5.33 hr of intermittent radiant heating and 6.5 min of intermittent aerodynamic heating of up to 1-min duration for differential pressures up to 6.2 kPa (0.9 psi) with no apparent degradation of thermal or structural integrity, as indicated by temperature distributions and results from load deflection tests and vibration surveys of natural frequencies.

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

NASA Technical Reports Server (NTRS)

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.

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

NASA Technical Reports Server (NTRS)

Townsend, Jacqueline A.; Powers, Charles E.; Viens, Michael J.; Ayres-Treusdell, Mary T.; 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 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' 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 FEP.

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

NASA Technical Reports Server (NTRS)

Townsend, Jacqueline A.; Powers, Charles E.; Viens, Michael J.; Ayres-Treusdell, Mary T.; Munoz, Bruno F.

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' 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(registered 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(registered trademark) FEP.

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

NASA Technical Reports Server (NTRS)

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.

Enhanced heat transfer characteristics of viscous liquid flows in a chevron plate heat exchanger

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muley, A.; Manglik, R.M.; Metwally, H.M.

1999-11-01

Thermal processing and manufacturing in the chemical, foods, pharmaceutical, hygiene products, and biochemical industries invariably involve heating and cooling of highly viscous fluid media. These fluids tend to flow in the low Reynolds number regime, inherently have relatively low heat transfer coefficients, and are often temperature sensitive and prone to thermal degradation in the presence of large temperature differences. In recent times, plate heat exchangers (PHEs) have found increasing usage in such applications, primarily due to their features that promote enhanced heat transfer, and provide for the flexibility in altering their unit thermal size with ease, close approach temperature operation,more » and mitigation of thermal degradation of the process fluid. Here, steady-state heat transfer and pressure drop data for single-phase viscous fluid flows (2 {le} Re {le} 400) in a single-pass U-type counterflow plate heat exchanger (PHE) with chevron plates are presented. With vegetable oil as test fluid (130 {lt} Pr {lt} 290), three different plate arrangements are employed: two symmetric ({beta} = 30 deg/30 deg and 60 deg/60 deg) and one mixed ({beta} = 30 deg/60 deg). The effects of chevron angle {beta}, corrugation aspect ratio {gamma}, and flow conditions (Re, Pr, {mu}/{mu}{sub w}) on Nu and f characteristics of the PHE are delineated. The results show a rather complex influence of plate surface corrugations on the enhanced thermal-hydraulic behavior. Relative to the performance of equivalent flat-plate packs, chevron plates sustain up to 2.9 times higher heat transfer rates on a fixed geometry and constant pumping power basis, and require up to 48% less surface area for the fixed heat load and pressure drop constraint.« less

Evaluation of the Epoxy/Antimony Trioxide Nanocomposites as Flame Retardant

NASA Astrophysics Data System (ADS)

Dheyaa, Balqees M.; Jassim, Widad H.; Hameed, Noor A.

2018-05-01

Antimony trioxide nanopowder was added for epoxy resin in various amount weight percentages (0, 2, 4, 6, 8, and 10) wt% to increase the combustion resistance and decrease the flammability for it. The study included three standard tests used to measure: limiting oxygen index (LOI), rate of burning (R.B), burning extent (E.B), burning time (T.B), maximum flame height (H) and residue percentage after burning in order to determine the effectiveness of the used additives to decrease the flammability of epoxy resin and increase the combustion resistance. Thermal test was done by using Lee’s disk to measure the thermal conductivity coefficient. The thermal stability and degradation kinetics of epoxy resin without reinforcement and with reinforcement by (10 wt%) were studied by using thermogravimetric analysis (TGA). The recorded results indicated that epoxy reinforced by (10 wt%) has a good effect as flame retardants for epoxy resin and active to inhibit burning and reduce the flammability.

Climate change disables coral bleaching protection on the Great Barrier Reef.

PubMed

Ainsworth, Tracy D; Heron, Scott F; Ortiz, Juan Carlos; Mumby, Peter J; Grech, Alana; Ogawa, Daisie; Eakin, C Mark; Leggat, William

2016-04-15

Coral bleaching events threaten the sustainability of the Great Barrier Reef (GBR). Here we show that bleaching events of the past three decades have been mitigated by induced thermal tolerance of reef-building corals, and this protective mechanism is likely to be lost under near-future climate change scenarios. We show that 75% of past thermal stress events have been characterized by a temperature trajectory that subjects corals to a protective, sub-bleaching stress, before reaching temperatures that cause bleaching. Such conditions confer thermal tolerance, decreasing coral cell mortality and symbiont loss during bleaching by over 50%. We find that near-future increases in local temperature of as little as 0.5°C result in this protective mechanism being lost, which may increase the rate of degradation of the GBR. Copyright © 2016, American Association for the Advancement of Science.

Interfacial thermal degradation in inverted organic solar cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Greenbank, William; Hirsch, Lionel; Wantz, Guillaume

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 inmore » 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.« less

Thermal degradation of terpenes: camphene, Δ-carene, limonene, and α -terpinene

Treesearch

Gerald W. McGraw; Richard W. Hemingway; Leonard L. Ingram; Catherine S. Canady; William B. McGraw

1999-01-01

Emissions from wood dryers have been of some concern for a number of years, and recent policy changes by the Environmental Protection Agency have placed emphasis upon the gaseous emissions that lead to the formation of particulate matter as small as 2.5 l m diameter. In this qualitative study, camphene, D 3 -carene, limonene, and a -terpinene were thermally degraded in...

New insight of hybrid membrane to degrade Congo red and Reactive yellow under sunlight.

PubMed

Rajeswari, A; Jackcina Stobel Christy, E; Pius, Anitha

2018-02-01

A study was carried out to investigate the degradation of organic contaminants (Congo red and Reactive yellow - 105) using cellulose acetate - polystyrene (CA-PS) membrane with and without ZnO impregnation. Scanning electron microscope (SEM), electron dispersive analysis of X-rays (EDAX), Fourier transform infrared spectrometer (FTIR), atomic force microscope (AFM) and thermogravimeric analysis (TG-DTA) analysis were carried out to characterize bare and ZnO impregnated CA-PS membranes. Membrane efficiency was also tested for pure water flux and antifouling performance. The modified membrane showed almost 85% water flux recovery. Blending of ZnO nanoparticles to CA-PS matrix could decrease membrane fouling and increase permeation quality of the membrane with above 90% of photocatalytic degradation efficiency for dyes. The rate of degradation of dyes was observed using UV-Vis spectrometer. Reusability of CA-PS-ZnO membrane was studied and no significant change was noted in the degradation efficiency until fourth cycle. Langmuir-Hinshelwood kinetic model well describes the photo degradation capacity and the degradation of dyes CR and RY - 105 exhibited pseudo-first order kinetics. The regression coefficient (R) of CR and RY - 105 found to be 0.99. The novelty of the prepared CA-PS-ZnO membrane is that it has better efficiency and high thermal stability than our previously reported material. Therefore, ZnO impregnated CA-PS membrane had proved to be an innovative alternative for the degradation of CR and RY - 105 dyes. Copyright © 2017 Elsevier B.V. All rights reserved.

Numerical and experimental study of the thermal degradation process during the atmospheric re-entry of a TiAl6V4 tank

NASA Astrophysics Data System (ADS)

Prévereaud, Y.; Vérant, J.-L.; Balat-Pichelin, M.; Moschetta, J.-M.

2016-05-01

To answer the question of space debris survivability during atmospheric entry ONERA uses its software named MUSIC/FAST. So, the first part of this paper is dedicated to the presentation of the ONERA tool and its validation by comparison with flight data and CFD computations. However, the influence of oxidation on the thermal degradation process and material properties in atmospheric entry conditions is still unknown. A second step is then devoted to the presentation of an experimental campaign investigating TA6V oxidation in atmospheric entry conditions, as the most of the debris found on ground are made of this material. Experiments have been realized using the MESOX facility implemented at the 6 kW solar furnace in PROMES-CNRS laboratory. Finally, an application of MUSIC/FAST is proposed on the atmospheric re-entry of a generic TA6V tank. Aiming at degradation assessment, a sensitive study to initial conditions is conducted. To complete computational analysis regarding degradation process by melting, a numerical analysis of the influence of oxidation on the thermal wall degradation during the tank atmospheric re-entry is presented as well.

Radiative process of two entanglement atoms in de Sitter spacetime

NASA Astrophysics Data System (ADS)

Liu, Xiaobao; Tian, Zehua; Wang, Jieci; Jing, Jiliang

2018-05-01

We investigate the radiative processes of a quantum system composed by two identical two-level atoms in the de Sitter spacetime, interacting with a conformally coupled massless scalar field prepared in the de Sitter-invariant vacuum. We discuss the structure of the rate of variations of the atomic energy for two static atoms. Following a procedure developed by Dalibard, Dupont-Roc, and Cohen-Tannoudji, our intention is to identify in a quantitative way the contributions of vacuum fluctuations and the radiation reaction to the generation of quantum entanglement and to the degradation of entangled states. We find that when the distance between two atoms larger than the characteristic length scale, the rate of variation of atomic energy in the de Sitter-invariant vacuum behaves differently compared with that in the thermal Minkowski spacetime. In particular, the generation and degradation of quantum entanglement can be enhanced or inhibited, which are dependent not only on the specific entangled state but also on the distance between the atoms.

In-operando high-speed tomography of lithium-ion batteries during thermal runaway

PubMed Central

Finegan, Donal P.; Scheel, Mario; Robinson, James B.; Tjaden, Bernhard; Hunt, Ian; Mason, Thomas J.; Millichamp, Jason; Di Michiel, Marco; Offer, Gregory J.; Hinds, Gareth; Brett, Dan J.L.; Shearing, Paul R.

2015-01-01

Prevention and mitigation of thermal runaway presents one of the greatest challenges for the safe operation of lithium-ion batteries. Here, we demonstrate for the first time the application of high-speed synchrotron X-ray computed tomography and radiography, in conjunction with thermal imaging, to track the evolution of internal structural damage and thermal behaviour during initiation and propagation of thermal runaway in lithium-ion batteries. This diagnostic approach is applied to commercial lithium-ion batteries (LG 18650 NMC cells), yielding insights into key degradation modes including gas-induced delamination, electrode layer collapse and propagation of structural degradation. It is envisaged that the use of these techniques will lead to major improvements in the design of Li-ion batteries and their safety features. PMID:25919582

Metallic phase-change materials for solar dynamic energy storage systems

NASA Astrophysics Data System (ADS)

Lauf, R. J.; Hamby, C., Jr.

1990-12-01

Solar (thermal) dynamic power systems for satellites require a heat storage system that is capable of operating the engine during eclipse. The conventional approach to this thermal storage problem is to use the latent heat of fluoride salts, which would melt during insolation and freeze during eclipse. Although candidate fluorides have large heats of fusion per unit mass, their poor thermal conductivity limits the rate at which energy can be transferred to and from the storage device. System performance is further limited by the high parasitic mass of the superalloy canisters needed to contain the salt. A new thermal storage system is described in which the phase-change material (PCM) is a metal (typically germanium) contained in modular graphite canisters. These modules exhibit good thermal conductivity and low parasitic mass, and they are physically and chemically stable. Prototype modules have survived over 600 melt/freeze cycles without degradation. Advanced concepts to further improve performance are described. These concepts include the selection of ternary eutectic alloys to provide a wider range of useful melting temperatures and the use of infiltration to control the location of liquid alloy and to compensate for differences in thermal expansion.

Degradation behavior of carbon nanotubes/phenol-furfuryl alcohol multifunctional composites with aerospace application

NASA Astrophysics Data System (ADS)

Conejo, L. S.; Costa, M. L.; Oishi, S. S.; Botelho, E. C.

2017-10-01

Lightweight and highly conductive composite associated with good impact and tribological properties could be used in the aerospace industry to replace metal for an aircraft skin and still provide effective shielding against electromagnetic interference (EMI). Also, phenol-furfuryl alcohol resins (PFA) are excellent candidates to replace existing thermoset matrices used for obtaining glassy carbon, both in its pure form and reinforced with nanoscale structures. The synthesis of PFA allow obtaining a resin with better properties than that showed by conventional phenolic resins and with synthesis and cure processes more controlled than observed for the furfuryl alcohol resin. This work has as main purpose the synthesis and thermal characterization of PFA resin and its nanostructured composites with different concentrations of carbon nanotubes (0, 0.1, 0.5 and 1.0 wt%). PFA resin was synthesized with 1:2:1 molar ratio of phenol/formaldehyde/furfuryl alcohol, according to the more appropriate condition obtained previously. The specimens were evaluated by thermogravimetry (TGA) to knowledge of the temperature of thermal degradation, either by actual analyses as simulated by simulation heating rate conversion software (known as Highway Simulation). The introduction of CNT in PFA sample does not affect its thermal stability. The values of residual weight found for samples with CNT additions are close to the values of the phenolic resin in the literature (about 60% residual weight).

Thermal behavior of extracted and delignified pine wood flour

Treesearch

Yao Chen; Mandla A. Tshabalala; Jianmin Gao; Nicole M. Stark; Yongming Fan; Rebecca E. Ibach

2014-01-01

To investigate the effect of extractives and lignin on the thermal stability of wood flour (WF), thermogravimetric analysis was used to determine thermal degradation behavior of extracted and delignified mixed pine WF. The contribution of lignin to thermal stability was greater than that of extractives. Removing extractives resulted in improved thermal stability by...

Inverse method to estimate kinetic degradation parameters of grape anthocyanins in wheat flour under simultaneously changing temperature and moisture.

PubMed

Lai, K P K; Dolan, K D; Ng, P K W

2009-06-01

Thermal and moisture effects on grape anthocyanin degradation were investigated using solid media to simulate processing at temperatures above 100 degrees C. Grape pomace (anthocyanin source) mixed with wheat pastry flour (1: 3, w/w dry basis) was used in both isothermal and nonisothermal experiments by heating the same mixture at 43% (db) initial moisture in steel cells in an oil bath at 80, 105, and 145 degrees C. To determine the effect of moisture on anthocyanin degradation, the grape pomace-wheat flour mixture was heated isothermally at 80 degrees C at constant moisture contents of 10%, 20%, and 43% (db). Anthocyanin degradation followed a pseudo first-order reaction with moisture. Anthocyanins degraded more rapidly with increasing temperature and moisture. The effects of temperature and moisture on the rate constant were modeled according to the Arrhenius and an exponential relationship, respectively. The nonisothermal reaction rate constant and activation energy (mean +/- standard error) were k(80 degrees C, 43% (db) moisture) = 2.81 x 10(-4)+/- 1.1 x 10(-6) s(-1) and DeltaE = 75273 +/- 197 J/g mol, respectively. The moisture parameter for the exponential model was 4.28 (dry basis moisture content)(-1). One possible application of this study is as a tool to predict the loss of anthocyanins in nutraceutical products containing grape pomace. For example, if the process temperature history and moisture history in an extruded snack fortified with grape pomace is known, the percentage anthocyanin loss can be predicted.

MODIS Solar Diffuser On-orbit Performance

NASA Technical Reports Server (NTRS)

Xiong, Xiaoxiong; Chen, H.; Choi, T.; Sun, J.; Angal, A.

2008-01-01

MODIS is a key instrument for the NASA Earth Observing System (EOS), currently operated on both the Terra and Aqua missions. Each MODIS instrument has 20 reflective solar bands (RSBs) and 16 thermal emissive bands (TEBs). MODIS RSB on-orbit calibration is reflectance based using an on-board solar diffuser (SD). The SD bi-directional reflectance factors (BRFs) were characterized pre-launch using reference diffuser samples, which are traceable to NIST reflectance standards. The SD BRF on-orbit degradation (or change) is tracked by another onboard device, called the solar diffuser stability monitor (SDSM). The SDSM is operated during each scheduled SD calibration event, making alternate observations of direct sunlight and the diffusely reflected sunlight from the SD. The time series of the ratios of SDSM's SD view to its Sun view provide SD degradation information. This paper presents and compares the Terra and Aqua MODIS SD on-orbit performance. Results show that the SD on-orbit degradation depends on the amount of solar exposure of the SD plate. In addition, it is strongly wavelengthdependent, with a larger degradation rate at shorter wavelengths. For Terra MODIS, an SD door anomaly occurred in May 2003 that led to a decision to fix the door permanently at an "open" position. Since then, the SD degradation rate has significantly increased due to more frequent solar exposure. As expected, the SD on-orbit performance directly impacts the RSB calibration performance. The lessons learned from MODIS on-orbit calibration will provide useful insights into the development and operation of future SD calibration systems.

Development and Fatigue Testing of Ceramic Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dong-Ming; Choi, Sung R.; Miller, Robert A.

2004-01-01

Ceramic thermal barrier coatings will play an increasingly important role in future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. Durability of the coating systems remains a critical issue with the ever-increasing temperature requirements. Thermal conductivity increase and coating degradation due to sintering and phase changes are known to be detrimental to coating performance. There is a need to characterize the coating thermal fatigue behavior and temperature limit, in order to potentially take full advantage of the current coating capability. In this study, thermal conductivity and cyclic fatigue behaviors of plasma-sprayed ZrO2-8wt%Y2O3 thermal barrier coatings were evaluated under high temperature, large thermal gradient and thermal cycling conditions. The coating degradation and failure processes were assessed by real-time monitoring of the coating thermal conductivity under the test conditions. The ceramic coating crack initiation and propagation driving forces and failure modes under the cyclic thermal loads will be discussed in light of the high temperature mechanical fatigue and fracture testing results.

Prediction of the lifetime of nitrile-butadiene rubber by FT-IR.

PubMed

Kawashima, Tetsuya; Ogawa, Toshio

2005-12-01

A quantitative measurement method with FT-IR was proposed for a thermal degradation analysis of nitrile-butadiene rubber (NBR). An NBR film was prepared as a model sample on a barium fluoride (BaF2) crystal plate, which was subjected to a heat treatment. The absorbances of various functional groups were measured directly by FT-IR after thermal degradation at high temperatures. By measuring the absorbances, it was possible to readily determine quantitatively each of the functional groups after the degradation of NBR. By assuming that the NBR lifetime was the point at which the absorbance of a carbon-carbon double bond reaches 45% of that prior to thermal treatment, a method for predicting the lifetime of NBR heated below 150 degrees C was proposed, by using an Arrhenius plot of the heating time versus heating temperature.

Thermal protection system (TPS) monitoring using acoustic emission

NASA Astrophysics Data System (ADS)

Hurley, D. A.; Huston, D. R.; Fletcher, D. G.; Owens, W. P.

2011-04-01

This project investigates acoustic emission (AE) as a tool for monitoring the degradation of thermal protection systems (TPS). The AE sensors are part of an array of instrumentation on an inductively coupled plasma (ICP) torch designed for testing advanced thermal protection aerospace materials used for hypervelocity vehicles. AE are generated by stresses within the material, propagate as elastic stress waves, and can be detected with sensitive instrumentation. Graphite (POCO DFP-2) is used to study gas-surface interaction during degradation of thermal protection materials. The plasma is produced by a RF magnetic field driven by a 30kW power supply at 3.5 MHz, which creates a noisy environment with large spikes when powered on or off. AE are waveguided from source to sensor by a liquid-cooled copper probe used to position the graphite sample in the plasma stream. Preliminary testing was used to set filters and thresholds on the AE detection system (Physical Acoustics PCI-2) to minimize the impact of considerable operating noise. Testing results show good correlation between AE data and testing environment, which dictates the physics and chemistry of the thermal breakdown of the sample. Current efforts for the project are expanding the dataset and developing statistical analysis tools. This study shows the potential of AE as a powerful tool for analysis of thermal protection material thermal degradations with the unique capability of real-time, in-situ monitoring.

Manufacturing of REBCO coils strongly bonded to cooling members with epoxy resin aimed at its application to Maglev

NASA Astrophysics Data System (ADS)

Mizuno, Katsutoshi; Ogata, Masafumi; Hasegawa, Hitoshi

2014-11-01

The REBCO coated conductor has been attracted attention because of its high current density in the presence of high magnetic field. If the coated conductor is applied to Maglev, the operational temperature of the on-board magnets will be over 40 K and energy consumption of cryocoolers will be reduced. That high operational temperature also means the absence of liquid helium. Therefore, reliable thermal coupling is desirable for cooling the coils. We propose an epoxy impregnated REBCO coil co-wound with PTFE tape. While the PTFE tape prevents the performance degradation of the coil, the epoxy resin bonds the coil to cooling members. We carried out three experiments to confirm that the coil structure which we propose has robust thermal coupling without the degradation. First, thermal resistances of paraffin and epoxy were measured varying the temperature from room temperature to 10 K. The measurement result indicates that paraffin has a risk of losing thermal coupling during cooling down. In another experiment, PTFE (polytetrafluoroethylene) tape insulator prevented performance degradation of a small epoxy impregnated REBCO coil, while another REBCO coil with polyimide tape showed clear performance degradation. Finally, we produced a racetrack REBCO coil with the same outer dimension as a Maglev on-board magnet coil. Although the racetrack coil was installed in a GFRP coil case and tightly bonded to the case by epoxy impregnation, any performance degradation was not observed.

The kinetics of reaction of the by-products of ablative materials at high temperatures and the rate of heat transfer between hot surfaces and reactive gases

NASA Technical Reports Server (NTRS)

Spokes, G. N.; Beadle, P. C.; Gac, N. A.; Golden, D. M.; King, K. D.; Benson, S. W.

1971-01-01

Research has been conducted by means of laboratory experiments to enhance understanding of the fundamental mechanisms of heterogeneous and homogeneous chemical reactions taking place during ablative processes that accompany the reentry or manned space vehicles into planetary atmospheres. Fundamental mechanisms of those chemical reactions believed to be important in the thermal degradation of ablative plastic heat shield materials, and the gases evolved, are described.

Effects of Environment on Creep Behavior of Nextel 720/Alumina-Mullite Ceramic Composite at 1200 deg C

DTIC Science & Technology

2008-03-01

creep life . This degradation increased with increasing temperatures. At 1000°, all specimens achieved creep run-out, defined as...strain measurement 29 Table 4. Summary of N720/AM creep data. Sample Environment Thermal Strain (%) E (GPa) Creep Stress (MPa) Creep Life (h...Material Creep Stress(MPa) Creep Life (h) Creep Strain (%) Secondary Creep Rate (s-1) N720/A 80 >100 0.798 1.5E-08 N720/A 100 41 1.520

Habitat degradation correlates with tolerance to climate-change related stressors in the green mussel Perna viridis from West Java, Indonesia.

PubMed

Wendling, Carolin Charlotte; Huhn, Mareike; Ayu, Nurina; Bachtiar, Ramadian; von Juterzenka, Karen; Lenz, Mark

2013-06-15

It is unclear whether habitat degradation correlates with tolerance of marine invertebrates to abiotic stress. We therefore tested whether resistance to climate change-related stressors differs between populations of the green mussel Perna viridis from a heavily impacted and a mostly pristine site in West Java, Indonesia. In laboratory experiments, we compared their oxygen consumption and mortality under lowered salinity (-13 and -18 units, both responses), hypoxia (0.5 mg/l, mortality only) and thermal stress (+7 °C, mortality only). Mussels from the eutrophied and polluted Jakarta Bay showed a significantly smaller deviation from their normal oxygen consumption and higher survival rates when stressed than their conspecifics from the unaffected Lada Bay. This shows that human induced habitat degradation correlates with mussel tolerance to environmental stress. We discuss possible mechanisms - e.g. the selection of tolerant genotypes or habitat-specific differences in the nutritional status of the mussels - that could explain our observation. Copyright © 2013 Elsevier Ltd. All rights reserved.

Undercutting Studies of Protected Kapton. H Exposed to In-Space and Ground-Based Atomic Oxygen

NASA Technical Reports Server (NTRS)

Snyder, Aaron; Banks, Bruce A.; Waters, Deborah L.

2006-01-01

This study is part of a Materials International Space Station Experiment (MISSE) sequence to characterize the performance of prospective spacecraft materials when subjected to the synergistic effects of the space environment. Atomic oxygen (AO) is the most prevalent species in low earth orbit (LEO). In this environment AO is mainly responsible for the erosion of hydrocarbons and halocarbon polymers. The AO erosion rates of Kapton (DuPont) H are known and well documented. Hence, it is customary to compare the AO erosion yields of candidate materials to the commonly accepted standard of this polyimide. The purpose of this study was to provide characterization of AO degradation of SiO(x) protected Kapton H film, which was subject during MISSE 2 to undercutting erosion beneath microscopic defects in the protective film, and compare the degradation resulting from hyperthermal ram (approx.4.5 eV) LEO AO to the degradation resulting from exposure to thermal ground-based (approx.0.04 eV) AO.

Microplastic Generation in the Marine Environment Through Degradation and Fragmentation

NASA Astrophysics Data System (ADS)

Perryman, M. E.; Jambeck, J.; Woodson, C. B.; Locklin, J.

2016-02-01

Plastic use has become requisite in our global economy; as population continues to increase, so too, will plastic production. At its end-of-life, some amount of plastic is mismanaged and ends up in the ocean. Once there, various environmental stresses eventually fragment plastic into microplastic pieces, now ubiquitous in the marine environment. Microplastics pose a serious threat to marine biota and possibly humans. Though the general mechanisms of microplastic formation are known, the rate and extent is not. Currently, no standard methodology for testing the formation of microplastic exists. We developed a replicable and flexible methodology for testing the formation of microplastics. We used this methodology to test the effects of UV, thermal, and mechanical stress on various types of plastic. We tested for fragmentation by measuring weight and size distribution, and looked for signs of degraded plastic using Fourier transform infrared spectroscopy. Though our results did not find any signs of fragmentation, we did see degradation. Additionally, we established a sound methodology and provided a benchmark for additional studies.

Chemical Changes in Proteins Produced by Thermal Processing.

ERIC Educational Resources Information Center

Dutson, T. R.; Orcutt, M. W.

1984-01-01

Discusses effects of thermal processing on proteins, focusing on (1) the Maillard reaction; (2) heat denaturation of proteins; (3) aggregation, precipitation, gelation, and degradation; and (4) other thermally induced protein reactions. Also discusses effects of thermal processing on muscle foods, egg proteins, fruits and vegetables, and cereal…

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.

PubMed

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.

Thermal Analysis of Acetylene Terminated Sulfone (ATS) Resin

DTIC Science & Technology

1990-01-18

Hydrogen Sulfide by Difference Gravimetry 71 (6) Analysis by Quantitative Proton Nuclear 72 Magnetic Resonance (NMR) Spectroscopy C.YI The Noncondensable...CARBONYL SULFIDE 24 DISTRIBUTION OF SULFUR IN THE PRODUCTS OF THERMAL 72 DEGRADATION TO 1020’C OF PRECURED ATS-G 25 GRAVIMETRY OF THE CONDENSABLE VOLATILE...procedure was devised making use of gravimetry in conjunction with proton NMR spectroscopy. The condensable volatile product fraction of degradation was

Thermal barrier coating life prediction model development

NASA Technical Reports Server (NTRS)

Demasi, J. T.; Sheffler, K. D.

1986-01-01

The objective of this program is to establish a methodology to predict Thermal Barrier Coating (TBC) life on gas turbine engine components. The approach involves experimental life measurement coupled with analytical modeling of relevant degradation modes. The coating being studied is a flight qualified two layer system, designated PWA 264, consisting of a nominal ten mil layer of seven percent yttria partially stabilized zirconia plasma deposited over a nominal five mil layer of low pressure plasma deposited NiCoCrAlY. Thermal barrier coating degradation modes being investigated include: thermomechanical fatigue, oxidation, erosion, hot corrosion, and foreign object damage.

Coulomb thermal properties and stability of the Io plasma torus

NASA Technical Reports Server (NTRS)

Barbosa, D. D.; Coroniti, F. V.; Eviatar, A.

1983-01-01

Coulomb collisional energy exchange rates are computed for a model of the Io plasma torus consisting of newly created pickup ions, a background of thermally degraded intermediary ions, and a population of cooler electrons. The electrons are collisionally heated by both the pickup ions and background ions and are cooled by electron impact excitation of plasma ions which radiate in the EUV. It is found that a relative concentration of S III pickup ions forbidden S III/electrons = 0.1 with a temperature of 340 eV can deliver energy to the electrons at a rate of 3 x 10 to the -13th erg/cu cm per sec, sufficient to power the EUV emissions in the Io torus. The model predicts a background ion temperature Ti of about 53 eV and an electron temperature Te of about 5.5 eV on the basis of steady-state energy balance relations at Coulomb rates. The model also predicts electron temperature fluctuations at the 30 percent level on a time scale of less than 11 hours, consistent with recent observations of this phenomenon.

Habitat degradation may affect niche segregation patterns in lizards

NASA Astrophysics Data System (ADS)

Pelegrin, N.; Chani, J. M.; Echevarria, A. L.; Bucher, E. H.

2013-08-01

Lizards partition resources in three main niche dimensions: time, space and food. Activity time and microhabitat use are strongly influenced by thermal environment, and may differ between species according to thermal requirements and tolerance. As thermal characteristics are influenced by habitat structure, microhabitat use and activity of lizards can change in disturbed habitats. We compared activity and microhabitat use of two abundant lizard species of the Semi-arid Chaco of Argentina between a restored and a highly degraded Chaco forest, to determine how habitat degradation affects lizard segregation in time and space, hypothesizing that as activity and microhabitat use of lizards are related to habitat structure, activity and microhabitat use of individual species can be altered in degraded habitats, thus changing segregation patterns between them. Activity changed from an overlapped pattern in a restored forest to a segregated pattern in a degraded forest. A similar trend was observed for microhabitat use, although to a less extent. No correlation was found between air temperature and lizard activity, but lizard activity varied along the day and among sites. Contrary to what was believed, activity patterns of neotropical diurnal lizards are not fixed, but affected by multiple factors related to habitat structure and possibly to interspecific interactions. Changes in activity patterns and microhabitat use in degraded forests may have important implications when analyzing the effects of climate change on lizard species, due to synergistic effects.

Degradability in vitro of polyurethanes based on synthetic atactic poly[(R,S)-3-hydroxybutyrate].

PubMed

Brzeska, J; Janeczek, H; Janik, H; Kowalczuk, M; Rutkowska, M

2015-01-01

The aim of the present study was to determine the degradability of aliphatic polyurethanes, based on a different amount of synthetic, atactic poly[(R,S)-3-hydroxybutyrate] (a-PHB), in hydrolytic (phosphate buffer) and oxidative (H2O2/CoCl2) solutions. The soft segments were built with atactic poly[(R,S)-3-hydroxybutyrate] and polycaprolactone or polyoxytetramethylenediols, whereas hard segments were the reaction product of 4,4'-methylenedicyclohexyl diisocyanate and 1,4-butanediol.The selected properties - density and morphology of polymer surfaces - which could influence the sensitivity of polymers to degradation processes - were analyzed.The analysis of molecular mass (GPC), thermal properties (DSC) and the sample weight changes were undertaken to estimate the degree of degradability of polymer samples after incubation in environments studied.Investigated polyurethanes were amorphous with the very low amount of crystalline phases of hard segments.The polyurethane synthesized with a poly[(R,S)-3-hydroxybutyrate] and polyoxytetramethylenediol at a molar ratio of NCO:OH=3.7:1 (prepolymer step) appeared as the most sensitive for both degradative solutions. Its weight and molecular mass losses were the highest in comparison to other investigated polyurethanes.It could be expected that playing with the amount of poly[(R,S)-3-hydroxybutyrate] in polyurethane synthesis the rate of polyurethane degradation after immersion in living body would be modeled.

Magnesium degradation observed in situ under flow by synchrotron radiation based microtomography

NASA Astrophysics Data System (ADS)

Feyerabend, Frank; Dose, Thomas; Xu, Yuling; Beckmann, Felix; Stekker, Michael; Willumeit-Römer, Regine; Schreyer, Andreas; Wilde, Fabian; Hammel, Jörg U.

2016-10-01

The use of degradable magnesium based implants is becoming clinically relevant, e.g. for the use as bone screws. Still there is a lack of analyzing techniques to characterize the in vitro degradation behavior of implant prototypes. The aim of this study was to design an in situ environment to continuously monitor the degradation processes under physiological conditions by time-lapse SRμCT. The use of physiological conditions was chosen to get a better approach to the in vivo situation, as it could be shown by many studies, that these conditions change on the one hand the degradation rate and on the other hand also the formed degradation products. The resulting in situ environment contains a closed bioreactor system to control and monitor the relevant parameters (37°C, 5 % O2, 20 % CO2) and to grant sterility of the setup. A flow cell was designed and manufactured from polyether etherketone (PEEK), which was chosen because of the good mechanical properties, high thermal and chemical resistance and radiographic translucency. Sterilization of the system including the sample was reached by a transient flush with 70 % ethanol and subsequent replacement by physiological medium (Modified Eagle Medium alpha). As proof of principle it could be shown that the system remained sterile during a beamtime of several days and that the continuous SRμCT imaging was feasible.

Prognostics Approach for Power MOSFET Under Thermal-Stress

NASA Technical Reports Server (NTRS)

Galvan, Jose Ramon Celaya; Saxena, Abhinav; Kulkarni, Chetan S.; Saha, Sankalita; Goebel, Kai

2012-01-01

The prognostic technique for a power MOSFET presented in this paper is based on accelerated aging of MOSFET IRF520Npbf in a TO-220 package. The methodology utilizes thermal and power cycling to accelerate the life of the devices. The major failure mechanism for the stress conditions is dieattachment degradation, typical for discrete devices with leadfree solder die attachment. It has been determined that dieattach degradation results in an increase in ON-state resistance due to its dependence on junction temperature. Increasing resistance, thus, can be used as a precursor of failure for the die-attach failure mechanism under thermal stress. A feature based on normalized ON-resistance is computed from in-situ measurements of the electro-thermal response. An Extended Kalman filter is used as a model-based prognostics techniques based on the Bayesian tracking framework. The proposed prognostics technique reports on preliminary work that serves as a case study on the prediction of remaining life of power MOSFETs and builds upon the work presented in [1]. The algorithm considered in this study had been used as prognostics algorithm in different applications and is regarded as suitable candidate for component level prognostics. This work attempts to further the validation of such algorithm by presenting it with real degradation data including measurements from real sensors, which include all the complications (noise, bias, etc.) that are regularly not captured on simulated degradation data. The algorithm is developed and tested on the accelerated aging test timescale. In real world operation, the timescale of the degradation process and therefore the RUL predictions will be considerable larger. It is hypothesized that even though the timescale will be larger, it remains constant through the degradation process and the algorithm and model would still apply under the slower degradation process. By using accelerated aging data with actual device measurements and real sensors (no simulated behavior), we are attempting to assess how such algorithm behaves under realistic conditions.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Q.; Hu, X; Wang, X

Water-insoluble regenerated silk materials are normally produced by increasing the {beta}-sheet content (silk II). In the present study water-insoluble silk films were prepared by controlling the very slow drying of Bombyx mori silk solutions, resulting in the formation of stable films with a predominant silk I instead of silk II structure. Wide angle X-ray scattering indicated that the silk films stabilized by slow drying were mainly composed of silk I rather than silk II, while water- and methanol-annealed silk films had a higher silk II content. The silk films prepared by slow drying had a globule-like structure at the coremore » surrounded by nano-filaments. The core region was composed of silk I and silk II, surrounded by hydrophilic nano-filaments containing random turns and {alpha}-helix secondary structures. The insoluble silk films prepared by slow drying had unique thermal, mechanical and degradative properties. Differential scanning calorimetry results revealed that silk I crystals had stable thermal properties up to 250 C, without crystallization above the T{sub g}, but degraded at lower temperatures than silk II structure. Compared with water- and methanol-annealed films the films prepared by slow drying had better mechanical ductility and were more rapidly enzymatically degraded, reflecting the differences in secondary structure achieved via differences in post processing of the cast silk films. Importantly, the silk I structure, a key intermediate secondary structure for the formation of mechanically robust natural silk fibers, was successfully generated by the present approach of very slow drying, mimicking the natural process. The results also point to a new mode of generating new types of silk biomaterials with enhanced mechanical properties and increased degradation rates, while maintaining water insolubility, along with a low {beta}-sheet content.« less

Investigating the Degradation Behaviors of a Therapeutic Monoclonal Antibody Associated with pH and Buffer Species.

PubMed

Zheng, Songyan; Qiu, Difei; Adams, Monica; Li, Jinjiang; Mantri, Rao V; Gandhi, Rajesh

2017-01-01

This study aimed in understanding the degradation behaviors of an IgG 1 subtype therapeutic monoclonal antibody A (mAb-A) associated with pH and buffer species. The information obtained in this study can augment conventional, stability-based screening paradigms by providing the direction necessary for efficient experimental design. Differential scanning calorimetry (DSC) was used for studying conformational stability. Dynamic light scattering (DLS) was utilized to generate B 22 *, a modified second virial coefficient for the character of protein-protein interaction. Size-exclusion chromatography (SEC) and hydrophobic interaction chromatography (HIC) were employed to separate degradation products. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) was used for determining the molecular size and liquid chromatography mass spectrometry (LC-MS) were used for identifying the sequence of the separated fragments. The results showed that both pH and buffer species played the roles in controlling the degradation behaviors of mAb-A, but the pH was more significant. In particular, pH 4.5 induced additional thermal transition peaks occurring at a low temperature compared with pH 6.5. A continual temperature-stress study illustrated that the additional thermal transition peaks related to the least stable structure and a greater fragmentation. Although mAb-A showed the comparable conformational structures and an identical amount of aggregates at time zero between the different types of buffer species at pH 6.5, the aggregation formation rate showed a buffer species-dependent discrepancy over a temperature-stress period. It was found that the levels of aggregations associated with the magnitudes of protein-protein interaction forces.

Fenton-like Degradation of Phenol Catalyzed by a Series of Fe-Containing Mixed Oxides Systems

NASA Astrophysics Data System (ADS)

Alhmoud, T. T.; Mahmoud, S. S.; Hammoudeh, A. Y.

2018-02-01

In our attempts to develop a solid catalyst to degrade organic pollutants in wastewater via the Fenton-like reaction, six Fe-containing mixed oxide systems were prepared by means of the sol-gel auto-combustion method to have the following stoichiometries: CuFe1.2O2.8, BaFe7.2O11.8, BaFe7.2Cu2O13.8, BaFe5.4V3O16.6, BaFe4.8Cu2V3O17.7 and Ag2Fe5.4V3O16.6. The prepared systems were thermally treated at 550°C, 650°C, 800°C and 1100°C, and then characterized by XRD to identify the present phases. The systems were tested with respect to their catalytic efficiency in the degradation of phenol (200 ppm) in water where CuFe1.2O2.8 was found to be the most reactive one (80% removal in 60 min). It showed thereby first-order kinetics and an enhanced behavior under irradiation with a 30-W LED light source. The positive role of irradiation was most obvious in the case of Ag2Fe5.4V3O16.6 in which almost complete conversion was achieved in 120 min compared to only 45% in the same period but without irradiation. However, increasing the temperature at which thermal treatment is performed was found to suppress the catalytic activity of the system. Due to their high efficiency and rather low leaching rates of constituents, CuFe1.2O2.8 or Ag2Fe5.4V3O16.6 seem to be very promising in the Fenton-like degradation of organic pollutants.

Syntheses and Degradations of Fluorinated Heterocyclics. 2; Perfluoroalkyl and Perfluroalkylether-1,2,4-Oxadiazoles

NASA Technical Reports Server (NTRS)

Paciorek, K. J. L.; Kratzer, R. H.; Kaufman, J.; Nakahara, J. H.; Rosser, R. W.; Parker, J. A.

1977-01-01

3-Perfluoroalkylether-5-perfluoro-n-heptyl-1,2,4-oxadiazole and 3,S-bis(perfluoroalkylether)-1,2,4-oxadiazole were synthesized and characterized. The 3, 5-bis(perfluoroalkylether)-l, 2,4-oxadiazole was subjected to thermal, thermal oxidative, and hydrolytic degradations at 235 and 325 C and was found to be stable under these conditions as evidenced by practically quantitative recovery of the test samples. In the presence of Jet-A fuel at 235 C a low degree of degradation, approximately 4%, was observed. 3,5-Bis(perfluoro-n-heptyl)-1,2,4-oxadiazole was found to be stable to attack by water at 325 C; however in air in the presence of jet-A at 235 C the extent of degradation was in excess of 10%.

Study on the thermal degradation of 3-MCPD esters in model systems simulating deodorization of vegetable oils.

PubMed

Ermacora, Alessia; Hrncirik, Karel

2014-05-01

The establishment of effective strategies for the mitigation of 3-MCPD esters in refined vegetable oils is restricted by limited knowledge of their mechanisms of formation and decomposition. In order to gain better understanding on the thermal stability of these compounds, a model system for mimicking oil refining conditions was developed. Pure 3-MCPD esters (3-MCPD dipalmitate and 3-MCPD dilaurate) were subjected to thermal treatment (180-260°C) and the degradation products where monitored over time (0-24h). After 24h of treatment, both 3-MCPD esters showed a significant degradation (ranging from 30% to 70%), correlating with the temperature applied. The degradation pathway, similar for both compounds, was found to involve isomerisation (very rapid, equilibrium was reached within 2h at 260°C), dechlorination and deacylation reactions. The higher relative abundance of non-chlorinated compounds, namely acylglycerols, in the first stages of the treatment suggested that dechlorination is preferred over deacylation with the conditions applied in this study. Copyright © 2013 Elsevier Ltd. All rights reserved.

Degradation sequence of young lunar craters from orbital infrared survey

NASA Technical Reports Server (NTRS)

Wieczorek, M. A.; Mendell, W. W.

1993-01-01

Using new software, nighttime thermal maps of the lunar surface have been generated from data obtained by the Apollo 17 Infrared Scanning Radiometer (ISR) in lunar orbit. Most of the thermal anomalies observed in the maps correspond to fresh lunar craters because blocks on the lunar surface maintain a thermal contrast relative to surrounding soil during the lunar night. Craters of Erastosthenian age and older - relatively young by lunar standards - have developed soil covers that make them almost indistinguishable from their surroundings in the thermal data. Thermal images of Copernican age craters show various stages of a degradation process, allowing the craters to be ranked by age. The ISR data should yield insights into lunar surface evolution as well as a more detailed understanding of the bombardment history after formation of the great mare basins.

Status Report - Cane Fiberboard Properties and Degradation Rates for Storage of the 9975 Shipping Package in KAMS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Daugherty, W. L.

Thermal, mechanical and physical properties have been measured on cane fiberboard samples following accelerated aging for up to approximately 7 years. The aging environments have included elevated temperature < 250 ?F (the maximum allowed service temperature for fiberboard in 9975 packages) and elevated humidity. The results from this testing have been analyzed, and aging models fit to the data. Correlations relating several properties (thermal conductivity, energy absorption, weight loss and height decrease) to their rate of change in potential storage environments have been developed. Combined with an estimate of the actual conditions the fiberboard experiences in KAMS, these models allowmore » development of service life predictions. Some of the predicted degradation rates presented in this report are relatively extreme. However, these relate to environments that do not exist within KAMS, or would be postulated only as upset conditions that would not likely persist for an extended period. For a typical package with ~10 watts internal heat load or less, and ambient temperatures below 90 ?F, the fiberboard experiences storage conditions less severe than any of the aging environments. Little or no degradation of the fiberboard is expected for typical storage conditions. It should be noted that the ultimate service life will be determined by the cumulative effect of degradation from all the conditions these packages might encounter. The assumptions and inputs behind the models in this report should be well understood before attempting to identify an actual service life in KAMS. Additional data continue to be collected to permit future refinements to the models and assumptions. For developing service life predictions, the ambient conditions within KAMS can be reasonably identified, and the temperature profiles within the various packages (with a range of heat loads and at varying locations within an array of packages) can be calculated. However, the humidity within the package is not as well characterized. While the outer drum does not provide an air-tight seal, it does greatly restrict the gain or loss of moisture in the fiberboard. Preliminary efforts have identified a relationship between the moisture content of fiberboard samples and the relative humidity of the surrounding air, but further work is needed in this area. Improvement in understanding this relationship might be realized with a change in the way humidity data are collected during field surveillances. It is recommended that the humidity be measured through a caplug hole before the package is removed from its storage location. The package would remain in thermal equilibrium, and anomalous humidity changes could be avoided. Further work should be performed to better define KAMS storage conditions and the environment within the 9975 shipping packages, and to identify appropriate limits for each property. This should be a joint effort by SRNL and NMM personnel. The results and model predictions presented in this report are applicable to 9975 packages with cane fiberboard overpack assemblies. A separate effort is underway to identify whether softwood fiberboard would behave similarly. In addition, the degradation models do not address the effects of non-conforming conditions such as the presence of excess moisture and mold, or beetle infestations.« less

Development and Operation of Arrays of TES x-ray Microcalorimeters Suitable for Constellation-X

NASA Technical Reports Server (NTRS)

Kilbourne, C. A.; Bandler, S. R.; Brown, A. D.; Chervenak, J. A.; Eckart, M. E.; Finkbeiner, F. M.; Iyomoto, N.; Kelley, R. L.; Porter, F. S.; Smith, S. J.;

[Municipal biowaste thermal-hydrolysis and ASBR anaerobic digestion].

PubMed

Hou, Hua-hua; Wang, Wei; Hu, Song; Xu, Yi-xian

2010-02-01

Thermal-hydrolysis can remarkably improve the solid organics dissolving efficiency of urban biomass waste, and anaerobic sequencing batch reactor (ASBR) was used to improve the efficiency of urban biomass waste anaerobic digestion. The optimum thermal-hydrolysis temperature and holding time was 175 degrees C and 60 min, the volatile suspended solid (VSS) dissolving ratio of kitchen waste, fruit-and-vegetable waste and sludge were 31.3%, 31.9% and 49.7%, respectively. Two ASBR and one continuous-flow stirred tank reactor (CSTR) were started at hydraulic retention time (HRT) = 20 d, COD organic loading rate (OLR) = 3.2-3.6 kg/(m3 x d). The biogas production volumes were 5656 mL/d(A1), 6335 mL/d(A2) and 3 103 mL/d(CSTR), respectively; VSS degradation ratios were 45.3% (A1), 50.87% (A2), 20.81% (CSTR), and the total COD (TCOD) removal rates were 88.1% (A1), 90% (A2), 72.6% (CSTR). In ASBR, organic solid and anaerobic microorganism were remained in the reactor during settling period. When HRT was 20 d, the solid retention time (SRT) was over 130 d, which made ASBR higher efficiency than CSTR.

Significant aspects on thermal degradation of hybrid biocomposite material

NASA Astrophysics Data System (ADS)

Bavan, D. Saravana; Kumar, G. C. Mohan

2013-06-01

Interest in use of bio fibers is increasing rapidly in structural and automotive applications because of few important properties such as low density, mechanical properties, renewability, biodegradation and sustainability. The present work is focused on fabricating a hybrid bio-composite material processed through compression molding technique. Natural fibers of maize and jute with bio polymeric resin of epoxidized soya bean oil are used as a matrix in obtaining a hybrid bio composite material. Thermal degradation of the prepared material is studied through Thermal gravimetric analyzer. Chemical treatment of the fibers was performed to have a better adhesion between the fibers and the matrix. The work is also surveyed on various parameters influencing the thermal properties and other aspects for a hybrid bio composite material.

Syntheses and Degradations of Fluorinated Heterocyclics. 3; Perfluoroalkyl and Perfluoroalkylether-1,3,4-Oxadiazoles

NASA Technical Reports Server (NTRS)

Paciorek, K. J. L.; Kaufman, J.; Nakahara, J. H.; Ito, T. I.; Kratzer, R. H.; Rosser, R. W.; Parker, J. A.

1977-01-01

2,5-Bis(perfluoro-n-heptyl)-, 2-perfluoroalkylether-5-perfluoro-n- heptyl- , and 2 , 5-bisperfluoroalkylether-1,3,4-oxadiazoles were synthesized and characterized. 2,5-Bis(perfluoro-n-heptyl)-1,3,4-oxadiazole was thermally and hydrolytically stable at 325 C; however, in the presence of air, degradation took place at 235 C. The perfluoroalkylether analogue exhibited thermal and hydrolytic stability at 325 C; it was found to be unaffected by jet-A fuel and air at 235 C. At 325 C in air some degradation occurred as evidenced by volatiles production, oxygen consumption, and 96% starting material recovery.

Degradation kinetics of ethylene-octene copolymer/wood flour biocomposites in dependence to filler content

NASA Astrophysics Data System (ADS)

Zykova, A. K.; Pantyukhov, P. V.; Monakhova, T. V.; Popov, A. A.

2017-06-01

This article is focused on thermal oxidative degradation and biodegradation in soil of biocomposites based on ethylene-octene copolymer (EOC), filled by wood flour (from 30 to 70% wt.), in dependence to the filler content. The study of oxidative degradation of composites was carried out at two temperatures (80 and 130°C respectively). The induction period and the rates of oxidation were determined. It was concluded that as filler content raises, the induction period increases. It can be explained by the higher specific area of composites in comparison with pure EOC. However, high filled composites (60 and 70 % of the filler) are oxidized with a huge induction period because polyphenols in the filler inhibit the oxidation process. Biodegradation test under laboratory conditions was carried out to investigate the biodegradability of the material. Composites with lower filler content have lower weight loss rate. Small particles are capsulated by polymer and are isolated from moisture and microorganisms. On the other hand, at a high filling of the composite small particles stick together and act as large ones. Such filler agglomerates are connected with each other and allow microorganisms to penetrate into the composite. It was concluded as filler content raises the mass loss increases.

Tagatose stability in milk and diet lemonade.

PubMed

Bell, Leonard N; Luecke, Katherine J

2012-01-01

The monosaccharide tagatose has been shown to behave physiologically as a prebiotic. To provide its healthful prebiotic effect to consumers, tagatose must not break down during food processing and storage. The objective of this study was to evaluate the storage and thermal stabilities of tagatose in milk and lemonade. Tagatose (0.9% to 1.5%) was added to commercially available shelf stable milk and diet lemonade. Samples were stored at 20, 40, 61, and 81 °C. Tagatose loss was monitored chromatographically. Pseudo-first-order rate constants for tagatose degradation were determined along with the reaction's activation energy. No tagatose degradation was observed in lemonade at temperatures equal to or less than 61 °C. Degradation occurred faster in milk because of its higher pH in comparison to lemonade and its dairy proteins enabling the Maillard reaction. The activation energy for tagatose degradation in milk was 24.6 kcal/mol. Using this activation energy, it was estimated that less than 0.1% tagatose would be lost during pasteurization and less than 4% would be lost during storage at 25 °C for 6 mo. Although tagatose degradation occurs in beverages, the extent of its loss during pasteurization and storage would be very low. Tagatose can be formulated into beverages with minimal concern about its degradation and the subsequent loss of prebiotic activity. Tagatose can be incorporated into beverages as a prebiotic to improve the healthful characteristics of the product without significant degradation. © 2011 Institute of Food Technologists®

Exploration on effects of 15 nm SiO2 filler on miscibility, thermal stability and ionic conductivity of PMMA/ENR 50 electrolytes

NASA Astrophysics Data System (ADS)

Zamri, S. F. M.; Latif, F. A.; Ali, A. M. M.; Ibrahim, R.; Azuan, S. I. H. M.; Kamaluddin, N.; Hadip, F.

2017-02-01

The effects of silicon dioxide (SiO2) (15 nm) filler on miscibility, thermal stability and ionic conductivity of polymethyl methacrylate/50% epoxidized narural rubber (PMMA/ENR 50) electrolytes were successfully explored. Samples were prepared by solvent casting method with tetrahydrofuran (THF) as solvent and doped with lithium tetrafluoroborate (LiBF4). Fourier transform infrared spectroscopy (FTIR) confirmed the present of hydrogen bond between PMMA and ENR 50. However, the hydrogen bond was reduced when SiO2 was added. Differential scanning calorimeter (DSC) analysis shows that PMMA/ENR 50 blends exhibit two glass transition temperatures (Tgs) recorded at -35 and 89 °C corresponding to the Tg of ENR 50 rich phase (Tg1) and PMMA rich phase (Tg2), respectively. However, the two Tgs almost merging and reduced when SiO2 was added. Tg1 was found increases as SiO2 weight percent increased. Thermogravimetric analysis (TGA) revealed that thermal degradation temperatures (Tds) of SiO2 filled PMMA/ENR 50 was similar as PMMA/ENR 50. Interestingly, thermal degradation temperatures of the loss of impurities (Td1) and thermal degradation temperatures of PMMA side chain (Td2) were increased when SiO2 was added. Meanwhile thermal degradation temperatures of main PMMA and ENR 50 main chain (Td3) was decreased as SiO2 was added. There was no significant change in Td1, Td2 and Td3 as SiO2 weight percent was varied. Electrochemical impedence spectroscopy (EIS) analysis shows that room temperature ionic conductivity of SiO2 filled PMMA/ENR 50 electrolytes were higher compaed PMMA/ENR 50 electrolyte with two conductivity maxima.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rochelle, Gary T; Seibert, Frank; Closmann, Fred

The objective of this work is to improve the process for CO{sub 2} capture by alkanolamine absorption/stripping by developing an alternative solvent, aqueous K{sub 2}CO3 promoted by piperazine (PZ). Pilot plant testing was performed in a 16.8-inch ID absorber and stripper with recirculation of air and CO{sub 2}. Three solvents (7 m MEA, 5 m K{sup +}/2.5 m PZ, and 6.4 m K{sup +}/1.6 m PZ) were tested in four campaigns with three different absorber packings. Pilot plant testing established that 5 m K{sup +}/2.5 m PZ requires two times less packing than 7 m MEA and three times lessmore » packing than 6.4 m K{sup +}/1.6 m PZ. A rigorous model of the thermodynamics and mass transfer was developed in the RateSep{trademark} block of AspenPlus{reg_sign}. The double matrix stripper reduces energy consumption by 5 to 15%. The best K{sup +}/PZ solvent, 4 m K{sup +}/4 m PZ, and the best process configuration, double matrix stripper with a double intercooled absorber, requires equivalent work of 40 kJ/mole CO{sub 2} to produce CO{sub 2} at 10 MPa. Inhibitor A is effective at reducing oxidative degradation over a wide range of metal concentrations and solvent types. Piperazine is resistant to oxidative degradation catalyzed by dissolved iron, but it oxidizes at rates comparable to monoethanolamine (MEA) in the presence of dissolved copper. The thermal degradation of MEA becomes significant at 120 C, but loaded piperazine solutions appear to be resistant to thermal degradation up to 135 C. The vapor pressure of PZ over typical lean solution at 40 C will be less than 25 ppm, which is less than the 40 ppm expected for MEA. Significant problems with foaming were encountered and alleviated by antifoamants in the pilot plant campaigns with K{sup +}/PZ. Potassium sulfate is not very soluble in 4 m K{sup +}/4 m PZ, so SO{sub 2} absorption and oxidation to sulfate in the bottom of the absorber may require operation with a slurry of potassium sulfate solids.« less

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

PubMed Central

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 activation energies for three transitions for cellulose and cellulose/PEG showed increasingly higher values for the transitions at higher temperatures. Key words:TGA, Bio-cellulose, PEG. PMID:28828153

Ultrasound assisted, thermally activated persulfate oxidation of coal tar DNAPLs.

PubMed

Peng, Libin; Wang, Li; Hu, Xingting; Wu, Peihui; Wang, Xueqing; Huang, Chumei; Wang, Xiangyang; Deng, Dayi

2016-11-15

The feasibility of ultrasound assisted, thermally activated persulfate for effective oxidation of twenty 2-6 ringed coal tar PAHs in a biphasic tar/water system and a triphasic tar/soil/water system were investigated and established. The results indicate that ultrasonic assistance, persulfate and elevated reaction temperature are all required to achieve effective oxidation of coal tar PAHs, while the heating needed can be provided by ultrasonic induced heating as well. Further kinetic analysis reveals that the oxidation of individual PAH in the biphasic tar/water system follows the first-order kinetics, and individual PAH oxidation rate is primary determined by the mass transfer coefficients, tar/water interfacial areas, the aqueous solubility of individual PAH and its concentration in coal tar. Based on the kinetic analysis and experimental results, the contributions of ultrasound, persulfate and elevated reaction temperature to PAHs oxidation were characterized, and the effects of ultrasonic intensity and oxidant dosage on PAHs oxidation efficiency were investigated. In addition, the results indicate that individual PAH degradability is closely related to its reactivity as well, and the high reactivity of 4-6 ringed PAHs substantially improves their degradability. Copyright © 2016 Elsevier B.V. All rights reserved.

Preparation of nano-TiO2/diatomite-based porous ceramics and their photocatalytic kinetics for formaldehyde degradation

NASA Astrophysics Data System (ADS)

Gao, Ru-qin; Sun, Qian; Fang, Zhi; Li, Guo-ting; Jia, Meng-zhe; Hou, Xin-mei

2018-01-01

Diatomite-based porous ceramics were adopted as carriers to immobilize nano-TiO2 via a hydrolysis-deposition technique. The thermal degradation of as-prepared composites was investigated using thermogravimetric-differential thermal analysis, and the phase and microstructure were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. The results indicated that the carriers were encapsulated by nano-TiO2 with a thickness of 300-450 nm. The main crystalline phase of TiO2 calcined at 650°C was anatase, and the average grain size was 8.3 nm. The FT-IR absorption bands at 955.38 cm-1 suggested that new chemical bonds among Ti, O, and Si had formed in the composites. The photocatalytic (PC) activity of the composites was investigated under UV irradiation. Furthermore, the photodegradation kinetics of formaldehyde was investigated using the composites as the cores of an air cleaner. A kinetics study showed that the reaction rate constants of the gas-phase PC reaction of formaldehyde were κ = 0.576 mg·m-3·min-1 and K = 0.048 m3/mg.

Thermal degradation products from PVC film in food-wrapping operations.

PubMed

Boettner, E A; Ball, G L

1980-07-01

Thermal degradation products of polyvinyl chloride (PVC) food-wrap films were studied under simulated supermarket conditons using a commercial wrapping machine with either a hot wire or a cool rod cutting device. A sampling hood was constructed around the wire/rod to confine and allow collection of thermal degradation products produced. Compounds analyzed and normal concentration ranges found included hydrogen chloride (1-10 micrograms per cut), plasticizer (1-50 micrograms per cut), benzene and toluene (each < 5-20 ng per cut), acrolein (25-150 ng per cut), and carbon monoxide (2-4 micrograms per cut) using the hot wire. Room air samples, collected during hot-wire cutting without the sampling hood, had < 0.25 ppm hydrogen chloride. Using the cool-rod cutting device hydrogen chloride, benzene, and toluene were not detected. Plasticizer was detected (25-86 micrograms per cut) using the cool rod.

Seawater infiltration effect on thermal degradation of fiber reinforced epoxy composites

NASA Astrophysics Data System (ADS)

Ibrahim, Mohd Haziq Izzuddin bin; Hassan, Mohamad Zaki bin; Ibrahim, Ikhwan; Rashidi, Ahmad Hadi Mohamed; Nor, Siti Fadzilah M.; Daud, Mohd Yusof Md

2018-05-01

Seawater salinity has been associated with the reduction of polymer structure durability. The aim of this study is to investigate the change in thermal degradation of fiber reinforced epoxy composite due to the presence of seawater. Carbon fiber, carbon/kevlar, fiberglass, and jute that reinforced with epoxy resin was laminated through hand-layup technique. Initially, these specimen was sectioned to 5×5 mm dimension, then immersed in seawater and distilled water at room temperature until it has thoroughly saturated. Following, the thermal degradation analysis using Differential Scanning Calorimetry (DSC), the thermic changes due to seawater infiltration was defined. The finding shows that moisture absorption reduces the glass transition temperature (Tg) of fiber reinforced epoxy composite. However, the glass transition temperature (Tg) of seawater infiltrated laminate composite is compareable with distilled water infiltrated laminate composite. The carbon fiber reinfored epoxy has the highest glass transition temperature out of all specimen.

Tribology. Mechanisms of antiwear tribofilm growth revealed in situ by single-asperity sliding contacts.

PubMed

Gosvami, N N; Bares, J A; Mangolini, F; Konicek, A R; Yablon, D G; Carpick, R W

2015-04-03

Zinc dialkyldithiophosphates (ZDDPs) form antiwear tribofilms at sliding interfaces and are widely used as additives in automotive lubricants. The mechanisms governing the tribofilm growth are not well understood, which limits the development of replacements that offer better performance and are less likely to degrade automobile catalytic converters over time. Using atomic force microscopy in ZDDP-containing lubricant base stock at elevated temperatures, we monitored the growth and properties of the tribofilms in situ in well-defined single-asperity sliding nanocontacts. Surface-based nucleation, growth, and thickness saturation of patchy tribofilms were observed. The growth rate increased exponentially with either applied compressive stress or temperature, consistent with a thermally activated, stress-assisted reaction rate model. Although some models rely on the presence of iron to catalyze tribofilm growth, the films grew regardless of the presence of iron on either the tip or substrate, highlighting the critical role of stress and thermal activation. Copyright © 2015, American Association for the Advancement of Science.

Mechanism and comparison of needle-type non-thermal direct and indirect atmospheric pressure plasma jets on the degradation of dyes

NASA Astrophysics Data System (ADS)

Attri, Pankaj; Yusupov, Maksudbek; Park, Ji Hoon; Lingamdinne, Lakshmi Prasanna; Koduru, Janardhan Reddy; Shiratani, Masaharu; Choi, Eun Ha; Bogaerts, Annemie

2016-10-01

Purified water supply for human use, agriculture and industry is the major global priority nowadays. The advanced oxidation process based on atmospheric pressure non-thermal plasma (NTP) has been used for purification of wastewater, although the underlying mechanisms of degradation of organic pollutants are still unknown. In this study we employ two needle-type atmospheric pressure non-thermal plasma jets, i.e., indirect (ID-APPJ) and direct (D-APPJ) jets operating at Ar feed gas, for the treatment of methylene blue, methyl orange and congo red dyes, for two different times (i.e., 20 min and 30 min). Specifically, we study the decolorization/degradation of all three dyes using the above mentioned plasma sources, by means of UV-Vis spectroscopy, HPLC and a density meter. We also employ mass spectroscopy to verify whether only decolorization or also degradation takes place after treatment of the dyes by the NTP jets. Additionally, we analyze the interaction of OH radicals with all three dyes using reactive molecular dynamics simulations, based on the density functional-tight binding method. This investigation represents the first report on the degradation of these three different dyes by two types of NTP setups, analyzed by various methods, and based on both experimental and computational studies.

Electrical short circuit and current overload tests on aircraft wiring

NASA Technical Reports Server (NTRS)

Cahill, Patricia

1995-01-01

The findings of electrical short circuit and current overload tests performed on commercial aircraft wiring are presented. A series of bench-scale tests were conducted to evaluate circuit breaker response to overcurrent and to determine if the wire showed any visible signs of thermal degradation due to overcurrent. Three types of wire used in commercial aircraft were evaluated: MIL-W-22759/34 (150 C rated), MIL-W-81381/12 (200 C rated), and BMS 1360 (260 C rated). A second series of tests evaluated circuit breaker response to short circuits and ticking faults. These tests were also meant to determine if the three test wires behaved differently under these conditions and if a short circuit or ticking fault could start a fire. It is concluded that circuit breakers provided reliable overcurrent protection. Circuit breakers may not protect wire from ticking faults but can protect wire from direct shorts. These tests indicated that the appearance of a wire subjected to a current that totally degrades the insulation looks identical to a wire subjected to a fire; however the 'fire exposed' conductor was more brittle than the conductor degraded by overcurrent. Preliminary testing indicates that direct short circuits are not likely to start a fire. Preliminary testing indicated that direct short circuits do not erode insulation and conductor to the extent that ticking faults did. Circuit breakers may not safeguard against the ignition of flammable materials by ticking faults. The flammability of materials near ticking faults is far more important than the rating of the wire insulation material.

Influence of the temperature and oxygen exposure in red Port wine: A kinetic approach.

PubMed

Oliveira, Carla Maria; Barros, António S; Silva Ferreira, António César; Silva, Artur M S

2015-09-01

Although phenolics are recognized to be related with health benefits by limiting lipid oxidation, in wine, they are the primary substrates for oxidation resulting in the quinone by-products with the participation of transition metal ions. Nevertheless, high quality Port wines require a period of aging in either bottle or barrels. During this time, a modification of sensory properties of wines such as the decrease of astringency or the stabilization of color is recognized to phenolic compounds, mainly attributed to anthocyanins and derived pigments. The present work aims to illustrate the oxidation of red Port wine based on its phenolic composition by the effect of both thermal and oxygen exposures. A kinetic approach toanthocyanins degradation was also achieved. For this purpose a forced red Port wine aging protocol was performed at four different storage temperatures, respectively, 20, 30, 35 and 40°C, and two adjusted oxygen saturation levels, no oxygen addition (treatment I), and oxygen addition (treatment II). Three hydroxycinnamic esters, three hydroxycinnamic acids, three hydroxybenzoic acids, two flavan-3-ols, and six anthocyanins were quantitated weekly during 63days, along with oxygen consumption. The most relevant phenolic oxidation markers were anthocyanins and catechin-type flavonoids, which had the highest decreases during the thermal and oxidative red Port wine process. Both temperature and oxygen treatments affected the rate of phenolic degradation. In addition, temperature seems to influence mostly the phenolics kinetic degradation. Copyright © 2015 Elsevier Ltd. All rights reserved.

Degradation Mechanisms in Aluminum Matrix Composites: Alumina/Aluminum and Boron/Aluminum. Ph.D. Thesis - North Carolina State Univ. at Raleigh

NASA Technical Reports Server (NTRS)

Olsen, G. C.

1981-01-01

The effects of fabrication and long term thermal exposure (up to 10,000 hours at 590 K) on two types of aluminum matrix composites were examined. An alumina/aluminum composite, was made of continuous alpha Al2O3 fibers in a matrix of commercially pure aluminum alloyed with 2.8% lithium. The mechanical properties of the material, the effect of isothermal exposure, cyclic thermal exposure, and fatigue are presented. Two degradation mechanisms are identified. One was caused by formation of a nonstoichiometric alumina during fabrication, the other by a loss of lithium to a surface reaction during long term thermal exposure. The other composite, boron/aluminum, made of boron fibers in an aluminum matrix, was investigated using five different aluminum alloys for the matrices. The mechanical properties of each material and the effect of isothermal and cyclic thermal exposure are presented. The effects of each alloy constituent on the degradation mechanisms are discussed. The effects of several reactions between alloy constituents and boron fibers on the composite properties are discussed.

Utilization of Tabula Rasa to Stabilize Bulk Lifetimes in n-Cz Silicon for High-Performance Solar Cell Processing

DOE Office of Scientific and Technical Information (OSTI.GOV)

LaSalvia, Vincenzo; Jensen, Mallory Ann; Youssef, Amanda

2016-11-21

We investigate a high temperature, high cooling-rate anneal Tabula Rasa (TR) and report its implications on n-type Czochralski-grown silicon (n-Cz Si) for photovoltaic fabrication. Tabula Rasa aims at dissolving and homogenizing oxygen precipitate nuclei that can grow during the cell process steps and degrade the cell performance due to their high internal gettering and recombination activity. The Tabula Rasa thermal treatment is performed in a clean tube furnace with cooling rates >100 degrees C/s. We characterize the bulk lifetime by Sinton lifetime and photoluminescence mapping just after Tabula Rasa, and after the subsequent cell processing. After TR, the bulk lifetimemore » surprisingly degrades to <; 0.1ms, only to recover to values equal or higher than the initial non-treated wafer (several ms), after typical high temperature cell process steps. Those include boron diffusion and oxidation; phosphorus diffusion/oxidation; ambient annealing at 850 degrees C; and crystallization annealing of tunneling-passivating contacts (doped polycrystalline silicon on 1.5 nm thermal oxide). The drastic lifetime improvement during high temperature cell processing is attributed to improved external gettering of metal impurities and annealing of intrinsic point defects. Time and injection dependent lifetime spectroscopy further reveals the mechanisms of lifetime improvement after Tabula Rasa treatment. Additionally, we report the efficacy of Tabula Rasa on n-type Cz-Si wafers and its dependence on oxygen concentration, correlated to position within the ingot.« less

Isolation of a thermophilic bacterium capable of low-molecular-weight polyethylene degradation.

PubMed

Jeon, Hyun Jeong; Kim, Mal Nam

2013-02-01

A thermophilic bacterium capable of low-molecular-weight polyethylene (LMWPE) degradation was isolated from a compost sample, and was identified as Chelatococcus sp. E1, through sequencing of the 16S rRNA gene. LMWPE was prepared by thermal degradation of commercial PE in a strict nitrogen atmosphere. LMWPE with a weight-average-molecular-weight (Mw) in the range of 1,700-23,700 was noticeably mineralized into CO(2) by the bacterium. The biodegradability of LMWPE decreased as the Mw increased. The low molecular weight fraction of LMWPE decreased significantly as a result of the degradation process, and thereby both the number-average-molecular-weight and Mw increased after biodegradation. The polydispersity of LMWPE was either narrowed or widened, depending on the initial Mw of LMWPE, due to the preferential elimination of the low molecular weight fraction, in comparison to the high molecular weight portion. LMWPE free from an extremely low molecular weight fraction was also mineralized by the strain at a remarkable rate, and FTIR peaks assignable to C-O stretching appeared as a result of microbial action. The FTIR peaks corresponding to alkenes also became more intense, indicating that dehydrogenations occurred concomitantly with microbial induced oxidation.

Mass loss of shuttle space suit orthofabric under simulated ionospheric atomic oxygen bombardment

NASA Technical Reports Server (NTRS)

Miller, W. L.

1985-01-01

Many polymeric materials used for thermal protection and insulation on spacecraft degrade significantly under prolonged bombardment by ionospheric atomic oxygen. The covering fabric of the multilayered shuttle space suit is composed of a loose weave of GORE-TEX fibers, Nomex and Kevlar-29, which are all polymeric materials. The complete evaluation of suit fabric degradation from ionospheric atomic oxygen is of importance in reevaluating suit lifetime and inspection procedures. The mass loss and visible physical changes of each test sample was determined. Kapton control samples and data from previous asher and flight tests were used to scale the results to reflect ionospheric conditions at about 220 km altitude. It is predicted that the orthofabric loses mass in the ionosphere at a rate of about 66% of the original orthofabric mass/yr. The outer layer of the two-layer orthofabric test samples shows few easily visible signs of degradation, even when observed at 440X. It is concluded that the orthofabric could suffer significant loss of performance after much less than a year of total exposure time, while the degradation might be undetectable in post flight visual examinations of space suits.

Novel Bi₁₂O₁₅Cl₆ Photocatalyst for the Degradation of Bisphenol A under Visible-Light Irradiation.

PubMed

Wang, Chu-Ya; Zhang, Xing; Song, Xiang-Ning; Wang, Wei-Kang; Yu, Han-Qing

2016-03-02

Bisphenol A (BPA), a typical endocrine-disrupting chemical, is widely present in water environments, and its efficient and cost-effective removal is greatly needed. Among various physicochemical methods for BPA degradation, visible-light-driven catalytic degradation of BPA is a promising approach because of its utilization of solar energy. Bismuth oxychloride (BiOCl) is recognized as an efficient photocatalyst, but its band gap, >3.0 eV, makes it inefficient for solar energy utilization, especially for degrading nondye pollutants like BPA. Thus, preparation and application of bismuth oxychloride photocatalysts with an increased visible-light activity are essential. In this work, inspired by density functional theory calculations, a novel bismuth oxychloride photocatalyst, Bi12O15Cl6, was designed. The nanosheets were successfully synthesized using a facile solvothermal method followed by a thermal treatment route. The prepared Bi12O15Cl6 nanosheets had a favorable energy band structure and thus exhibited a superior visible-light photocatalytic activity for degrading BPA. The BPA degradation rate by the Bi12O15Cl6 was determined to be 13.6 and 8.7 times faster than those for BiOCl and TiO2 (P25), respectively. The photogenerated reactive species and degradation intermediates were identified, and the photocatalytic mechanism was elucidated. Furthermore, the as-synthesized Bi12O15Cl6 nanosheets remained stable in the photocatalytic process and could be used repeatedly, demonstrating their promising application in the degradation of diverse pollutants in water and wastewater.

Development and Testing of Ceramic Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Choi, Sung R.; Miller, Robert A.

2004-01-01

Ceramic thermal barrier coatings will play an increasingly important role in future gas turbine engines because of their ability to effectively protect the engine components and further raise engine temperatures. Durability of the coating systems remains a critical issue with the ever-increasing temperature requirements. Thermal conductivity increase and coating degradation due to sintering and phase changes are known to be detrimental to coating performance. There is a need to characterize the coating behavior and temperature limits, in order to potentially take full advantage of the current coating capability, and also accurately assess the benefit gained from advanced coating development. In this study, thermal conductivity behavior and cyclic durability of plasma-sprayed ZrO2-8wt%Y2O3 thermal barrier coatings were evaluated under laser heat-flux simulated high temperature, large thermal gradient and thermal cycling conditions. The coating degradation and failure processes were assessed by real-time monitoring of the coating thermal conductivity under the test conditions. The ceramic coating crack propagation driving forces and resulting failure modes will be discussed in light of high temperature mechanical fatigue and fracture testing results.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liuyun, Jiang, E-mail: jlytxg@163.com; Chengdong, Xiong; Lixin, Jiang

Graphical abstract: In this manuscript, we initiated a systematic study to investigate the effect of HA on thermal properties, inner structure, reduction of mechanical strength, surface morphology and the surface deposit of n-HA/PLGA composite with respect to the soaking time. The results showed that n-HA played an important role in improving the degradation behavior of n-HA/PLGA composite, which can accelerate the degradation of n-HA/PLGA composite and endow it with bioactivity, after n-HA was detached from PLGA during the degradation, so that n-HA/PLGA composite may have a more promising prospect of the clinical application than pure PLGA as bone fracture internalmore » fixation materials, and the results would be of reference significance to predict the in vivo degradation and biological properties. - Highlights: • Effect of n-HA on degradation behavior of n-HA/PLGA composite was investigated. • Degradation behaviors of n-HA/PLGA and PLGA were carried out in SBF for 6 months. • Viscosity, thermal properties, inner structure and bending strength were tested. • n-HA can accelerate the degradation and endows it with bioactivity. - Abstract: To investigate the effect of hydroxyapatite(HA) on the degradation behavior of hydroxyapatite/poly(lactic-co-glycolic) acid (HA/PLGA) nanocomposite, the degradation experiment of n-HA/PLGA composite and pure PLGA were carried out by soaking in simulated body fluid(SBF) at 37 °C for 1, 2, 4 and 6 months. The change of intrinsic viscosity, thermal properties, inner structure, bending strength reduction, surface morphology and the surface deposit of n-HA/PLGA composite and pure PLGA with respect to the soaking time were investigated by means of UbbeloHde Viscometer, differential scanning calorimeter (DSC), scanning electron microscope(SEM), electromechanical universal tester, a conventional camera and X-ray diffraction (XRD). The results showed that n-HA played an important role in improving the degradation behavior of n-HA/PLGA composite, which can accelerate the degradation PLGA and endow it with bioactivity, after n-HA was detached from PLGA during the degradation, so that n-HA/PLGA composite may have a more promising prospect of the clinical application than pure PLGA as bone fracture internal fixation materials.« less

Thermal Remote Sensing and the Thermodynamics of Ecosystem Development

NASA Technical Reports Server (NTRS)

Luvall, Jeffrey C.; Rickman, Doug; Fraser, Roydon F.

2013-01-01

Thermal remote sensing can provide environmental measuring tools with capabilities for measuring ecosystem development and integrity. Recent advances in applying principles of nonequilibrium thermodynamics to ecology provide fundamental insights into energy partitioning in ecosystems. Ecosystems are nonequilibrium systems, open to material and energy flows, which grow and develop structures and processes to increase energy degradation. More developed terrestrial ecosystems will be more effective at dissipating the solar gradient (degrading its exergy content) and can be measured by the effective surface temperature of the ecosystem on a landscape scale. Ecosystems are viewed as open thermodynamic systems with a large gradient impressed on them by the exergy flux from the sun. Ecosystems, according to the restated second law, develop in ways that systematically increases their ability to degrade the incoming solar exergy, hence negating it's ability to set up even larger gradients. Thus it should be expected that more mature ecosystems degrade the exergy they capture more completely than a less developed ecosystem. The degree to which incoming solar exergy is degraded is a function of the surface temperature of the ecosystem. If a group of ecosystems receives the same amount of incoming radiation, we would expect that the most mature ecosystem would reradiate its energy at the lowest quality level and thus would have the lowest surface temperature (coldest black body temperature). Initial development work was done using NASA's airborne Thermal Infrared Multispectral Scanner (TIMS) followed by the use of a multispectral visible and thermal scanner-Airborne Thermal and Land Applications Sensor (ATLAS). Luvall and his coworkers have documented ecosystem energy budgets, including tropical forests, midlatitude varied ecosystems, and semiarid ecosystems. These data show that under similar environmental conditions (air temperature, relative humidity, winds, and solar irradiance) and within a given biome type, the more developed the ecosystem, the cooler it's surface temperature and the more degraded the quality of it's reradiated energy. HyspIRI is a hyperspectral visible/Near IR and multispectral thermal future global satellite mission that will collect data to study the world's ecosystems and will provide a benchmark on the state of the worlds ecosystems against which future changes can be assessed. HyspIRI will provide global data sets that will provide a means for measuring ecosystem development and integrity.

Thermal Remote Sensing and the Thermodynamics of Ecosystem Development

NASA Technical Reports Server (NTRS)

Luvall, Jeffrey C.; Rickman, Doug.; Fraser, Roydon F.

2013-01-01

Thermal remote sensing can provide environmental measuring tools with capabilities for measuring ecosystem development and integrity. Recent advances in applying principles of nonequilibrium thermodynamics to ecology provide fundamental insights into energy partitioning in ecosystems. Ecosystems are nonequilibrium systems, open to material and energy flows, which grow and develop structures and processes to increase energy degradation. More developed terrestrial ecosystems will be more effective at dissipating the solar gradient (degrading its exergy content) and can be measured by the effective surface temperature of the ecosystem on a landscape scale. Ecosystems are viewed as open thermodynamic systems with a large gradient impressed on them by the exergy flux from the sun. Ecosystems, according to the restated second law, develop in ways that systematically increases their ability to degrade the incoming solar exergy, hence negating it's ability to set up even larger gradients. Thus it should be expected that more mature ecosystems degrade the exergy they capture more completely than a less developed ecosystem. The degree to which incoming solar exergy is degraded is a function of the surface temperature of the ecosystem. If a group of ecosystems receives the same amount of incoming radiation, we would expect that the most mature ecosystem would reradiate its energy at the lowest quality level and thus would have the lowest surface temperature (coldest black body temperature). Initial development work was done using NASA's airborne Thermal Infrared Multispectral Scanner (TIMS) followed by the use of a multispectral visible and thermal scanner- Airborne Thermal and Land Applications Sensor (ATLAS). Luvall and his coworkers have documented ecosystem energy budgets, including tropical forests, midlatitude varied ecosystems, and semiarid ecosystems. These data show that under similar environmental conditions (air temperature, relative humidity, winds, and solar irradiance) and within a given biome type, the more developed the ecosystem, the cooler it's surface temperature and the more degraded the quality of it's reradiated energy. HyspIRI is a hyperspectral visible/Near IR and multispectral thermal future global satellite mission that will collect data to study the world's ecosystems and will provide a benchmark on the state of the worlds ecosystems against which future changes can be assessed. HyspIRI will provide global data sets that will provide a means for measuring ecosystem development and integrity.

Fate of deoxynivalenol and deoxynivalenol-3-glucoside during cereal-based thermal food processing: a review study.

PubMed

Wu, Qinghua; Kuča, Kamil; Humpf, Hans-Ulrich; Klímová, Blanka; Cramer, Benedikt

2017-02-01

Deoxynivalenol (DON), the most commonly occurring trichothecene in nature, may affect animal and human health through causing diarrhea, vomiting, gastrointestinal inflammation, and immunomodulation. DON-3-glucoside (DON-3G) as a major plant metabolite of the mycotoxin is another "emerging" food safety issue in recent years. Humans may experience potential health risks by consuming DON-contaminated food products. Thus, it is crucial for human and animal health to study also the degradation of DON and DON-3G during thermal food processing. Baking, boiling, steaming, frying, and extrusion cooking are commonly used during thermal food processing and have promising effects on the reduction of mycotoxins in food. For DON, however, the observed effects of these methods, as reported in numerous studies, are ambiguous and do not present a clear picture with regard to reduction or transformation. This review summarized the influence of thermal processing on the stability of DON and the formation of degradation/conversion products. Besides this, also a release of DON and DON-3G from food matrix as well as the release of DON from DON-3G during processing is discussed. In addition, some conflicting findings as reported from the studies on thermal processing as well as cause-effect relationships of the different thermal procedures are explored. Finally, the potential toxic profiles of DON degradation products are discussed as well when data are available.

Thermal barrier coating life prediction model

NASA Technical Reports Server (NTRS)

Hillery, R. V.; Pilsner, B. H.

1985-01-01

This is the first report of the first phase of a 3-year program. Its objectives are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system, then to develop and verify life prediction models accounting for these degradation modes. The first task (Task I) is to determine the major failure mechanisms. Presently, bond coat oxidation and bond coat creep are being evaluated as potential TBC failure mechanisms. The baseline TBC system consists of an air plasma sprayed ZrO2-Y2O3 top coat, a low pressure plasma sprayed NiCrAlY bond coat, and a Rene'80 substrate. Pre-exposures in air and argon combined with thermal cycle tests in air and argon are being utilized to evaluate bond coat oxidation as a failure mechanism. Unexpectedly, the specimens pre-exposed in argon failed before the specimens pre-exposed in air in subsequent thermal cycles testing in air. Four bond coats with different creep strengths are being utilized to evaluate the effect of bond coat creep on TBC degradation. These bond coats received an aluminide overcoat prior to application of the top coat to reduce the differences in bond coat oxidation behavior. Thermal cycle testing has been initiated. Methods have been selected for measuring tensile strength, Poisson's ratio, dynamic modulus and coefficient of thermal expansion both of the bond coat and top coat layers.

Thermal degradation and morphological studies on raw and reinforced polyacrylic rubbers

NASA Astrophysics Data System (ADS)

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.

Boron nitride nanotubes included thermally cross-linked gelatin-glucose scaffolds show improved properties.

PubMed

Şen, Özlem; Culha, Mustafa

2016-02-01

Boron nitride nanotubes (BNNTs) are increasingly investigated for their medical and biomedical applications due to their unique properties such as resistance to oxidation, thermal and electrical insulation, and biocompatibility. BNNTs can be used to enhance mechanical strength of biomedical structures such as scaffolds in tissue engineering applications. In this study, we report the use of BNNTs and hydroxylated BNNTs (BNNT-OH) to improve the properties of gelatin-glucose scaffolds prepared with electrospinning technique. Human dermal fibroblast (HDF) cells are used for the toxicity assessment and cell seeding studies. It is found that the addition of BNNTs into the scaffold does not influence cell viability, decreases the scaffold degradation rate, and improves cell attachment and proliferation compared to only-gelatin scaffold. Copyright © 2015 Elsevier B.V. All rights reserved.

Effect of particle- and specimen-level transport on product state in compacted-powder combustion synthesis and thermal debinding of polymers from molded powders

NASA Astrophysics Data System (ADS)

Oliveira, Amir Antonio Martins

The existence of large gradients within particles and fast temporal variations in the temperature and species concentration prevents the use of asymptotic approximations for the closure of the volume-averaged, specimen-level formulations. In this case a solution of the particle-level transport problem is needed to complement the specimen-level volume-averaged equations. Here, the use of combined specimen-level and particle-level models for transport in reactive porous media is demonstrated with two examples. For the gasless compacted-powder combustion synthesis, a three-scale model is developed. The specimen-level model is based on the volume-averaged equations for species and temperature. Local thermal equilibrium is assumed and the macroscopic mass diffusion and convection fluxes are neglected. The particle-level model accounts for the interparticle diffusion (i.e., the liquid migration from liquid-rich to liquid-lean regions) and the intraparticle diffusion (i.e., the species mass diffusion within the product layer formed at the surface of the high melting temperature component). It is found that the interparticle diffusion controls the extent of conversion to the final product, the maximum temperature, and to a smaller degree the propagation velocity. The intraparticle diffusion controls the propagation velocity and to a smaller degree the maximum temperature. The initial stages of thermal degradation of EVA from molded specimens is modeled using volume-averaged equations for the species and empirical models for the kinetics of the thermal degradation, the vapor-liquid equilibrium, and the diffusion coefficient of acetic acid in the molten polymer. It is assumed that a bubble forms when the partial pressure of acetic acid exceeds the external ambient pressure. It is found that the removal of acetic acid is characterized by two regimes, a pre-charge dominated regime and a generation dominated regime. For the development of an optimum debinding schedule, the heating rate is modulated to avoid bubbling, while the concentration and temperature follow the bubble-point line for the mixture. The results show a strong dependence on the presence of a pre-charge. It is shown that isolation of the pre-charge effect by using temporary lower heating rates results in an optimum schedule for which the process time is reduced by over 70% when compared to a constant heating rate schedule.

Probing collagen-enzyme mechanochemistry in native tissue with dynamic, enzyme-induced creep

PubMed Central

Zareian, Ramin; Church, Kelli P.; Saeidi, Nima; Flynn, Brendan P.; Beale, John W.; Ruberti, Jeffrey W.

2012-01-01

Mechanical strain or stretch of collagen has been shown to be protective of fibrils against both thermal and enzymatic degradation. The details of this mechanochemical relationship could change our understanding of load-bearing tissue formation, growth, maintenance and disease in vertebrate animals. However, extracting a quantitative relationship between strain and the rate of enzymatic degradation is extremely difficult in bulk tissue due to confounding diffusion effects. In this investigation, we develop a dynamic, enzyme-induced creep assay and diffusion/reaction rate scaling arguments to extract a lower bound on the relationship between strain and the cutting rate of bacterial collagenase (BC) at low strains. The assay method permits continuous, forced probing of enzyme-induced strain which is very sensitive to degradation rate differences between specimens at low initial strain. The results, obtained on uniaxially-loaded strips of bovine corneal tissue (0.1, 0.25 or 0.5 N), demonstrate that small differences in strain alter the enzymatic cutting rate of the BC substantially. It was estimated that a change in tissue elongation of only 1.5% (at ~5% strain) reduces the maximum cutting-rate of the enzyme by more than half. Estimation of the average load per monomer in the tissue strips indicates that this protective “cutoff” occurs when the collagen monomers are transitioning from an entropic to an energetic mechanical regime. The continuous tracking of the enzymatic cleavage rate as a function of strain during the initial creep response indicates that the decrease in the cleavage rate of the BC is non-linear (initially-steep between 4.5 and 6.5% then flattens out from 6.5–9.5%). The high sensitivity to strain at low strain implies that even lightly-loaded collagenous tissue may exhibit significant strain-protection. The dynamic, enzyme-induced creep assay described herein has the potential to permit the rapid characterization of collagen/enzyme mechanochemistry in many different tissue types. PMID:20429513

Smouldering Combustion of Soil Organic Matter: Inverse Modelling of the Thermal and Oxidative Degradation Kinetics

NASA Astrophysics Data System (ADS)

Huang, Xinyan; Rein, Guillermo

2013-04-01

Smouldering combustion of soil organic matter (SOM) such as peatlands leads to the largest fires on Earth and posses a possible positive feedback mechanism to climate change. In this work, a kinetic model, including 3-step chemical reactions and 1-step water evaporation is proposed to describe drying, pyrolysis and oxidation behaviour of peat. Peat is chosen as the most important type of SOM susceptible to smoudering, and a Chinese boreal peat sample is selected from the literature. A lumped model of mass loss based on four Arrhenius-type reactions is developed to predict its thermal and oxidative degradation under a range of heating rates. A genetic algorithm is used to solve the inverse problem, and find a group of kinetic and stoichiometric parameters for this peat that provides the best match to the thermogravimetric (TG) data from literature. A multi-objective fitness function is defined using the measurements of both mass loss and mass-loss rate in inert and normal atmospheres under a range of heating rates. Piece-wise optimization is conducted to separate the low temperature drying (<450 K) from the higher temperature pyrolysis and oxidation reaction (>450 K). Modelling results shows the proposed 3-step chemistry is the unique simplest scheme to satisfy all given TG data of this particular peat type. Afterward, this kinetic model and its kinetic parameters are incorporated into a simple one-dimensional species model to study the relative position of each reaction inside a smoulder front. Computational results show that the species model agrees with experimental observations. This is the first time that the smouldering kinetics of SOM is explained and predicted, thus helping to understanding this important natural and widespread phenomenon.

Using a 3D profiler and infrared camera to monitor oven loading in fully cooked meat operations

NASA Astrophysics Data System (ADS)

Stewart, John; Giorges, Aklilu

2009-05-01

Ensuring meat is fully cooked is an important food safety issue for operations that produce "ready to eat" products. In order to kill harmful pathogens like Salmonella, all of the product must reach a minimum threshold temperature. Producers typically overcook the majority of the product to ensure meat in the most difficult scenario reaches the desired temperature. A difficult scenario can be caused by an especially thick piece of meat or by a surge of product into the process. Overcooking wastes energy, degrades product quality, lowers the maximum throughput rate of the production line and decreases product yield. At typical production rates of 6000lbs/hour, these losses from overcooking can have a significant cost impact on producers. A wide area 3D camera coupled with a thermal camera was used to measure the thermal mass variability of chicken breasts in a cooking process. Several types of variability are considered including time varying thermal mass (mass x temperature / time), variation in individual product geometry and variation in product temperature. The automatic identification of product arrangement issues that affect cooking such as overlapping product and folded products is also addressed. A thermal model is used along with individual product geometry and oven cook profiles to predict the percentage of product that will be overcooked and to identify products that may not fully cook in a given process.

The Feasibility of Conformal Thermal Therapy with Transurethral Ultrasound Heating Applicators and MR Temperature Feedback

NASA Astrophysics Data System (ADS)

Choy, Vanessa; Tang, Kee; Wachsmuth, Jeff; Chopra, Rajiv; Bronskill, Michael

2006-05-01

Transurethral thermal therapy offers a minimally invasive alternative for the treatment of prostate diseases including benign prostate hyperplasia (BPH) and prostate cancer. Accurate heating of a targeted region of the gland can be achieved through the use of a rotating directional heating source incorporating planar ultrasound transducers, and the implementation of active temperature feedback along the beam direction during heating provided by magnetic resonance (MR) thermometry. The performance of this control method with practical spatial, temporal, and temperature resolution (such as angular alignment, spatial resolution, update rate for temperature feedback (imaging time), and the presence of noise) for thermal feedback using a clinical 1.5 T MR scanner was investigated in simulations. As expected, the control algorithm was most sensitive to the presence of noise, with noticeable degradation in its performance above ±2°C of temperature uncertainty. With respect to temporal resolution, acceptable performance was achieved at update rates of 5s or faster. The control algorithm was relatively insensitive to reduced spatial resolution due to the broad nature of the heating pattern produced by the heating applicator, this provides an opportunity to improve signal-to-noise ratio (SNR). The overall simulation results confirm that existing clinical 1.5T MR imagers are capable of providing adequate temperature feedback for transurethral thermal therapy without special pulse sequences or enhanced imaging hardware.

Non-thermal plasma for exhaust gases treatment

NASA Astrophysics Data System (ADS)

Alva R., Elvia; Pacheco P., Marquidia; Gómez B., Fernando; Pacheco P., Joel; Colín C., Arturo; Sánchez-Mendieta, Víctor; Valdivia B., Ricardo; Santana D., Alfredo; Huertas C., José; Frías P., Hilda

2015-09-01

This article describes a study on a non-thermal plasma device to treat exhaust gases in an internal combustion engine. Several tests using a plasma device to treat exhaust gases are conducted on a Honda GX200-196 cm3 engine at different rotational speeds. A plasma reactor could be efficient in degrading nitrogen oxides and particulate matter. Monoxide and carbon dioxide treatment is minimal. However, achieving 1%-3% degradation may be interesting to reduce the emission of greenhouse gases.

Extension of operational regime in high-temperature plasmas and effect of ECRH on ion thermal transport in the LHD

NASA Astrophysics Data System (ADS)

Takahashi, H.; Nagaoka, K.; Murakami, S.; Osakabe, M.; Nakano, H.; Ida, K.; Tsujimura, T. I.; Kubo, S.; Kobayashi, T.; Tanaka, K.; Seki, R.; Takeiri, Y.; Yokoyama, M.; Maeta, S.; Nakata, M.; Yoshinuma, M.; Yamada, I.; Yasuhara, R.; Ido, T.; Shimizu, A.; Tsuchiya, H.; Tokuzawa, T.; Goto, M.; Oishi, T.; Morita, S.; Suzuki, C.; Emoto, M.; Tsumori, K.; Ikeda, K.; Kisaki, M.; Shimozuma, T.; Yoshimura, Y.; Igami, H.; Makino, R.; Seki, T.; Kasahara, H.; Saito, K.; Kamio, S.; Nagasaki, K.; Mutoh, T.; Kaneko, O.; Morisaki, T.; the LHD Experiment Group

2017-08-01

A simultaneous high ion temperature (T i) and high electron temperature (T e) regime was successfully extended due to an optimized heating scenario in the LHD. Such high-temperature plasmas were realized by the simultaneous formation of an electron internal transport barrier (ITB) and an ion ITB by the combination of high power NBI and ECRH. Although the ion thermal confinement was degraded in the plasma core with an increase of T e/T i by the on-axis ECRH, it was found that the ion thermal confinement was improved at the plasma edge. The normalized ion thermal diffusivity {χ\\text{i}}/T\\text{i}1.5 at the plasma edge was reduced by 70%. The improvement of the ion thermal confinement at the edge led to an increase in T i in the entire plasma region, even though the core transport was degraded.

Thermoreflectance spectroscopy—Analysis of thermal processes in semiconductor lasers

NASA Astrophysics Data System (ADS)

Pierścińska, D.

2018-01-01

This review focuses on theoretical foundations, experimental implementation and an overview of experimental results of the thermoreflectance spectroscopy as a powerful technique for temperature monitoring and analysis of thermal processes in semiconductor lasers. This is an optical, non-contact, high spatial resolution technique providing high temperature resolution and mapping capabilities. Thermoreflectance is a thermometric technique based on measuring of relative change of reflectivity of the surface of laser facet, which provides thermal images useful in hot spot detection and reliability studies. In this paper, principles and experimental implementation of the technique as a thermography tool is discussed. Some exemplary applications of TR to various types of lasers are presented, proving that thermoreflectance technique provides new insight into heat management problems in semiconductor lasers and in particular, that it allows studying thermal degradation processes occurring at laser facets. Additionally, thermal processes and basic mechanisms of degradation of the semiconductor laser are discussed.

Thermally induced processes in mixtures of aluminum with organic acids after plastic deformations under high pressure

NASA Astrophysics Data System (ADS)

Zhorin, V. A.; Kiselev, M. R.; Roldugin, V. I.

2017-11-01

DSC is used to measure the thermal effects of processes in mixtures of solid organic dibasic acids with powdered aluminum, subjected to plastic deformation under pressures in the range of 0.5-4.0 GPa using an anvil-type high-pressure setup. Analysis of thermograms obtained for the samples after plastic deformation suggests a correlation between the exothermal peaks observed around the temperatures of degradation of the acids and the thermally induced chemical reactions between products of acid degradation and freshly formed surfaces of aluminum particles. The release of heat in the mixtures begins at 30-40°C. The thermal effects in the mixtures of different acids change according to the order of acid reactivity in solutions. The extreme baric dependences of enthalpies of thermal effects are associated with the rearrangement of the electron subsystem of aluminum upon plastic deformation at high pressures.

Quantifying deforestation and forest degradation with thermal response.

PubMed

Lin, Hua; Chen, Yajun; Song, Qinghai; Fu, Peili; Cleverly, James; Magliulo, Vincenzo; Law, Beverly E; Gough, Christopher M; Hörtnagl, Lukas; Di Gennaro, Filippo; Matteucci, Giorgio; Montagnani, Leonardo; Duce, Pierpaolo; Shao, Changliang; Kato, Tomomichi; Bonal, Damien; Paul-Limoges, Eugénie; Beringer, Jason; Grace, John; Fan, Zexin

2017-12-31

Deforestation and forest degradation cause the deterioration of resources and ecosystem services. However, there are still no operational indicators to measure forest status, especially for forest degradation. In the present study, we analysed the thermal response number (TRN, calculated by daily total net radiation divided by daily temperature range) of 163 sites including mature forest, disturbed forest, planted forest, shrubland, grassland, savanna vegetation and cropland. TRN generally increased with latitude, however the regression of TRN against latitude differed among vegetation types. Mature forests are superior as thermal buffers, and had significantly higher TRN than disturbed and planted forests. There was a clear boundary between TRN of forest and non-forest vegetation (i.e. grassland and savanna) with the exception of shrubland, whose TRN overlapped with that of forest vegetation. We propose to use the TRN of local mature forest as the optimal TRN (TRN opt ). A forest with lower than 75% of TRN opt was identified as subjected to significant disturbance, and forests with 66% of TRN opt was the threshold for deforestation within the absolute latitude from 30° to 55°. Our results emphasized the irreplaceable thermal buffer capacity of mature forest. TRN can be used for early warning of deforestation and degradation risk. It is therefore a valuable tool in the effort to protect forests and prevent deforestation. Copyright © 2017 Elsevier B.V. All rights reserved.

Thermal and photo-stability of the antioxidant potential of Spirulina platensis powder.

PubMed

Colla, L M; Bertol, C D; Ferreira, D J; Bavaresco, J; Costa, J A V; Bertolin, T E

2017-01-01

This work aimed to evaluate the thermal and photo stability of the antioxidant potential (AP) of the Spirulina platensis biomass. Thermal stability was established at 25ºC, 40ºC and 50ºC for 60 days, in the dark, protected from light. Photo stability was evaluated using UV (15 W, λ = 265 nm) and fluorescent (20 W, 0.16 A, power factor FP > 0.5, 50/60 Hz, 60 lm/w, 1200 lm) light for 90 days in capsules, glass and Petri dishes, at room temperature. The AP of the biomass in these conditions was determined at intervals (every 7 and 30 days in the studies of thermal and photo stability, respectively) using the induction of the oxidation of a lipid system by heat and aeration. In this lipid system, the biomass submitted to degradation was used as an antioxidant. The kinetics of the reaction was determined by the Arrhenius method. Thermal degradation was found to follow zero order kinetics, whereas photo degradation followed first order kinetics. The AP decreased 50% after 50 days at 25°C. At 40°C and 50°C, the AP decreased more than 50% after 35 and 21 days of exposition, respectively. The decrease of the AP of Spirulina was more sensible to UV and fluorescence light. After 30 days of exposition, the AP decreased more than 50% in all storage conditions tested. The antioxidant potential of Spirulina platensis is easily degraded when the biomass is exposed to heat and light, indicating the need for care to be taken in its storage.

Water Vapor Corrosion in EBC Constituent Materials

NASA Technical Reports Server (NTRS)

Kowalski, Benjamin; Fox, Dennis; Jacobson, Nathan S.

2017-01-01

Environmental Barrier Coating (EBC) materials are sought after to protect ceramic matrix composites (CMC) in high temperature turbine engines. CMCs are particularly susceptible to degradation from oxidation, Ca-Al-Mg-Silicate (CMAS), and water vapor during high temperature operation which necessitates the use of EBCs. However, the work presented here focuses on water vapor induced recession in EBC constituent materials. For example, in the presence of water vapor, silica will react to form Si(OH)4 (g) which will eventually corrode the material away. To investigate the recession rate in EBC constituent materials under high temperature water vapor conditions, thermal gravimetric analysis (TGA) is employed. The degradation process can then be modeled through a simple boundary layer expression. Ultimately, comparisons are made between various single- and poly-crystalline materials (e.g. TiO2, SiO2) against those found in literature.

Persistence of alprazolam in river water according to forced and non-forced degradation assays: adsorption to sediment and long-term degradation products.

PubMed

Jiménez, Juan J; Sánchez, María I; Muñoz, Beatriz E; Pardo, Rafael

2017-08-01

Alprazolam is a pharmaceutical compound that it is detected in surface waters. Some degradation studies in aqueous solutions and pharmaceutical products are available, but there is no reliable information about its stability in river water. Here, assays have been conducted under forced biological, photochemical, and thermal conditions, and under non-forced conditions, to estimate the fate of alprazolam in river water and know its degradation products. The forced assays indicated that the biological and photochemical degradation of alprazolam was negligible; heating at 70°C for a long time barely affected it. The degradation of alprazolam in river water at 100 μg/L was about 5% after 36 weeks, keeping the water under a natural day-night cycle at room temperature and limiting partially the exposure to sunlight as happens inside a body of water; no change in concentration was observed when the monitoring was performed at 2 μg/L. The results suggest the persistence of alprazolam in surface water and a possible accumulation over time. Residues were monitored by ultra-pressure liquid chromatography/quadrupole time-of-flight/mass spectrometry after solid-phase extraction; nine degradation products were found and the structures for most of them were proposed from the molecular formulae and fragmentation observed in high-resolution tandem mass spectra. (5-chloro-2-(3-methyl-4H-1,2,4-triazol-4-yl)phenyl)(phenyl)methanol was the main long-term transformation product in conditions that simulate those in a mass of water. The degradation rate in presence of sediment was equally very low under non-forced conditions; adsorption coefficients of alprazolam and major degradation products were calculated. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

Stability, Antioxidant Capacity and Degradation Kinetics of Pelargonidin-3-glucoside Exposed to Ultrasound Power at Low Temperature.

PubMed

Sun, Jianxia; Mei, Zhouxiong; Tang, Yajuan; Ding, Lijun; Jiang, Guichuan; Zhang, Chi; Sun, Aidong; Bai, Weibin

2016-08-24

As an alternative preservation method to thermal treatment, ultrasound is a novel non-thermal processing technology that can significantly avoid undesirable nutritional changes. However, recently literature indicated that anthocyanin degradation occurred when high amplitude ultrasound was applied to juice. This work mainly studied the effect of ultrasound on the stability and antioxidant capacity of pelargonidin-3-glucoside (Pg-3-glu) and the correlation between anthocyanin degradation and •OH generation in a simulated system. Results indicated that the spectral intensities of Pg-3-glu decreased with increasing ultrasound power (200-500 W) and treatment time (0-60 min). The degradation trend was consistent with first-order reaction kinetics (R² > 0.9100). Further study showed that there was a good linear correlation between Pg-3-glu degradation and •OH production (R² = 0.8790), which indicated the important role of •OH in the degradation of anthocyanin during ultrasound exposure. Moreover, a decrease in the antioxidant activity of solution(s) containing Pg-3-glu as evaluated by the DPPH and FRAP methods was observed after ultrasound treatment.

Degradation of Hubble Space Telescope Metallized Teflon(trademark) FEP Thermal Control Materials

NASA Technical Reports Server (NTRS)

Hansen, Patricia A.; Townsend, Jacqueline A.; Yoshikawa, Yukio; Castro, J. David; Triolo, Jack J.; Peters, Wanda C.

1998-01-01

The mechanical and optical properties of the metallized Teflon Fluorinated Ethylene Propylene (FEP) thermal control materials on the Hubble Space Telescope (HST) have degraded over the seven years the telescope has been in orbit. Astronaut observations and photographic documentation from the Second Servicing Mission revealed severe cracks of the multi-layer insulation (MLI) blanket outer layer in many locations around the telescope, particularly on solar facing surfaces. Two samples, the outer Teflon FEP MLI layer and radiator surfaces, were characterized post- mission through exhaustive mechanical, thermal, chemical, and optical testing. The observed damage to the thermal control materials, the sample retrieval and handling, and the significant changes to the radiator surfaces of HST will be discussed. Each of these issues is addressed with respect to current and future mission requirements.

Coating effects on thermal properties of carbon carbon and carbon silicon carbide composites for space thermal protection systems

NASA Astrophysics Data System (ADS)

Albano, M.; Morles, R. B.; Cioeta, F.; Marchetti, M.

2014-06-01

Many are the materials for hot structures, but the most promising one are the carbon based composites nowadays. This is because they have good characteristics with a high stability at high temperatures, preserving their mechanical properties. Unfortunately, carbon reacts rapidly with oxygen and the composites are subjected to oxidation degradation. From this point of view CC has to be modified in order to improve its thermal and oxidative resistance. The most common solutions are the use of silicon carbide into the carbon composites matrix (SiC composites) to make the thermal properties increase and the use of coating on the surface in order to protect the composite from the space plasma effects. Here is presented an experimental study on coating effects on these composites. Thermal properties of coated and non coated materials have been studied and the thermal impact on the matrix and surface degradation is analyzed by a SEM analysis.

Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various fibers

NASA Technical Reports Server (NTRS)

Bowles, Kenneth J.

1990-01-01

An experimental study was conducted to measure the thermo-oxidative stability of PMR-15 polymer matrix composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers that were studied included graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber-sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

Mechanism-Based Design for High-Temperature, High-Performance Composites. Book 1

DTIC Science & Technology

1997-09-01

with low thermal expansion and stiffness. Despite their importance in determining the performance of CMC structures, thermal properties have...continuous fibers Cox and Zok 669 account for degradation in the thermal expansion and conductivity of cross-ply laminates in the presence of...inherent disadvantages persist. Oxides generally exhibit higher thermal expansion and lower thermal conductivity than SiC-based CMCs and will

Digital Simulation Of Precise Sensor Degradations Including Non-Linearities And Shift Variance

NASA Astrophysics Data System (ADS)

Kornfeld, Gertrude H.

1987-09-01

Realistic atmospheric and Forward Looking Infrared Radiometer (FLIR) degradations were digitally simulated. Inputs to the routine are environmental observables and the FLIR specifications. It was possible to achieve realism in the thermal domain within acceptable computer time and random access memory (RAM) requirements because a shift variant recursive convolution algorithm that well describes thermal properties was invented and because each picture element (pixel) has radiative temperature, a materials parameter and range and altitude information. The computer generation steps start with the image synthesis of an undegraded scene. Atmospheric and sensor degradation follow. The final result is a realistic representation of an image seen on the display of a specific FLIR.

Evaluation of Fuel Cell Operation and Degradation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, Mark; Gemmen, Randall; Richards, George

The concepts of area specific resistance (ASR) and degradation are developed for different fuel cell operating modes. The concepts of exergetic efficiency and entropy production were applied to ASR and degradation. It is shown that exergetic efficiency is a time-dependent function useful describing the thermal efficiency of a fuel cell and the change in thermal efficiency of a degrading fuel cell. Entropy production was evaluated for the cases of constant voltage operation and constant current operation of the fuel cell for a fuel cell undergoing ohmic degradation. It was discovered that the Gaussian hypergeometric function describes the cumulative entropy andmore » electrical work produced by fuel cells operating at constant voltage. The Gaussian hypergeometric function is found in many applications in modern physics. This paper builds from and is an extension of several papers recently published by the authors in the Journal of The Electrochemical Society (ECS), ECS Transactions, Journal of Power Sources, and the Journal of Fuel Cell Science and Technology.« less

High-power UV-LED degradation: Continuous and cycled working condition influence

NASA Astrophysics Data System (ADS)

Arques-Orobon, F. J.; Nuñez, N.; Vazquez, M.; Segura-Antunez, C.; González-Posadas, V.

2015-09-01

High-power (HP) UV-LEDs can replace UV lamps for real-time fluoro-sensing applications by allowing portable and autonomous systems. However, HP UV-LEDs are not a mature technology, and there are still open issues regarding their performance evolution over time. This paper presents a reliability study of 3 W UV-LEDs, with special focus on LED degradation for two working conditions: continuous and cycled (30 s ON and 30 s OFF). Accelerated life tests are developed to evaluate the influence of temperature and electrical working conditions in high-power LEDs degradation, being the predominant failure mechanism the degradation of the package. An analysis that includes dynamic thermal and optical HP UV-LED measurements has been performed. Static thermal and stress simulation analysis with the finite element method (FEM) identifies the causes of package degradation. Accelerated life test results prove that HP UV-LEDs working in cycled condition have a better performance than those working in continuous condition.

A Novel Approach to Detect Accelerated Aged and Surface-Mediated Degradation in Explosives by UPLC-ESI-MS.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beppler, Christina L

2015-12-01

A new approach was created for studying energetic material degradation. This approach involved detecting and tentatively identifying non-volatile chemical species by liquid chromatography-mass spectrometry (LC-MS) with multivariate statistical data analysis that form as the CL-20 energetic material thermally degraded. Multivariate data analysis showed clear separation and clustering of samples based on sample group: either pristine or aged material. Further analysis showed counter-clockwise trends in the principal components analysis (PCA), a type of multivariate data analysis, Scores plots. These trends may indicate that there was a discrete shift in the chemical markers as the went from pristine to aged material, andmore » then again when the aged CL-20 mixed with a potentially incompatible material was thermally aged for 4, 6, or 9 months. This new approach to studying energetic material degradation should provide greater knowledge of potential degradation markers in these materials.« less

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

NASA Astrophysics Data System (ADS)

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).

Evaluation of Dowfrost(TM) HD as a Thermal Control Fluid for Constellation Vehicles

NASA Technical Reports Server (NTRS)

Lee, Steve

2009-01-01

A test was conducted from November 2008 to January 2009 to help determine the compatibility of an inhibited propylene glycol/water solution with planned Constellation vehicles. Dowfrost(TradeMark) HD was selected as the baseline for Orion, as well as other Constellation systems. Therefore, the same Dowfrost(TradeMark) HD/Water solution planned for Orion was chosen for this test. The fluid was subjected to a thermal fluid loop that had flightlike properties, as compared to Orion. The fluid loop had similar wetted materials, temperatures, flow rates, and aluminum wetted surface area to fluid volume ratio. The test was designed to last for 10 years, the life expectancy of the lunar habitat. However, the test lasted less than two months. System filters became clogged with precipitate, rendering the fluid system inoperable. Upon examination of the precipitate, it was determined that the precipitate composition contained aluminum, which could have only come from materials in the test stand, as aluminum is not part of the Dowfrost(TradeMark HD composition. Also, the fluid pH was determined to have increased from 10.1, at the first test sample, to 12.2, at the completion of the test. This high of a pH is corrosive to aluminum and was certainly a contributing factor to the development of precipitate. Chemical analyses and bench-top tests are currently ongoing to determine the underlying cause for this rapid degradation of the fluid. Hamilton Sundstrand, the contractor developing the Orion thermal fluid loop, is performing a parallel effort to not only understand the cause of fluid degradation in the test, but also to investigate solutions to avoid this problem in the Orion s thermal control system. JSC also consulted with the Hamilton Sundstrand team in the development of this test and the subsequent analysis.

Method of radiation degradation of PTFE under vacuum conditions

NASA Astrophysics Data System (ADS)

Korenev, Sergey

2004-09-01

A new method of radiation degradation of Polytetrafluoroethylene (PTFE) under vacuum conditions is considered in this report. The combination of glow gas discharge and electrical surface discharge (on surface and inside PTFE) increases the efficiency of thermal-radiation degradation. The main mechanism of this degradation method consists of the breaking of C-C and C-F bonds. The vacuum conditions allow decreasing of the concentration of toxic compounds, such as a HF. Experimental results for degradation of PTFE are presented.

Practical Approaches to Forced Degradation Studies of Vaccines.

PubMed

Hasija, Manvi; Aboutorabian, Sepideh; Rahman, Nausheen; Ausar, Salvador F

2016-01-01

During the early stages of vaccine development, forced degradation studies are conducted to provide information about the degradation properties of vaccine formulations. In addition to supporting the development of analytical methods for the detection of degradation products, these stress studies are used to identify optimal long-term storage conditions and are part of the regulatory requirements for the submission of stability data. In this chapter, we provide detailed methods for forced degradation analysis under thermal, light, and mechanical stress conditions.

Nondestructive evaluation of composite materials by electrical resistance measurement

NASA Astrophysics Data System (ADS)

Mei, Zhen

This dissertation investigates electrical resistance measurement for nondestructive evaluation of carbon fiber (CF) reinforced polymer matrix composites. The method involves measuring the DC electrical resistance in either the longitudinal or through thickness direction. The thermal history and thermal properties of thermoplastic/CF composites were studied by longitudinal and through-thickness resistance measurements. The resistance results were consistent with differential scanning calorimetry (DSC) and thermomechanical analysis (TMA) results. The resistance measurements gave more information on the melting of the polymer matrix than TMA. They were more sensitive to the glass transition of the polymer matrix than DSC. The through-thickness resistance decreased as autohesion progressed. The activation energy of autohesion was 21.2 kJ/mol for both nylon-6 and polyphenylene sulfide (PPS)/CF composites. Adhesive bonding and debonding were monitored in real-time by measurement of the through-thickness resistance between the adherends in an adhesive joint during heating and subsequent cooling. Debonding occurred during cooling when the pressure or temperature during prior bonding was not sufficiently high. A long heating time below the melting temperature (T m) was found to be detrimental to subsequent PPS adhesive joint development above Tm, due to curing reactions below Tm and consequent reduced mass flow response above Tm. A high heating rate (small heating time) enhanced the bonding more than a high pressure. The longitudinal resistance measurement was used to investigate the effects of temperature and stress on the interface between a concrete substrate and its epoxy/CF composite retrofit. The resistance of the retrofit was increased by bond degradation, whether the degradation was due to heat or stress. The degradation was reversible. Irreversible disturbance in the fiber arrangement occurred slightly as thermal or load cycling occurred, as indicated by the resistance decreasing cycle by cycle. This dissertation also addresses the use of the electrical resistance method to observe thermal and mechanical damage in real time. A temperature increase caused the interlaminar contact resistance to decrease reversibly within each thermal cycle, while thermal damage caused the resistance to decrease abruptly and irreversibly, due to matrix molecular movement and the consequent increase in the chance of fibers of one lamina touching those of an adjacent lamina. The through-thickness volume resistivity irreversibly and gradually decreased upon mechanical damage, which was probably fiber-matrix debonding. Moreover, it reversibly and abruptly increased upon matrix micro-structural change, which occurred reversibly near the peak stress of a stress cycle.

Mechanisms of propylene glycol and triacetin pyrolysis.

PubMed

Laino, Teodoro; Tuma, Christian; Moor, Philippe; Martin, Elyette; Stolz, Steffen; Curioni, Alessandro

2012-05-10

Propylene glycol and triacetin are chemical compounds, commonly used as food additives. Though the usage of the pure chemicals is not considered harmful when used as dietary supplements, little is known about the nature of their thermal degradation products and the impact they may have on human health. For these reasons, in this manuscript we investigate the thermal decomposition mechanisms of both neutral propylene glycol and triacetin in the gas phase by a novel simulation framework. This is based on a free energy sampling methodology followed by an accurate energy refinement. Structures, Gibbs free energy barriers, and rate constants at 800 K were computed for the different steps involved in the two pyrolytic processes. The thermal decomposition mechanisms found theoretically for propylene glycol and triacetin were validated by a qualitative experimental investigation using gas-phase chromatography-mass spectroscopy, with excellent agreement. The results provide a validation of the novel simulation framework and shed light on the potential hazard to the health that propylene glycol and triacetin may have when exposed to high temperatures.

Facile fabrication of HDPE-g-MA/nanodiamond nanocomposites via one-step reactive blending.

PubMed

Song, Ping'an; Yu, Youming; Wu, Qiang; Fu, Shenyuan

2012-06-29

In this letter, nanocomposites based on maleic anhydride grafted high density polyethylene (HDPE-g-MA) and amine-functionalized nanodiamond (ND) were fabricated via one-step reactive melt-blending, generating a homogeneous dispersion of ND, as evidenced by transmission electron microscope observations. Thermal analysis results suggest that addition of ND does not affect significantly thermal stability of polymer matrix in nitrogen. However, it was interestingly found that incorporating pure ND decreases the thermal oxidation degradation stability temperature, but blending amino-functionalized ND via reactive processing significantly enhances it of HDPE in air condition. Most importantly, cone tests revealed that both ND additives and reactive blending greatly reduce the heat release rate of HDPE. The results suggest that ND has a potential application as flame retardant alternative for polymers. Tensile results show that adding ND considerably enhances Young's modulus, and reactive blending leads to further improvement in Young's modulus while hardly reducing the elongation at break of HDPE.

Facile fabrication of HDPE-g-MA/nanodiamond nanocomposites via one-step reactive blending

PubMed Central

2012-01-01

In this letter, nanocomposites based on maleic anhydride grafted high density polyethylene (HDPE-g-MA) and amine-functionalized nanodiamond (ND) were fabricated via one-step reactive melt-blending, generating a homogeneous dispersion of ND, as evidenced by transmission electron microscope observations. Thermal analysis results suggest that addition of ND does not affect significantly thermal stability of polymer matrix in nitrogen. However, it was interestingly found that incorporating pure ND decreases the thermal oxidation degradation stability temperature, but blending amino-functionalized ND via reactive processing significantly enhances it of HDPE in air condition. Most importantly, cone tests revealed that both ND additives and reactive blending greatly reduce the heat release rate of HDPE. The results suggest that ND has a potential application as flame retardant alternative for polymers. Tensile results show that adding ND considerably enhances Young’s modulus, and reactive blending leads to further improvement in Young’s modulus while hardly reducing the elongation at break of HDPE. PMID:22747773

Effect of EVA on thermal stability, flammability, mechanical properties of HDPE/EVA/Mg(OH)2 composites

NASA Astrophysics Data System (ADS)

Cao, R.; Deng, Z. L.; Ma, Y. H.; Chen, X. L.

2017-06-01

In this work, ethylene vinyl acetate (EVA) is introduced to improve the properties of high-density polyethylene (HDPE)/magnesium hydroxide (MH) composites. The thermal stability, flame retardancy and mechanical properties of HDPE/EVA/MH composites are investigated and discussed. With increasing content of EVA, the limiting oxygen index (LOI) of the composites increases. The thermal stability analysis shows that the initial decomposition temperature begins at a low temperature; however, the residues of the composites at 600°C increase when HDPE is replaced by small amounts of EVA. The early degradation absorbs heat, dilute oxygen and residue. During this process, it protects the matrix inside. Compared with the HDPE/MH and EVA/MH composites, the ternary HDPE/EVA/MH composites exhibit better flame retardancy by increasing the LOI values, and reducing the heat release rate (HRR) and total heat release (THR). With increasing content of EVA, the mechanical properties can also be improved, which is attributed to the good affinity between EVA and MH particles.

Fly ash reinforced thermoplastic vulcanizates obtained from waste tire powder.

PubMed

Sridhar, V; Xiu, Zhang Zhen; Xu, Deng; Lee, Sung Hyo; Kim, Jin Kuk; Kang, Dong Jin; Bang, Dae-Suk

2009-03-01

Novel thermoplastic composites made from two major industrial and consumer wastes, fly ash and waste tire powder, have been developed. The effect of increasing fly ash loadings on performance characteristics such as tensile strength, thermal, dynamic mechanical and magnetic properties has been investigated. The morphology of the blends shows that fly ash particles have more affinity and adhesion towards the rubbery phase when compared to the plastic phase. The fracture surface of the composites shows extensive debonding of fly ash particles. Thermal analysis of the composites shows a progressive increase in activation energy with increase in fly ash loadings. Additionally, morphological studies of the ash residue after 90% thermal degradation shows extensive changes occurring in both the polymer and filler phases. The processing ability of the thermoplastics has been carried out in a Monsanto processability testing machine as a function of shear rate and temperature. Shear thinning behavior, typical of particulate polymer systems, has been observed irrespective of the testing temperatures. Magnetic properties and percolation behavior of the composites have also been evaluated.

Performance and Reliability of Bonded Interfaces for High-temperature Packaging: Annual Progress Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeVoto, Douglas J.

2017-10-19

As maximum device temperatures approach 200 °Celsius, continuous operation, sintered silver materials promise to maintain bonds at these high temperatures without excessive degradation rates. A detailed characterization of the thermal performance and reliability of sintered silver materials and processes has been initiated for the next year. Future steps in crack modeling include efforts to simulate crack propagation directly using the extended finite element method (X-FEM), a numerical technique that uses the partition of unity method for modeling discontinuities such as cracks in a system.

Degradation free epoxy impregnation of REBCO coils and cables

NASA Astrophysics Data System (ADS)

Barth, C.; Bagrets, N.; Weiss, K.-P.; Bayer, C. M.; Bast, T.

2013-05-01

In applications utilizing high-temperature superconductors (HTS) under high mechanical loads as high-field magnets or rotors of generators and motors, the rare-earth-barium-copper-oxide (REBCO) tapes have to be stabilized mechanically. This is achieved using support structures of structural materials and filling the voids in the support through the impregnation of the tapes. The impregnation prevents movement of the tapes and distributes mechanical loads evenly. With high mechanical strengths and low sensitivities to rapid temperature changes, epoxy resins are desired materials for the impregnation of superconductor tapes. However, a strong decrease of the current-carrying capabilities was observed in previous epoxy-impregnated REBCO coils. In this work the thermal expansion mismatches between epoxy resins and REBCO tapes are identified as the cause of these degradations. Fillers are used to reduce the thermal expansions of glues and resins. Mixtures with varying filler contents are analyzed systematically. Their thermal expansions and the corresponding degradations of short REBCO tape samples are measured. A mixture of epoxy resin and filler is found which allows degradation-free impregnation of REBCO tapes. This mixture is validated on a 1.2 m long 15 × 5 Roebel-assembled-coated-conductor (RACC) cable from Industrial Research Limited (IRL).

The effects of 1 kW class arcjet thruster plumes on spacecraft charging and spacecraft thermal control materials

NASA Technical Reports Server (NTRS)

Bogorad, A.; Lichtin, D. A.; Bowman, C.; Armenti, J.; Pencil, E.; Sarmiento, C.

1992-01-01

Arcjet thrusters are soon to be used for north/south stationkeeping on commercial communications satellites. A series of tests was performed to evaluate the possible effects of these thrusters on spacecraft charging and the degradation of thermal control material. During the tests the interaction between arcjet plumes and both charged and uncharged surfaces did not cause any significant material degradation. In addition, firing an arcjet thruster benignly reduced the potential of charged surfaces to near zero.

Impact of Thermal Degradation of Cyanidin-3-O-Glucoside of Haskap Berry on Cytotoxicity of Hepatocellular Carcinoma HepG2 and Breast Cancer MDA-MB-231 Cells

PubMed Central

Pace, Eric; Jiang, Yuanyuan; Clemens, Amy; Crossman, Tennille

2018-01-01

Cyanidin-3-O-glucoside (C3G), the predominant anthocyanin in haskap berries (Lonicera caerulea L.), possesses antioxidant and many other biological activities. This study investigated the impact of temperature and pH on the degradation of the C3G-rich haskap fraction. The effect of the thermal degradation products on the viability of hepatocellular carcinoma HepG2 and breast cancer MDA-MB-231 cells was also studied in vitro. Using column chromatography, the C3G-rich fraction was isolated from acetone extracts of haskap berries. The C3G stability in these fractions was studied under elevated temperatures (70 °C and 90 °C) at three different pH values (2.5, 4, and 7) by monitoring the concentration of C3G and its major degradation products, protocatechuic acid (PCA) and phloroglucinaldehyde (PGA), using liquid chromatography mass spectrometry. Significant degradation of C3G was observed at elevated temperatures and at neutral pH. Conversely, the PCA and PGA concentration increased at higher pH and temperature. Similar to C3G, neutral pH also has a prominent effect on the degradation of PGA, which is further accelerated by heating. The C3G-rich fraction exhibited dose-dependent inhibitory effects on cell metabolic activity when the HepG2 cells were exposed for 48 h. Interestingly, PGA but not PCA exhibited cytotoxic effects against both MDA-MB-231 and HepG2 cells. The results suggest that thermal food processing of haskap could influence its biological properties due to the degradation of C3G. PMID:29382057

Impact of Thermal Degradation of Cyanidin-3-O-Glucoside of Haskap Berry on Cytotoxicity of Hepatocellular Carcinoma HepG2 and Breast Cancer MDA-MB-231 Cells.

PubMed

Pace, Eric; Jiang, Yuanyuan; Clemens, Amy; Crossman, Tennille; Rupasinghe, H P Vasantha

2018-01-27

Cyanidin-3 -O -glucoside (C3G), the predominant anthocyanin in haskap berries ( Lonicera caerulea L.), possesses antioxidant and many other biological activities. This study investigated the impact of temperature and pH on the degradation of the C3G-rich haskap fraction. The effect of the thermal degradation products on the viability of hepatocellular carcinoma HepG2 and breast cancer MDA-MB-231 cells was also studied in vitro. Using column chromatography, the C3G-rich fraction was isolated from acetone extracts of haskap berries. The C3G stability in these fractions was studied under elevated temperatures (70 °C and 90 °C) at three different pH values (2.5, 4, and 7) by monitoring the concentration of C3G and its major degradation products, protocatechuic acid (PCA) and phloroglucinaldehyde (PGA), using liquid chromatography mass spectrometry. Significant degradation of C3G was observed at elevated temperatures and at neutral pH. Conversely, the PCA and PGA concentration increased at higher pH and temperature. Similar to C3G, neutral pH also has a prominent effect on the degradation of PGA, which is further accelerated by heating. The C3G-rich fraction exhibited dose-dependent inhibitory effects on cell metabolic activity when the HepG2 cells were exposed for 48 h. Interestingly, PGA but not PCA exhibited cytotoxic effects against both MDA-MB-231 and HepG2 cells. The results suggest that thermal food processing of haskap could influence its biological properties due to the degradation of C3G.

Thermal Degradation of Synthetic Cathinones: Implications for Forensic Toxicology.

PubMed

Kerrigan, Sarah; Savage, Megan; Cavazos, Cassandra; Bella, Paige

2016-01-01

The synthetic cathinones represent an important class of designer drugs. The widespread attention and publicity associated with these psychostimulants have resulted in numerous legislative actions at state and federal levels throughout the USA. These amphetamine-like compounds are characterized by a β-keto functional group. Although the synthetic cathinones share many properties of their phenethylamine counterparts, the presence of the ketone moiety is responsible for a number of unique and distinct differences in terms of their chemical characteristics and properties. Thermal degradation of methcathinone was first reported several decades ago but has received limited attention. In this study, we identified in situ thermal degradation products for 18 cathinones during gas chromatography-mass spectrometry (GC-MS) analysis. Oxidative degradation arises from the loss of two hydrogens, yielding a characteristic 2 Da mass shift. Degradation products were characterized by prominent iminium base peaks with mass-to-charge ratios 2 Da lower than the parent drug, and in the case of the pyrrolidine-containing cathinones, prominent molecular ions arising from the 2,3-enamine. Chromatographic and mass spectroscopic data are described for 4-ethylmethcathinone, 4-methylethcathinone, buphedrone, butylone, ethcathinone, ethylone, flephedrone, 3,4-methylenedioxy-α-pyrrolidinobutiophenone, 3,4-methylenedioxypyrovalerone, mephedrone, methcathinone, methedrone, methylone, 4-methyl-α-pyrrolidinobutiophenone, naphyrone, pentedrone, pentylone and pyrovalerone. Degradation was minimized by lowering injection temperatures, residence time in the inlet and eliminating active sites during chromatographic analysis. Chromatographic and mass spectral data for the cathinone degradation products are presented and discussed within the context of forensic toxicological analysis, selection of appropriate instrumental methods and implications for the interpretation of results. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Degradation product characterization of therapeutic oligonucleotides using liquid chromatography mass spectrometry.

PubMed

Elzahar, N M; Magdy, N; El-Kosasy, Amira M; Bartlett, Michael G

2018-05-01

Synthetic antisense phosphorothioate oligonucleotides (PS) have undergone rapid development as novel therapeutic agents. The increasing significance of this class of drugs requires significant investment in the development of quality control methods. The determination of the many degradation pathways of such complex molecules presents a significant challenge. However, an understanding of the potential impurities that may arise is necessary to continue to advance these powerful new therapeutics. In this study, four different antisense oligonucleotides representing several generations of oligonucleotide therapeutic agents were evaluated under various stress conditions (pH, thermal, and oxidative stress) using ion-pairing reversed-phase liquid chromatography tandem mass spectrometry (IP-RPLC-MS/MS) to provide in-depth characterization and identification of the degradation products. The oligonucleotide samples were stressed under different pH values at 45 and 90 °C. The main degradation products were observed to be losses of nucleotide moieties from the 3'- and 5'-terminus, depurination, formation of terminal phosphorothioates, and production of ribose, ribophosphorothioates (Rp), and phosphoribophosphorothioates (pRp). Moreover, the effects of different concentrations of hydrogen peroxide were studied resulting in primarily extensive desulfurization and subsequent oxidation of the phosphorothioate linkage to produce the corresponding phosphodiester. The reaction kinetics for the degradation of the oligonucleotides under the different stress conditions were studied and were found to follow pseudo-first-order kinetics. Differences in rates exist even for oligonucleotides of similar length but consisting of different sequences. Graphical abstract Identification of degradation products across several generations of oligonucleotide therapeutics using LC-MS.

The role of labile sulfur compounds in thermochemical sulfate reduction

USGS Publications Warehouse

Amrani, A.; Zhang, T.; Ma, Q.; Ellis, G.S.; Tang, Y.

2008-01-01

The reduction of sulfate to sulfide coupled with the oxidation of hydrocarbons to carbon dioxide, commonly referred to as thermochemical sulfate reduction (TSR), is an important abiotic alteration process that most commonly occurs in hot carbonate petroleum reservoirs. In the present study we focus on the role that organic labile sulfur compounds play in increasing the rate of TSR. A series of gold-tube hydrous pyrolysis experiments were conducted with n-octane and CaSO4 in the presence of reduced sulfur (e.g. H2S, S??, organic S) at temperatures of 330 and 356 ??C under a constant confining pressure. The in-situ pH was buffered to 3.5 (???6.3 at room temperature) with talc and silica. For comparison, three types of oil with different total S and labile S contents were reacted under similar conditions. The results show that the initial presence of organic or inorganic sulfur compounds increases the rate of TSR. However, organic sulfur compounds, such as 1-pentanethiol or diethyldisulfide, were significantly more effective in increasing the rate of TSR than H2S or elemental sulfur (on a mole S basis). The increase in rate is achieved at relatively low concentrations of 1-pentanethiol, less than 1 wt% of the total n-octane, which is comparable to the concentration of organic S that is common in many oils (???0.3 wt%). We examined several potential reaction mechanisms to explain the observed reactivity of organic LSC. First, the release of H2S from the thermal degradation of thiols was discounted as an important mechanism due to the significantly greater reactivity of thiol compared to an equivalent amount of H2S. Second, we considered the generation of olefines in association with the elimination of H2S during thermal degradation of thiols because olefines are much more reactive than n-alkanes during TSR. In our experiments, olefines increased the rate of TSR, but were less effective than 1-pentanethiol and other organic LSC. Third, the thermal decomposition of organic LSC creates free-radicals that in turn might initiate a radical chain-reaction that creates more reactive species. Experiments involving radical initiators, such as diethyldisulfide and benzyldisulfide, did not show an increase in reactivity compared to 1-pentanethiol. Therefore, we conclude that none of these can sufficiently explain our observations of the initial stages of TSR; they may, however, be important in the later stages. In order to gain greater insight into the potential mechanism for the observed reactivity of these organic sulfur compounds during TSR, we applied density functional theory-based molecular modeling techniques to our system. The results of these calculations indicate that 1-pentanethiol or its thermal degradation products may directly react with sulfate and reduce the activation energy required to rupture the first S-O bond through the formation of a sulfate ester. This study demonstrates the importance of labile sulfur compounds in reducing the onset timing and temperature of TSR. It is therefore essential that labile sulfur concentrations are taken into consideration when trying to make accurate predictions of TSR kinetics and the potential for H2S accumulation in petroleum reservoirs. ?? 2008.

The role of labile sulfur compounds in thermochemical sulfate reduction

NASA Astrophysics Data System (ADS)

Amrani, Alon; Zhang, Tongwei; Ma, Qisheng; Ellis, Geoffrey S.; Tang, Yongchun

2008-06-01

The reduction of sulfate to sulfide coupled with the oxidation of hydrocarbons to carbon dioxide, commonly referred to as thermochemical sulfate reduction (TSR), is an important abiotic alteration process that most commonly occurs in hot carbonate petroleum reservoirs. In the present study we focus on the role that organic labile sulfur compounds play in increasing the rate of TSR. A series of gold-tube hydrous pyrolysis experiments were conducted with n-octane and CaSO4 in the presence of reduced sulfur (e.g. H2S, S°, organic S) at temperatures of 330 and 356 °C under a constant confining pressure. The in-situ pH was buffered to 3.5 (∼6.3 at room temperature) with talc and silica. For comparison, three types of oil with different total S and labile S contents were reacted under similar conditions. The results show that the initial presence of organic or inorganic sulfur compounds increases the rate of TSR. However, organic sulfur compounds, such as 1-pentanethiol or diethyldisulfide, were significantly more effective in increasing the rate of TSR than H2S or elemental sulfur (on a mole S basis). The increase in rate is achieved at relatively low concentrations of 1-pentanethiol, less than 1 wt% of the total n-octane, which is comparable to the concentration of organic S that is common in many oils (∼0.3 wt%). We examined several potential reaction mechanisms to explain the observed reactivity of organic LSC. First, the release of H2S from the thermal degradation of thiols was discounted as an important mechanism due to the significantly greater reactivity of thiol compared to an equivalent amount of H2S. Second, we considered the generation of olefines in association with the elimination of H2S during thermal degradation of thiols because olefines are much more reactive than n-alkanes during TSR. In our experiments, olefines increased the rate of TSR, but were less effective than 1-pentanethiol and other organic LSC. Third, the thermal decomposition of organic LSC creates free-radicals that in turn might initiate a radical chain-reaction that creates more reactive species. Experiments involving radical initiators, such as diethyldisulfide and benzyldisulfide, did not show an increase in reactivity compared to 1-pentanethiol. Therefore, we conclude that none of these can sufficiently explain our observations of the initial stages of TSR; they may, however, be important in the later stages. In order to gain greater insight into the potential mechanism for the observed reactivity of these organic sulfur compounds during TSR, we applied density functional theory-based molecular modeling techniques to our system. The results of these calculations indicate that 1-pentanethiol or its thermal degradation products may directly react with sulfate and reduce the activation energy required to rupture the first S-O bond through the formation of a sulfate ester. This study demonstrates the importance of labile sulfur compounds in reducing the onset timing and temperature of TSR. It is therefore essential that labile sulfur concentrations are taken into consideration when trying to make accurate predictions of TSR kinetics and the potential for H2S accumulation in petroleum reservoirs.

A pantropical analysis of the impacts of forest degradation and conversion on local temperature.

PubMed

Senior, Rebecca A; Hill, Jane K; González Del Pliego, Pamela; Goode, Laurel K; Edwards, David P

2017-10-01

Temperature is a core component of a species' fundamental niche. At the fine scale over which most organisms experience climate (mm to ha), temperature depends upon the amount of radiation reaching the Earth's surface, which is principally governed by vegetation. Tropical regions have undergone widespread and extreme changes to vegetation, particularly through the degradation and conversion of rainforests. As most terrestrial biodiversity is in the tropics, and many of these species possess narrow thermal limits, it is important to identify local thermal impacts of rainforest degradation and conversion. We collected pantropical, site-level (<1 ha) temperature data from the literature to quantify impacts of land-use change on local temperatures, and to examine whether this relationship differed aboveground relative to belowground and between wet and dry seasons. We found that local temperature in our sample sites was higher than primary forest in all human-impacted land-use types (N = 113,894 daytime temperature measurements from 25 studies). Warming was pronounced following conversion of forest to agricultural land (minimum +1.6°C, maximum +13.6°C), but minimal and nonsignificant when compared to forest degradation (e.g., by selective logging; minimum +1°C, maximum +1.1°C). The effect was buffered belowground (minimum buffering 0°C, maximum buffering 11.4°C), whereas seasonality had minimal impact (maximum buffering 1.9°C). We conclude that forest-dependent species that persist following conversion of rainforest have experienced substantial local warming. Deforestation pushes these species closer to their thermal limits, making it more likely that compounding effects of future perturbations, such as severe droughts and global warming, will exceed species' tolerances. By contrast, degraded forests and belowground habitats may provide important refugia for thermally restricted species in landscapes dominated by agricultural land.

Thermal regime of an ice-wedge polygon landscape near Barrow, Alaska

NASA Astrophysics Data System (ADS)

Daanen, R. P.; Liljedahl, A. K.

2017-12-01

Tundra landscapes are changing all over the circumpolar Arctic due to permafrost degradation. Soil cracking and infilling of meltwater repeated over thousands of years form ice wedges, which produce the characteristic surface pattern of ice-wedge polygon tundra. Rapid top-down thawing of massive ice leads to differential ground subsidence and sets in motion a series of short- and long-term hydrological and ecological changes. Subsequent responses in the soil thermal regime drive further permafrost degradation and/or stabilization. Here we explore the soil thermal regime of an ice-wedge polygon terrain near Utqiagvik (formerly Barrow) with the Water balance Simulation Model (WaSiM). WaSiM is a hydro-thermal model developed to simulate the water balance at the watershed scale and was recently refined to represent the hydrological processes unique to cold climates. WaSiM includes modules that represent surface runoff, evapotranspiration, groundwater, and soil moisture, while active layer freezing and thawing is based on a direct coupling of hydrological and thermal processes. A new snow module expands the vadose zone calculations into the snow pack, allowing the model to simulate the snow as a porous medium similar to soil. Together with a snow redistribution algorithm based on local topography, this latest addition to WaSiM makes simulation of the ground thermal regime much more accurate during winter months. Effective representation of ground temperatures during winter is crucial in the simulation of the permafrost thermal regime and allows for refined predictions of future ice-wedge degradation or stabilization.

Thermal characterization of Titan's tholins by simultaneous TG-MS, DTA, DSC analysis

NASA Astrophysics Data System (ADS)

Nna-Mvondo, Delphine; de la Fuente, José L.; Ruiz-Bermejo, Marta; Khare, Bishun; McKay, Christopher P.

2013-09-01

Three samples of Titan's tholins synthesized in laboratory under simulated Titan's conditions and presenting different degrees of exposure to ambient atmosphere have been used to study in detail their thermal behavior using thermogravimetry coupled with a mass spectrometer (TG-MS), differential thermal analysis (DTA) and differential scanning calorimetry (DSC). The degradation of Titan's tholins under inert atmosphere follows a three-step consecutive decomposition: a drying stage (>150 °C) where moisture is desorbed, this stage indicated the high hydrophilicity of the tholins; a second stage, the main pyrolysis stage (150-575 °C) where endothermic decomposition begins releasing mainly ammonia, HCN, acetonitrile, and methane over a broad temperature range. Few other hydrocarbon fragments such as ethylene and propane are released but no cyclic molecules, aliphatic or aromatic, are observed. The last stage (>575 °C) is the carbonization of the material leading to a non-crystalline graphitic residue. The thermal degradation under oxygen atmosphere shows the same stages as in argon, with a shift of the thermogravimetric peaks toward lower temperatures indicating a lower thermal stability. The last stage in this case is an oxidative combustion of the char residue. This research concludes that even if Titan tholins, subjected to air contamination for few minutes to several years (varying with the storage conditions) transform to produce different C/N and C/O ratios and thermal stabilities, they undergo the same thermal degradation phases and products. This suggests that the studied three tholins have a similar main chemical structure which does not alter by the air exposure. We discuss on the possible nature of this structure.

Development of capability for microtopography-resolving simulations of hydrologic processes in permafrost affected regions

NASA Astrophysics Data System (ADS)

Painter, S.; Moulton, J. D.; Berndt, M.; Coon, E.; Garimella, R.; Lewis, K. C.; Manzini, G.; Mishra, P.; Travis, B. J.; Wilson, C. J.

2012-12-01

The frozen soils of the Arctic and subarctic regions contain vast amounts of stored organic carbon. This carbon is vulnerable to release to the atmosphere as temperatures warm and permafrost degrades. Understanding the response of the subsurface and surface hydrologic system to degrading permafrost is key to understanding the rate, timing, and chemical form of potential carbon releases to the atmosphere. Simulating the hydrologic system in degrading permafrost regions is challenging because of the potential for topographic evolution and associated drainage network reorganization as permafrost thaws and massive ground ice melts. The critical process models required for simulating hydrology include subsurface thermal hydrology of freezing/thawing soils, thermal processes within ice wedges, mechanical deformation processes, overland flow, and surface energy balances including snow dynamics. A new simulation tool, the Arctic Terrestrial Simulator (ATS), is being developed to simulate these coupled processes. The computational infrastructure must accommodate fully unstructured grids that track evolving topography, allow accurate solutions on distorted grids, provide robust and efficient solutions on highly parallel computer architectures, and enable flexibility in the strategies for coupling among the various processes. The ATS is based on Amanzi (Moulton et al. 2012), an object-oriented multi-process simulator written in C++ that provides much of the necessary computational infrastructure. Status and plans for the ATS including major hydrologic process models and validation strategies will be presented. Highly parallel simulations of overland flow using high-resolution digital elevation maps of polygonal patterned ground landscapes demonstrate the feasibility of the approach. Simulations coupling three-phase subsurface thermal hydrology with a simple thaw-induced subsidence model illustrate the strong feedbacks among the processes. D. Moulton, M. Berndt, M. Day, J. Meza, et al., High-Level Design of Amanzi, the Multi-Process High Performance Computing Simulator, Technical Report ASCEM-HPC-2011-03-1, DOE Environmental Management, 2012.

Al and Si Alloying Effect on Solder Joint Reliability in Sn-0.5Cu for Automotive Electronics

NASA Astrophysics Data System (ADS)

Hong, Won Sik; Oh, Chulmin; Kim, Mi-Song; Lee, Young Woo; Kim, Hui Joong; Hong, Sung Jae; Moon, Jeong Tak

2016-12-01

To suppress the bonding strength degradation of solder joints in automotive electronics, we proposed a mid-temperature quaternary Pb-free Sn-0.5Cu solder alloy with minor Pd, Al, Si and Ge alloying elements. We manufactured powders and solder pastes of Sn-0.5Cu-(0.01,0.03)Al-0.005Si-(0.006-0.007)Ge alloys ( T m = 230°C), and vehicle electronic control units used for a flame-retardant-4 printed circuit board with an organic solderability preservative finish were assembled by a reflow soldering process. To investigate the degradation properties of solder joints used in engine compartments, thermal cycling tests were conducted from -40°C to 125°C (10 min dwell) for 1500 cycles. We also measured the shear strength of the solder joints in various components and observed the microstructural evolution of the solder joints. Based on these results, intermetallic compound (IMC) growth at the solder joints was suppressed by minor Pd, Al and Si additions to the Sn-0.5Cu alloy. After 1500 thermal cycles, IMC layers thicknesses for 100 parts per million (ppm) and 300 ppm Al alloy additions were 6.7 μm and 10 μm, compared to the as-reflowed bonding thicknesses of 6 μm and 7 μm, respectively. Furthermore, shear strength degradation rates for 100 ppm and 300 ppm Al(Si) alloy additions were at least 19.5%-26.2%. The cause of the improvement in thermal cycling reliability was analyzed using the (Al,Cu)-Sn, Si-Sn and Al-Sn phases dispersed around the Cu6Sn5 intermetallic at the solder matrix and bonding interfaces. From these results, we propose the possibility of a mid-temperature Sn-0.5Cu(Pd)-Al(Si)-Ge Pb-free solder for automotive engine compartment electronics.

Thermal design and verification of an instrument cooling system for infrared detectors utilizing the Oxford Stirling cycle refrigerator

NASA Technical Reports Server (NTRS)

Werrett, Stephen; Seivold, Alfred L.

1990-01-01

A detailed nodal computer model was developed to thermally represent the hardware, and sensitivity studies were performed to evaluate design parameters and orbital environmental effects of an instrument cooling system for IR detectors. Thermal-vacuum testing showed excellent performance of the system and a correspondence with math model predictions to within 3 K. Results show cold stage temperature sensitivity to cold patch backload, outer stage external surface emittance degradation, and cold stage emittance degradation, respectively. The increase in backload on the cold patch over the mission lifetime is anticipated to be less than 3.0 watts, which translates to less than a 3-degree increase in detector temperatures.

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

PubMed

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.

Sonochemical degradation of ofloxacin in aqueous solutions.

PubMed

Hapeshi, E; Achilleos, A; Papaioannou, A; Valanidou, L; Xekoukoulotakis, N P; Mantzavinos, D; Fatta-Kassinos, D

2010-01-01

The use of low frequency (20 kHz), high energy ultrasound for the degradation of the antibiotic ofloxacin in water was investigated. Experiments were performed with a horn-type ultrasound generator at varying applied power densities (130-640 W/L), drug concentrations (5-20 mg/L), hydrogen peroxide concentrations (0-100 mM) and sparging gases (air, oxygen, nitrogen and argon). In general, conversion (which was assessed following sample absorbance at 288 nm) increased with increasing ultrasound energy and peroxide concentration and decreasing initial drug concentration. Moreover, reactions under an argon atmosphere were faster than with diatomic gases, possibly due to argon's physical properties (e.g. solubility, thermal conductivity and specific heat ratio) favoring sonochemical activity. Overall, low to moderate levels of ofloxacin degradation were achieved (i.e. it never exceeded 50%), thus indicating that radical reactions in the liquid bulk rather than thermal reactions in the vicinity of the cavitation bubble are responsible for ofloxacin degradation.

Cu-modified alkalinized g-C3N4 as photocatalytically assisted heterogeneous Fenton-like catalyst

NASA Astrophysics Data System (ADS)

Dong, Qimei; Chen, Yingying; Wang, Lingli; Ai, Shasha; Ding, Hanming

2017-12-01

Alkalinized graphitic carbon nitride (CNK-OH) has been synthesized by one-step thermal poly-condensation method, and Cu-modified alkalinized g-C3N4 (Cu-CNK-OH) has been prepared by impregnation approach over CNK-OH. These copper species in Cu-CNK-OH are embedded in the frame of CNK-OH mostly via the Cu-N bonds. Cu-CNK-OH has been employed as a heterogeneous Fenton-like catalyst to degrade rhodamine B (RhB). Both the production efficiency of hydroxyl radicals and the transformation rate of Cu(II)/Cu(I) redox pair increase under visible-light irradiation. As a result, Cu-CNK-OH exhibits improved Fenton-like catalytic activity on the degradation of RhB. The synergetic interaction between Fenton-like process and photocatalytic process also contributes such improvement. The hydroxyl radicals and holes are the major reactive species in the photocatalytically assisted Fenton-like process. This study provides a valuable strategy for metal modification of alkalinized g-C3N4 with enhanced Fenton-like catalytic performance for the degradation of organic contaminants.

Degradation of free tryptophan in a cookie model system and its application in commercial samples.

PubMed

Morales, Francisco J; Açar, Ozge C; Serpen, Arda; Arribas-Lorenzo, Gema; Gökmen, Vural

2007-08-08

The stability of free tryptophan (Trp) was examined in five cookie-resembling models at varying baking temperatures and durations. Trp was measured by HPLC coupled with a fluorescent detector. Trp degradation was significantly greater in cookies formulated with glucose compared with sucrose, regardless of the temperatures and durations of baking. A lag period was clearly observed in cookies formulated with sucrose. The type of sugar used in the dough formulation affected not only the thermal destruction kinetics but also the degree of degradation of free Trp. However, the type of leavening agent (ammonium bicarbonate versus sodium bicarbonate) did not affect the rate of Trp destruction as happens in Maillard-driven reactions. In addition, the free Trp content was analyzed in nine different flours and sixty-two commercial cookies, and it was found that free Trp varied from 0.4 to 1287.9 mg/kg for rice and wheat bran, respectively. It was found that free Trp was significantly higher in dietetic commercial samples formulated with wheat bran compared with other flours.

[Effect of temperature on the aerobic degradation of vitamin C in citric fruit juices].

PubMed

Alvarado, J D; Palacios Viteri, N

1989-12-01

By means of the method of the 2,4-dinitrophenylhydrazine the total ascorbic acid content in lima, lemon, tangerine and grapefruit juices, fresh and kept at four temperatures and different times, was determined. It was confirmed that in all the cases, the aerobic degradation of ascorbic acid follows a kinetic first order and that the values of the reaction rate are different between species and even between varieties of lemon and tangerine. The values of the equation terms are reported, and examples of application given. Within a range from 20 degrees to 92 degrees C, the effect of temperature on the velocity of the ascorbic acid degradation is described satisfactorily following the Arrhenius equation, in accordance with which, the corresponding values of activation energy are calculated to compare them with other published values. With the simple application of the method, in two steps, and considering that the L-ascorbic acid and the L-dehydroascorbic acid are predominant, the results can be used to calculate the vitamin C losses in citric fruit juices, indicated when they are processed by traditional thermal treatments.

Degradation of Perfluorooctanoic Acid and Perfluoroctane Sulfonate by Enzyme Catalyzed Oxidative Humification Reactions

NASA Astrophysics Data System (ADS)

Huang, Q.

2016-12-01

Poly- and perfluoroalkyl substances (PFASs) are alkyl based chemicals having multiple or all hydrogens replaced by fluorine atoms, and thus exhibit high thermal and chemical stability and other unusual characteristics. PFASs have been widely used in a wide variety of industrial and consumer products, and tend to be environmentally persistent. Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are two representative PFASs that have drawn particular attention because of their ubiquitous presence in the environment, resistance to degradation and toxicity to animals. This study examined the decomposition of PFOA and PFOS in enzyme catalyzed oxidative humification reactions (ECOHR), a class of reactions that are ubiquitous in the environment involved in natural organic humification. Reaction rates and influential factors were examined, and high-resolution mass spectrometry was used to identify possible products. Fluorides and partially fluorinated compounds were identified as likely products from PFOA and PFOS degradation, which were possibly formed via a combination of free radical decomposition, rearrangements and coupling processes. The findings suggest that PFOA and PFOS may be transformed during humification, and ECOHR can potentially be used for the remediation of these chemicals.

Comparative study on the process behavior and reaction kinetics in sonocatalytic degradation of organic dyes by powder and nanotubes TiO2.

PubMed

Pang, Yean Ling; Abdullah, Ahmad Zuhairi

2012-05-01

Sonocatalytic degradation of various organic dyes (Congo Red, Reactive Blue 4, Methyl Orange, Rhodamine B and Methylene Blue) catalyzed by powder and nanotubes TiO(2) was studied. Both catalysts were characterized using transmission electron microscope (TEM), surface analyzer, Raman spectroscope and thermal gravimetric analyzer (TGA). Sonocatalytic activity of powder and nanotubes TiO(2) was elucidated based on the degradation of various organic dyes. The former catalyst was favorable for treatment of anionic dyes, while the latter was more beneficial for cationic dyes. Sonocatalytic activity of TiO(2) nanotubes could be up to four times as compared to TiO(2) powder under an ultrasonic power of 100 W and a frequency of 42 kHz. This was associated with the higher surface area and the electrostatic attraction between dye molecules and TiO(2) nanotubes. Fourier transform-infrared spectrometer (FT-IR) was used to identify changes that occurred on the functional group in Rhodamine B molecules and TiO(2) nanotubes after the reaction. Sonocatalytic degradation of Rhodamine B by TiO(2) nanotubes apparently followed the Langmuir-Hinshelwood adsorption kinetic model with surface reaction rate of 1.75 mg/L min. TiO(2) nanotubes were proven for their high potential to be applied in sonocatalytic degradation of organic dyes. Copyright © 2011 Elsevier B.V. All rights reserved.

Microwave atmospheric pressure plasma jets for wastewater treatment: Degradation of methylene blue as a model dye.

PubMed

García, María C; Mora, Manuel; Esquivel, Dolores; Foster, John E; Rodero, Antonio; Jiménez-Sanchidrián, César; Romero-Salguero, Francisco J

2017-08-01

The degradation of methylene blue in aqueous solution as a model dye using a non thermal microwave (2.45 GHz) plasma jet at atmospheric pressure has been investigated. Argon has been used as feed gas and aqueous solutions with different concentrations of the dye were treated using the effluent from plasma jet in a remote exposure. The removal efficiency increased as the dye concentration decreased from 250 to 5 ppm. Methylene blue degrades after different treatment times, depending on the experimental plasma conditions. Thus, kinetic constants up to 0.177 min -1 were obtained. The higher the Ar flow, the faster the degradation rate. Optical emission spectroscopy (OES) was used to gather information about the species present in the gas phase, specifically excited argon atoms. Argon excited species and hydrogen peroxide play an important role in the degradation of the dye. In fact, the conversion of methylene blue was directly related to the density of argon excited species in the gas phase and the concentration of hydrogen peroxide in the aqueous liquid phase. Values of energy yield at 50% dye conversion of 0.296 g/kWh were achieved. Also, the use of two plasma applicators in parallel has been proven to improve energy efficiency. Copyright © 2017 Elsevier Ltd. All rights reserved.

Thermal aging of electrolytes used in lithium-ion batteries - An investigation of the impact of protic impurities and different housing materials

NASA Astrophysics Data System (ADS)

Handel, Patricia; Fauler, Gisela; Kapper, Katja; Schmuck, Martin; Stangl, Christoph; Fischer, Roland; Uhlig, Frank; Koller, Stefan

2014-12-01

Thermal degradation products in lithium-ion batteries result mainly from hydrolysis sensitivity of lithium hexafluorophosphate (LiPF6). As organic carbonate solvents contain traces of protic impurities, the thermal decomposition of electrolytes is enhanced. Therefore, resulting degradation products are studied with nuclear magnetic resonance spectroscopy (NMR) and gas chromatography mass spectrometry (GC-MS). The electrolyte contains 1 M LiPF6 in a binary mixture of ethylene carbonate (EC) and diethylene carbonate (DEC) in a ratio of 1:2 (v/v) and is aged at ambient and elevated temperature. The impact of protic impurities, either added as deionized water or incorporated in positive electrode material, upon aging is investigated. Further, the influence of different housing materials on the electrolyte degradation is shown. Difluorophosphoric acid is identified as main decomposition product by NMR-spectroscopy. Traces of other decomposition products are determined by headspace GC-MS. Acid-base and coulometric titration are used to determine the total amount of acid and water content upon aging, respectively. The aim of this investigation is to achieve profound understanding about the thermal decomposition of one most common used electrolyte in a battery-like housing material.

Investigation on γ-irradiated PP/ethylene acrylic elastomer TPVs by rheological and thermal approaches

NASA Astrophysics Data System (ADS)

Dutta, Anindya; Ghosh, Anup K.

2018-03-01

Polypropylene (PP) was melt blended with varying concentration of ethylene acrylic elastomer (AEM) in a twin screw extruder and then γ-irradiated at several radiation doses to achieve a series of thermoplastic vulcanizates (TPV). The effect of AEM concentration and γ-irradiation on flow characteristics, crystallization and thermal degradation of blends were explained using melt dynamic rheology, differential scanning calorimetry and thermogravimetric analysis. Gel content values and dynamic rheological data of PP and AEM at different radiation doses confirmed the incessant scissioning of PP chains with radiation doses except for highest radiation dose, where crosslinking of PP chains took place and the incessant crosslinking of AEM chains irrespective of radiation doses. Oxidative degradation of PP was confirmed by FTIR spectroscopy, which also exhibited absence of any chemical interaction between two constituent polymers. Normalized crystallinity and melting point of compositions, obtained from DSC, decreased with the radiation doses. Furthermore, with the radiation doses clear shifts of maxima of the melting peak towards the lower temperature were observed for neat PP and blends. Thermal stability of PP and blends, as observed by TGA, reduced significantly with irradiation; whereas for AEM, no discernable change was observed. Enhanced chain scissioning of PP in presence of AEM reduced the thermal stability of blends, especially at lower irradiation. This reduction of thermal stability was established by "rule of mixture", applied to the activation energy of thermal degradation. Thus, optimization of radiation doses to prepare TPVs was established.

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

NASA Technical Reports Server (NTRS)

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.

Effect of high surface area activated carbon on thermal degradation of jet fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gergova, K.; Eser, S.; Arumugam, R.

1995-05-01

Different solid carbons added to jet fuel during thermal stressing cause substantial changes in pyrolytic degradation reactions. Activated carbons, especially high surface area activated carbons were found to be very effective in suppressing solid deposition on metal reactor walls during stressing at high temperatures (425 and 450{degrees}C). The high surface area activated carbon PX-21 prevented solid deposition on reactor walls even after 5h at 450{degrees}C. The differences seen in the liquid product composition when activated carbon is added indicated that the carbon surfaces affect the degradation reactions. Thermal stressing experiments were carried out on commercial petroleum-derived JPTS jet fuel. Wemore » also used n-octane and n-dodecane as model compounds in order to simplify the study of the chemical changes which take place upon activated carbon addition. In separate experiments, the presence of a hydrogen donor, decalin, together with PX-21 was also studied.« less

Bayesian Framework Approach for Prognostic Studies in Electrolytic Capacitor under Thermal Overstress Conditions

NASA Technical Reports Server (NTRS)

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

2012-01-01

Electrolytic capacitors are used in several applications ranging from power supplies for safety critical avionics equipment to power drivers for electro-mechanical actuator. Past experiences show that capacitors tend to degrade and fail faster when subjected to high electrical or thermal stress conditions during operations. This makes them good candidates for prognostics and health management. Model-based prognostics captures system knowledge in the form of physics-based models of components in order to obtain accurate predictions of end of life based on their current state of heal th and their anticipated future use and operational conditions. The focus of this paper is on deriving first principles degradation models for thermal stress conditions and implementing Bayesian framework for making remaining useful life predictions. Data collected from simultaneous experiments are used to validate the models. Our overall goal is to derive accurate models of capacitor degradation, and use them to remaining useful life in DC-DC converters.

Effects of fluorine incorporation into β-Ga2O3

NASA Astrophysics Data System (ADS)

Yang, Jiangcheng; Fares, Chaker; Ren, F.; Sharma, Ribhu; Patrick, Erin; Law, Mark E.; Pearton, S. J.; Kuramata, Akito

2018-04-01

β-Ga2O3 rectifiers fabricated on lightly doped epitaxial layers on bulk substrates were exposed to CF4 plasmas. This produced a significant decrease in Schottky barrier height relative to unexposed control diodes (0.68 eV compared to 1.22 eV) and degradation in ideality factor (2.95 versus 1.01 for the control diodes). High levels of F (>1022 cm-3) were detected in the near-surface region by Secondary Ion Mass Spectrometry. The diffusion of fluorine into the Ga2O3 was thermally activated with an activation energy of 1.24 eV. Subsequent annealing in the range 350-400 °C brought recovery of the diode characteristics and an increase in barrier height to a value larger than in the unexposed control diodes (1.36 eV). Approximately 70% of the initial F was removed from the Ga2O3 by 400 °C, with the surface outgas rate also being thermally activated with an activation energy of 1.23 eV. Very good fits to the experimental data were obtained by integrating physics of the outdiffusion mechanisms into the Florida Object Oriented Process Simulator code and assuming that the outgas rate from the surface was mediated through fluorine molecule formation. The fluorine molecule forward reaction rate had an activation energy of 1.24 eV, while the reversal rate of this reaction had an activation energy of 0.34 eV. The net carrier density in the drift region of the rectifiers decreased after CF4 exposure and annealing at 400 °C. The data are consistent with a model in which near-surface plasma-induced damage creates degraded Schottky barrier characteristics, but as the samples are annealed, this damage is removed, leaving the compensation effect of Si donors by F- ions. The barrier lowering and then enhancement are due to the interplay between surface defects and the chemical effects of the fluorine.

Heat transfer mechanisms in pulsating heat-pipes with nanofluid

NASA Astrophysics Data System (ADS)

Gonzalez, Miguel; Kelly, Brian; Hayashi, Yoshikazu; Kim, Yoon Jo

2015-01-01

In this study, the effect of silver nanofluid on a pulsating heat-pipe (PHP) thermal performance was experimentally investigated to figure out how nanofluid works with PHP. A closed loop PHP was built with 3 mm diameter tubes. Thermocouples and pressure transducers were installed for fluid and surface temperature and pressure measurements. The operating temperature of the PHP varied from 30-100 °C, with power rates of 61 W and 119 W. The fill ratio of 30%, 50%, and 70% were tested. The results showed that the evaporator heat transfer performance was degraded by the addition of nanoparticles due to increased viscosity at high power rate, while the positive effects of high thermal conductivity and enhanced nucleate boiling worked better at low power rate. In the condenser section, owing to the relatively high liquid content, nanofluid more effectively improved the heat transfer performance. However, since the PHP performance was dominantly affected by evaporator heat transfer performance, the overall benefit of enhanced condenser section performance was greatly limited. It was also observed that the poor heat transfer performance with nanofluid at the evaporator section led to lower operating pressure of PHP.

Visible light responsive sulfated rare earth doped TiO(2)@fumed SiO(2) composites with mesoporosity: enhanced photocatalytic activity for methyl orange degradation.

PubMed

Zhan, Changchao; Chen, Feng; Yang, Jintao; Dai, Daoxing; Cao, Xiaohua; Zhong, Mingqiang

2014-02-28

Visible light (VL) responsive mesoporous sulfated rare earth ions (Nd(3+), La(3+), Y(3+)) incorporated TiO2@fumed SiO2 photocatalysts were prepared by sol-gel method with P123 (EO20PO70EO20) as a template. The resultant samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), N2 adsorption-desorption measurements (BET), UV-vis diffuse reflectance spectroscopy, photoluminescence (PL) spectra, Fourier transform infrared spectroscopy (FTIR) and thermal analyses (TG-DTA). In comparison with nondoped sample, RE-doped samples showed not only an increase in the surface areas and pore volumes, but also an inhibition of titania phase transition from anatase to rutile. Photo-degradation results revealed that RE-doped samples could greatly improve the photocatalytic activity, and the experimental degradation rates of methyl orange (MO) were higher than that catalyzed by undoped samples and Degussa P-25, obeyed the order of Nd(3+)>La(3+)>Y(3+). Nd-doped sample expressed the highest photoactivity and the optimal dosage was 0.25mol%, which resulted in MO degradation rates of 99.8% and 90.05% irradiation under UV for 60min and VL (λ>400nm) for 40h, respectively. The enhanced photocatalytic activity could be attributed to the higher specific area, good crystallinity, strong VL absorption and effective separation of photogenerated electron-hole pairs in the catalyst. Copyright © 2014 Elsevier B.V. All rights reserved.

UPLC and LC-MS studies on degradation behavior of irinotecan hydrochloride and development of a validated stability-indicating ultra-performance liquid chromatographic method for determination of irinotecan hydrochloride and its impurities in pharmaceutical dosage forms.

PubMed

Kumar, Navneet; Sangeetha, Dhanaraj; Reddy, Sunil P

2012-10-01

The objective of the current investigation was to study the degradation behavior of irinotecan hydrochloride under different International Conference on Harmonization (ICH) recommended stress conditions using ultra-performance liquid chromatography and liquid chromatography-mass spectrometry and to establish a validated stability-indicating reverse-phase ultra-performance liquid chromatographic method for the quantitative determination of irinotecan hydrochloride and its seven impurities and degradation products in pharmaceutical dosage forms. Irinotecan hydrochloride was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal and photolytic degradation. Irinotecan hydrochloride was found to degrade significantly in oxidative and base hydrolysis and photolytic degradation conditions. The degradation products were well resolved from the main peak and its impurities, thus proving the stability-indicating power of the method. Chromatographic separation was achieved on a Waters Acquity BEH C8 (100 × 2.1 mm) 1.7-µm column with a mobile phase containing a gradient mixture of solvent A (0.02M KH(2)PO(4) buffer, pH 3.4) and solvent B (a mixture of acetonitrile and methanol in the ratio of 62:38 v/v). The mobile phase was delivered at a flow rate of 0.3 mL/min with ultraviolet detection at 220 nm. The run time was 8 min, within which irinotecan and its seven impurities and degradation products were satisfactorily separated. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness. This method was also suitable for the assay determination of irinotecan hydrochloride in pharmaceutical dosage forms.

The role of waste thermal water in the soil degradation

NASA Astrophysics Data System (ADS)

Balog, Kitti; Farsang, Andrea

2010-05-01

Thermal water exploitation is widespread, because it is considered to a "green" renewable energy source, the transporter of the Earth crust's heat. It is suitable for very diverse purposes: balneology, heating, mineral water, municipal hot water supply, technological water, etc. After usage, large amount of thermal water becomes sewage water with high concentrations of salts, heavy metals, ammonia, nitrate, and high temperature. Besides that, most of these waters have an unfavourable ion composition. Na+ (and in some cases Mg+) is predominant among cations. A common way of treatment is to let off the waste thermal water in unlined ground channels to leak into the soil. This can cause physical and chemical soil degradation. Continouos Na+ supply occurs, that occupies the place of Ca2+ on the ion exchange surfaces. Thus, adverse effects of Na+ can appear, like formation of extreme moisture regime, peptization, liquefaction. Beside Na+, Mg2+ also helps the formation of physical degradation in the soil. High water retain and unfavourable structure evolves. Not only the physical features of the soil are touched, fertility of production sites as well. Namely sorrounding the unlined ground channels, agricultural areas are seated, so it is important to protect productivity of the soil to maintain yield. Because of the seepage of high salt concentration waters, salt accumulation can be observed near to the channel lines. The investigated sample sites are located in the Great Hungarian Plane. We determined the main pollutants of the thermal waters, and the effects to the sorrounding soils. On two selected investigation areas (Cserkeszőlő, Tiszakécske) salt profiles and Na+ adsorption isotherms are presented to characterize soil degradation. Genetic soil types are differ on the investigated areas, so the aspect of impact is different, as well.

Micro- and nano-scale characterization to study the thermal degradation of cement-based materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lim, Seungmin, E-mail: lim76@illinois.edu; Mondal, Paramita

2014-06-01

The degradation of hydration products of cement is known to cause changes in the micro- and nano-structure, which ultimately drive thermo-mechanical degradation of cement-based composite materials at elevated temperatures. However, a detailed characterization of these changes is still incomplete. This paper presents results of an extensive experimental study carried out to investigate micro- and nano-structural changes that occur due to exposure of cement paste to high temperatures. Following heat treatment of cement paste up to 1000 °C, damage states were studied by compressive strength test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) atomic force microscopy (AFM) and AFM image analysis.more » Using experimental results and research from existing literature, new degradation processes that drive the loss of mechanical properties of cement paste are proposed. The development of micro-cracks at the interface between unhydrated cement particles and paste matrix, a change in C–S–H nano-structure and shrinkage of C–S–H, are considered as important factors that cause the thermal degradation of cement paste. - Highlights: • The thermal degradation of hydration products of cement is characterized at micro- and nano-scale using scanning electron microscopy (SEM) and atomic force microscopy (AFM). • The interface between unhydrated cement particles and the paste matrix is considered the origin of micro-cracks. • When cement paste is exposed to temperatures above 300 ºC, the nano-structure of C-S-H becomes a more loosely packed globular structure, which could be indicative of C-S-H shrinkage.« less

Comparative kinetic analysis on thermal degradation of some cephalosporins using TG and DSC data

PubMed Central

2013-01-01

Background The thermal decomposition of cephalexine, cefadroxil and cefoperazone under non-isothermal conditions using the TG, respectively DSC methods, was studied. In case of TG, a hyphenated technique, including EGA, was used. Results The kinetic analysis was performed using the TG and DSC data in air for the first step of cephalosporin’s decomposition at four heating rates. The both TG and DSC data were processed according to an appropriate strategy to the following kinetic methods: Kissinger-Akahira-Sunose, Friedman, and NPK, in order to obtain realistic kinetic parameters, even if the decomposition process is a complex one. The EGA data offer some valuable indications about a possible decomposition mechanism. The obtained data indicate a rather good agreement between the activation energy’s values obtained by different methods, whereas the EGA data and the chemical structures give a possible explanation of the observed differences on the thermal stability. A complete kinetic analysis needs a data processing strategy using two or more methods, but the kinetic methods must also be applied to the different types of experimental data (TG and DSC). Conclusion The simultaneous use of DSC and TG data for the kinetic analysis coupled with evolved gas analysis (EGA) provided us a more complete picture of the degradation of the three cephalosporins. It was possible to estimate kinetic parameters by using three different kinetic methods and this allowed us to compare the Ea values obtained from different experimental data, TG and DSC. The thermodegradation being a complex process, the both differential and integral methods based on the single step hypothesis are inadequate for obtaining believable kinetic parameters. Only the modified NPK method allowed an objective separation of the temperature, respective conversion influence on the reaction rate and in the same time to ascertain the existence of two simultaneous steps. PMID:23594763

High-temperature degradation-free rapid thermal annealing of GaAs and InP

NASA Astrophysics Data System (ADS)

Pearton, Stephen J.; Katz, Avishay; Geva, Michael

1991-04-01

Rapid thermal annealing of GaAs and InP within enclosed SiC-coated graphite susceptors is shown to eliminate slip formation during implant activation treatments and to provide much better protection against surface degradation at the edges of wafers compared to the more conventional proximity method. Two different types of susceptor were investigated-the first type must be charged with As or P prior to the annealing cycles while the second type incorporates small reservoirs into the susceptor which provide a continuous overpressure of the group V species. Degradation-free annealing of patterned metallized wafers is possible using the latter type of susceptor. The activation of Si and Be implants in GaAs by RTA is also discussed.

Low-Temperature Aging of Delta-Ferrite in 316L SS Welds; Changes in Mechanical Properties and Etching Properties

NASA Astrophysics Data System (ADS)

Abe, Hiroshi; Shimizu, Keita; Watanabe, Yutaka

Thermal aging embrittlement of LWR components made of stainless cast (e.g. CF-8 and CF-8M) is a potential degradation issue, and careful attention has been paid on it. Although welds of austenitic stainless steels (SSs) have γ-δ duplex microstructure, which is similar to that of the stainless cast, examination on thermal aging characteristics of the SS welds is very limited. In order to evaluate thermal aging behavior of weld metal of austenitic stainless steel, the 316L SS weld metal has been prepared and changes in mechanical properties and in etching properties at isothermal aging at 335°C have been investigated. The hardness of the ferrite phase has increased with aging, while the hardness of austenite phase has stayed same. It has been suggested that spinodal decomposition has occurred in δ-ferrite by the 335°C aging. The etching rates of δ-ferrite at immersion test in 5wt% hydrochloric acid solution have been also investigated using an AFM technique. The etching rate of ferrite phase has decreased consistently with the increase in hardness of ferrite phase. It has been thought that this characteristic is also caused by spinodal decomposition of ferrite into chromium-rich (α') and iron-rich (α).

Preparation and properties studies of UV-curable silicone modified epoxy resin composite system.

PubMed

Yu, Zhouhui; Cui, Aiyong; Zhao, Peizhong; Wei, Huakai; Hu, Fangyou

2018-01-01

Modified epoxy suitable for ultraviolet (UV) curing is prepared by using organic silicon toughening. The curing kinetics of the composite are studied by dielectric analysis (DEA), and the two-phase compatibility of the composite is studied by scanning electron microscopy (SEM). The tensile properties, heat resistance, and humidity resistance of the cured product are explored by changing the composition ratio of the silicone and the epoxy resin. SEM of silicone/epoxy resin shows that the degree of cross-linking of the composites decreases with an increase of silicone resin content. Differential thermal analysis indicates that the glass transition temperature and the thermal stability of the composites decrease gradually with an increase of silicone resin content. The thermal degradation rate in the high temperature region, however, first decreases and then increases. In general, after adding just 10%-15% of the silicone resin and exposing to light for 15 min, the composite can still achieve a better curing effect. Under such conditions, the heat resistance of the cured product decreases a little. The tensile strength is kept constant so that elongation at breakage is apparently improved. The change rate after immersion in distilled water at 60°C for seven days is small, which shows excellent humidity resistance.

An imaging-based photometric and colorimetric measurement method for characterizing OLED panels for lighting applications

NASA Astrophysics Data System (ADS)

Zhu, Yiting; Narendran, Nadarajah; Tan, Jianchuan; Mou, Xi

2014-09-01

The organic light-emitting diode (OLED) has demonstrated its novelty in displays and certain lighting applications. Similar to white light-emitting diode (LED) technology, it also holds the promise of saving energy. Even though the luminous efficacy values of OLED products have been steadily growing, their longevity is still not well understood. Furthermore, currently there is no industry standard for photometric and colorimetric testing, short and long term, of OLEDs. Each OLED manufacturer tests its OLED panels under different electrical and thermal conditions using different measurement methods. In this study, an imaging-based photometric and colorimetric measurement method for OLED panels was investigated. Unlike an LED that can be considered as a point source, the OLED is a large form area source. Therefore, for an area source to satisfy lighting application needs, it is important that it maintains uniform light level and color properties across the emitting surface of the panel over a long period. This study intended to develop a measurement procedure that can be used to test long-term photometric and colorimetric properties of OLED panels. The objective was to better understand how test parameters such as drive current or luminance and temperature affect the degradation rate. In addition, this study investigated whether data interpolation could allow for determination of degradation and lifetime, L70, at application conditions based on the degradation rates measured at different operating conditions.

Plasmachemical degradation of azo dyes by humid air plasma: Yellow Supranol 4 GL, Scarlet Red Nylosan F3 GL and industrial waste.

PubMed

Abdelmalek, F; Gharbi, S; Benstaali, B; Addou, A; Brisset, J L

2004-05-01

A recent non-thermal plasma technique (i.e., a gliding arc discharge which generates reactive species at atmospheric pressure) is tested for pollution abatement of dyes dispersed in synthetic solutions and industrial effluents. Yellow Supranol 4 GL (YS) and Scarlet Red Nylosan F3 GL (SRN) are toxic synthetic dyes widely used in the Algerian textile industry and frequently present in liquid wastes of manufacture plants. Classical removal treatment processes are not efficient enough, so that the presence of dyes in liquid effluents may cause serious environmental problems, in connection with reusing waste waters for irrigation. The degradation processes achieved by the oxidising species formed in the plasma are followed by UV/VIS spectroscopy and by chemical oxygen demand measurements. They are almost complete (i.e., 92.5% for YS and 90% for dilute SRN) and rapidly follow pseudo-first-order laws, with overall estimated rate constants 3 x 10(-4) and 4 x 10(-4)s-1 for YS and SRN, respectively. The degradation rate constant for the industrial mixture (i.e., k = 1.45 x 10(-3)s-1) is a mean value for two consecutive steps (210(-3) and 6 x 10(-5)s-1) measured at the absorption peaks of the major constituent dyes, YS and SRN.

Glass transition of anhydrous starch by fast scanning calorimetry.

PubMed

Monnier, Xavier; Maigret, Jean-Eudes; Lourdin, Denis; Saiter, Allisson

2017-10-01

By means of fast scanning calorimetry, the glass transition of anhydrous amorphous starch has been measured. With a scanning rate of 2000Ks -1 , thermal degradation of starch prior to the glass transition has been inhibited. To certify the glass transition measurement, structural relaxation of the glassy state has been investigated through physical aging as well as the concept of limiting fictive temperature. In both cases, characteristic enthalpy recovery peaks related to the structural relaxation of the glass have been observed. Thermal lag corrections based on the comparison of glass transition temperatures measured by means of differential and fast scanning calorimetry have been proposed. The complementary investigations give an anhydrous amorphous starch glass transition temperature of 312±7°C. This estimation correlates with previous extrapolation performed on hydrated starches. Copyright © 2017 Elsevier Ltd. All rights reserved.

Discrete component bonding and thick film materials study. [of capacitor chips bonded with solders and conductive epoxies

NASA Technical Reports Server (NTRS)

Kinser, D. L.

1976-01-01

The bonding reliability of discrete capacitor chips bonded with solders and conductive epoxies was examined along with the thick film resistor materials consisting of iron oxide phosphate and vanadium oxide phosphates. It was concluded from the bonding reliability studies that none of the wide range of types of solders examined is capable of resisting failure during thermal cycling while the conductive epoxy gives substantially lower failure rates. The thick film resistor studies proved the feasibility of iron oxide phosphate resistor systems although some environmental sensitivity problems remain. One of these resistor compositions has inadvertently proven to be a candidate for thermistor applications because of the excellent control achieved upon the temperature coefficient of resistance. One new and potentially damaging phenomenon observed was the degradation of thick film conductors during the course of thermal cycling.

Quantification and analysis of color stability based on thermal transient behavior in white LED lamps.

PubMed

Nisa Khan, M

2017-09-20

We present measurement and analysis of color stability over time for two categories of white LED lamps based on their thermal management scheme, which also affects their transient lumen depreciation. We previously reported that lumen depreciation in LED lamps can be minimized by properly designing the heat sink configuration that allows lamps to reach a thermal equilibrium condition quickly. Although it is well known that lumen depreciation degrades color stability of white light since color coordinates vary with total lumen power by definition, quantification and characterization of color shifts based on thermal transient behavior have not been previously reported in literature for LED lamps. Here we provide experimental data and analysis of transient color shifts for two categories of household LED lamps (from a total of six lamps in two categories) and demonstrate that reaching thermal equilibrium more quickly provides better stability for color rendering, color temperature, and less deviation of color coordinates from the Planckian blackbody locus line, which are all very important characterization parameters of color for white light. We report for the first time that a lamp's color degradation from the turn-on time primarily depends on thermal transient behavior of the semiconductor LED chip, which experiences a wavelength shift as well as a decrease in its dominant wavelength peak value with time, which in turn degrades the phosphor conversion. For the first time, we also provide a comprehensive quantitative analysis that differentiates color degradation due to the heat rise in GaN/GaInN LED chips and subsequently the boards these chips are mounted on-from that caused by phosphor heating in a white LED module. Finally, we briefly discuss why there are some inevitable trade-offs between omnidirectionality and color and luminous output stability in current household LED lamps and what will help eliminate these trade-offs in future lamp designs.

System overview on electromagnetic compensation for reflector antenna surface distortion

NASA Technical Reports Server (NTRS)

Acosta, R. J.; Zaman, A. J.; Terry, J. D.

1993-01-01

The system requirements and hardware implementation for electromagnetic compensation of antenna performance degradations due to thermal effects was investigated. Future commercial space communication antenna systems will utilize the 20/30 GHz frequency spectrum and support very narrow multiple beams (0.3 deg) over wide angle field of view (15-20 beamwidth). On the ground, portable and inexpensive very small aperture terminals (VSAT) for transmitting and receiving video, facsimile and data will be employed. These types of communication system puts a very stringent requirement on spacecraft antenna beam pointing stability (less than .01 deg), high gain (greater than 50 dB) and very lowside lobes (less than -25 dB). Thermal analysis performed on the advanced communication technology satellite (ACTS) has shown that the reflector surfaces, the mechanical supporting structures and metallic surfaces on the spacecraft body will distort due thermal effects from a varying solar flux. The antenna performance characteristics (e.g., pointing stability, gain, side lobe, etc.) will degrade due to thermal distortion in the reflector surface and supporting structures. Specifically, antenna RF radiation analysis has shown that pointing error is the most sensitive antenna performance parameter to thermal distortions. Other antenna parameters like peak gain, cross polarization level (beam isolation), and side lobe level will also degrade with thermal distortions. In order to restore pointing stability and in general antenna performance several compensation methods were proposed. In general these compensation methods can be classified as being either of mechanical or electromagnetic type. This paper will address only the later one. In this approach an adaptive phased array antenna feed is used to compensate for the antenna performance degradation. Extensive work has been devoted to demonstrate the feasibility of adaptive feed compensation on space communication antenna systems. This paper addresses the system requirements for such a system and identify candidate technologies (analog and digital) for possible hardware implementation.

Surface coating of ceria nanostructures for high-temperature oxidation protection

NASA Astrophysics Data System (ADS)

Aadhavan, R.; Bhanuchandar, S.; Babu, K. Suresh

2018-04-01

Stainless steels are used in high-temperature structural applications but suffer from degradation at an elevated temperature of operation due to thermal stress which leads to spallation. Ceria coating over chromium containing alloys induces protective chromia layer formation at alloy/ceria interface thereby preventing oxidative degradation. In the present work, three metals of differing elemental composition, namely, AISI 304, AISI 410, and Inconel 600 were tested for high-temperature stability in the presence and absence of ceria coating. Nanoceria was used as the target to deposit the coating through electron beam physical vapor deposition method. After isothermal oxidation at 1243 K for 24 h, Ceria coated AISI 304 and Inconel 600 exhibited a reduced rate of oxidation by 4 and 1 orders, respectively, in comparison with the base alloy. The formation of spinel structure was found to be lowered in the presence of ceria due to the reduced migration of cations from the alloy.

Sodium alginate/gelatin with silica nanoparticles a novel hydrogel for 3D printing

NASA Astrophysics Data System (ADS)

Soni, Raghav; Roopavath, Uday Kiran; Mahanta, Urbashi; Deshpande, A. S.; Rath, S. N.

2018-05-01

Sodium alginate/gelatin hydrogels are promising materials for 3D bio-printing due to its good biocompatibility and biodegradability. Gelatin is used for thermal crosslinking and its cell adhesion properties. Hence patient specific sodium alginate/gelatin hydrogel scaffolds can be bio-fabricated in a temperature range of 4-14 oC. In this study we made an attempt to introduce silica (SiO2) nanoparticles in the polymer network of sodium alginate (2.5%)/gelatin (8%) hydrogel at different concentrations (w/v) as 0%, 1.25%, 2.5%, 5%, and 7.5%. The effect of silica nanoparticles on viscosity, swelling behavior, and degradation rate are analyzed. Hydrogels with 5% silica nanoparticles show significantly less swelling and degradation when compared to other concentrations. The viscosity of the hydrogels gradually increases up to 5% addition of silica nanoparticles enhancing the stability of 3D printed structures.

Fungal Beta-Glucosidases: A Bottleneck in Industrial Use of Lignocellulosic Materials

PubMed Central

Sørensen, Annette; Lübeck, Mette; Lübeck, Peter S.; Ahring, Birgitte K.

2013-01-01

Profitable biomass conversion processes are highly dependent on the use of efficient enzymes for lignocellulose degradation. Among the cellulose degrading enzymes, beta-glucosidases are essential for efficient hydrolysis of cellulosic biomass as they relieve the inhibition of the cellobiohydrolases and endoglucanases by reducing cellobiose accumulation. In this review, we discuss the important role beta-glucosidases play in complex biomass hydrolysis and how they create a bottleneck in industrial use of lignocellulosic materials. An efficient beta-glucosidase facilitates hydrolysis at specified process conditions, and key points to consider in this respect are hydrolysis rate, inhibitors, and stability. Product inhibition impairing yields, thermal inactivation of enzymes, and the high cost of enzyme production are the main obstacles to commercial cellulose hydrolysis. Therefore, this sets the stage in the search for better alternatives to the currently available enzyme preparations either by improving known or screening for new beta-glucosidases. PMID:24970184

Mission Performance of the GLAS Thermal Control System - 7 Years In Orbit

NASA Technical Reports Server (NTRS)

Grob, Eric W.

2010-01-01

ICESat (Ice, Cloud and land Elevation Satellite) was launched in 2003 carrying a single science instrument - the Geoscience Laser Altimeter System (GLAS). Its primary mission was to measure polar ice thickness. The GLAS thermal control architecture utilized propylene Loop Heat Pipe (LHP) technology to provide selectable and stable temperature control for the lasers and other electronics over a widely varying mission thermal environment. To minimize expected degradation of the radiators, Optical Solar Reflectors (OSRs) were used for both LHP radiators to minimize degradation caused by UV exposure in the various spacecraft attitudes necessary throughout the mission. Developed as a Class C mission, with selective redundancy, the thermal architecture was single st ring, except for temperature sensors used for heater control during normal operations. Although originally planned for continuous laser operations over the nominal three year science mission, laser anomalies limited operations to discrete measurement campaigns repeated throughout the year. For trending of the science data, these periods were selected to occur at approximately the same time each year, which resulted in operations during similar attitudes and beta angles. Despite the laser life issues, the LHPs have operated nearly continuously over this time, being non-operational for only brief periods. Using mission telemetry, this paper looks at the performance of the thermal subsystem during these periods and provides an assessment of radiator degradation over the mission lifetime.

Improved thermal stability of methylsilicone resins by compositing with N-doped graphene oxide/Co3O4 nanoparticles

NASA Astrophysics Data System (ADS)

Jiang, Bo; Zhao, Liwei; Guo, Jiang; Yan, Xingru; Ding, Daowei; Zhu, Changcheng; Huang, Yudong; Guo, Zhanhu

2016-06-01

Nanoparticles play important roles in enhancing the thermal-resistance of hosting polymer resins. Despite tremendous efforts, developing thermally stable methylsilicone resin at high temperatures is still a challenge. Herein, we report a strategy to increase the activation energy to slow down the decomposition/degradation of methylsilicone resin using synergistic effects between the Co3O4 nanoparticles and the nitrogen doped graphene oxide. The N-doped graphene oxides composited with Co3O4 nanoparticles were prepared by hydrolysis of cobalt nitrate hexahydrate in the presence of graphene oxide and were incorporated into the methylsilicone resin. Two-stage decompositions were observed, i.e., 200-300 and 400-500 °C. The activation energy for the low temperature region was enhanced by 47.117 kJ/mol (vs. 57.76 kJ/mol for pure resin). The enhanced thermal stability was due to the fact that the nanofillers prevented the silicone hydroxyl chain ends ``biting'' to delay the degradation. The activation energy for high-temperature region was enhanced by 11.585 kJ/mol (vs. 171.95 kJ/mol for pure resin). The nanofillers formed a protective layer to isolate oxygen from the hosting resin. The mechanism for the enhanced thermal stability through prohibited degradation with synergism of these nitrogen-doped graphene oxide nanocomposites was proposed as well.

Correlation of trap states with negative bias thermal illumination stress stabilities in amorphous In-Ga-Zn-O thin-film transistors studied by photoinduced transient spectroscopy

NASA Astrophysics Data System (ADS)

Hayashi, Kazushi; Ochi, Mototaka; Hino, Aya; Tao, Hiroaki; Goto, Hiroshi; Kugimiya, Toshihiro

2017-03-01

Negative bias thermal illumination stress (NBTIS) stabilities in amorphous In-Ga-Zn-O (a-IGZO) thin-film transistors (TFTs) were studied by photoinduced transient spectroscopy (PITS). The degradation of TFT performance correlated with trap states in the channel region of a-IGZO TFTs with an etch stop layer (ESL). A prominent peak at approximately 100 K was observed in a-IGZO formed under a partial pressure (p/p) of 4% O2. With increasing O2 p/p, an apparent shoulder of around 230 K appeared in PITS spectra. A higher flow rate of SiH4/N2O for the ESL deposition induced trap states associated with the 230 K peak. The peak at approximately 100 K could originate from the depletion of Zn by preannealing, while the peak at approximately 230 K should be attributed to the oxygen-deficient and/or Zn-rich defects due to the formation of OH in a-IGZO. The trap states in a-IGZO TFTs gave rise to degradation in terms of NBTIS. The threshold voltage shift (ΔV th) was 2.5 V, but it increased with the O2 p/p as well as the flow rate of SiH4/N2O for ESL deposition. The time dependence of ΔV th suggested that hydrogen from the ESL and/or in the a-IGZO thin films was incorporated and modified the trap states in the channel region of the a-IGZO TFTs.

Posttest calculations of bundle quench test CORA-13 with ATHLET-CD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bestele, J.; Trambauer, K.; Schubert, J.D.

Gesellschaft fuer Anlagen- und Reaktorsicherheit is developing, in cooperation with the Institut fuer Kernenergetik und Energiesysteme, Stuttgart, the system code Analysis of Thermalhydraulics of Leaks and Transients with Core Degradation (ATHLET-CD). The code consists of detailed models of the thermal hydraulics of the reactor coolant system. This thermo-fluid dynamics module is coupled with modules describing the early phase of the core degradation, like cladding deformation, oxidation and melt relocation, and the release and transport of fission products. The assessment of the code is being done by the analysis of separate effect tests, integral tests, and plant events. The code willmore » be applied to the verification of severe accident management procedures. The out-of-pile test CORA-13 was conducted by Forschungszentrum Karlsruhe in their CORA test facility. The test consisted of two phases, a heatup phase and a quench phase. At the beginning of the quench phase, a sharp peak in the hydrogen generation rate was observed. Both phases of the test have been calculated with the system code ATHLET-CD. Special efforts have been made to simulate the heat losses and the flow distribution in the test facility and the thermal hydraulics during the quench phase. In addition to previous calculations, the material relocation and the quench phase have been modeled. The temperature increase during the heatup phase, the starting time of the temperature escalation, and the maximum temperatures have been calculated correctly. At the beginning of the quench phase, an increased hydrogen generation rate has been calculated as measured in the experiment.« less

Investigation of Thermal and Viscoelastic Properties of Polymers Relevant to Hot Melt Extrusion, IV: Affinisol™ HPMC HME Polymers.

PubMed

Gupta, Simerdeep Singh; Solanki, Nayan; Serajuddin, Abu T M

2016-02-01

Most cellulosic polymers cannot be used as carriers for preparing solid dispersion of drugs by hot melt extrusion (HME) due to their high melt viscosity and thermal degradation at high processing temperatures. Three HME-grade hydroxypropyl methylcelluloses, namely Affinisol™ HPMC HME 15 cP, Affinisol™ HPMC HME 100 cP, and Affinisol™ HPMC HME 4 M, have recently been introduced by The Dow Chemical Co. to enable the preparation of solid dispersion at lower and more acceptable processing temperatures. In the present investigation, physicochemical properties of the new polymers relevant to HME were determined and compared with that of Kollidon(®) VA 64. Powder X-ray diffraction (PXRD), modulated differential scanning calorimetry (mDSC), thermogravimetric analysis (TGA), moisture sorption, rheology, and torque analysis by melt extrusion were applied. PXRD and mDSC showed that the Affinisol™ polymers were amorphous in nature. According to TGA, the onset of degradation for all polymers was >220°C. The Affinisol™ polymers exhibited less hygroscopicity than Kollidon(®) VA 64 and another HPMC polymer, Methocel™ K100LV. The complex viscosity profiles of the Affinisol™ polymers as a function of temperature were similar. The viscosity of the Affinisol™ polymers was highly sensitive to the shear rate applied, and unlike Kollidon(®) VA 64, the viscosity decreased drastically when the angular frequency was increased. Because of the very high shear rate encountered during melt extrusion, Affinisol™ polymers showed capability of being extruded at larger windows of processing temperatures as compared to that of Kollidon(®) VA 64.

Functionalized Polymeric Membrane with Enhanced Mechanical and Biological Properties to Control the Degradation of Magnesium Alloy.

PubMed

Wong, Hoi Man; Zhao, Ying; Leung, Frankie K L; Xi, Tingfei; Zhang, Zhixiong; Zheng, Yufeng; Wu, Shuilin; Luk, Keith D K; Cheung, Kenneth M C; Chu, Paul K; Yeung, Kelvin W K

2017-04-01

To achieve enhanced biological response and controlled degradation of magnesium alloy, a modified biodegradable polymer coating called polycaprolactone (PCL) is fabricated by a thermal approach in which the heat treatment neither alters the chemical composition of the PCL membrane nor the rate of magnesium ion release, pH value, or weight loss, compared with the untreated sample. The changes in the crystallinity, hydrophilicity, and oxygen content of heat-treated PCL coating not only improve the mechanical adhesion strength between the coating and magnesium substrate but also enhance the biological properties. Moreover, the thermally modified sample can lead to higher spreading and elongation of osteoblasts, due to the enhanced hydrophilicity and CO to CO functional group ratio. In the analyses of microcomputed tomography from one to four weeks postoperation, the total volume of new bone formation on the heat-treated sample is 10%-35% and 70%-90% higher than that of the untreated and uncoated controls, respectively. Surprisingly, the indentation modulus of the newly formed bone adjacent to the heat-treated sample is ≈20% higher than that of both controls. These promising results reveal the clinical potential of the modified PCL coating on magnesium alloy in orthopedic applications. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Design and Characterization of High-strength Bond Coats for Improved Thermal Barrier Coating Durability

NASA Astrophysics Data System (ADS)

Jorgensen, David John

High pressure turbine blades in gas turbine engines rely on thermal barrier coating (TBC) systems for protection from the harsh combustion environment. These coating systems consist of a ceramic topcoat for thermal protection, a thermally grown oxide (TGO) for oxidation passivation, and an intermetallic bond coat to provide compatibility between the substrate and ceramic over-layers while supplying aluminum to sustain Al2O 3 scale growth. As turbine engines are pushed to higher operating temperatures in pursuit of better thermal efficiency, the strength of industry-standard bond coats limits the lifetime of these coating systems. Bond coat creep deformation during thermal cycling leads to a failure mechanism termed rumpling. The interlayer thermal expansion differences, combined with TGO-imposed growth stresses, lead to the development of periodic undulations in the bond coat. The ceramic topcoat has low out-of-plane compliance and thus detaches and spalls from the substrate, resulting in a loss of thermal protection and subsequent degradation of mechanical properties. New creep resistant Ni3Al bond coats were designed with improved high-temperature strength to inhibit this type of premature failure at elevated temperatures. These coatings resist rumpling deformation while maintaining compatibility with the other layers in the system. Characterization methods are developed to quantify rumpling and assess the TGO-bond coat interface toughness of experimental systems. Cyclic oxidation experiments at 1163 °C show that the Ni3Al bond coats do not experience rumpling but have faster oxide growth rates and are quicker to spall TGO than the (Pt,Ni)Al benchmark. However, the Ni 3Al coatings outperformed the benchmark by over threefold in TBC system life due to a higher resistance to rumpling (mechanical degradation) while maintaining adequate oxidation passivation. The Ni3Al coatings eventually grow spinel NiAl2O4 on top of the protective Al2O3 layer, which leads to the detachment of the ceramic topcoat. Furthermore, bilayer Ni3Al+NiAl architectures have been investigated to improve the oxidation performance of the monolithic Ni 3Al coatings while maintaining their high strength. These bilayer architectures are shown to improve the cyclic oxidation performance of the monolithic layers and increase the TBC system life. The design, characterization, and experimentation of these coatings is discussed and related to the development of high-strength coatings.

Furan in Thermally Processed Foods - A Review

PubMed Central

Seok, Yun-Jeong; Her, Jae-Young; Kim, Yong-Gun; Kim, Min Yeop; Jeong, Soo Young; Kim, Mina K.; Lee, Jee-yeon; Kim, Cho-il; Yoon, Hae-Jung

2015-01-01

Furan (C4H4O) is a volatile compound formed mostly during the thermal processing of foods. The toxicity of furan has been well documented previously, and it was classified as “possible human carcinogen (Group 2B)” by the International Agency for Research on Cancer. Various pathways have been reported for the formation of furan, that is, thermal degradation and/or thermal rearrangement of carbohydrates in the presence of amino acids, thermal degradation of certain amino acids, including aspartic acid, threonine, α-alanine, serine, and cysteine, oxidation of ascorbic acid at higher temperatures, and oxidation of polyunsaturated fatty acids and carotenoids. Owing to the complexity of the formation mechanism, a vast number of studies have been published on monitoring furan in commercial food products and on the potential strategies for reducing furan. Thus, we present a comprehensive review on the current status of commercial food monitoring databases and the possible furan reduction methods. Additionally, we review analytical methods for furan detection and the toxicity of furan. PMID:26483883

Structure-activity relationships between sterols and their thermal stability in oil matrix.

PubMed

Hu, Yinzhou; Xu, Junli; Huang, Weisu; Zhao, Yajing; Li, Maiquan; Wang, Mengmeng; Zheng, Lufei; Lu, Baiyi

2018-08-30

Structure-activity relationships between 20 sterols and their thermal stabilities were studied in a model oil system. All sterol degradations were found to be consistent with a first-order kinetic model with determination of coefficient (R 2 ) higher than 0.9444. The number of double bonds in the sterol structure was negatively correlated with the thermal stability of sterol, whereas the length of the branch chain was positively correlated with the thermal stability of sterol. A quantitative structure-activity relationship (QSAR) model to predict thermal stability of sterol was developed by using partial least squares regression (PLSR) combined with genetic algorithm (GA). A regression model was built with R 2 of 0.806. Almost all sterol degradation constants can be predicted accurately with R 2 of cross-validation equals to 0.680. Four important variables were selected in optimal QSAR model and the selected variables were observed to be related with information indices, RDF descriptors, and 3D-MoRSE descriptors. Copyright © 2018 Elsevier Ltd. All rights reserved.

Aqueous ethylenediamine for CO(2) capture.

PubMed

Zhou, Shan; Chen, Xi; Nguyen, Thu; Voice, Alexander K; Rochelle, Gary T

2010-08-23

Aqueous ethylenediamine (EDA) has been investigated as a solvent for CO(2) capture from flue gas. EDA can be used at 12 M (mol kg(-1) H(2)O) with an acceptable viscosity of 16 cP (1 cP=10(-3) Pa s) with 0.48 mol CO(2) per equivalent of EDA. Similar to monoethanolamine (MEA), EDA can be used up to 120 degrees C in a stripper without significant thermal degradation. Inhibitor A will effectively eliminate oxidative degradation. Above 120 degrees C, loaded EDA degrades with the production of its cyclic urea and other related compounds. Unlike piperazine, when exposed to oxidative degradation, EDA does not result in excessive foaming. Over much of the loading range, the CO(2) absorption rate with 12 M EDA is comparable to 7 M MEA. However, at typical rich loading, 12 M EDA absorbs CO(2) 2 times slower than 7 M MEA. The capacity of 12 M EDA is 0.72 mol CO(2)/(kg H(2)O+EDA) (for P(CO(2) )=0.5 to 5 kPa at 40 degrees C), which is about double that of MEA. The apparent heat of CO(2) desorption in EDA solution is 84 kJ mol(-1) CO(2); greater than most other amine systems.

Plastics to fuel: A review

USDA-ARS?s Scientific Manuscript database

This paper reviews recent developments in catalytic and non-catalytic degradation of waste plastics into fuels. Thermal degradation decomposes plastic into three fractions: gas, crude oil, and solid residue. Crude oil from non-catalytic pyrolysis is usually composed of higher boiling point hydrocarb...

Qualification test procedures and results for Honeywell solar collector subsystem, single-family residence

NASA Technical Reports Server (NTRS)

1977-01-01

The test procedures and results in qualifying the Honeywell single family residence solar collector subsystem are presented. Testing was done in the following areas: pressure, service loads, hail, solar degradation, pollutants, thermal degradation, and outgassing.

Accelerated Aging in Electrolytic Capacitors for Prognostics

NASA Technical Reports Server (NTRS)

Celaya, Jose R.; Kulkarni, Chetan; Saha, Sankalita; Biswas, Gautam; Goebel, Kai Frank

2012-01-01

The focus of this work is the analysis of different degradation phenomena based on thermal overstress and electrical overstress accelerated aging systems and the use of accelerated aging techniques for prognostics algorithm development. Results on thermal overstress and electrical overstress experiments are presented. In addition, preliminary results toward the development of physics-based degradation models are presented focusing on the electrolyte evaporation failure mechanism. An empirical degradation model based on percentage capacitance loss under electrical overstress is presented and used in: (i) a Bayesian-based implementation of model-based prognostics using a discrete Kalman filter for health state estimation, and (ii) a dynamic system representation of the degradation model for forecasting and remaining useful life (RUL) estimation. A leave-one-out validation methodology is used to assess the validity of the methodology under the small sample size constrain. The results observed on the RUL estimation are consistent through the validation tests comparing relative accuracy and prediction error. It has been observed that the inaccuracy of the model to represent the change in degradation behavior observed at the end of the test data is consistent throughout the validation tests, indicating the need of a more detailed degradation model or the use of an algorithm that could estimate model parameters on-line. Based on the observed degradation process under different stress intensity with rest periods, the need for more sophisticated degradation models is further supported. The current degradation model does not represent the capacitance recovery over rest periods following an accelerated aging stress period.

Oxidation of clofibric acid in aqueous solution using a non-thermal plasma discharge or gamma radiation

NASA Astrophysics Data System (ADS)

Madureira, Joana; Ceriani, Elisa; Pinhão, Nuno; Marotta, Ester; Melo, Rita; Cabo Verde, Sandra; Paradisi, Cristina; Margaça, Fernanda M. A.

2017-11-01

In this work, we study degradation of clofibric acid (CFA) in aqueous solution using either ionizing radiation from a $^{60}$Co source or a non-thermal plasma produced by discharges in the air above the solution. The results obtained with the two technologies are compared in terms of effectiveness of CFA degradation and its by-products. In both cases the CFA degradation follows a quasi-exponential decay in time well modelled by a kinetic scheme which considers the competition between CFA and all reaction intermediates for the reactive species generated in solution as well as the amount of the end product formed. A new degradation law is deduced to explain the results. Although the end-product CO$_2$ was detected and the CFA conversion found to be very high under the studied conditions, HPLC analysis reveals several degradation intermediates still bearing the aromatic ring with the chlorine substituent. The extent of mineralization is rather limited. The energy yield is found to be higher in the gamma radiation experiments.

Oxidation of clofibric acid in aqueous solution using a non-thermal plasma discharge or gamma radiation.

PubMed

Madureira, Joana; Ceriani, Elisa; Pinhão, Nuno; Marotta, Ester; Melo, Rita; Cabo Verde, Sandra; Paradisi, Cristina; Margaça, Fernanda M A

2017-11-01

In this work, we study degradation of clofibric acid (CFA) in aqueous solution using either ionizing radiation from a 60 Co source or a non-thermal plasma produced by discharges in the air above the solution. The results obtained with the two technologies are compared in terms of effectiveness of CFA degradation and its by-products. In both cases the CFA degradation follows a quasi-exponential decay in time well modelled by a kinetic scheme which considers the competition between CFA and all reaction intermediates for the reactive species generated in solution as well as the amount of the end product formed. A new degradation law is deduced to explain the results. Although the end-product CO 2 was detected and the CFA conversion found to be very high under the studied conditions, HPLC analysis reveals several degradation intermediates still bearing the aromatic ring with the chlorine substituent. The extent of mineralization is rather limited. The energy yield is found to be higher in the gamma radiation experiments. Copyright © 2017 Elsevier Ltd. All rights reserved.

A validated stability-indicating UPLC method for desloratadine and its impurities in pharmaceutical dosage forms.

PubMed

Rao, Dantu Durga; Satyanarayana, N V; Malleswara Reddy, A; Sait, Shakil S; Chakole, Dinesh; Mukkanti, K

2010-02-05

A novel stability-indicating gradient reverse phase ultra-performance liquid chromatographic (RP-UPLC) method was developed for the determination of purity of desloratadine in presence of its impurities and forced degradation products. The method was developed using Waters Aquity BEH C18 column with mobile phase containing a gradient mixture of solvents A and B. The eluted compounds were monitored at 280nm. The run time was 8min within which desloratadine and its five impurities were well separated. Desloratadine was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal and photolytic degradation. Desloratadine was found to degrade significantly in oxidative and thermal stress conditions and stable in acid, base, hydrolytic and photolytic degradation conditions. The degradation products were well resolved from main peak and its impurities, thus proved the stability-indicating power of the method. The developed method was validated as per ICH guidelines with respect to specificity, linearity, limit of detection, limit of quantification, accuracy, precision and robustness. This method was also suitable for the assay determination of desloratadine in pharmaceutical dosage forms.

Thermal stability, antioxidant, and anti-inflammatory activity of curcumin and its degradation product 4-vinyl guaiacol.

PubMed

Esatbeyoglu, Tuba; Ulbrich, Katrin; Rehberg, Clemens; Rohn, Sascha; Rimbach, Gerald

2015-03-01

Curcumin is a secondary plant metabolite present in Curcuma longa L. Since curcumin is widely used as a food colorant in thermally processed food it may undergo substantial chemical changes which in turn could affect its biological activity. In the current study, curcumin was roasted at 180 °C up to 70 minutes and its kinetic of degradation was analyzed by means of HPLC-PDA and LC-MS, respectively. Roasting of curcumin resulted in the formation of the degradation products vanillin, ferulic acid, and 4-vinyl guaiacol. In cultured hepatocytes roasted curcumin as well as 4-vinyl guaiacol enhanced the transactivation of the redox-regulated transcription factor Nrf2, known to be centrally involved in cellular stress response and antioxidant defense mechanisms. The antioxidant enzyme paraoxonase 1 was induced by roasted curcumin and 4-vinyl guaiacol. Furthermore, roasted curcumin and 4-vinyl guaiacol decreased interleukin-6 gene expression in lipopolysaccharide stimulated murine macrophages. Current data suggest that curcumin undergoes degradation due to roasting and its degradation product exhibit significant biological activity in cultured cells.

Thin HTSC films produced by a polymer metal precursor technique

NASA Astrophysics Data System (ADS)

Lampe, L. v.; Zygalsky, F.; Hinrichsen, G.

In precursors the metal ions are combined with acid groups of polymethacrylic acid (PMAA), polyacrylic acid (PAA) or novolac. Compared to thermal degradation temperature of pure polymers those of precursors are low. Precursors films were patterned by UV lithography. Diffractometric investigations showed that the c-axis oriented epitaxial films of YBa 2Cu 3O x and Bi 2Sr 2CaCu 2O x originated from amorphous metal oxide films, which were received after thermal degradation of the precursor. Transition temperatures and current densities were determined by electric resistivity measurements.

Thermal Remote Sensing and the Thermodynamics of Ecosystem Development

NASA Technical Reports Server (NTRS)

Luvall, Jeffrey C.; Kay, James J.; Fraser, Roydon F.

2000-01-01

Thermal remote sensing can provide environmental measuring tools with capabilities for measuring ecosystem development and integrity. Recent advances in applying principles of nonequilibrium thermodynamics to ecology provide fundamental insights into energy partitioning in ecosystems. Ecosystems are nonequilibrium systems, open to material and energy flows, which grow and develop structures and processes to increase energy degradation. More developed terrestrial ecosystems will be more effective at dissipating the solar gradient (degrading its energy content). This can be measured by the effective surface temperature of the ecosystem on a landscape scale.

Impact of Improved Heat Sinking of an X-Ray Calorimeter Array on Crosstalk, Noise, and Background Events

NASA Technical Reports Server (NTRS)

Kilbourne, C. A.; Adams, J. S.; Brekosky, R. P.; Chervenak, J. A.; Chiao, M. P.; Kelley, R. L.; Kelly, D. P.; Porter, F. S.

2011-01-01

The x-ray calorimeter array of the Soft X-ray Spectrometer (SXS) of the Astro-H satellite will incorporate a silicon thermistor array produced during the development of the X-Ray Spectrometer (XRS) of the Suzaku satellite. On XRS, inadequate heat sinking of the array led to several non-ideal effects. The thermal crosstalk, while too small to be confused with x-ray signals, nonetheless contributed a noise term that could be seen as a degradation in energy resolution at high flux. When energy was deposited in the silicon frame around the active elements of the array, such as by a cosmic ray, the resulting pulse in the temperature of the frame resulted in coincident signal pulses on most of the pixels. In orbit, the resolution was found to depend on the particle background rate. In order to minimize these effects on SXS, heat-sinking gold was applied to areas on the front and back of the array die, which was thermally anchored to the gold of its fanout board via gold wire bonds. The thermal conductance from the silicon chip to the fanout board was improved over that of XRS by an order of magnitude. This change was sufficient for essentially eliminating frame events and allowing high-resolution to be attained at much higher counting rates. We will present the improved performance, the measured crosstalk, and the results of the thermal characterization of such arrays.

Thermal barrier coating life prediction model

NASA Technical Reports Server (NTRS)

Pilsner, B. H.; Hillery, R. V.; Mcknight, R. L.; Cook, T. S.; Kim, K. S.; Duderstadt, E. C.

1986-01-01

The objectives of this program are to determine the predominant modes of degradation of a plasma sprayed thermal barrier coating system, and then to develop and verify life prediction models accounting for these degradation modes. The program is divided into two phases, each consisting of several tasks. The work in Phase 1 is aimed at identifying the relative importance of the various failure modes, and developing and verifying life prediction model(s) for the predominant model for a thermal barrier coating system. Two possible predominant failure mechanisms being evaluated are bond coat oxidation and bond coat creep. The work in Phase 2 will develop design-capable, causal, life prediction models for thermomechanical and thermochemical failure modes, and for the exceptional conditions of foreign object damage and erosion.

High temperature ablation of kaolinite layered silicate/phenolic resin/asbestos cloth nanocomposite.

PubMed

Bahramian, Ahmad Reza; Kokabi, Mehrdad; Famili, Mohammad Hossein Navid; Beheshty, Mohammad Hossein

2008-01-15

The successful return of re-entry space vehicle, which is subjected to severe aerodynamic heating, is largely accompanied by some provisions to reduce the heat transfer to the structure. Heat shield is the best protection means which undergoes physical, chemical, and mostly endothermal transformations. The objective of this work is to investigate the ablating, charring, and thermal degradation behaviour of heat shield resol-type phenolic resin/kaolinite/asbestos cloth nanocomposite by oxyacetylene flame test with an external heat flux of 8 x 10(9)W/m(2) and 3000 K hot gas temperature and thermal analyzer techniques. Kinetic parameters of thermal degradation and temperature distribution at the back surface of the nanocomposite heat shield were determined and compared with that of composite counterpart.

Pitch based foam with particulate

DOEpatents

Klett, James W.

2001-01-01

A thermally conductive, pitch based foam composite having a particulate content. The particulate alters the mechanical characteristics of the foam without severely degrading the foam thermal conductivity. The composite is formed by mixing the particulate with pitch prior to foaming.

Review of Thermal Spray Coating Applications in the Steel Industry: Part 2—Zinc Pot Hardware in the Continuous Galvanizing Line

NASA Astrophysics Data System (ADS)

Matthews, S.; James, B.

2010-12-01

This two-part article series reviews the application of thermal spray coating technology in the production of steel and steel sheet products. Part 2 of this article series is dedicated to coating solutions in the continuous galvanizing line. The corrosion mechanisms of Fe- and Co-based bulk materials are briefly reviewed as a basis for the development of thermal spray coating solutions. WC-Co thermal spray coatings are commonly applied to low Al-content galvanizing hardware due to their superior corrosion resistance compared to Fe and Co alloys. The effect of phase degradation, carbon content, and WC grain size are discussed. At high Al concentrations, the properties of WC-Co coatings degrade significantly, leading to the application of oxide-based coatings and corrosion-resistant boride containing coatings. The latest results of testing are summarized, highlighting the critical coating parameters.

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

PubMed

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.

An Effective Electrical Resonance-Based Method to Detect Delamination in Thermal Barrier Coating

NASA Astrophysics Data System (ADS)

Kim, Jong Min; Park, Jae-Ha; Lee, Ho Girl; Kim, Hak-Joon; Song, Sung-Jin; Seok, Chang-Sung; Lee, Young-Ze

2017-12-01

This research proposes a simple yet highly sensitive method based on electrical resonance of an eddy-current probe to detect delamination of thermal barrier coating (TBC). This method can directly measure the mechanical characteristics of TBC compared to conventional ultrasonic testing and infrared thermography methods. The electrical resonance-based method can detect the delamination of TBC from the metallic bond coat by shifting the electrical impedance of eddy current testing (ECT) probe coupling with degraded TBC, and, due to this shift, the resonant frequencies near the peak impedance of ECT probe revealed high sensitivity to the delamination. In order to verify the performance of the proposed method, a simple experiment is performed with degraded TBC specimens by thermal cyclic exposure. Consequently, the delamination with growth of thermally grown oxide in a TBC system is experimentally identified. Additionally, the results are in good agreement with the results obtained from ultrasonic C-scanning.

An Effective Electrical Resonance-Based Method to Detect Delamination in Thermal Barrier Coating

NASA Astrophysics Data System (ADS)

Kim, Jong Min; Park, Jae-Ha; Lee, Ho Girl; Kim, Hak-Joon; Song, Sung-Jin; Seok, Chang-Sung; Lee, Young-Ze

2018-02-01

This research proposes a simple yet highly sensitive method based on electrical resonance of an eddy-current probe to detect delamination of thermal barrier coating (TBC). This method can directly measure the mechanical characteristics of TBC compared to conventional ultrasonic testing and infrared thermography methods. The electrical resonance-based method can detect the delamination of TBC from the metallic bond coat by shifting the electrical impedance of eddy current testing (ECT) probe coupling with degraded TBC, and, due to this shift, the resonant frequencies near the peak impedance of ECT probe revealed high sensitivity to the delamination. In order to verify the performance of the proposed method, a simple experiment is performed with degraded TBC specimens by thermal cyclic exposure. Consequently, the delamination with growth of thermally grown oxide in a TBC system is experimentally identified. Additionally, the results are in good agreement with the results obtained from ultrasonic C-scanning.

Powder-Derived High-Conductivity Coatings for Copper Alloys

NASA Technical Reports Server (NTRS)

Thomas-Ogbuji, Linus U.

2003-01-01

Makers of high-thermal-flux engines prefer copper alloys as combustion chamber liners, owing to a need to maximize heat dissipation. Since engine environments are strongly oxidizing in nature and copper alloys generally have inadequate resistance to oxidation, the liners need coatings for thermal and environmental protection; however, coatings must be chosen with great care in order to avoid significant impairment of thermal conductivity. Powder-derived chromia- and alumina- forming alloys are being studied under NASA's programs for advanced reusable launch vehicles to succeed the space shuttle fleet. NiCrAlY and Cu-Cr compositions optimized for high thermal conductivity have been tested for static and cyclic oxidation, and for susceptibility to blanching - a mode of degradation arising from oxidation-reduction cycling. The results indicate that the decision to coat the liners or not, and which coating/composition to use, depends strongly on the specific oxidative degradation mode that prevails under service conditions.

Lumen degradation and chromaticity shift in glass and silicone based high-power phosphor-converted white-emitting diodes under thermal tests

NASA Astrophysics Data System (ADS)

Cheng, Wood-Hi; Tsai, Chun-Chin; Wang, Jimmy

2011-10-01

The lumen degradation and chromaticity shift in glass and silicone based high-power phosphor-converted white-emitting diodes (PC-WLEDs) under accelerated thermal tests at 150°C, 200°C, and 250°C are presented and compared. The glass based PC-WLEDs exhibited better thermal stability than the silicone by 4.8 time reductions in lumen loss 6.8 time reductions in chromaticity shift at 250°C, respectively. The mean-time-to-failure (MTTF) evaluation of glass and silicone based high-power PC-WLEDs in accelerated thermal tests is also presented and compared. The results showed that the glass based PC-WLEDs exhibited higher MTTF than the silicone by 7.53 times in lumen loss and 14.4 times in chromaticity shift at 250°C, respectively. The thermal performance of lumen, chromaticity, and MTTF investigations demonstrated that the thermal stability of the glass based PC-WLEDs were better than the silicone. A better thermal stability phosphor layer of glass as encapsulation material may be beneficial to the many applications where the LED modules with high power and high reliability are demanded.

Modeling of the heat transfer performance of plate-type dispersion nuclear fuel elements

NASA Astrophysics Data System (ADS)

Ding, Shurong; Huo, Yongzhong; Yan, XiaoQing

2009-08-01

Considering the mutual actions between fuel particles and the metal matrix, the three-dimensional finite element models are developed to simulate the heat transfer behaviors of dispersion nuclear fuel plates. The research results indicate that the temperatures of the fuel plate might rise more distinctly with considering the particle swelling and the degraded surface heat transfer coefficients with increasing burnup; the local heating phenomenon within the particles appears when their thermal conductivities are too low. With rise of the surface heat transfer coefficients, the temperatures within the fuel plate decrease; the temperatures of the fuel plate are sensitive to the variations of the heat transfer coefficients whose values are lower, but their effects are weakened and slight when the heat transfer coefficients increase and reach a certain extent. Increasing the heat generation rate leads to elevating the internal temperatures. The temperatures and the maximum temperature differences within the plate increase along with the particle volume fractions. The surface thermal flux goes up along with particle volume fractions and heat generation rates, but the effects of surface heat transfer coefficients are not evident.

New Melting Data of the Two Polymorphs of Prednisolone.

PubMed

Corvis, Yohann; Négrier, Philippe; Soulestin, Jérémie; Espeau, Philippe

2016-10-04

Prednisolone is known to exist in two anhydrous solid polymorphic forms. The substance is known to degrade upon melting, resulting in erroneous melting data, as shown by the widely scattered results reported in the literature. In this article, thermal analyses carried out at different scan rates show that the onset temperature and the enthalpy value of the signal increase with the scan rate and reach plateau values for high scan rates. Owing to flash scanning calorimetry, the plateau value for the temperature has been identified as the "true" temperature of melting of both polymorphs. This consistent set of new thermodynamic data on the two solid forms leads to the conclusion that both forms are unambiguously enantiotropes of each other. The solid-solid transition has been observed experimentally for the first time and has been confirmed by calculation.

Thermal degradation products formed from carotenoids during a heat-induced degradation process of paprika oleoresins (Capsicum annuum L.).

PubMed

Pérez-Gálvez, Antonio; Rios, José J; Mínguez-Mosquera, María Isabel

2005-06-15

The high-temperature treatment of paprika oleoresins (Capsicum annuum L.) modified the carotenoid profile, yielding several degradation products, which were analyzed by HPLC-APCI-MS. From the initial MS data, compounds were grouped in two sets. Set 1 grouped compounds with m/z 495, and set 2 included compounds with m/z 479, in both cases for the protonated molecular mass. Two compounds of the first set were tentatively identified as 9,10,11,12,13,14,19,20-octanor-capsorubin (compound II) and 9,10,11,12,13,14,19,20-octanor-5,6-epoxide-capsanthin (compound IV), after isolation by semipreparative HPLC and analysis by EI-MS. Compounds VII, VIII, and IX from set 2 were assigned as 9,10,11,12,13,14,19,20-octanor-capsanthin and isomers, respectively. As these compounds were the major products formed in the thermal process, it was possible to apply derivatization techniques (hydrogenation and silylation) to analyze them by EI-MS, before and after chemical derivatization. Taking into account structures of the degradation products, the cyclization of polyolefins could be considered as the general reaction pathway in thermally induced reactions, yielding in the present study xylene as byproduct and the corresponding nor-carotenoids.

Thermal degradation of hexachlorobenzene in the presence of calcium oxide at 340-400 °C.

PubMed

Yin, Keqing; Gao, Xingbao; Sun, Yifei; Zheng, Lei; Wang, Wei

2013-11-01

Hexachlorobenzene (HCB) in the milligram range was co-heated with calcium oxide (CaO) powder in sealed glass ampoules at 340-400 °C. The heated samples were characterized and analyzed by Raman spectroscopy, elemental analysis, gas chromatography/mass spectrometry, ion chromatography, and thermal/optical carbon analysis. The degradation products of HCB were studied at different temperatures and heated times. The amorphous carbon was firstly quantitatively evaluated and was thought to be important fate of the C element of HCB. The yield of amorphous carbon in products increased with heating time, for samples treated for 8h at 340, 380 °C and 400 °C, the value were 17.5%, 34.8% and 50.2%, respectively. After identification of the dechlorination products, the HCB degradation on CaO at 340-400 °C was supposed to through dechlorination/polymerization pathway, which is induced by electron transfer, generate chloride ions and form high-molecular weight intermediates with significant levels of both hydrogen and chlorine, and finally form amorphous carbon. Higher temperature was beneficial for the dechlorination/polymerization efficiency. The results are helpful for clarifying the reaction mechanism for thermal degradation of chlorinated aromatics in alkaline matrices. Copyright © 2013 Elsevier Ltd. All rights reserved.

Humidity effects on soluble core mechanical and thermal properties (polyvinyl alcohol/microballoon composite) type CG extendospheres, volume 2

NASA Technical Reports Server (NTRS)

1993-01-01

This document constitutes the final report for the study of humidity effects and loading rate on soluble core (PVA/MB composite material) mechanical and thermal properties under Contract No. 100345. This report describes test results procedures employed, and any unusual occurrences or specific observations associated with this test program. The primary objective of this work was to determine if cured soluble core filler material regains its tensile and compressive strength after exposure to high humidity conditions and following a drying cycle. Secondary objectives include measurements of tensile and compressive modulus, and Poisson's ratio, and coefficient of thermal expansion (CTE) for various moisture exposure states. A third objective was to compare the mechanical and thermal properties of the composite using 'SG' and 'CG' type extendospheres. The proposed facility for the manufacture of soluble cores at the Yellow Creek site incorporates no capability for the control of humidity. Recent physical property tests performed with the soluble core filler material showed that prolonged exposure to high humidity significantly degradates in strength. The purpose of these tests is to determine if the product, process or facility designs require modification to avoid imparting a high risk condition to the ASRM.

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

NASA Astrophysics Data System (ADS)

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.

Skylab D024 thermal control coatings and polymeric films experiment

NASA Technical Reports Server (NTRS)

Lehn, William L.; Hurley, Charles J.

1992-01-01

The Skylab D024 Thermal Control Coatings and Polymeric Films Experiment was designed to determine the effects of the external Skylab space environment on the performance and properties of a wide variety of selected thermal control coatings and polymeric films. Three duplicate sets of thermal control coatings and polymeric films were exposed to the Skylab space environment for varying periods of time during the mission. The specimens were retrieved by the astronauts during extravehicular activities (EVA) and placed in hermetically sealed return containers, recovered, and returned to the Wright Laboratory/Materials Laboratory/WPAFB, Ohio for analysis and evaluation. Postflight analysis of the three sets of recovered thermal control coatings indicated that measured changes in specimen thermo-optical properties were due to a combination of excessive contamination and solar degradation of the contaminant layer. The degree of degradation experienced over-rode, obscured, and compromised the measurement of the degradation of the substrate coatings themselves. Results of the analysis of the effects of exposure on the polymeric films and the contamination observed are also presented. The D024 results were used in the design of the LDEF M0003-5 Thermal Control Materials Experiment. The results are presented here to call to the attention of the many other LDEF experimenters the wealth of directly related, low earth orbit, space environmental exposure data that is available from the ten or more separate experiments that were conducted during the Skylab mission. Results of these experiments offer data on the results of low altitude space exposure on materials recovered from space with exposure longer than typical STS experiments for comparison with the LDEF results.

Stability-indicating UPLC method for determining related substances and degradants in dronedarone.

PubMed

Pydimarry, Surya Prakash Rao; Cholleti, Vijay Kumar; Vangala, Ranga Reddy

2014-08-01

A simple, sensitive and reproducible method was developed on ultra-performance liquid chromatography coupled with photodiode array detection for the quantitative determination of dronedarone hydrochloride (DRO) in drug substance and pharmaceutical dosage forms. The method is applicable for the quantification of related substances and assays of drug substances. Chromatographic separation was achieved on Acquity UPLC BEH C8 100 mm, 2.1 mm and 1.7 µm columns, using gradient elution within a short run time of 10.0 min. The eluted compounds were monitored at 288 nm, the flow rate was 0.5 mL/min and the column oven temperature was maintained at 40°C. The resolution of DRO and 11 impurities (potentials and by-products) was greater than 2.0 for all pairs of components. The high correlation coefficient value (>0.9995) indicates the clear correlations between the concentrations of investigated compound and their peak areas within the test ranges. The repeatability and intermediate precision, expressed by the relative standard deviation, were less than 2.5%. The accuracy and validity of the method were further ascertained by performing recovery studies via a spike method. The accuracy of the method, expressed as relative error, was satisfactory. No interference was observed from concomitant substances normally added to the tablets. DRO was subjected to the stress conditions of oxidative, acid, base, hydrolytic, thermal and photolytic degradation. DRO was found to degrade significantly in acid and base stress conditions and to remain stable in thermal, photolytic degradation, oxidative and hydrolytic conditions. The degradation products were well resolved from primary peak and its impurities, proving that the method is stability indicating. The developed method was validated as per International Conference on Harmonization guidelines with respect to specificity, limit of detection, limit of quantification, linearity, accuracy, precision, solution stability and robustness. This method is also suitable for the determination of DRO drug substance and pharmaceutical dosage forms. © The Author [2013]. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Some aspects of the hot corrosion of thermal barrier coatings

NASA Technical Reports Server (NTRS)

Jones, Robert L.

1995-01-01

This paper provides a pro tem review of the hot corrosion of zirconia-based thermal barrier coatings for engine applications. Emphasis is placed on trying to understand the chemical reactions, and such other mechanisms as can be identified, that cause corrosive degradation of the thermal barrier coating. The various approaches taken in attempts to improve the hot corrosion resistance of thermal barrier coatings are also briefly described and critiqued.

Ceramic Matrix Composites: High Temperature Effects. (Latest Citations from the Aerospace Database)

NASA Technical Reports Server (NTRS)

1997-01-01

The bibliography contains citations concerning the development and testing of ceramic matrix composites for high temperature use. Tests examining effects of the high temperatures on bond strength, thermal degradation, oxidation, thermal stress, thermal fatigue, and thermal expansion properties are referenced. Applications of the composites include space structures, gas turbine and engine components, control surfaces for spacecraft and transatmospheric vehicles, heat shields, and heat exchangers.

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

PubMed

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 technology.

Some Oobservations of the Role of Component Size in Solder Joint Degradation under Thermal Cycling Environments

NASA Technical Reports Server (NTRS)

Winslow, J.; Wen, L-C.

1995-01-01

Experimental results will be presented from a continuing investigation into the influence of component size and configuration of thermal cycling lifetimes, observed in a set of quadpak electronic component packages.

Long Term Degradation of Resin for High Temperature Composites

NASA Technical Reports Server (NTRS)

Patekar, Kaustubh A.

2000-01-01

The durability of polymer matrix composites exposed to harsh environments is a major concern. Surface degradation and damage are observed in polyimide composites used in air at 125 to 300 C. It is believed that diffusion of oxygen into the material and oxidative chemical reactions in the matrix are responsible. Previous work has characterized and modeled diffusion behavior, and thermogravimetric analyses (TGAs) have been carried out in nitrogen, air, and oxygen to provide quantitative information on thermal and oxidative reactions. However, the model developed using these data was not able to capture behavior seen in isothermal tests, especially those of long duration. A test program that focuses on lower temperatures and makes use of isothermal tests was undertaken to achieve a better understanding of the degradation reactions under use conditions. A new low-cost technique was developed to collect chemical degradation data for isothermal tests lasting over 200 hr in the temperature range 125 to 300 C. Results indicate complex behavior not captured by the previous TGA tests, including the presence of weight-adding reactions. Weight gain reactions dominated in the 125 to 225 C temperature range, while weight loss reactions dominated beyond 225 C. The data obtained from isothermal tests was used to develop a new model of the material behavior. This model was able to fully capture the behavior seen in the tests up to 275 C. Correlation of the current model with both isothermal data at 300 C and high rate TGA test data is mediocre. At 300 C and above, the reaction mechanisms appear to change. Attempts (which failed) to measure non-oxidative degradation indicate that oxidative reactions dominate the degradation at low temperatures. Based on this work, long term isothermal testing in an oxidative atmosphere is recommended for studying the degradation behavior of this class of materials.

Mir Cooperative Solar Array Project Accelerated Life Thermal Cycling Test

NASA Technical Reports Server (NTRS)

Hoffman, David J.; Scheiman, David A.

1996-01-01

The Mir Cooperative Solar Array (MCSA) project was a joint U.S./Russian effort to build a photovoltaic (PV) solar array and deliver it to the Russian space station Mir. The MCSA will be used to increase the electrical power on Mir and provide PV array performance data in support of Phase 1 of the International Space Station. The MCSA was brought to Mir by space shuttle Atlantis in November 1995. This report describes an accelerated thermal life cycle test which was performed on two samples of the MCSA. In eight months time, two MCSA solar array 'mini' panel test articles were simultaneously put through 24,000 thermal cycles. There was no significant degradation in the structural integrity of the test articles and no electrical degradation, not including one cell damaged early and removed from consideration. The nature of the performance degradation caused by this one cell is briefly discussed. As a result of this test, changes were made to improve some aspects of the solar cell coupon-to-support frame interface on the flight unit. It was concluded from the results that the integration of the U.S. solar cell modules with the Russian support structure would be able to withstand at least 24,000 thermal cycles (4 years on-orbit). This was considered a successful development test.

Pressure effects on the thermal stability of SiC fibers

NASA Technical Reports Server (NTRS)

Jaskowiak, Martha H.; Dicarlo, James A.

1986-01-01

Commercially available polymer derived SiC fibers were treated at temperatures from 1000 to 2200 C in vacuum and argon gas pressure of 1 and 1360 atm. Effects of gas pressure on the thermal stability of the fibers were determined through property comparison between the pressure treated fibers and vacuum treated fibers. Investigation of the thermal stability included studies of the fiber microstructure, weight loss, grain growth, and tensile strength. The 1360 atm argon gas treatment was found to shift the onset of fiber weight loss from 1200 to above 1500 C. Grain growth and tensile strength degradation were correlated with weight loss and were thus also inhibited by high pressure treatments. Additional heat treatment in 1 atm argon of the fibers initially treated at 1360 atm argon caused further weight loss and tensile strength degradation, thus indicating that high pressure inert gas conditions would be effective only in delaying fiber strength degradation. However, if the high gas pressure could be maintained throughout composite fabrication, then the composites could be processed at higher temperatures.

UV-visible spectroscopic estimation of photodegradation of rhodamine-B dye using tin(IV) oxide nanoparticles.

PubMed

Sangami, G; Dharmaraj, N

2012-11-01

Nanocrystalline, tin(IV) oxide (SnO(2)) particles has been prepared by thermal decomposition of tin oxalate precursor obtained from the reactions of tin(IV) chloride and sodium oxalate using eggshell membrane (ESM). The as-prepared SnO(2) nanoparticles were characterized by thermal studies, transmission electron microscopy (TEM), powder X-ray diffraction (XRD), Raman, FT-IR and UV-visible studies and used as a photocatalyst for the degradation of rhodamine-B (Rh-B) dye. The size of the prepared nanoparticles was in the range of 5-12nm as identified from the TEM images. Powder XRD data revealed the presence of a tetragonal, rutile crystalline phase of the tin(IV) oxide nanoparticles. Thermal analysis showed that the decomposition of tin oxalate precursor to yield the titled tin(IV) oxide nanoparticles was completed below 500°C. The extent of degradation of Rh-B in the presence of SnO(2) monitored by absorption spectral measurements demonstrated that 94.48% of the selected dye was degraded upon irradiation with UV light for 60 min. Copyright © 2012 Elsevier B.V. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

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

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,more » 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.« less

Preheated milk proteins improve the stability of grape skin anthocyanins extracts.

PubMed

He, Zhiyong; Xu, Mingzhu; Zeng, Maomao; Qin, Fang; Chen, Jie

2016-11-01

The effects of casein and whey proteins, preheated at 40-100°C and 45-60°C for 15min, respectively, on color loss and anthocyanins degradation in grape skin anthocyanins extracts (GSAE) at pH 3.2 and 6.3 were evaluated. Preheating milk proteins effectively improved their protective effects against color loss and anthocyanins degradation in GSAE solutions during thermal treatment (at 80°C for 2h), H2O2 oxidation (0.005% H2O2 for 1h) and illumination (at 5000lx for 5 d). Whey proteins and casein, preheated at 50°C and 60°C for 15min, respectively, demonstrated the optimal protective effects. However, preheated whey proteins had a better protective effect on the thermal, oxidation and photo stability of GSAE, decreasing the thermal, oxidative and photo degradation of anthocyanins in GSAE 71.59%, 32.22% and 56.92% at pH 3.2 and 54.91%, 22.89% and 46.68% at pH 6.3, respectively. Copyright © 2016 Elsevier Ltd. All rights reserved.

Liquid phase products and solid deposit formation from thermally stressed model jet fuels

NASA Technical Reports Server (NTRS)

Kim, W. S.; Bittker, D. A.

1984-01-01

The relationship between solid deposit formation and liquid degradation product concentration was studied for the high temperature (400 C) stressing of three hydrocarbon model fuels. A Jet Fuel Thermal Oxidation Tester was used to simulate actual engine fuel system conditions. The effects of fuel type, dissolved oxygen concentration, and hot surface contact time (reaction time) were studied. Effects of reaction time and removal of dissolved oxygen on deposit formation were found to be different for n-dodecane and for 2-ethylnaphthalene. When ten percent tetralin is added to n-dodecane to give a simpler model of an actual jet fuel, the tetralin inhibits both the deposit formation and the degradation of n-dodecane. For 2-ethylnaphthalene primary product analyses indicate a possible self-inhibition at long reaction times of the secondary reactions which form the deposit precursors. The mechanism of the primary breakdown of these fuels is suggested and the primary products which participate in these precursor-forming reactions are identified. Some implications of the results to the thermal degradation of real jet fuels are given.

Degradation of alachlor in aqueous solution by using hydrodynamic cavitation.

PubMed

Wang, Xikui; Zhang, Yong

2009-01-15

The degradation of alachlor aqueous solution by using hydrodynamic cavitation was systematically investigated. It was found that alachlor in aqueous solution can be deomposed with swirling jet-induced cavitation. The degradation can be described by a pseudo-first-order kinetics and the degradation rate was found to be 4.90x10(-2)min(-1). The effects of operating parameters such as fluid pressure, solution temperature, initial concentration of alachlor and medium pH on the degradation rates of alachlor were also discussed. The results showed that the degradation rates of alachlor increased with increasing pressure and decreased with increasing initial concentration. An optimum temperature of 40 degrees C existed for the degradation rate of alachlor and the degradation rate was also found to be slightly depend on medium pH. Many degradation products formed during the process, and some of them were qualitatively identified by GC-MS.

Solar dynamic heat receiver thermal characteristics in low earth orbit

NASA Technical Reports Server (NTRS)

Wu, Y. C.; Roschke, E. J.; Birur, G. C.

1988-01-01

A simplified system model is under development for evaluating the thermal characteristics and thermal performance of a solar dynamic spacecraft energy system's heat receiver. Results based on baseline orbit, power system configuration, and operational conditions, are generated for three basic receiver concepts and three concentrator surface slope errors. Receiver thermal characteristics and thermal behavior in LEO conditions are presented. The configuration in which heat is directly transferred to the working fluid is noted to generate the best system and thermal characteristics. as well as the lowest performance degradation with increasing slope error.

Pathway and rate-limiting step of glyphosate degradation by Aspergillus oryzae A-F02.

PubMed

Fu, Gui-Ming; Chen, Yan; Li, Ru-Yi; Yuan, Xiao-Qiang; Liu, Cheng-Mei; Li, Bin; Wan, Yin

2017-09-14

Aspergillus oryzae A-F02, a glyphosate-degrading fungus, was isolated from an aeration tank in a pesticide factory. The pathway and rate-limiting step of glyphosate (GP) degradation were investigated through metabolite analysis. GP, aminomethylphosphonic acid (AMPA), and methylamine were detected in the fermentation liquid of A. oryzae A-F02, whereas sarcosine and glycine were not. The pathway of GP degradation in A. oryzae A-F02 was revealed: GP was first degraded into AMPA, which was then degraded into methylamine. Finally, methylamine was further degraded into other products. Investigating the effects of the exogenous addition of substrates and metabolites showed that the degradation of GP to AMPA is the rate-limiting step of GP degradation by A. oryzae A-F02. In addition, the accumulation of AMPA and methylamine did not cause feedback inhibition in GP degradation. Results showed that degrading GP to AMPA was a crucial step in the degradation of GP, which determines the degradation rate of GP by A. oryzae A-F02.

Highly Bendable In-Ga-ZnO Thin Film Transistors by Using a Thermally Stable Organic Dielectric Layer

PubMed Central

Kumaresan, Yogeenth; Pak, Yusin; Lim, Namsoo; kim, Yonghun; Park, Min-Ji; Yoon, Sung-Min; Youn, Hyoc-Min; Lee, Heon; Lee, Byoung Hun; Jung, Gun Young

2016-01-01

Flexible In-Ga-ZnO (IGZO) thin film transistor (TFT) on a polyimide substrate is produced by employing a thermally stable SA7 organic material as the multi-functional barrier and dielectric layers. The IGZO channel layer was sputtered at Ar:O2 gas flow rate of 100:1 sccm and the fabricated TFT exhibited excellent transistor performances with a mobility of 15.67 cm2/Vs, a threshold voltage of 6.4 V and an on/off current ratio of 4.5 × 105. Further, high mechanical stability was achieved by the use of organic/inorganic stacking of dielectric and channel layers. Thus, the IGZO transistor endured unprecedented bending strain up to 3.33% at a bending radius of 1.5 mm with no significant degradation in transistor performances along with a superior reliability up to 1000 cycles. PMID:27876893

Highly Bendable In-Ga-ZnO Thin Film Transistors by Using a Thermally Stable Organic Dielectric Layer.

PubMed

Kumaresan, Yogeenth; Pak, Yusin; Lim, Namsoo; Kim, Yonghun; Park, Min-Ji; Yoon, Sung-Min; Youn, Hyoc-Min; Lee, Heon; Lee, Byoung Hun; Jung, Gun Young

2016-11-23

Flexible In-Ga-ZnO (IGZO) thin film transistor (TFT) on a polyimide substrate is produced by employing a thermally stable SA7 organic material as the multi-functional barrier and dielectric layers. The IGZO channel layer was sputtered at Ar:O 2 gas flow rate of 100:1 sccm and the fabricated TFT exhibited excellent transistor performances with a mobility of 15.67 cm 2 /Vs, a threshold voltage of 6.4 V and an on/off current ratio of 4.5 × 10 5 . Further, high mechanical stability was achieved by the use of organic/inorganic stacking of dielectric and channel layers. Thus, the IGZO transistor endured unprecedented bending strain up to 3.33% at a bending radius of 1.5 mm with no significant degradation in transistor performances along with a superior reliability up to 1000 cycles.

Thermal properties of Bentonite Modified with 3-aminopropyltrimethoxysilane

NASA Astrophysics Data System (ADS)

Pramono, E.; Pratiwi, W.; Wahyuningrum, D.; Radiman, C. L.

2018-03-01

Chemical modifications of Bentonite (BNT) clay have been carried out by using 3-aminoprophyltrimethoxysilane (APS) in various solvent media. The degradation properties of products (BNTAPS) were characterized by thermogravimetric analysis (TGA). Samples were heated at 30 to 700°C with a heating rate 10 deg/min, and the total silane-grafted amount was determined by calculating the weight loss at 200 – 600°C. The thermogram of TGA showed that there were three main decomposition regions which are attributed to the elimination of physically adsorbed water, decomposition of silane and dehydroxylation of Bentonite. High weight loss attributed to the thermal decomposition of silane was observed between 200 to 550°C. Quantitative analysis of grafted silane results high silane loaded using a solvent with high surface energy, which indicates the type of solvent affected interaction and adsorption of APS in BNT platelets.

Radiation Induced Degradation of the White Thermal Control Paints Z-93 and Z-93P

NASA Technical Reports Server (NTRS)

Edwards, D. L.; Zwiener, J. M.; Wertz, G. E.; Vaughn, J. A.; Kamenetzky, R. R.; Finckenor, M. M.; Meshishnek, M. J.

1996-01-01

This paper details a comparison analysis of the zinc oxide pigmented white thermal control paints Z-93 and Z-93P. Both paints were simultaneously exposed to combined space environmental effects and analyzed using an in-vacuo reflectance technique. The dose applied to the paints was approximately equivalent to 5 years in a geosynchronous orbit. This comparison analysis showed that Z-93P is an acceptable substitute for Z-93. Irradiated samples of Z-93 and Z-93P were subjected to additional exposures of ultraviolet (UV) radiation and analyzed using the in-vacuo reflectance technique to investigate UV activated reflectance recovery. Both samples showed minimal UV activated reflectance recovery after an additional 190 equivalent sun hour (ESH) exposure. Reflectance response utilizing nitrogen as a repressurizing gas instead of air was also investigated. This investigation found the rates of reflectance recovery when repressurized with nitrogen are slower than when repressurized with air.

Radiation Induced Degradation of White Thermal Control Paint

NASA Technical Reports Server (NTRS)

Edwards, D. L.; Zwiener, J. M.; Wertz, G. E.; Vaughn, Jason A.; Kamenetzky, Rachel R.; Finckenor, M. M.; Meshishnek, M. J.

1999-01-01

This paper details a comparison analysis of the zinc-oxide pigmented white thermal control paints Z-93 and Z-93P. Both paints were simultaneously exposed to combined space environmental effects and analyzed using an in-vacuo reflectance technique. The dose applied to the paints was approximately equivalent to 5 yr in a geosynchronous orbit. This comparison analysis showed that Z-93P is an acceptable substitute for Z-93. Irradiated samples of Z-93 and Z-93P were subjected to additional exposures of ultraviolet (UV) radiation and analyzed using the in-vacuo reflectance technique to investigate UV activated reflectance recovery. Both samples showed minimal UV activated reflectance recovery after an additional 190 equivalent Sun hour (ESH) exposure. Reflectance response utilizing nitrogen as a repressurizing gas instead of air was also investigated. This investigation found the rates of reflectance recovery when repressurized with nitrogen are slower than when repressurized with air.