Thermal Stability of Zone Melting p-Type (Bi, Sb)2Te3 Ingots and Comparison with the Corresponding Powder Metallurgy Samples

NASA Astrophysics Data System (ADS)

Jiang, Chengpeng; Fan, Xi'an; Hu, Jie; Feng, Bo; Xiang, Qiusheng; Li, Guangqiang; Li, Yawei; He, Zhu

2018-04-01

During the past few decades, Bi2Te3-based alloys have been investigated extensively because of their promising application in the area of low temperature waste heat thermoelectric power generation. However, their thermal stability must be evaluated to explore the appropriate service temperature. In this work, the thermal stability of zone melting p-type (Bi, Sb)2Te3-based ingots was investigated under different annealing treatment conditions. The effect of service temperature on the thermoelectric properties and hardness of the samples was also discussed in detail. The results showed that the grain size, density, dimension size and mass remained nearly unchanged when the service temperature was below 523 K, which suggested that the geometry size of zone melting p-type (Bi, Sb)2Te3-based materials was stable below 523 K. The power factor and Vickers hardness of the ingots also changed little and maintained good thermal stability. Unfortunately, the thermal conductivity increased with increasing annealing temperature, which resulted in an obvious decrease of the zT value. In addition, the thermal stabilities of the zone melting p-type (Bi, Sb)2Te3-based materials and the corresponding powder metallurgy samples were also compared. All evidence implied that the thermal stabilities of the zone-melted (ZMed) p-type (Bi, Sb)2Te3 ingots in terms of crystal structure, geometry size, power factor (PF) and hardness were better than those of the corresponding powder metallurgy samples. However, their thermal stabilities in terms of zT values were similar under different annealing temperatures.

Performance evaluation of a conformal thermal monitoring sheet (TMS) sensor array for measurement of surface temperature distributions during superficial hyperthermia treatments

PubMed Central

Arunachalam, K.; Maccarini, P.; Juang, T.; Gaeta, C.; Stauffer, P. R.

2009-01-01

Purpose This paper presents a novel conformal thermal monitoring sheet sensor array with differential thermal sensitivity for measuring temperature distributions over large surface areas. Performance of the sensor array is evaluated in terms of thermal accuracy, mechanical stability and conformity to contoured surfaces, probe self heating under irradiation from microwave and ultrasound hyperthermia sources, and electromagnetic field perturbation. Materials and Methods A prototype TMS with 4×4 array of fiberoptic sensors embedded between two flexible and thermally conducting polyimide films was developed as an alternative to the standard 1-2 mm diameter plastic catheter based probes used in clinical hyperthermia. Computed tomography images and bending tests were performed to evaluate the conformability and mechanical stability respectively. Irradiation and thermal barrier tests were conducted and thermal response of the prototype was compared with round cross-sectional clinical probes. Results Bending and conformity tests demonstrated higher flexibility, dimensional stability and close conformity to human torso. Minimal perturbation of microwave fields and low probe self heating was observed when irradiated with 915MHz microwave and 3.4MHz ultrasound sources. The transient and steady state thermal responses of the TMS array were superior compared to the clinical probes. Conclusions A conformal TMS sensor array with improved thermal sensitivity and dimensional stability was investigated for real-time skin temperature monitoring. This fixed-geometry, body-conforming array of thermal sensors allows fast and accurate characterization of two-dimensional temperature distributions over large surface areas. The prototype TMS demonstrates significant advantages over clinical probes for characterizing skin temperature distributions during hyperthermia treatments of superficial tissue disease. PMID:18465416

Comparative evaluation of thermal decomposition behavior and thermal stability of powdered ammonium nitrate under different atmosphere conditions.

PubMed

Yang, Man; Chen, Xianfeng; Wang, Yujie; Yuan, Bihe; Niu, Yi; Zhang, Ying; Liao, Ruoyu; Zhang, Zumin

2017-09-05

In order to analyze the thermal decomposition characteristics of ammonium nitrate (AN), its thermal behavior and stability under different conditions are studied, including different atmospheres, heating rates and gas flow rates. The evolved decomposition gases of AN in air and nitrogen are analyzed with a quadrupole mass spectrometer. Thermal stability of AN at different heating rates and gas flow rates are studied by differential scanning calorimetry, thermogravimetric analysis, paired comparison method and safety parameter evaluation. Experimental results show that the major evolved decomposition gases in air are H 2 O, NH 3 , N 2 O, NO, NO 2 and HNO 3 , while in nitrogen, H 2 O, NH 3 , NO and HNO 3 are major components. Compared with nitrogen atmosphere, lower initial and end temperatures, higher heat flux and broader reaction temperature range are obtained in air. Meanwhile, higher air gas flow rate tends to achieve lower reaction temperature and to reduce thermal stability of AN. Self-accelerating decomposition temperature of AN in air is much lower than that in nitrogen. It is considered that thermostability of AN is influenced by atmosphere, heating rate and gas flow rate, thus changes of boundary conditions will influence its thermostability, which is helpful to its safe production, storage, transportation and utilization. Copyright © 2017 Elsevier B.V. All rights reserved.

Sintering Characteristics of Multilayered Thermal Barrier Coatings Under Thermal Gradient and Isothermal High Temperature Annealing Conditions

NASA Technical Reports Server (NTRS)

Rai, Amarendra K.; Schmitt, Michael P.; Bhattacharya, Rabi; Zhu, Dongming; Wolfe, Douglas E.

2014-01-01

Pyrochlore oxides have most of the relevant attributes for use as next generation thermal barrier coatings such as phase stability, low sintering kinetics and low thermal conductivity. One of the issues with the pyrochlore oxides is their lower toughness and therefore higher erosion rate compared to the current state-of-the-art TBC material, yttria (6 to 8 wt%) stabilized zirconia (YSZ). In this work, sintering characteristics were investigated for novel multilayered coating consisted of alternating layers of pyrochlore oxide viz Gd2Zr2O7 and t' low k (rare earth oxide doped YSZ). Thermal gradient and isothermal high temperature (1316 C) annealing conditions were used to investigate sintering and cracking in these coatings. The results are then compared with that of relevant monolayered coatings and a baseline YSZ coating.

Thermal stability of corn oil flavoured with Thymus capitatus under heating and deep-frying conditions.

PubMed

Karoui, Iness Jabri; Dhifi, Wissal; Jemia, Meriam Ben; Marzouk, Brahim

2011-03-30

The thermal stability of corn oil flavoured with thyme flowers was determined and compared with that of the original refined corn oil (control). The oxidative stability index (OSI) was measured and samples were exposed to heating (30 min at 150, 180 and 200 °C) and deep-frying (180 °C). Changes in peroxide value (PV), free fatty acid (FFA) content, specific absorptivity values (K(232) and K(270)), colour and chlorophyll, carotenoid and total phenol contents were monitored. The OSI and heating results showed that thyme incorporation was effective against thermal oxidation based on the increased induction time observed for the flavoured oil (6.48 vs 4.36 h), which was characterised by lower PV, FFA content, K(232) and K(270) than the control oil after heating from 25 to 200 °C, with higher red and yellow colour intensities and chlorophyll, carotenoid and total phenol contents. The deep-frying test showed the accelerated deterioration of both oils in the presence of French fries. Compared with the control oil, the thyme-flavoured oil showed improved thermal stability after heating. This could be attributed to the presence of thyme pigments and antioxidant compounds allowing extended oil thermal resistance. Copyright © 2011 Society of Chemical Industry.

Thermally stable and high reflectivity Al-doped silver thin films deposited by magnetron sputtering

NASA Astrophysics Data System (ADS)

Loka, Chadrasekhar; Lee, Kwang; Joo, Sin Yong; Lee, Kee-Sun

2018-03-01

Thermally stable, high reflectance thin film coatings are indispensable in optoelectronic devices, especially as a potential back reflector for LEDs and solar cells. The silver has the drawback of agglomerating easily and poor thermal stability, which is limiting its application as a highly reflective coating in various optoelectronic applications. In this study, improved thermal stability by modification of the Ag film into an Ag/Al-doped Ag structure has been confirmed. In this paper, the surface morphology, optical reflectance, and thermal stability of the Ag/Al-doped Ag are investigated. The Ag/Al-doped Ag/sapphire films showed excellent thermal stability after annealing the films at 523 K with the highest reflectance about ∼86% as compared to the pure Ag films. The grain growth analysis results revealed that the Al-doping is effective to restrain the severe grain growth of silver films. The Auger electron spectroscopy results revealed that the outer diffusion of aluminum and the formation of Al-O bond at the outermost silver layer which is beneficial to retard the Ag grain growth.

Comparison of stabilization by Vitamin E and 2,6-di-tert-butylphenols during polyethylene radio-thermal-oxidation

NASA Astrophysics Data System (ADS)

Richaud, Emmanuel

2014-10-01

This paper reports a compilation of data for PE+Vitamin E and 2,6-di-tert-butylphenols oxidation in radio-thermal ageing. Data unambiguously show that Vitamin E reacts with Prad and POOrad whereas 2,6-di-tert-butyl phenols only react with POOrad. Kinetic parameters of the stabilization reactions for both kinds of antioxidants were tentatively extracted from phenol depletion curves, and discussed regarding the structure of the stabilizer. They were also used for completing an existing kinetic model used for predicting the stabilization by antioxidants. This one permits to compare the efficiency of stabilizer with dose rate or sample thickness.

Comparative study of resist stabilization techniques for metal etch processing

NASA Astrophysics Data System (ADS)

Becker, Gerry; Ross, Matthew F.; Wong, Selmer S.; Minter, Jason P.; Marlowe, Trey; Livesay, William R.

1999-06-01

This study investigates resist stabilization techniques as they are applied to a metal etch application. The techniques that are compared are conventional deep-UV/thermal stabilization, or UV bake, and electron beam stabilization. The electron beam tool use din this study, an ElectronCure system from AlliedSignal Inc., ELectron Vision Group, utilizes a flood electron source and a non-thermal process. These stabilization techniques are compared with respect to a metal etch process. In this study, two types of resist are considered for stabilization and etch: a g/i-line resist, Shipley SPR-3012, and an advanced i-line, Shipley SPR 955- Cm. For each of these resist the effects of stabilization on resist features are evaluated by post-stabilization SEM analysis. Etch selectivity in all cases is evaluated by using a timed metal etch, and measuring resists remaining relative to total metal thickness etched. Etch selectivity is presented as a function of stabilization condition. Analyses of the effects of the type of stabilization on this method of selectivity measurement are also presented. SEM analysis was also performed on the features after a compete etch process, and is detailed as a function of stabilization condition. Post-etch cleaning is also an important factor impacted by pre-etch resist stabilization. Results of post- etch cleaning are presented for both stabilization methods. SEM inspection is also detailed for the metal features after resist removal processing.

Can green solvents be alternatives for thermal stabilization of collagen?

PubMed

Mehta, Ami; Rao, J Raghava; Fathima, Nishter Nishad

2014-08-01

"Go Green" campaign is gaining light for various industrial applications where water consumption needs to be reduced. To resolve this, industries have adopted usage of green, organic solvents, as an alternative to water. For leather making, tanning industry consumes gallons of water. Therefore, for adopting green solvents in leather making, it is necessary to evaluate its influence on type I collagen, the major protein present in the skin matrix. The thermal stability of collagen from rat tail tendon fiber (RTT) treated with seven green solvents namely, ethanol, ethyl lactate, ethyl acetate, propylene carbonate, propylene glycol, polyethylene glycol-200 and heptane was determined using differential scanning calorimetry (DSC). Crosslinking efficiency of basic chromium sulfate and wattle on RTT in green solvents was determined. DSC thermograms show increase in thermal stability of RTT collagen against heat with green solvents (>78°C) compared to water (63°C). In the presence of crosslinkers, RTT demonstrated thermal stability >100°C in some green solvents, resulting in increased intermolecular forces between collagen, solvent and crosslinkers. The significant improvement in thermal stability of collagen potentiates the capability of green solvents as an alternative for water. Copyright © 2014 Elsevier B.V. All rights reserved.

Low concentration graphene nanoplatelets for shape stabilization and thermal transfer reinforcement of Mannitol: a phase change material for a medium-temperature thermal energy system

NASA Astrophysics Data System (ADS)

Jing, Gu; Dehong, Xia; Li, Wang; Wenqing, Ao; Zhaodong, Qi

2018-03-01

We report herein a novel series of Mannitol/GNPs (graphene nanoplatelets) composites with incremental GNPs loadings from 1 wt% to 10 wt% for further applications in medium-temperature thermal energy system. The phase change behavior and thermal conductivity of Mannitol/GNPs composite, a nanostructured PCM, have been evaluated as a function of GNPs content. Compared to the pristine Mannitol, the resultant stabilized composite with 8 wt% of GNPs displays an extremely high 1054% enhancement in thermal conductivity, and inherits 92% of phase change enthalpy of bulk Mannitol PCM (phase change material). More importantly, 92%Mannitol/GNPs composite still preserves its initial shape without any leakage even when subjected to a 400 consecutive melting/re-solidification cycles. The resulting Mannitol composites exhibit excellent chemical compatibility, large phase change enthalpy and improved thermal reliability, as compared to base PCM, which stands distinct in its class of organic with reference to the past literatures.

Thermal properties of black phosphorene and doped phosphorene (C, N & O): A DFT study

NASA Astrophysics Data System (ADS)

Devi, Anjna; Singh, Amarjeet

2018-04-01

In this work, we present the results from a DFT based computational study of pristine phosphorene and doped (C, N & O) phosphorene. We systematically investigated the lattice thermal properties of black phosphorene and the effect of doping on its thermal properties. We first determined the vibrational properties of pristine and doped phosphorene and from these results we calculated their thermal properties. We doped the phosphorene with C, N and O and observed that the structural stability of doped phosphorene decreases, while the thermal stability is increased as compared to pristine phosphorene. The presence of finite temperature effects in the doped system can contribute to acceleration of progress in future nano-scale technology.

Comparative Solid-State Stability of Perindopril Active Substance vs. Pharmaceutical Formulation

PubMed Central

Buda, Valentina; Andor, Minodora; Ledeti, Adriana; Ledeti, Ionut; Vlase, Gabriela; Vlase, Titus; Cristescu, Carmen; Voicu, Mirela; Suciu, Liana; Tomescu, Mirela Cleopatra

2017-01-01

This paper presents the results obtained after studying the thermal stability and decomposition kinetics of perindopril erbumine as a pure active pharmaceutical ingredient as well as a solid pharmaceutical formulation containing the same active pharmaceutical ingredient (API). Since no data were found in the literature regarding the spectroscopic description, thermal behavior, or decomposition kinetics of perindopril, our goal was the evaluation of the compatibility of this antihypertensive agent with the excipients in the tablet under ambient conditions and to study the effect of thermal treatment on the stability of perindopril erbumine. ATR-FTIR (Attenuated Total Reflectance Fourier Transform Infrared) spectroscopy, thermal analysis (thermogravimetric mass curve (TG—thermogravimetry), derivative thermogravimetric mass curve (DTG), and heat flow (HF)) and model-free kinetics were chosen as investigational tools. Since thermal behavior is a simplistic approach in evaluating the thermal stability of pharmaceuticals, in-depth kinetic studies were carried out by classical kinetic methods (Kissinger and ASTM E698) and later with the isoconversional methods of Friedman, Kissinger-Akahira-Sunose and Flynn-Wall-Ozawa. It was shown that the main thermal degradation step of perindopril erbumine is characterized by activation energy between 59 and 69 kJ/mol (depending on the method used), while for the tablet, the values were around 170 kJ/mol. The used excipients (anhydrous colloidal silica, microcrystalline cellulose, lactose, and magnesium stearate) should be used in newly-developed generic solid pharmaceutical formulations, since they contribute to an increased thermal stability of perindopril erbumine. PMID:28098840

Thermal conductivity of zirconia thermal barrier coatings

NASA Technical Reports Server (NTRS)

Dinwiddie, R. B.; Beecher, S. C.; Nagaraj, B. A.; Moore, C. S.

1995-01-01

Thermal barrier coatings (TBC's) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBC's is of primary importance. Physical vapor description (PVD) and plasma spraying (PS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The PS coatings were applied with either standard power or hollow sphere particles. The hollow sphere particles yielded a lower density and lower thermal conductivity coating. The thermal conductivity of both fully and partially stabilized zirconia, before and after thermal aging, will be compared. The thermal conductivity of the coatings permanently increase upon being exposed to high temperatures. These increases are attributed to microstructural changes within the coatings. Sintering of the as fabricated plasma sprayed lamellar structure is observed by scanning electron microscopy of coatings isothermally heat treated at temperatures greater than 1100 C. During this sintering process the planar porosity between lamella is converted to a series of small spherical pores. The change in pore morphology is the primary reason for the observed increase in thermal conductivity. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the PVD coatings are less susceptible to thermal aging effects, preliminary results suggest that they have a higher thermal conductivity than PS coatings, both before and after thermal aging. The increases in thermal conductivity due to thermal aging for partially stabilized plasma sprayed zirconia have been found to be less than for fully stabilized plasma sprayed zirconia coatings. The high temperature thermal diffusivity data indicates that if these coatings reach a temperature above 1100 C during operation, they will begin to lose their effectiveness as a thermal barrier.

Thermal conductivity of zirconia thermal barrier coatings

NASA Technical Reports Server (NTRS)

Dinwiddie, R. B.; Beecher, S. C.; Nagaraj, B. A.; Moore, C. S.

1995-01-01

Thermal barrier coatings (TBC's) applied to the hot gas components of turbine engines lead to enhanced fuel efficiency and component reliability. Understanding the mechanisms which control the thermal transport behavior of the TBC's is of primary importance. Physical vapor deposition (PVD) and plasma spraying (PS) are the two most commonly used coating techniques. These techniques produce coatings with unique microstructures which control their performance and stability. The PS coatings were applied with either standard powder or hollow sphere particles. The hollow sphere particles yielded a lower density and lower thermal conductivity coating. The thermal conductivity of both fully and partially stabilized zirconia, before and after thermal aging, will be compared. The thermal conductivity of the coatings permanently increases upon exposed to high temperatures. These increases are attributed to microstructural changes within the coatings. Sintering of the as-fabricated plasma sprayed lamellar structure is observed by scanning electron microscopy of coatings isothermally heat treated at temperatures greater than 1100 C. During this sintering process the planar porosity between lamella is converted to a series of small spherical pores. The change in pore morphology is the primary reason for the observed increase in thermal conductivity. This increase in thermal conductivity can be modeled using a relationship which depends on both the temperature and time of exposure. Although the PVD coatings are less susceptible to thermal aging effects, preliminary results suggest that they have a higher thermal conductivity than PS coatings, both before and after thermal aging. The increases in thermal conductivity due to thermal aging for partially stabilized plasma sprayed zirconia have been found to be less than for fully stabilized plasma sprayed zirconia coatings. The high temperature thermal diffusivity data indicate that if these coatings reach a temperature above 1100 C during operation, they will begin to lose their effectiveness as a thermal barrier.

Sequence-Based Analysis of Thermal Adaptation and Protein Energy Landscapes in an Invasive Blue Mussel (Mytilus galloprovincialis).

PubMed

Saarman, Norah P; Kober, Kord M; Simison, W Brian; Pogson, Grant H

2017-10-01

Adaptive responses to thermal stress in poikilotherms plays an important role in determining competitive ability and species distributions. Amino acid substitutions that affect protein stability and modify the thermal optima of orthologous proteins may be particularly important in this context. Here, we examine a set of 2,770 protein-coding genes to determine if proteins in a highly invasive heat tolerant blue mussel (Mytilus galloprovincialis) contain signals of adaptive increases in protein stability relative to orthologs in a more cold tolerant M. trossulus. Such thermal adaptations might help to explain, mechanistically, the success with which the invasive marine mussel M. galloprovincialis has displaced native species in contact zones in the eastern (California) and western (Japan) Pacific. We tested for stabilizing amino acid substitutions in warm tolerant M. galloprovincialis relative to cold tolerant M. trossulus with a generalized linear model that compares in silico estimates of recent changes in protein stability among closely related congeners. Fixed substitutions in M. galloprovincialis were 3,180.0 calories per mol per substitution more stabilizing at genes with both elevated dN/dS ratios and transcriptional responses to heat stress, and 705.8 calories per mol per substitution more stabilizing across all 2,770 loci investigated. Amino acid substitutions concentrated in a small number of genes were more stabilizing in M. galloprovincialis compared with cold tolerant M. trossulus. We also tested for, but did not find, enrichment of a priori GO terms in genes with elevated dN/dS ratios in M. galloprovincialis. This might indicate that selection for thermodynamic stability is generic across all lineages, and suggests that the high change in estimated protein stability that we observed in M. galloprovincialis is driven by selection for extra stabilizing substitutions, rather than by higher incidence of selection in a greater number of genes in this lineage. Nonetheless, our finding of more stabilizing amino acid changes in the warm adapted lineage is important because it suggests that adaption for thermal stability has contributed to M. galloprovincialis' superior tolerance to heat stress, and that pairing tests for positive selection and tests for transcriptional response to heat stress can identify candidates of protein stability adaptation. © The Author 2017. Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.

Extreme temperature stability of thermally insulating graphene-mesoporous-silicon nanocomposite

NASA Astrophysics Data System (ADS)

Kolhatkar, Gitanjali; Boucherif, Abderraouf; Rahim Boucherif, Abderrahim; Dupuy, Arthur; Fréchette, Luc G.; Arès, Richard; Ruediger, Andreas

2018-04-01

We demonstrate the thermal stability and thermal insulation of graphene-mesoporous-silicon nanocomposites (GPSNC). By comparing the morphology of GPSNC carbonized at 650 °C as-formed to that after annealing, we show that this nanocomposite remains stable at temperatures as high as 1050 °C due to the presence of a few monolayers of graphene coating on the pore walls. This does not only make this material compatible with most thermal processes but also suggests applications in harsh high temperature environments. The thermal conductivity of GPSNCs carbonized at temperatures in the 500 °C-800 °C range is determined through Raman spectroscopy measurements. They indicate that the thermal conductivity of the composite is lower than that of silicon, with a value of 13 ± 1 W mK-1 at room temperature, and not affected by the thin graphene layer, suggesting a role of the high concentration of carbon related-defects as indicated by the high intensity of the D-band compared to G-band of the Raman spectra. This morphological stability at high temperature combined with a high thermal insulation make GPSNC a promising candidate for a broad range of applications including microelectromechanical systems and thermal effect microsystems such as flow sensors or IR detectors. Finally, at 120 °C, the thermal conductivity remains equal to that at room temperature, attesting to the potential of using our nanocomposite in devices that operate at high temperatures such as microreactors for distributed chemical conversion, solid oxide fuel cells, thermoelectric devices or thermal micromotors.

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.

Enhancement of Aviation Fuel Thermal Stability Characterization Through Application of Ellipsometry

NASA Technical Reports Server (NTRS)

Browne, Samuel Tucker; Wong, Hubert; Hinderer, Cameron Branch; Klettlinger, Jennifer

2012-01-01

ASTM D3241/Jet Fuel Thermal Oxidation Tester (JFTOT) procedure, the standard method for testing thermal stability of conventional aviation turbine fuels is inherently limited due to the subjectivity in the color standard for tube deposit rating. Quantitative assessment of the physical characteristics of oxidative fuel deposits provides a more powerful method for comparing the thermal oxidation stability characteristics of fuels, especially in a research setting. We propose employing a Spectroscopic Ellipsometer to determine the film thickness and profile of oxidative fuel deposits on JFTOT heater tubes. Using JP-8 aviation fuel and following a modified ASTM D3241 testing procedure, the capabilities of the Ellipsometer will be demonstrated by measuring oxidative fuel deposit profiles for a range of different deposit characteristics. The testing completed in this report was supported by the NASA Fundamental Aeronautics Subsonics Fixed Wing Project

Simultaneous thermal stability and phase change speed improvement of Sn15Sb85 thin film through erbium doping

NASA Astrophysics Data System (ADS)

Zou, Hua; Zhu, Xiaoqin; Hu, Yifeng; Sui, Yongxing; Sun, Yuemei; Zhang, Jianhao; Zheng, Long; Song, Zhitang

2016-12-01

In general, there is a trade off between the phase change speed and thermal stability in chalcogenide phase change materials, which leads to sacrifice the one in order to ensure the other. For improving the performance, doping is a widely applied technological process. Here, we fabricated Er doped Sn15Sb85 thin films by magnetron sputtering. Compared with the pure Sn15Sb85, we show that Er doped Sn15Sb85 thin films exhibit simultaneous improvement over the thermal stability and the phase change speed. Thus, our results suggest that Er doping provides the opportunity to solve the contradiction. The main reason for improvement of both thermal stability and crystallization speed is due to the existence of Er-Sb and Er-Sn bonds in Er doped Sn15Sb85 films. Hence, Er doped Sn15Sb85 thin films are promising candidates for the phase change memory application, and this method could be extended to other lanthanide-doped phase change materials.

Polyethylene Glycol Based Graphene Aerogel Confined Phase Change Materials with High Thermal Stability.

PubMed

Fu, Yang; Xiong, Weilai; Wang, Jianying; Li, Jinghua; Mei, Tao; Wang, Xianbao

2018-05-01

Polyethylene glycol (PEG) based graphene aerogel (GA) confined shaped-stabilized phase change materials (PCMs) are simply prepared by a one-step hydrothermal method. Three-dimensional GA inserted by PEG molecule chains, as a supporting material, obtained by reducing graphene oxide sheets, is used to keep their stabilized shape during a phase change process. The volume of GA is obviously expended after adding PEG, and only 9.8 wt% of GA make the composite achieve high energy efficiency without leakage during their phase change because of hydrogen bonding widely existing in the GA/PEG composites (GA-PCMs). The heat storage energy of GA-PCMs is 164.9 J/g, which is 90.2% of the phase change enthalpy of pure PEG. In addition, this composite inherits the natural thermal properties of graphene and thus shows enhanced thermal conductivity compared with pure PEG. This novel study provides an efficient way to fabricate shape-stabilized PCMs with a high content of PEG for thermal energy storage.

Thermal precipitation fluorescence assay for protein stability screening.

PubMed

Fan, Junping; Huang, Bo; Wang, Xianping; Zhang, Xuejun C

2011-09-01

A simple and reliable method of protein stability assessment is desirable for high throughput expression screening of recombinant proteins. Here we described an assay termed thermal precipitation fluorescence (TPF) which can be used to compare thermal stabilities of recombinant protein samples directly from cell lysate supernatants. In this assay, target membrane proteins are expressed as recombinant fusions with a green fluorescence protein tag and solubilized with detergent, and the fluorescence signals are used to report the quantity of the fusion proteins in the soluble fraction of the cell lysate. After applying a heat shock, insoluble protein aggregates are removed by centrifugation. Subsequently, the amount of remaining protein in the supernatant is quantified by in-gel fluorescence analysis and compared to samples without a heat shock treatment. Over 60 recombinant membrane proteins from Escherichia coli were subject to this screening in the presence and absence of a few commonly used detergents, and the results were analyzed. Because no sophisticated protein purification is required, this TPF technique is suitable to high throughput expression screening of recombinant membrane proteins as well as soluble ones and can be used to prioritize target proteins based on their thermal stabilities for subsequent large scale expression and structural studies. Copyright © 2011 Elsevier Inc. All rights reserved.

Effects of the thermal sterilization procedure on polymeric products

NASA Technical Reports Server (NTRS)

Campbell, B. A.; Kalfayan, S. H.

1971-01-01

Properties of samples are tested, after thermal exposure, and values are compared with unexposed samples. Thermal stability or compatibility ratings of formulated or compounded organic polymers using trade names are made and degree of change in measured properties is assessed. Products are rated compatible, marginal, or not compatible.

X-ray Crystallographic Structure of Thermophilic Rhodopsin: IMPLICATIONS FOR HIGH THERMAL STABILITY AND OPTOGENETIC FUNCTION.

PubMed

Tsukamoto, Takashi; Mizutani, Kenji; Hasegawa, Taisuke; Takahashi, Megumi; Honda, Naoya; Hashimoto, Naoki; Shimono, Kazumi; Yamashita, Keitaro; Yamamoto, Masaki; Miyauchi, Seiji; Takagi, Shin; Hayashi, Shigehiko; Murata, Takeshi; Sudo, Yuki

2016-06-03

Thermophilic rhodopsin (TR) is a photoreceptor protein with an extremely high thermal stability and the first characterized light-driven electrogenic proton pump derived from the extreme thermophile Thermus thermophilus JL-18. In this study, we confirmed its high thermal stability compared with other microbial rhodopsins and also report the potential availability of TR for optogenetics as a light-induced neural silencer. The x-ray crystal structure of TR revealed that its overall structure is quite similar to that of xanthorhodopsin, including the presence of a putative binding site for a carotenoid antenna; but several distinct structural characteristics of TR, including a decreased surface charge and a larger number of hydrophobic residues and aromatic-aromatic interactions, were also clarified. Based on the crystal structure, the structural changes of TR upon thermal stimulation were investigated by molecular dynamics simulations. The simulations revealed the presence of a thermally induced structural substate in which an increase of hydrophobic interactions in the extracellular domain, the movement of extracellular domains, the formation of a hydrogen bond, and the tilting of transmembrane helices were observed. From the computational and mutational analysis, we propose that an extracellular LPGG motif between helices F and G plays an important role in the thermal stability, acting as a "thermal sensor." These findings will be valuable for understanding retinal proteins with regard to high protein stability and high optogenetic performance. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Thermal expansion behavior of LDEF metal matrix composites

NASA Technical Reports Server (NTRS)

Le, Tuyen D.; Steckel, Gary L.

1993-01-01

The thermal expansion behavior of Long Duration Exposure Facility (LDEF) metal matrix composite materials was studied by (1) analyzing the flight data that was recorded on orbit to determine the effects of orbital time and heating/cooling rates on the performance of the composite materials, and (2) characterizing and comparing the thermal expansion behavior of post-flight LDEF and lab-control samples. The flight data revealed that structures in space are subjected to nonuniform temperature distributions, and thermal conductivity of a material is an important factor in establishing a uniform temperature distribution and avoiding thermal distortion. The flight and laboratory data showed that both Gr/Al and Gr/Mg composites were stabilized after prolonged thermal cycling on orbit. However, Gr/Al composites showed more stable thermal expansion behavior than Gr/Mg composites and offer advantages for space structures particularly where very tight thermal stability requirements in addition to high material performance must be met.

Investigation on Thermal Properties of Kenaf Fibre Reinforced Polyurethane Bio-Composites

NASA Astrophysics Data System (ADS)

Athmalingam, Mathan; Vicki, W. V.

2018-01-01

This research focuses on the effect of Kenaf fibre on thermal properties of Polyurethane (PU) reinforced kenaf bio-composites. The samples were prepared using the polymer casting method with different percentages of kenaf fibre content (5 wt%, 10 wt%, 15 wt%). The thermal properties of Kenaf/PU bio-composite are determined through the Thermogravimetric Analysis and Differential Scanning Calorimeter test. The TGA results revealed that 10 wt% Kenaf/PU bio-composite appeared to be more stable. DSC results show that the glass transition temperature (Tg) value of 10 wt% Kenaf/PU composite is significant to pure polyurethane. It can be said that the thermal stability of 10 wt% Kenaf/PU bio-composite exhibits higher thermal stability compared to other samples.

Flame-resistant pure and hybrid woven fabrics from basalt

NASA Astrophysics Data System (ADS)

Jamshaid, H.; Mishra, R.; Militky, J.

2017-10-01

This work has been formulated to investigate the burning behavior of different type of fabrics. The main concentration is to see how long the fabric resists after it catches the fire and the propagation of fire can be reduced by using flame resistant fiber i.e basalt. Basalt fiber is an environmental friendly material with low input, high output, low energy consumption and less emission. The goal of present investigations is to show the dependence of fabric flammability on its structure parameters i.e weave type, blend type etc. Fabric weaves have strong effect on flammability properties. Plain weave has the lowest burning rate as the density of the plain weave fabric is more and the structure is tight which gives less chances of flame passing through the fabric. Thermal stability is evaluated with TGA of all hybrid and nonhybrid fabrics and compared. The thermal stability of the basalt fiber is excellent. When comparing thermal analysis curves for hybrid samples it demonstrates that thermal stability of the samples containing basalt is much higher than the non- hybrid samples. Percentage weight loss is less in hybrid samples as compared to non-hybrid samples. The effectiveness of hybridization on samples may be indicated by substantial lowering of the decomposition mass. Correlation was made between flammability with the infrared radiations (IR)

Solid-cryogen-stabilized, cable-in-conduit (CIC) superconducting cables

NASA Astrophysics Data System (ADS)

Voccio, J. P.; Michael, P. C.; Bromberg, L.; Hahn, S.

2015-12-01

This paper considers the use of a solid cryogen as a means to stabilize, both mechanically and thermally, magnesium diboride (MgB2) superconducting strands within a dual-channel cable-in-conduit (CIC) cable for use in AC applications, such as a generator stator winding. The cable consists of two separate channels; the outer channel contains the superconducting strands and is filled with a fluid (liquid or gas) that becomes solid at the device operating temperature. Several options for fluid will be presented, such as liquid nitrogen, hydrocarbons and other chlorofluorocarbons (CFCs) that have a range of melting temperatures and volumetric expansions (from solid at operating temperature to fixed volume at room temperature). Implications for quench protection and conductor stability, enhanced through direct contact with the solid cryogen, which has high heat capacity and thermal conductivity (compared with helium gas), will be presented. Depending on the cryogen, the conductor will be filled initially either with liquid at atmospheric conditions or a gas at high pressure (∼100 atm). After cooldown, the cryogen in the stranded-channel will be solid, essentially locking the strands in place, preventing strand motion and degradation due to mechanical deformation while providing enhanced thermal capacity for stability and protection. The effect of cryogen porosity is also considered. The relatively high heat capacity of solid cryogens at these lower temperatures (compared to gaseous helium) enhances the thermal stability of the winding. During operation, coolant flow through the open inner channel will minimize pressure drop.

Chemical and thermal stability of core-shelled magnetite nanoparticles and solid silica

NASA Astrophysics Data System (ADS)

Cendrowski, Krzysztof; Sikora, Pawel; Zielinska, Beata; Horszczaruk, Elzbieta; Mijowska, Ewa

2017-06-01

Pristine nanoparticles of magnetite were coated by solid silica shell forming core/shell structure. 20 nm thick silica coating significantly enhanced the chemical and thermal stability of the iron oxide. Chemical and thermal stability of this structure has been compared to the magnetite coated by mesoporous shell and pristine magnetite nanoparticles. It is assumed that six-membered silica rings in a solid silica shell limit the rate of oxygen diffusion during thermal treatment in air and prevent the access of HCl molecules to the core during chemical etching. Therefore, the core/shell structure with a solid shell requires a longer time to induce the oxidation of iron oxide to a higher oxidation state and, basically, even strong concentrated acid such as HCl is not able to dissolve it totally in one month. This leads to the desired performance of the material in potential applications such as catalysis and environmental protection.

Preparation, characterization, and thermal stability of β-cyclodextrin/soybean lecithin inclusion complex.

PubMed

Wang, Xinge; Luo, Zhigang; Xiao, Zhigang

2014-01-30

β-Cyclodextrin (β-CD), which is widely used to increase the stability, solubility, and bioavailability of guests, can form host-guest inclusion complexes with a wide variety of organic molecules. In this study the β-CD/soybean lecithin inclusion complex was prepared. The effect of reaction parameters such as reaction temperature, reaction time and the molar ratio of β-CD/soybean lecithin on inclusion ratio were studied. The inclusion ratio of the product prepared under the optimal conditions of β-CD/soybean lecithin molar ratio 2:1, reaction temperature 60°C reaction time 2h was 40.2%. The results of UV-vis, DSC, XRD and FT-IR spectrum indicated the formation of inclusion complex. The thermal stability experiment indicated that the thermal stability of soybean lecithin in inclusion complex was significantly improved compared with free soybean lecithin. Copyright © 2013 Elsevier Ltd. All rights reserved.

High-Thermal- and Air-Stability Cathode Material with Concentration-Gradient Buffer for Li-Ion Batteries.

PubMed

Shi, Ji-Lei; Qi, Ran; Zhang, Xu-Dong; Wang, Peng-Fei; Fu, Wei-Gui; Yin, Ya-Xia; Xu, Jian; Wan, Li-Jun; Guo, Yu-Guo

2017-12-13

Delivery of high capacity with high thermal and air stability is a great challenge in the development of Ni-rich layered cathodes for commercialized Li-ion batteries (LIBs). Herein we present a surface concentration-gradient spherical particle with varying elemental composition from the outer end LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM) to the inner end LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA). This cathode material with the merit of NCM concentration-gradient protective buffer and the inner NCA core shows high capacity retention of 99.8% after 200 cycles at 0.5 C. Furthermore, this cathode material exhibits much improved thermal and air stability compared with bare NCA. These results provide new insights into the structural design of high-performance cathodes with high energy density, long life span, and storage stability materials for LIBs in the future.

Comparative Thermal Degradation Patterns of Natural Yellow Colorants Used in Foods.

PubMed

Giménez, Pedro J; Fernández-López, José A; Angosto, José M; Obón, José M

2015-12-01

There is a great interest in natural yellow colorants due to warnings issued about certain yellow food colorings of synthetic origin. However, no comparative studies have been reported of their thermal stability. For this reason, the thermal stabilities of six natural yellow colorants used in foods--lutein, riboflavin, curcumin, ß-carotene, gardenia yellow and Opuntia betaxanthins--were studied in simple solutions over a temperature range 30-90 °C. Spectral properties and visual color were investigated during 6 h of heat treatment. Visual color was monitored from the CIEL*a*b* parameters. The remaining absorbance at maximum wavelength and the total color difference were used to quantify color degradation. The rate of color degradation increased as the temperature rose. The results showed that the thermal degradation of the colorants followed a first-order reaction kinetics. The reaction rate constants and half-life periods were determined as being central to understanding the color degradation kinetics. The temperature-dependent degradation was adequately modeled on the Arrhenius equation. Activation energies ranged from 3.2 kJmol(-1) (lutein) to 43.7 kJmol(-1) (Opuntia betaxanthins). ß-carotene and lutein exhibited high thermal stability, while betaxanthins and riboflavin degraded rapidly as temperature increased. Gardenia yellow and curcumin were in an intermediate position.

Investigating the Thermal and Phase Stability of Nanocrystalline Ni-W Produced by Electrodeposition, Sputtering, and Mechanical Alloying

NASA Astrophysics Data System (ADS)

Marvel, Christopher Jonathan

The development of nanocrystalline materials has been increasingly pursued over the last few decades. They have been shown to exhibit superior properties compared to their coarse-grain counterparts, and thus present a tremendous opportunity to revolutionize the performance of nanoscale devices or bulk structural materials. However, nanocrystalline materials are highly prone to grain growth, and if the nanocrystalline grains coarsen, the beneficial properties are lost. There is a strong effort to determine the most effective thermal stability mechanisms to avoid grain growth, but the physical nature of nanocrystalline grain growth is still unclear due to a lack of detailed understanding of nanocrystalline microstructures. Furthermore, the influence of contamination has scarcely been explored with advanced transmission electron microscopy techniques, nor has there been a direct comparison of alloys fabricated with different bulk processes. Therefore, this research has applied aberration-corrected scanning transmission electron microscopy to characterize nanocrystalline Ni-W on the atomic scale and elucidate the physical grain growth behavior. Three primary objectives were pursued: (1) explore the thermal stability mechanisms of nanocrystalline Ni-W, (2) evaluate the phase stability of Ni-W and link any findings to grain growth behavior, and (3) compare the influences of bulk fabrication processing, including electrodeposition, DC magnetron sputtering, and mechanical alloying, on the thermal stability and phase stability of Ni-W. Several thermal stability mechanisms were identified throughout the course of this research. First and foremost, W-segregation was scarcely observed to grain boundaries, and it is unclear if W-segregation improves thermal stability contrary to most reports in the 2 literature. Long-range Ni4W chemical ordering was observed in alloys with more than 20 at.% W, and it is likely Ni4W domains reduce grain boundary mobility. In addition, lattice diffusivity calculations conceptually suggested that increasing W alloying concentrations can decrease the grain growth rate. The strongest evidence of grain growth stagnation was via nanoscale oxide particle drag in highly contaminated electrodeposited alloys. Interestingly, W-segregation was also detected to the oxide phase boundaries and revealed a potential indirect mechanism of thermal stability. The phase stability of pure and contaminated Ni-W alloys was investigated with density functional theory. Primarily, the calculations suggested that the intermetallic phases NiW and NiW2 are thermodynamically unstable, meaning the binary phase diagram is incorrect, but the ternary carbides Ni 6W6C and Ni2W4C are stable. Several Ni-W binary and Ni-W-C ternary phase diagrams were constructed using a simplified CALPHAD approach to improve the understanding of Ni-W phase stability. Lastly, it was determined that the fabrication process greatly influences the impurity types and concentrations of the alloys, and therefore greatly dictate which thermal stability mechanisms are active. Mechanically alloyed samples were found to be the most resistant to grain growth. The findings of this research will hopefully guide future efforts to design more thermally stable nanocrystalline alloys. The link between phase stability and grain growth behavior of Ni-W was thoroughly discussed, as well as the dependence of bulk fabrication processing on the contamination found in the alloys. Ultimately, this research has greatly expanded the general understanding of nanocrystalline Ni-W microstructures, and it is likely that similar phenomena occur in other nanocrystalline systems.

Evaluation of electron beam stabilization for ion implant processing

NASA Astrophysics Data System (ADS)

Buffat, Stephen J.; Kickel, Bee; Philipps, B.; Adams, J.; Ross, Matthew F.; Minter, Jason P.; Marlowe, Trey; Wong, Selmer S.

1999-06-01

With the integration of high energy ion implant processes into volume CMOS manufacturing, the need for thick resist stabilization to achieve a stable ion implant process is critical. With new photoresist characteristics, new implant end station characteristics arise. The resist outgassing needs to be addressed as well as the implant profile to ensure that the dosage is correct and the implant angle does not interfere with other underlying features. This study compares conventional deep-UV/thermal with electron beam stabilization. The electron beam system used in this study utilizes a flood electron source and is a non-thermal process. These stabilization techniques are applied to a MeV ion implant process in a CMOS production process flow.

Effect of silicon and oxygen dopants on the stability of hydrogenated amorphous carbon under harsh environmental conditions

DOE PAGES

Mangolini, Filippo; Krick, Brandon A.; Jacobs, Tevis D. B.; ...

2017-12-27

Harsh environments pose materials durability challenges across the automotive, aerospace, and manufacturing sectors, and beyond. While amorphous carbon materials have been used as coatings in many environmentally-demanding applications owing to their unique mechanical, electrical, and optical properties, their limited thermal stability and high reactivity in oxidizing environments have impeded their use in many technologies. Silicon- and oxygen-containing hydrogenated amorphous carbon (a-C:H:Si:O) films are promising for several applications because of their higher thermal stability and lower residual stress compared to hydrogenated amorphous carbon (a-C:H). However, an understanding of their superior thermo-oxidative stability compared to a-C:H is lacking, as it has beenmore » inhibited by the intrinsic challenge of characterizing an amorphous, multi-component material. Here, we show that introducing silicon and oxygen in a-C:H slightly enhances the thermal stability in vacuum, but tremendously increases the thermo-oxidative stability and the resistance to degradation upon exposure to the harsh conditions of low Earth orbit (LEO). The latter is demonstrated by having mounted samples of a-C:H:Si:O on the exterior of the International Space Station via the Materials International Space Station (MISSE) mission 7b. Exposing lightly-doped a-C:H:Si:O to elevated temperatures under aerobic conditions or to LEO causes carbon volatilization in the near-surface region, producing a silica surface layer that protects the underlying carbon from further removal. In conclusion, these findings provide a novel physically-based understanding of the superior stability of a-C:H:Si:O in harsh environments compared to a-C:H.« less

Effect of silicon and oxygen dopants on the stability of hydrogenated amorphous carbon under harsh environmental conditions

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

Mangolini, Filippo; Krick, Brandon A.; Jacobs, Tevis D. B.

Harsh environments pose materials durability challenges across the automotive, aerospace, and manufacturing sectors, and beyond. While amorphous carbon materials have been used as coatings in many environmentally-demanding applications owing to their unique mechanical, electrical, and optical properties, their limited thermal stability and high reactivity in oxidizing environments have impeded their use in many technologies. Silicon- and oxygen-containing hydrogenated amorphous carbon (a-C:H:Si:O) films are promising for several applications because of their higher thermal stability and lower residual stress compared to hydrogenated amorphous carbon (a-C:H). However, an understanding of their superior thermo-oxidative stability compared to a-C:H is lacking, as it has beenmore » inhibited by the intrinsic challenge of characterizing an amorphous, multi-component material. Here, we show that introducing silicon and oxygen in a-C:H slightly enhances the thermal stability in vacuum, but tremendously increases the thermo-oxidative stability and the resistance to degradation upon exposure to the harsh conditions of low Earth orbit (LEO). The latter is demonstrated by having mounted samples of a-C:H:Si:O on the exterior of the International Space Station via the Materials International Space Station (MISSE) mission 7b. Exposing lightly-doped a-C:H:Si:O to elevated temperatures under aerobic conditions or to LEO causes carbon volatilization in the near-surface region, producing a silica surface layer that protects the underlying carbon from further removal. In conclusion, these findings provide a novel physically-based understanding of the superior stability of a-C:H:Si:O in harsh environments compared to a-C:H.« less

Thermal stability of mullite RMn₂O₅ (R  =  Bi, Y, Pr, Sm or Gd): combined density functional theory and experimental study.

PubMed

Li, Chenzhe; Thampy, Sampreetha; Zheng, Yongping; Kweun, Joshua M; Ren, Yixin; Chan, Julia Y; Kim, Hanchul; Cho, Maenghyo; Kim, Yoon Young; Hsu, Julia W P; Cho, Kyeongjae

2016-03-31

Understanding and effectively predicting the thermal stability of ternary transition metal oxides with heavy elements using first principle simulations are vital for understanding performance of advanced materials. In this work, we have investigated the thermal stability of mullite RMn2O5 (R  =  Bi, Pr, Sm, or Gd) structures by constructing temperature phase diagrams using an efficient mixed generalized gradient approximation (GGA) and the GGA  +  U method. Simulation predicted stability regions without corrections on heavy elements show a 4-200 K underestimation compared to our experimental results. We have found the number of d/f electrons in the heavy elements shows a linear relationship with the prediction deviation. Further correction on the strongly correlated electrons in heavy elements could significantly reduce the prediction deviations. Our corrected simulation results demonstrate that further correction of R-site elements in RMn2O5 could effectively reduce the underestimation of the density functional theory-predicted decomposition temperature to within 30 K. Therefore, it could produce an accurate thermal stability prediction for complex ternary transition metal oxide compounds with heavy elements.

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

Carbohydrates and thermal analysis reflects changes in soil organic matter stability after forest expansion on abandoned grassland

NASA Astrophysics Data System (ADS)

Guidi, Claudia; Vesterdal, Lars; Cannella, David; Leifeld, Jens; Gianelle, Damiano; Rodeghiero, Mirco

2014-05-01

Grassland abandonment, followed by progressive forest expansion, is the dominant land-use change in the Southern Alps, Europe. Land-use change can affect not only the amount of organic matter (OM) in soil but also its composition and stability. Our objective was to investigate changes in organic matter properties after forest expansion on abandoned grasslands, combining analysis of carbohydrates, indicative of labile OM compounds with prevalent plant or microbial origin, with thermal analysis. Thermal analysis was used as a rapid assessment method for the characterization of SOM stability. A land-use gradient was investigated in four land-use types in the subalpine area of Trentino region, Italy: i) managed grassland, mown and fertilized for the past 100 years; ii) grassland abandoned since 10 years, with sparse shrubs and Picea abies saplings; iii) early-stage forest, dominated by P. abies and established on a grassland abandoned around 1970; iv) old forest, dominated by Fagus sylvatica and P. abies. Mineral soil was sampled at three subplots in each land use type with eight soil cores, which were subsequently pooled by depth (0-5 cm, 5-10 cm, 10-20 cm). Sugars were extracted from bulk soil samples through acid hydrolysis with H2SO4 (0.5 M). The analytical composition of sugar monomers was performed with HPAEC technology (Dionex ICS5000), equipped with PAD-detection. Thermal stability was assessed with a differential scanning calorimeter DSC100, heating soil samples up to 600°C at a heating rate of 10°C min-1 in synthetic air. Peak height (W g OC-1) of 1st DSC exotherm, dominated by burning of labile OM compounds, was used as thermal stability index. In the abandoned grassland, carbohydrates compounds accounted for a greater proportion of soil OC than in other land use types. Microbially derived sugars, as rhamnose and galactose, were more abundant in managed and abandoned grasslands compared with early-stage and old forest. The amount of thermally labile sugars, estimated as the peak height of the 1st exotherm, was higher in the abandoned grassland compared with managed grassland and old forest in 0-5 cm depth. Moreover, thermally labile compounds were higher in early-stage than in old forest in 0-5 cm depth. A highly significant correlation was found between thermally labile compounds and carbohydrate content in soil (P = 0.008, r = 0.725). The obtained results suggest that both thermally-labile compounds and carbohydrates are more abundant soon after grassland abandonment, which can lead to lower OM stability. The combination of chemical and thermal analysis of OM can thus provide useful insights on organic matter composition and stability.

Thermal transport in boron nitride nanotorus—towards a nanoscopic thermal shield

NASA Astrophysics Data System (ADS)

Loh, G. C.; Baillargeat, D.

2013-11-01

Nanotori, or nanorings, are topological variants of nanotubes and are conceived to have different properties from their tubular form. In this study, the toroidal arrangement of boron nitride is introduced. Using classical molecular dynamics simulations, the thermal behaviour (thermal conductivity and thermal stability) of the boron nitride nanotorus and its relationship with the structural characteristics are investigated. Its circumferential thermal rectification strength displays a linear dependence on the bending coefficient of the nanostructure. Surface kinks are relatively inconsequential on its circumferential mode of conduction, as compared to its axial sense. The circumferential conductivity in the diffusive regime is calculated to be approximately 10 W/m K, while the axial conductivity is more than tenfold of this value. All nanotori with different toroidal characters show excellent thermal stability at extremely high temperatures approaching 3400 K. With consideration to its favourable properties, a thermal shield made up of a parallel row of nanotori is proposed as a nanoscale thermal insulation device.

Thermal stability and degradation kinetics of kenaf/sol-gel silica hybrid

NASA Astrophysics Data System (ADS)

Yusof, F. A. M.; Hashim, A. S.; Tajudin, Z.

2017-12-01

Thermal stability and degradation kinetics of kenaf/sol-gel silica hybrid materials was investigated by thermogravimetric analysis (TGA). Model-free iso-conversion Flynn-Wall-Ozawa (FWO) and Coats-Redfern-modified (CRm) were chosen to evaluate the activation energy of the kenaf (KF) and kenaf/sol-gel silica (KFS) at heating rates (β) of 10, 20, 30 and 40 °C/min. The results shows that an apparent activation energy was increased for the kenaf/sol-gel silica hybrid (211.59 kJ/mol for FWO and 191.55 kJ/mol for CRm) as compared to kenaf fiber (202.84 kJ/mol for FWO and 186.20 kJ/mol for CRm). Other parameters such as integral procedure decomposition temperature (IPDT), final residual weight (Rf), temperature of maximum degradation rate (Tmax) and residual at maximum temperature (RTmax) were obtained from TGA curves, additionally confirmed the thermal stability of the kenaf/sol-gel silica hybrid. These activation energy values and other findings developed the simplified approach in order to understand the thermal stability and degradation kinetics behavior of kenaf/sol-gel silica hybrid materials.

Precise Stabilization of the Optical Frequency of WGMRs

NASA Technical Reports Server (NTRS)

Savchenkov, Anatoliy; Matsko, Andrey; Matsko, Andrey; Yu, Nan; Maleki, Lute; Iltchenko, Vladimir

2009-01-01

Crystalline whispering gallery mode resonators (CWGMRs) made of crystals with axial symmetry have ordinary and extraordinary families of optical modes. These modes have substantially different thermo-refractive constants. This results in a very sharp dependence of differential detuning of optical frequency on effective temperature. This frequency difference compared with clock gives an error signal for precise compensation of the random fluctuations of optical frequency. Certain crystals, like MgF2, have turnover points where the thermo-refractive effect is completely nullified. An advantage for applications using WGMRs for frequency stabilization is in the possibility of manufacturing resonators out of practically any optically transparent crystal. It is known that there are crystals with negative and zero thermal expansion at some specific temperatures. Doping changes properties of the crystals and it is possible to create an optically transparent crystal with zero thermal expansion at room temperature. With this innovation s stabilization technique, the resultant WGMR will have absolute frequency stability The expansion of the resonator s body can be completely compensated for by nonlinear elements. This results in compensation of linear thermal expansion (see figure). In three-mode, the MgF2 resonator, if tuned at the turnover thermal point, can compensate for all types of random thermal-related frequency drift. Simplified dual-mode method is also available. This creates miniature optical resonators with good short- and long-term stability for passive secondary frequency ethalon and an active resonator for active secondary frequency standard (a narrowband laser with long-term stability).

Stability of Silica- and Enzyme-Treated Palm Oil Under Deep Frying Conditions.

PubMed

Karim, Nur Azwani Ab; Noor, Ahmadilfitri Md; Lee, Yee-Ying; Lai, Oi-Ming

2015-12-01

The oxidative and thermal stability of low diglycerides palm oil produced via silica treatment (sPO) and enzymatic treatment (ePO) compared with standard quality palm oil (SQ) and premium quality palm oil (PQ) was investigated. Both of the oils displayed better oxidative stability compared with SQ as well as significantly higher (P < 0.05) thermal resistance and oxidative strength than SQ and PQ due to lower amounts of partial glycerides. Although the initial induction periods (IPs) of sPO and ePO were significantly lower compared with SQ and PQ, both the oils showed slower drops in their IP values. The darkening effect after frying was significantly (P < 0.05) slower in sPO compared with SQ, PQ, and ePO. Besides, there is no difference p > 0.05 in the rate of FFA formation between sPO and PQ. The anisidine value and peroxide values were lowest in sPO, followed by ePO, PQ, and SQ. © 2015 Institute of Food Technologists®

A fully integrated oven controlled microelectromechanical oscillator -- Part I. Design and fabrication

DOE PAGES

Wojciechowski, Kenneth E.; Baker, Michael S.; Clews, Peggy J.; ...

2015-06-24

Our paper reports the design and fabrication of a fully integrated oven controlled microelectromechanical oscillator (OCMO). This paper begins by describing the limits on oscillator frequency stability imposed by the thermal drift and electronic properties (Q, resistance) of both the resonant tank circuit and feedback electronics required to form an electronic oscillator. An OCMO is presented that takes advantage of high thermal isolation and monolithic integration of both micromechanical resonators and electronic circuitry to thermally stabilize or ovenize all the components that comprise an oscillator. This was achieved by developing a processing technique where both silicon-on-insulator complementary metal-oxide-semiconductor (CMOS) circuitrymore » and piezoelectric aluminum nitride, AlN, micromechanical resonators are placed on a suspended platform within a standard CMOS integrated circuit. Operation at microscale sizes achieves high thermal resistances (~10 °C/mW), and hence thermal stabilization of the oscillators at very low-power levels when compared with the state-of-the-art ovenized crystal oscillators, OCXO. This constant resistance feedback circuit is presented that incorporates on platform resistive heaters and temperature sensors to both measure and stabilize the platform temperature. Moreover, the limits on temperature stability of the OCMO platform and oscillator frequency imposed by the gain of the constant resistance feedback loop, placement of the heater and temperature sensing resistors, as well as platform radiative and convective heat losses are investigated.« less

Structural, quantum chemical, vibrational and thermal studies of a hydrogen bonded zwitterionic co-crystal (nicotinic acid: pyrogallol)

NASA Astrophysics Data System (ADS)

Prabha, E. Arockia Jeya Yasmi; Kumar, S. Suresh; Athimoolam, S.; Sridhar, B.

2017-02-01

In the present work, a new co-crystal of nicotinic acid with pyrogallol (NICPY) has been grown in the zwitterionic form and the corresponding structural, vibrational, thermal, solubility and anti-cancer characteristics have been reported. The single crystal X-ray diffraction analysis confirms that the structural molecular packing of the crystal stabilized through N-H⋯O and O-H⋯O hydrogen bond. The stabilization energy of the hydrogen bond motifs were calculated in the solid state. Vibrational spectral studies such as Fourier transform-infrared (FT-IR) and FT-Raman were adopted to understand the zwitterionic co-crystalline nature of the compound, which has been compared with theoretically calculated vibrational frequencies. The thermal stability of the grown co-crystal was analyzed by TG/DTA study. The solubility of the NICPY co-crystal was investigated in water at different temperature and compared with that of the nicotinic acid, which is the parent compound of NICPY co-crystal. The grown crystals were treated with human cervical cancer cell line (HeLa) to analyze the cytotoxicity of NICPY crystals and compared with the parent compound, which shows that NICPY has moderate activity against human cervical cancer cell line.

Spherical nanocrystalline cellulose (NCC) from oil palm empty fruit bunch pulp via ultrasound assisted hydrolysis.

PubMed

Zianor Azrina, Z A; Beg, M Dalour H; Rosli, M Y; Ramli, Ridzuan; Junadi, Norhafzan; Alam, A K M Moshiul

2017-04-15

Nanocrystalline cellulose (NCC) was isolated from oil palm empty fruit bunch pulp (EFBP) using ultrasound assisted acid hydrolysis. The obtained NCC was analysed using FESEM, XRD, FTIR, and TGA, and compared with raw empty fruit bunch fibre (REFB), empty fruit bunch pulp (EFBP), and treated empty fruit bunch pulp (TEFBP). Based on FESEM analysis, it was found that NCC has a spherical shaped after acid hydrolysis with the assistance of ultrasound. This situation was different compared to previous studies that obtained rod-like shaped of NCC. Furthermore, the crystallinity of NCC is higher compared to REFB and EFBP. According to thermal stability, the NCC obtained shows remarkable sign of high thermal stability compared to REFB and EFBP. Copyright © 2017 Elsevier Ltd. All rights reserved.

Effective Identification on Adulteration of Polyethylene With Post-consumer Ones

NASA Astrophysics Data System (ADS)

Zhao, S.; Qin, W. B.; Guo, J. F.; Liu, J.; Wang, Y. L.; Zhang, W.; Zhao, X. Y.; Wang, L.

2018-05-01

This paper mainly describes the effective identification of the adulteration of polyethylene with post-consumer ones. Degradation would be happened when multiple processings occurred. The melt flow index (MFI) analysis, thermal gravimetric analysis (TGA), differential scanning calorimeter (DSC) were used to characterize the processability and thermal stabilities of virgin polyethylene and recycled polyethylene which adulterated post-consumer PE. The results indicated that MFI of PE increased with the increasing doping content. Adulterating reclaimed PE had effects on the thermal stability of PE, which led to lower thermal decomposition temperature. Melting peak of recycled LLDPE varied from merely single to double, which differently compared differently with virgin LLDPE. Besides, with the doping content of post-consumer LDPE, the melting temperature had a decreasing tendency.

Evaluation of the Lifetime and Thermal Conductivity of Dysprosia-Stabilized Thermal Barrier Coating Systems

NASA Astrophysics Data System (ADS)

Curry, Nicholas; Markocsan, Nicolaie; Östergren, Lars; Li, Xin-Hai; Dorfman, Mitch

2013-08-01

The aim of this study was the further development of dysprosia-stabilized zirconia coatings for gas turbine applications. The target for these coatings was a longer lifetime and higher insulating performance compared to today's industrial standard thermal barrier coating. Two morphologies of ceramic top coat were studied: one using a dual-layer system and the second using a polymer to generate porosity. Evaluations were carried out using a laser flash technique to measure thermal properties. Lifetime testing was conducted using thermo-cyclic fatigue testing. Microstructure was assessed with SEM and Image analysis was used to characterize porosity content. The results show that coatings with an engineered microstructure give performance twice that of the present reference coating.

Selection considerations between ZERODUR® and silicon carbide for dimensionally-stable spaceborne optical telescopes in two-earth-orbits

NASA Astrophysics Data System (ADS)

Hull, Tony; Westerhoff, Thomas; Weidmann, Gunter

2015-09-01

A key consideration in defining a space telescope mission is definition of the optical materials. This selection defines both the performance of the system and system complexity and cost. Optimal material selection for system stability must consider the thermal environment and its variation. Via numerical simulations, we compare the thermal and structural-mechanical behavior of ZERODUR® and SiC as mirror substrates for telescope assemblies in space. SiC has significantly larger CTE values then ZERODUR®, but also its thermal diffusivity k/(ρcp) is larger, and that helps to homogenize thermal gradients in the mirror. Therefore it is not obvious at first glance which material performs with better dimensional stability under realistic unsteady, inhomogeneous thermal loads. We specifically examine the telescope response to transient, gradient driving, thermal environments representative of low- and high-earth- orbits.

Implementation of Active Thermal Control (ATC) for the Soil Moisture Active and Passive (SMAP) Radiometer

NASA Technical Reports Server (NTRS)

Mikhaylov, Rebecca; Kwack, Eug; French, Richard; Dawson, Douglas; Hoffman, Pamela

2014-01-01

NASA's Earth Observing Soil Moisture Active and Passive (SMAP) Mission is scheduled to launch in November 2014 into a 685 kilometer near-polar, sun-synchronous orbit. SMAP will provide comprehensive global mapping measurements of soil moisture and freeze/thaw state in order to enhance understanding of the processes that link the water, energy, and carbon cycles. The primary objectives of SMAP are to improve worldwide weather and flood forecasting, enhance climate prediction, and refine drought and agriculture monitoring during its three year mission. The SMAP instrument architecture incorporates an L-band radar and an L-band radiometer which share a common feed horn and parabolic mesh reflector. The instrument rotates about the nadir axis at approximately 15 revolutions per minute, thereby providing a conically scanning wide swath antenna beam that is capable of achieving global coverage within three days. In order to make the necessary precise surface emission measurements from space, the electronics and hardware associated with the radiometer must meet tight short-term (instantaneous and orbital) and long-term (monthly and mission) thermal stabilities. Maintaining these tight thermal stabilities is quite challenging because the sensitive electronics are located on a fast spinning platform that can either be in full sunlight or total eclipse, thus exposing them to a highly transient environment. A passive design approach was first adopted early in the design cycle as a low-cost solution. With careful thermal design efforts to cocoon and protect all sensitive components, all stability requirements were met passively. Active thermal control (ATC) was later added after the instrument Preliminary Design Review (PDR) to mitigate the threat of undetected gain glitches, not for thermal-stability reasons. Gain glitches are common problems with radiometers during missions, and one simple way to avoid gain glitches is to use the in-flight set point programmability that ATC affords to operate the radiometer component away from the problematic temperature zone. A simple ThermXL model (10 nodes) was developed to exercise quick trade studies among various proposed control algorithms: Modified P control vs. PI control. The ThermXL results were then compared with the detailed Thermal Desktop (TD) model for corroboration. Once done, the simple ThermXL model was used to evaluate parameter effects such as temperature digitization, heater size and gain margin, time step, and voltage variation of power supply on the ATC performance. A Modified P control algorithm was implemented into the instrument flight electronics based on the ThermXL results. The thermal short-term stability margin decreased by 10 percent with ATC and a wide temperature error band (plus or minus 0.1 degrees Centigrade) compared to the original passive thermal design. However, a tighter temperature error band (plus or minus 0.1 degrees Centigrade) increased the thermal short-term stability margin by a factor of three over the passive thermal design. The current ATC design provides robust thermal control, tighter stability, and greater in-flight flexibility even though its implementation was prompted by non-thermal performance concerns.

Structural changes and thermal stability of charged LiNixMnyCozO₂ cathode materials studied by combined in situ time-resolved XRD and mass spectroscopy.

PubMed

Bak, Seong-Min; Hu, Enyuan; Zhou, Yongning; Yu, Xiqian; Senanayake, Sanjaya D; Cho, Sung-Jin; Kim, Kwang-Bum; Chung, Kyung Yoon; Yang, Xiao-Qing; Nam, Kyung-Wan

2014-12-24

Thermal stability of charged LiNixMnyCozO2 (NMC, with x + y + z = 1, x:y:z = 4:3:3 (NMC433), 5:3:2 (NMC532), 6:2:2 (NMC622), and 8:1:1 (NMC811)) cathode materials is systematically studied using combined in situ time-resolved X-ray diffraction and mass spectroscopy (TR-XRD/MS) techniques upon heating up to 600 °C. The TR-XRD/MS results indicate that the content of Ni, Co, and Mn significantly affects both the structural changes and the oxygen release features during heating: the more Ni and less Co and Mn, the lower the onset temperature of the phase transition (i.e., thermal decomposition) and the larger amount of oxygen release. Interestingly, the NMC532 seems to be the optimized composition to maintain a reasonably good thermal stability, comparable to the low-nickel-content materials (e.g., NMC333 and NMC433), while having a high capacity close to the high-nickel-content materials (e.g., NMC811 and NMC622). The origin of the thermal decomposition of NMC cathode materials was elucidated by the changes in the oxidation states of each transition metal (TM) cations (i.e., Ni, Co, and Mn) and their site preferences during thermal decomposition. It is revealed that Mn ions mainly occupy the 3a octahedral sites of a layered structure (R3̅m) but Co ions prefer to migrate to the 8a tetrahedral sites of a spinel structure (Fd3̅m) during the thermal decomposition. Such element-dependent cation migration plays a very important role in the thermal stability of NMC cathode materials. The reasonably good thermal stability and high capacity characteristics of the NMC532 composition is originated from the well-balanced ratio of nickel content to manganese and cobalt contents. This systematic study provides insight into the rational design of NMC-based cathode materials with a desired balance between thermal stability and high energy density.

Structural changes and thermal stability of charged LiNi xMn yCo zO 2 cathode materials studied by combined in situ time-resolved XRD and mass spectroscopy

DOE PAGES

Bak, Seong -Min; Hu, Enyuan; Zhou, Yongning; ...

2014-11-24

Thermal stability of charged LiNi xMn yCo zO 2 (NMC, with x + y + z = 1, x:y:z = 4:3:3 (NMC433), 5:3:2 (NMC532), 6:2:2 (NMC622), and 8:1:1 (NMC811)) cathode materials is systematically studied using combined in situ time- resolved X-ray diffraction and mass spectroscopy (TR-XRD/MS) techniques upon heating up to 600 °C. The TR-XRD/MS results indicate that the content of Ni, Co, and Mn significantly affects both the structural changes and the oxygen release features during heating: the more Ni and less Co and Mn, the lower the onset temperature of the phase transition (i.e., thermal decomposition) and themore » larger amount of oxygen release. Interestingly, the NMC532 seems to be the optimized composition to maintain a reasonably good thermal stability, comparable to the low-nickel-content materials (e.g., NMC333 and NMC433), while having a high capacity close to the high-nickel-content materials (e.g., NMC811 and NMC622). The origin of the thermal decomposition of NMC cathode materials was elucidated by the changes in the oxidation states of each transition metal (TM) cations (i.e., Ni, Co, and Mn) and their site preferences during thermal decomposition. It is revealed that Mn ions mainly occupy the 3a octahedral sites of a layered structure (R3¯m) but Co ions prefer to migrate to the 8a tetrahedral sites of a spinel structure (Fd3¯m) during the thermal decomposition. Such element-dependent cation migration plays a very important role in the thermal stability of NMC cathode materials. The reasonably good thermal stability and high capacity characteristics of the NMC532 composition is originated from the well-balanced ratio of nickel content to manganese and cobalt contents. As a result, this systematic study provides insight into the rational design of NMC-based cathode materials with a desired balance between thermal stability and high energy density.« less

Thermal and aqueous stability improvement of graphene oxide enhanced diphenylalanine nanocomposites

NASA Astrophysics Data System (ADS)

Ryan, Kate; Neumayer, Sabine M.; Maraka, Harsha Vardhan R.; Buchete, Nicolae-Viorel; Kholkin, Andrei L.; Rice, James H.; Rodriguez, Brian J.

2017-12-01

Nanocomposites of diphenylalanine (FF) and carbon based materials provide an opportunity to overcome drawbacks associated with using FF micro- and nanostructures in nanobiotechnology applications, in particular their poor structural stability in liquid solutions. In this study, FF/graphene oxide (GO) composites were found to self-assemble into layered micro- and nanostructures, which exhibited improved thermal and aqueous stability. Dependent on the FF/GO ratio, the solubility of these structures was reduced to 35.65% after 30 min as compared to 92.4% for pure FF samples. Such functional nanocomposites may extend the use of FF structures to e.g. biosensing, electrochemical, electromechanical or electronic applications.

X-ray Crystallographic Structure of Thermophilic Rhodopsin

PubMed Central

Tsukamoto, Takashi; Mizutani, Kenji; Hasegawa, Taisuke; Takahashi, Megumi; Honda, Naoya; Hashimoto, Naoki; Shimono, Kazumi; Yamashita, Keitaro; Yamamoto, Masaki; Miyauchi, Seiji; Takagi, Shin; Hayashi, Shigehiko; Murata, Takeshi; Sudo, Yuki

2016-01-01

Thermophilic rhodopsin (TR) is a photoreceptor protein with an extremely high thermal stability and the first characterized light-driven electrogenic proton pump derived from the extreme thermophile Thermus thermophilus JL-18. In this study, we confirmed its high thermal stability compared with other microbial rhodopsins and also report the potential availability of TR for optogenetics as a light-induced neural silencer. The x-ray crystal structure of TR revealed that its overall structure is quite similar to that of xanthorhodopsin, including the presence of a putative binding site for a carotenoid antenna; but several distinct structural characteristics of TR, including a decreased surface charge and a larger number of hydrophobic residues and aromatic-aromatic interactions, were also clarified. Based on the crystal structure, the structural changes of TR upon thermal stimulation were investigated by molecular dynamics simulations. The simulations revealed the presence of a thermally induced structural substate in which an increase of hydrophobic interactions in the extracellular domain, the movement of extracellular domains, the formation of a hydrogen bond, and the tilting of transmembrane helices were observed. From the computational and mutational analysis, we propose that an extracellular LPGG motif between helices F and G plays an important role in the thermal stability, acting as a “thermal sensor.” These findings will be valuable for understanding retinal proteins with regard to high protein stability and high optogenetic performance. PMID:27129243

Enhancement of thermal stability and water resistance in yttrium-doped GeO{sub 2}/Ge gate stack

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

Lu, Cimang, E-mail: cimang@adam.t.u-tokyo.ac.jp; Hyun Lee, Choong; Zhang, Wenfeng

2014-03-03

We have systematically investigated the material and electrical properties of yttrium-doped GeO{sub 2} (Y-GeO{sub 2}) on Germanium (Ge). A significant improvement of both thermal stability and water resistance were demonstrated by Y-GeO{sub 2}/Ge stack, compared to that of pure GeO{sub 2}/Ge stack. The excellent electrical properties of Y-GeO{sub 2}/Ge stacks with low D{sub it} were presented as well as enhancement of dielectric constant in Y-GeO{sub 2} layer, which is beneficial for further equivalent oxide thickness scaling of Ge gate stack. The improvement of thermal stability and water resistance are discussed both in terms of the Gibbs free energy lowering andmore » network modification of Y-GeO{sub 2}.« less

Effects of high hydrostatic pressure or hydrophobic modification on thermal stability of xanthine oxidase.

PubMed

Halalipour, Ali; Duff, Michael R; Howell, Elizabeth E; Reyes-De-Corcuera, José I

2017-08-01

The effect of high hydrostatic pressure (HHP) on the kinetics of thermal inactivation of xanthine oxidase (XOx) from bovine milk was studied. Inactivation of XOx followed pseudo-first-order kinetics at 0.1-300MPa and 55.0-70.0°C. High pressure up to at least 300MPa stabilized XOx at all the studied temperatures. The highest stabilization effect of HHP on XOx was at 200-300MPa at 55.0 and 58.6°C, and at 250-300MPa at 62.3-70.0°C. The stability of XOx increased 9.5 times at 300MPa and 70.0°C compared to atmospheric pressure at the same temperature. The activation energy of inactivation of XOx decreased with pressure and was 1.9 times less at 300MPa (97.0±8.2kJmol -1 ) than at 0.1MPa (181.7±12.1kJmol -1 ). High pressure decreased the dependence of the rate constant of inactivation to temperature effects compared to atmospheric pressure. The stabilizing effect of HHP on XOx was highest at 70.0°C where the activation volume of inactivation of XOx was 28.9±2.9cm 3 mol -1 . A second approach to try to increase XOx stability involved hydrophobic modification using aniline or benzoate. However, the thermal stability of XOx remained unaffected after 8-14 modifications of carboxyl side groups per XOx monomer with aniline, or 12-17 modifications of amino side groups per XOx monomer with benzoate. Copyright © 2017 Elsevier Inc. All rights reserved.

Crystallization and mechanical properties of reinforced PHBV composites using melt compounding: Effect of CNCs and CNFs.

PubMed

Jun, Du; Guomin, Zhao; Mingzhu, Pan; Leilei, Zhuang; Dagang, Li; Rui, Zhang

2017-07-15

Nanocellulose reinforced poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) composites were prepared using melt compounding. The effects of nanocellulose types (CNCs and CNFs) and nanocellulose content (1, 2, 3, 4, 5, 6 and 7wt%) on the crystallization, thermal and mechanical properties of PHBV composites were systematically compared in this study. The thermal stability of PHBV composites was improved by both CNCs and CNFs. CNFs with a higher thermal stability leaded to a higher thermal stability of PHBV composites. Both CNCs and CNFs induced a reduction in the crystalline size of PHBV spherulites. Furthermore, CNCs could act as a better nucleating agent for PHBV than did CNFs. CNCs and CNFs showed reinforcing effects in PHBV composites. At the equivalent content of nanocellulose, CNCs led to a higher tensile modulus of PHBV composites than did CNFs. 1wt% CNCs/PHBV composites exhibited the most optimum mechanical properties. Copyright © 2017 Elsevier Ltd. All rights reserved.

Thermally Stable Cellulose Nanocrystals toward High-Performance 2D and 3D Nanostructures.

PubMed

Jia, Chao; Bian, Huiyang; Gao, Tingting; Jiang, Feng; Kierzewski, Iain Michael; Wang, Yilin; Yao, Yonggang; Chen, Liheng; Shao, Ziqiang; Zhu, J Y; Hu, Liangbing

2017-08-30

Cellulose nanomaterials have attracted much attention in a broad range of fields such as flexible electronics, tissue engineering, and 3D printing for their excellent mechanical strength and intriguing optical properties. Economic, sustainable, and eco-friendly production of cellulose nanomaterials with high thermal stability, however, remains a tremendous challenge. Here versatile cellulose nanocrystals (DM-OA-CNCs) are prepared through fully recyclable oxalic acid (OA) hydrolysis along with disk-milling (DM) pretreatment of bleached kraft eucalyptus pulp. Compared with the commonly used cellulose nanocrystals from sulfuric acid hydrolysis, DM-OA-CNCs show several advantages including large aspect ratio, carboxylated surface, and excellent thermal stability along with high yield. We also successfully demonstrate the fabrication of high-performance films and 3D-printed patterns using DM-OA-CNCs. The high-performance films with high transparency, ultralow haze, and excellent thermal stability have the great potential for applications in flexible electronic devices. The 3D-printed patterns with porous structures can be potentially applied in the field of tissue engineering as scaffolds.

A highly efficient silole-containing dithienylethene with excellent thermal stability and fatigue resistance: a promising candidate for optical memory storage materials.

PubMed

Chan, Jacky Chi-Hung; Lam, Wai Han; Yam, Vivian Wing-Wah

2014-12-10

Diarylethene compounds are potential candidates for applications in optical memory storage systems and photoswitchable molecular devices; however, they usually show low photocycloreversion quantum yields, which result in ineffective erasure processes. Here, we present the first highly efficient photochromic silole-containing dithienylethene with excellent thermal stability and fatigue resistance. The photochemical quantum yields for photocyclization and photocycloreversion of the compound are found to be high and comparable to each other; the latter of which is rarely found in diarylethene compounds. These would give rise to highly efficient photoswitchable material with effective writing and erasure processes. Incorporation of the silole moiety as a photochromic dithienylethene backbone also was demonstrated to enhance the thermal stability of the closed form, in which the thermal backward reaction to the open form was found to be negligible even at 100 °C, which leads to a promising candidate for use as photoswitchable materials and optical memory storage.

Atomic Layer Deposition Al2O3 Coatings Significantly Improve Thermal, Chemical, and Mechanical Stability of Anodic TiO2 Nanotube Layers

PubMed Central

2017-01-01

We report on a very significant enhancement of the thermal, chemical, and mechanical stability of self-organized TiO2 nanotubes layers, provided by thin Al2O3 coatings of different thicknesses prepared by atomic layer deposition (ALD). TiO2 nanotube layers coated with Al2O3 coatings exhibit significantly improved thermal stability as illustrated by the preservation of the nanotubular structure upon annealing treatment at high temperatures (870 °C). In addition, a high anatase content is preserved in the nanotube layers against expectation of the total rutile conversion at such a high temperature. Hardness of the resulting nanotube layers is investigated by nanoindentation measurements and shows strongly improved values compared to uncoated counterparts. Finally, it is demonstrated that Al2O3 coatings guarantee unprecedented chemical stability of TiO2 nanotube layers in harsh environments of concentrated H3PO4 solutions. PMID:28291942

Local time dependence of the thermal structure in the Venusian equatorial region revealed by Akatsuki radio occultation measurements

NASA Astrophysics Data System (ADS)

Ando, H.; Fukuhara, T.; Takagi, M.; Imamura, T.; Sugimoto, N.; Sagawa, H.

2017-12-01

The radio occultation technique is one of the most useful methods to retrieve vertical temperature profiles in planetary atmospheres. Ultra-Stable Oscillator (USO) onboard Venus Climate Orbiter, Akatsuki, enables us to investigate the thermal structure of the Venus atmosphere between about 40-90 km levels. It is expected that 35 temperature profiles will be obtained by the radio occultation measurements of Akatsuki until August 2017. Static stability derived from the temperature profiles shows its local time dependence above the cloud top level at low-latitudes equatorward of 25˚. The vertical profiles of the static stability in the dawn and dusk regions have maxima at 77 km and 82 km levels, respectively. A general circulation model (GCM) for the Venus atmosphere (AFES-Venus) reproduced the thermal structures above the cloud top qualitatively consistent with the radio occultation measurements; the maxima of the static stability are seen both in the dawn and dusk regions, and the local maximum of the static stability in the dusk region is located at a highler level than in the dawn region. Comparing the thermal structures between the radio occultation measurements and the GCM results, it is suggested that the distribution of the static stability above the cloud top could be strongly affected by the diurnal tide. The thermal tide influences on the thermal structure as well as atmospheric motions above the cloud level. In addition, it is shown that zonally averaged zonal wind at about 80 km altitude could be roughly estimated from the radio occultation measurements using the dispersion relation of the internal gravity wave.

The role of stabilization centers in protein thermal stability

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

Magyar, Csaba; Gromiha, M. Michael; Sávoly, Zoltán

2016-02-26

The definition of stabilization centers was introduced almost two decades ago. They are centers of noncovalent long range interaction clusters, believed to have a role in maintaining the three-dimensional structure of proteins by preventing their decay due to their cooperative long range interactions. Here, this hypothesis is investigated from the viewpoint of thermal stability for the first time, using a large protein thermodynamics database. The positions of amino acids belonging to stabilization centers are correlated with available experimental thermodynamic data on protein thermal stability. Our analysis suggests that stabilization centers, especially solvent exposed ones, do contribute to the thermal stabilizationmore » of proteins. - Highlights: • Stabilization centers contribute to thermal stabilization of protein structures. • Stabilization center content correlates with melting temperature of proteins. • Exposed stabilization center content correlates with stability even in hyperthermophiles. • Stability changing mutations are frequently found at stabilization centers.« less

Lightweight ZERODUR: Validation of Mirror Performance and Mirror Modeling Predictions

NASA Technical Reports Server (NTRS)

Hull, Tony; Stahl, H. Philip; Westerhoff, Thomas; Valente, Martin; Brooks, Thomas; Eng, Ron

2017-01-01

Upcoming spaceborne missions, both moderate and large in scale, require extreme dimensional stability while relying both upon established lightweight mirror materials, and also upon accurate modeling methods to predict performance under varying boundary conditions. We describe tests, recently performed at NASA's XRCF chambers and laboratories in Huntsville Alabama, during which a 1.2 m diameter, f/1.2988% lightweighted SCHOTT lightweighted ZERODUR(TradeMark) mirror was tested for thermal stability under static loads in steps down to 230K. Test results are compared to model predictions, based upon recently published data on ZERODUR(TradeMark). In addition to monitoring the mirror surface for thermal perturbations in XRCF Thermal Vacuum tests, static load gravity deformations have been measured and compared to model predictions. Also the Modal Response(dynamic disturbance) was measured and compared to model. We will discuss the fabrication approach and optomechanical design of the ZERODUR(TradeMark) mirror substrate by SCHOTT, its optical preparation for test by Arizona Optical Systems (AOS). Summarize the outcome of NASA's XRCF tests and model validations

Lightweight ZERODUR®: Validation of mirror performance and mirror modeling predictions

NASA Astrophysics Data System (ADS)

Hull, Anthony B.; Stahl, H. Philip; Westerhoff, Thomas; Valente, Martin; Brooks, Thomas; Eng, Ron

2017-01-01

Upcoming spaceborne missions, both moderate and large in scale, require extreme dimensional stability while relying both upon established lightweight mirror materials, and also upon accurate modeling methods to predict performance under varying boundary conditions. We describe tests, recently performed at NASA’s XRCF chambers and laboratories in Huntsville Alabama, during which a 1.2m diameter, f/1.29 88% lightweighted SCHOTT lightweighted ZERODUR® mirror was tested for thermal stability under static loads in steps down to 230K. Test results are compared to model predictions, based upon recently published data on ZERODUR®. In addition to monitoring the mirror surface for thermal perturbations in XRCF Thermal Vacuum tests, static load gravity deformations have been measured and compared to model predictions. Also the Modal Response (dynamic disturbance) was measured and compared to model. We will discuss the fabrication approach and optomechanical design of the ZERODUR® mirror substrate by SCHOTT, its optical preparation for test by Arizona Optical Systems (AOS), and summarize the outcome of NASA’s XRCF tests and model validations.

Thermal stability of detonation-produced micro and nanodiamonds

NASA Astrophysics Data System (ADS)

Efremov, V. P.; Zakatilova, E. I.; Maklashova, I. V.; Shevchenko, N. V.

2018-01-01

Detonation nanodiamonds are produced at utilization of high explosives. When an explosive blasts in a water environment, the detonation products contain microdiamonds, and in a gaseous medium, nanodiamonds. It is known that with decreasing size the influence of the surface energy of particles on their properties increases. Thus, it is interesting to compare the properties of detonation nano and microdiamonds. In this study, we have examined the thermal stability of diamond materials by synchronous thermal analysis. The experiments were performed at atmospheric pressure in argon flow for different heating rates in a range from room temperature to 1500 °C. Samples of initial and annealed micro and nanomaterials were studied using electron microscopy, x-ray and x-ray-fluorescence analysis. It was established that thermal and structural properties of micro and nanodiamonds differ substantially.

Encapsulation of β-carotene within ferritin nanocages greatly increases its water-solubility and thermal stability.

PubMed

Chen, Lingli; Bai, Guangling; Yang, Rui; Zang, Jiachen; Zhou, Ting; Zhao, Guanghua

2014-04-15

Carotenoids may play a number of potential health benefits for human. However, their use in food industry is limited mostly because of their poor water-solubility and low thermal stability. Ferritins are widely distributed in nature with a shell-like structure which offers a great opportunity to improve the water-solubility and thermal stability of the carotenoids by encapsulation. In this work, recombinant human H-chain ferritin (rHuHF) was prepared and used to encapsulate β-carotene, a typical compound among carotenoids, by taking advantage of the reversible dissociation and reassembly characteristic of apoferritin in different pH environments. Results from high-performance liquid chromatography (HPLC), UV/Vis spectroscopy and transmission electron microscope (TEM) indicated that β-carotene molecules were successfully encapsulated within protein cages with a β-carotene/protein molar ratio of 12.4-1. Upon such encapsulation, these β-carotene-containing apoferritin nanocomposites were water-soluble. Interestingly, the thermal stability of the β-carotene encapsulated within apoferritin nanocages was markedly improved as compared to free β-carotene. These new properties might be favourable to the utilisation of β-carotene in food industry. Copyright © 2013 Elsevier Ltd. All rights reserved.

Improvement of the thermal stability of Nb:TiO2-x samples for uncooled infrared detectors

NASA Astrophysics Data System (ADS)

Reddy, Y. Ashok Kumar; Kang, In-Ku; Shin, Young Bong; Lee, Hee Chul

2018-01-01

In order to reduce the sun-burn effect in a sample of the bolometric material Nb:TiO2-x , oxygen annealing was carried out. This effect can be examined by comparing thermal stability test results between the as-deposited and oxygen-atmosphere-annealed samples under high-temperature exposure conditions. Structural studies confirm the presence of amorphous and rutile phases in the as-deposited and annealed samples, respectively. Composition studies reveal the offset of oxygen vacancies in the Nb:TiO2-x samples through oxygen-atmosphere annealing. The oxygen atoms were diffused and seemed to occupy the vacant sites in the annealed samples. As a result, the annealed samples show better thermal stability performance than the as-deposited samples. The universal bolometric parameter (β) values were slightly decreased in the oxygen-annealed Nb:TiO2-x samples. Although bolometric performance was slightly decreased in the oxygen-annealed samples, high thermal stability would be the most essential factor in the case of special applications, such as the military and space industries. Finally, these results will be very useful for reducing the sun-burn effect in infrared detectors.

Flexibility and Stability Trade-Off in Active Site of Cold-Adapted Pseudomonas mandelii Esterase EstK.

PubMed

Truongvan, Ngoc; Jang, Sei-Heon; Lee, ChangWoo

2016-06-28

Cold-adapted enzymes exhibit enhanced conformational flexibility, especially in their active sites, as compared with their warmer-temperature counterparts. However, the mechanism by which cold-adapted enzymes maintain their active site stability is largely unknown. In this study, we investigated the role of conserved D308-Y309 residues located in the same loop as the catalytic H307 residue in the cold-adapted esterase EstK from Pseudomonas mandelii. Mutation of D308 and/or Y309 to Ala or deletion resulted in increased conformational flexibility. Particularly, the D308A or Y309A mutant showed enhanced substrate affinity and catalytic rate, as compared with wild-type EstK, via enlargement of the active site. However, all mutant EstK enzymes exhibited reduced thermal stability. The effect of mutation was greater for D308 than Y309. These results indicate that D308 is not preferable for substrate selection and catalytic activity, whereas hydrogen bond formation involving D308 is critical for active site stabilization. Taken together, conformation of the EstK active site is constrained via flexibility-stability trade-off for enzyme catalysis and thermal stability. Our study provides further insights into active site stabilization of cold-adapted enzymes.

Thermal Stability and Surface Wettability Studies of Polylactic Acid/Halloysite Nanotube Nanocomposite Scaffold for Tissue Engineering Studies

NASA Astrophysics Data System (ADS)

Nizar, M. Mohd; Hamzah, M. S. A.; Razak, S. I. Abd; Mat Nayan, N. H.

2018-03-01

This paper reports the preliminary study about the incorporation of halloysite nanotubes (HNT) into polylactic acid (PLA) scaffold to improve the thermal resistance and surface wettability properties. The fabrication of the porous scaffold requires a simple yet effective technique with low-cost materials within freeze extraction method. The thermal stability of PLA/HNT scaffold compared to neat PLA scaffold achieved with increased content of HNT by 5 wt%. Moreover, the surface wettability of the scaffold also shows a positive impact with high content of HNT by 5 wt%. This new nanocomposite scaffold may have high potential as a suitable template for tissue regeneration.

Thermal stability of bubble domains in ferromagnetic discs

NASA Astrophysics Data System (ADS)

Hrkac, G.; Bance, S.; Goncharov, A.; Schrefl, T.; Suess, D.

2007-05-01

The transition and thermal stability of disc-shaped ferromagnetic particles at the temperature of T = 300 K with a uniaxial anisotropy along the symmetry axis from a bi-domain to a single domain state has been studied. The nudge elastic band method was used to map the energy landscape and to calculate the energy barrier between the transition states. For single FePt disc-shaped particles with perpendicular anisotropy three transition configurations have been found: single domain, stripe- and stable bubble domains at zero applied field. The single domain configuration along the positive anisotropy axis is reached by an annihilation process of the domain wall and the all-down state by a complex domain expansion process. Magnetization configurations in two interacting discs show an increase in thermal stability compared with single disc systems, which is attributed to the interacting magnetostatic energy between the two particles.

International Standards on stability of digital prints

NASA Astrophysics Data System (ADS)

Adelstein, Peter Z.

2010-06-01

The International Standards Organization (ISO) is a worldwide recognized standardizing body which has responsibility for standards on permanence of digital prints. This paper is an update on the progress made to date by ISO in writing test methods in this area. Three technologies are involved, namely ink jet, dye diffusion thermal transfer (dye-sublimation) and electrophotography. Two types of test methods are possible, namely comparative tests and predictive tests. To date a comparative test on water fastness has been published and final balloting is underway on a comparative test on humidity fastness. Predictive tests are being finalized on thermal stability and pollution susceptibility. The test method on thermal stability is intended to predict the print life during normal aging. One of the testing concerns is that some prints do not show significant image change in practical testing times. The test method on pollution susceptibility only deals with ozone and assumes that the reciprocity law applies. This law assumes that a long time under a low pollutant concentration is equivalent to a short time under the high concentration used in the test procedure. Longer term studies include a predictive test for light stability and the preparation of a material specification. The latter requires a decision about the proper colour target to be used and what constitutes an unacceptable colour change. Moreover, a specification which gives a predictive life is very dependent upon the conditions the print encounters and will only apply to specific levels of temperature, ozone and light.

The role of glycosylation and domain interactions in the thermal stability of human angiotensin-converting enzyme.

PubMed

O'Neill, Hester G; Redelinghuys, Pierre; Schwager, Sylva L U; Sturrock, Edward D

2008-09-01

The N and C domains of somatic angiotensin-converting enzyme (sACE) differ in terms of their substrate specificity, inhibitor profiling, chloride dependency and thermal stability. The C domain is thermally less stable than sACE or the N domain. Since both domains are heavily glycosylated, the effect of glycosylation on their thermal stability was investigated by assessing their catalytic and physicochemical properties. Testis ACE (tACE) expressed in mammalian cells, mammalian cells in the presence of a glucosidase inhibitor and insect cells yielded proteins with altered catalytic and physicochemical properties, indicating that the more complex glycans confer greater thermal stabilization. Furthermore, a decrease in tACE and N-domain N-glycans using site-directed mutagenesis decreased their thermal stability, suggesting that certain N-glycans have an important effect on the protein's thermodynamic properties. Evaluation of the thermal stability of sACE domain swopover and domain duplication mutants, together with sACE expressed in insect cells, showed that the C domain contained in sACE is less dependent on glycosylation for thermal stabilization than a single C domain, indicating that stabilizing interactions between the two domains contribute to the thermal stability of sACE and are decreased in a C-domain-duplicating mutant.

Mechanical performance and thermal stability of glass fiber reinforced silica aerogel composites based on co-precursor method by freeze drying

NASA Astrophysics Data System (ADS)

Zhou, Ting; Cheng, Xudong; Pan, Yuelei; Li, Congcong; Gong, Lunlun; Zhang, Heping

2018-04-01

In order to maintain the integrity, glass fiber (GF) reinforced silica aerogel composites were synthesized using methltrimethoxysilane (MTMS) and water glass co-precursor by freeze drying method. The composites were characterized by scanning electron microscopy, Brunauer-Emmett-Teller analysis, uniaxial compressive test, three-point bending test, thermal conductivity analysis, contact angle test, TG-DSC analysis. It was found that the molar ratio of MTMS/water glass could significantly affect the properties of composites. The bulk density and thermal conductivity first decreased and then increased with the increasing molar ratio. The composites showed remarkable mechanical strength and flexibility compared with pure silica aerogel. Moreover, when the molar ratio is 1.8, the composites showed high specific surface area (870.9 m2/g), high contact angle (150°), great thermal stability (560 °C) and low thermal conductivity (0.0248 W/m·K). These outstanding properties indicate that GF/aerogels have broad prospects in the field of thermal insulation.

Thermotropic Properties of Thermophilic, Mesophilic, and Psychrophilic Blue-green Algae

PubMed Central

Chen, Chang-Hwei; Berns, Donald S.

1980-01-01

Thermotropic properties of blue-green algae grown at high, room, and low temperatures in H2O and D2O media were studied by highly sensitive differential scanning microcalorimetry. The thermograms of these organisms contain an endothermal peak in the temperature range of 50 to 70 C with an endothermal heat ranging from 0.14 to 1.91 joules per gram organism. The temperature at which the endothermal peak occurs is comparable with the thermal denaturation temperature of phycocyanin, the major biliprotein isolated from these algae. A good correlation can be found for the relative thermal stability of various organisms with that of the isolated biliproteins. The ability of these algae to resist thermal disruption is correlated with the thermal environments in which these algal cells grow. The thermal stability of normal algae is in the order of thermophile > mesophile > psychrophile. It was found that the deuterated mesophilic algae were less able to resist thermal disruption than ordinary mesophilic algae. PMID:16661485

Ultra-flexible and robust transparent electrodes by embedding silver nanowires into polyimide matrix

NASA Astrophysics Data System (ADS)

Zhao, Rong Rong; Yu, Ming Shi; Wang, Guan Cheng; Liu, Wei; Chen, Tong Lai

2018-06-01

Silver nanowires (AgNWs) percolated films have been extensively considered as promising candidates for alternative transparent electrodes. However, due to their high surface roughness, poor adhesion and thermal stability, their practical use in transparent conducting film application is still heavily limited. In this paper, we report ultra-flexible transparent electrodes by imbedding AgNWs into polyimide (PI) thin films to achieve smooth surface, pronounced thermal stability, and high adhesion. Besides the excellent electrical conductivity of about 7-13Ω/□ in sheet resistance, the obtained AgNWs/PI films have excellent transparency and mechanical resilience due to the intrinsic physical and chemical properties of PI organic polymer. By embedding AgNWs into PI, the surface roughness of AgNWs percolated films can be reduced from 39.5 nm to 6 nm (RMS values), and the adhesion of AgNWs to PI is greatly enhanced if compared to the case of only AgNWs onto glass or plastic substrates. Additionally, the AgNWs/PI films show extraordinary stability in terms of electrical conductivity after the arbitrary twisting and thermal heating test, respectively, which are demonstrated by the electrical-thermal measurements via thermal IR imaging.

Improving the thermal stability of cellobiohydrolase Cel7A from Hypocrea jecorina by directed evolution.

PubMed

Goedegebuur, Frits; Dankmeyer, Lydia; Gualfetti, Peter; Karkehabadi, Saeid; Hansson, Henrik; Jana, Suvamay; Huynh, Vicky; Kelemen, Bradley R; Kruithof, Paulien; Larenas, Edmund A; Teunissen, Pauline J M; Ståhlberg, Jerry; Payne, Christina M; Mitchinson, Colin; Sandgren, Mats

2017-10-20

Secreted mixtures of Hypocrea jecorina cellulases are able to efficiently degrade cellulosic biomass to fermentable sugars at large, commercially relevant scales. H. jecorina Cel7A, cellobiohydrolase I, from glycoside hydrolase family 7, is the workhorse enzyme of the process. However, the thermal stability of Cel7A limits its use to processes where temperatures are no higher than 50 °C. Enhanced thermal stability is desirable to enable the use of higher processing temperatures and to improve the economic feasibility of industrial biomass conversion. Here, we enhanced the thermal stability of Cel7A through directed evolution. Sites with increased thermal stability properties were combined, and a Cel7A variant (FCA398) was obtained, which exhibited a 10.4 °C increase in T m and a 44-fold greater half-life compared with the wild-type enzyme. This Cel7A variant contains 18 mutated sites and is active under application conditions up to at least 75 °C. The X-ray crystal structure of the catalytic domain was determined at 2.1 Å resolution and showed that the effects of the mutations are local and do not introduce major backbone conformational changes. Molecular dynamics simulations revealed that the catalytic domain of wild-type Cel7A and the FCA398 variant exhibit similar behavior at 300 K, whereas at elevated temperature (475 and 525 K), the FCA398 variant fluctuates less and maintains more native contacts over time. Combining the structural and dynamic investigations, rationales were developed for the stabilizing effect at many of the mutated sites. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Thermal-Mechanical Stability of Single Crystal Oxide Refractive Concentrators for High-Temperature Solar Thermal Propulsion

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Jacobson, Nathan S.; Miller, Robert A.

1999-01-01

Single crystal oxides such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO) and sapphire (Al2O3) are candidate refractive secondary concentrator materials for high temperature solar propulsion applications. However, thermo-mechanical reliability of these components in severe thermal environments during the space mission sun/shade transition is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions, and thus provide vital information for the component design. In this paper, a controlled heat flux thermal shock test approach is established for the single crystal oxide materials using a 3.0 kW continuous wave CO2 laser, with a wavelength 10.6 micron. Thermal fracture behavior and failure mechanisms of these oxide materials are investigated and critical temperature gradients are determined under various temperature and heating conditions. The test results show that single crystal sapphire is able to sustain the highest temperature gradient and heating-cooling rate, and thus exhibit the best thermal shock resistance, as compared to the yttria-stabilized zirconia, yttrium aluminum garnet and magnesium oxide.

Thermal abuse performance of high-power 18650 Li-ion cells

NASA Astrophysics Data System (ADS)

Roth, E. P.; Doughty, D. H.

High-power 18650 Li-ion cells have been developed for hybrid electric vehicle applications as part of the DOE Advanced Technology Development (ATD) program. The thermal abuse response of two advanced chemistries (Gen1 and Gen2) were measured and compared with commercial Sony 18650 cells. Gen1 cells consisted of an MCMB graphite based anode and a LiNi 0.85Co 0.15O 2 cathode material while the Gen2 cells consisted of a MAG10 anode graphite and a LiNi 0.80Co 0.15 Al 0.05O 2 cathode. Accelerating rate calorimetry (ARC) and differential scanning calorimetry (DSC) were used to measure the thermal response and properties of the cells and cell materials up to 400 °C. The MCMB graphite was found to result in increased thermal stability of the cells due to more effective solid electrolyte interface (SEI) formation. The Al stabilized cathodes were seen to have higher peak reaction temperatures that also gave improved cell thermal response. The effects of accelerated aging on cell properties were also determined. Aging resulted in improved cell thermal stability with the anodes showing a rapid reduction in exothermic reactions while the cathodes only showed reduced reactions after more extended aging.

Thermal-Mechanical Stability of Single Crystal Oxide Refractive Concentrators for High-Temperature Solar Thermal Propulsion

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Jacobson, Nathan S.; Miller, Robert A.

1999-01-01

Single crystal oxides such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO) and sapphire (Al2O3) are candidate refractive secondary concentrator materials for high temperature solar propulsion applications. However, thermo-mechanical reliability of these components in severe thermal environments during the space mission sun/shade transition is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions, and thus provide vital information for the component design. In this paper, a controlled heat flux thermal shock test approach is established for the single crystal oxide materials using a 3.0 kW continuous wave CO2 laser, with a wavelength 10.6 micron. Thermal fracture behavior and failure mechanisms of these oxide materials are investigated and critical temperature gradients are determined under various temperature and heating conditions. The test results show that single crystal sapphire is able to sustain the highest temperature gradient and heating-cooling rate, and thus exhibit the best thermal shock resistance, as compared to the yttria-stabilized zirconia, yttrium aluminum garnet, and magnesium oxide.

Designing and Thermal Analysis of Safe Lithium Ion Cathode Materials for High Energy Applications

NASA Astrophysics Data System (ADS)

Hu, Enyuan

Safety is one of the most critical issues facing lithium-ion battery application in vehicles. Addressing this issue requires the integration of several aspects, especially the material chemistry and the battery thermal management. First, thermal stability investigation was carried out on an attractive high energy density material LiNi0.5Mn1.5O4. New findings on the thermal-stability and thermal-decomposition-pathways related to the oxygen-release are discovered for the high-voltage spinel Li xNi0.5Mn1.5O4 (LNMO) with ordered (o-) and disordered (d-) structures at fully delithiated (charged) state using a combination of in situ time-resolved x-ray diffraction (TR-XRD) coupled with mass spectroscopy (MS) and x-ray absorption spectroscopy (XAS). Both fully charged o--LixNi0.5Mn1.5O 4 and d-LixNi0.5Mn1.5O 4 start oxygen-releasing structural changes at temperatures below 300 °C, which is in sharp contrast to the good thermal stability of the 4V-spinel LixMn2O4 with no oxygen being released up to 375 °C. This is mainly caused by the presence of Ni4+ in LNMO, which undergoes dramatic reduction during the thermal decomposition. In addition, charged o-LNMO shows better thermal stability than the d-LNMO counterpart, due to the Ni/Mn ordering and smaller amount of the rock-salt impurity phase in o-LNMO. Newly identified two thermal-decomposition-pathways from the initial LixNi0.5Mn1.5O 4 spinel to the final NiMn2O4-type spinel structure with and without the intermediate phases (NiMnO3 and alpha-Mn 2O3) are found to play key roles in thermal stability and oxygen release of LNMO during thermal decomposition. In addressing the safety issue associated with LNMO, Fe is selected to partially substitute Ni and Mn simultaneously utilizing the electrochemical activity and structure-stabilizing high spin Fe3+. The synthesized LiNi1/3Mn4/3Fe1/3O4 showed superior thermal stability and satisfactory electrochemical performance. At charged state, it is able to withstand the temperature as high as 500°C without observable oxygen release. It shows comparable cyclability performance to the LNMO material with better rate capability. The undiminished high voltage capacity is due to the electrochemical activity of Fe in the system. Fe also plays the key role of stabilizing the system at Fe3O4 type spinel phase against further phase transformation to the rock salt phase, accounting for the superior thermal stability of LiNi1/3Mn 4/3Fe1/3O4. Thermal analysis of the lithium-ion battery indicates the key role of electric current in contributing to a thermal runaway. FLUENT simulation on a 10-cell battery shows that under fast discharging conditions, the temperature level can easily reach the threshold of malfunction and the battery temperature features a large distribution of 18°C. Simple air cooling is not effective enough in addressing the problem. Designed air cooling or liquid cooling is required for the normal operation of lithium-ion batteries in vehicles.

Investigation into photostability of soybean oils by thermal lens spectroscopy

NASA Astrophysics Data System (ADS)

Savi, E. L.; Malacarne, L. C.; Baesso, M. L.; Pintro, P. T. M.; Croge, C.; Shen, J.; Astrath, N. G. C.

2015-06-01

Assessment of photochemical stability is essential for evaluating quality and the shelf life of vegetable oils, which are very important aspects of marketing and human health. Most of conventional methods used to investigate oxidative stability requires long time experimental procedures with high consumption of chemical inputs for the preparation or extraction of sample compounds. In this work we propose a time-resolved thermal lens method to analyze photostability of edible oils by quantitative measurement of photoreaction cross-section. An all-numerical routine is employed to solve a complex theoretical problem involving photochemical reaction, thermal lens effect, and mass diffusion during local laser excitation. The photostability of pure oil and oils with natural and synthetic antioxidants is investigated. The thermal lens results are compared with those obtained by conventional methods, and a complete set of physical properties of the samples is presented.

The mechanical and thermal characteristics of phenolic foam reinforced with kaolin powder and glass fiber fabric

NASA Astrophysics Data System (ADS)

Xiao, Wenya; Huang, Zhixiong; Ding, Jie

2017-12-01

In this work, kaolin powder and glass fiber fabric were added to PF in order to improve its thermal stability and mechanical property. Micro-structures of carbonized PF with kaolin powder were inspected by scanning electron microscopy (SEM) to demonstrate the filler’s pinning effect. SEM results illustrated modified PF had well morphology after high-temperature heat treatment. The Fourier transform infrared spectrometer (FTIR) test was carried out and found that kaolin powder only physically dispersed in PF. The compression test and thermal weight loss test were done on two groups of modified PF (Group A: add powder and fabric; Group B: add powder only). Results showed that all modified PF were better than pure PF, while foams with powder and fabric showed better mechanical characteristic and thermal stability compared with foams with powder only.

Ambient temperature effects on broadband UV-B measurements using fluorescent phosphor (MgWO4)-based detectors

NASA Technical Reports Server (NTRS)

Dichter, Bronislaw K.; Beaubien, David J.; Beaubien, Arthur F.

1994-01-01

Results of field tests on a group of broadband UV-B pyranometers are presented. A brief description of the instrument is given. The effects of ambient temperature on thermally unregulated fluorescent phosphor (Robertson type) meters are presented and compared with the performance of thermally stabilized instruments. Means for correcting data from thermally unregulated instruments, where the prevailing ambient temperatures are known, are outlined.

Advanced study of thermal behaviour of CSZ comparing with the classic YSZ coating

NASA Astrophysics Data System (ADS)

Dragomirescu, A.; Constantin, N.; Ştefan, A.; Manoliu, V.; Truşcă, R.

2017-01-01

Thermal barrier coatings (TBC) are advanced materials typically applied to metal surfaces subjected to extreme temperatures to protect them and increase their lifetime. Ceria stabilized zirconia ceramic layer (CSZ) is increasingly used as an alternative improved as replace for classical TBC system - yttria stabilized zirconia - thanks to superior properties, including mechanical and high resistance to thermal corrosion. The paper describes the thermal shock testing of two types of thermal barrier coatings used to protect a nickel super alloy. For the experimental procedure, it was used plate samples from nickel super alloy with a bond coat and a ceramic top coat. The top coat was different: on some samples, it was used YSZ and on others CSZ. Ni based super alloys have good corrosion resistance in reducing environments action, but poor in oxidizing conditions. Extreme environments can lead to loss of material by oxidation / corrosion, along with decreased mechanical properties of the substrate due to damaging elements which diffuses into the substrate at high temperatures. Using laboratory equipment, the TBC systems were exposed repeatedly to extreme high temperatures for a short time and then cooled. After the thermal shock tests, the samples were morph-structured characterized using electronic microscopy to analyze the changes. The experimental results were compared to rank the TBC systems in order of performance.

Radioactive nuclear waste stabilization - Aspects of solid-state molecular engineering and applied geochemistry

NASA Technical Reports Server (NTRS)

Haggerty, S. E.

1983-01-01

Stabilization techniques for the storage of radioactive wastes are surveyed, with emphasis on immobilization in a primary barrier of synthetic rock. The composition, half-life, and thermal-emission characteristics of the wastes are shown to require thermally stable immobilization enduring at least 100,000 years. Glass materials are determined to be incapable of withstanding the expected conditions, average temperatures of 100-500 C for the first 100 years. The geological-time stability of crystalline materials, ceramics or synthetic rocks, is examined in detail by comparing their components with similar naturally occurring minerals, especially those containing the same radioactive elements. The high-temperature environment over the first 100 years is seen as stabilizing, since it can recrystallize radiation-induced metamicts. The synthetic-rock stabilization technique is found to be essentially feasible, and improvements are suggested, including the substitution of nepheline with freudenbergite and priderite for alkaline-waste stabilization, the maintenance of low oxygen fugacity, and the dilution of the synthetic-rock pellets into an inert medium.

Conserved tyrosine 182 residue in hyperthermophilic esterase EstE1 plays a critical role in stabilizing the active site.

PubMed

Truongvan, Ngoc; Chung, Hye-Shin; Jang, Sei-Heon; Lee, ChangWoo

2016-03-01

An aromatic amino acid, Tyr or Trp, located in the esterase active site wall, is highly conserved, with hyperthermophilic esterases showing preference for Tyr and lower temperature esterases showing preference for Trp. In this study, we investigated the role of Tyr(182) in the active site wall of hyperthermophilic esterase EstE1. Mutation of Tyr to Phe or Ala had a moderate effect on EstE1 thermal stability. However, a small-to-large mutation such as Tyr to His or Trp had a devastating effect on thermal stability. All mutant EstE1 enzymes showed reduced catalytic rates and enhanced substrate affinities as compared with wild-type EstE1. Hydrogen bond formation involving Tyr(182) was unimportant for maintaining EstE1 thermal stability, as the EstE1 structure is already adapted to high temperatures via increased intramolecular interactions. However, removal of hydrogen bond from Tyr(182) significantly decreased EstE1 catalytic activity, suggesting its role in stabilization of the active site. These results suggest that Tyr is preferred over a similarly sized Phe residue or bulky His or Trp residue in the active site walls of hyperthermophilic esterases for stabilizing the active site and regulating catalytic activity at high temperatures.

Monitoring the Thermal Parameters of Different Edible Oils by Using Thermal Lens Spectrometry

NASA Astrophysics Data System (ADS)

Jiménez-Pérez, J. L.; Cruz-Orea, A.; Lomelí Mejia, P.; Gutierrez-Fuentes, R.

2009-08-01

Several vegetable edible oils (sunflower, canola, soya, and corn) were used to study the thermal diffusivity of edible oils. Thermal lens spectrometry (TLS) was applied to measure the thermal properties. The results showed that the obtained thermal diffusivities with this technique have good agreement when compared with literature values. In this technique an Ar+ laser and intensity stabilized He-Ne laser were used as the heating source and probe beam, respectively. These studies may contribute to a better understanding of the physical properties of edible oils and the quality of these important foodstuffs.

Improved pharmacokinetics of mercaptopurine afforded by a thermally robust hemihydrate.

PubMed

Kersten, Kortney M; Matzger, Adam J

2016-04-18

Structural and thermal data were obtained for a novel hemihydrate of 6-mercaptopurine. The hemihydrate shows increased solubility and bioavailability when compared to the monohydrate form, better stability against conversion in aqueous media than the anhydrate form, and a dehydration temperature of 240 °C, the highest of any known hydrate crystal.

Development of polyisocyanurate pour foam formulation for space shuttle external tank thermal protection system

NASA Technical Reports Server (NTRS)

Harvey, James A.; Butler, John M.; Chartoff, Richard P.

1988-01-01

Four commercially available polyisocyanurate polyurethane spray-foam insulation formulations are used to coat the external tank of the space shuttle. There are several problems associated with these formulations. For example, some do not perform well as pourable closeout/repair systems. Some do not perform well at cryogenic temperatures (poor adhesion to aluminum at liquid nitrogen temperatures). Their thermal stability at elevated temperatures is not adequate. A major defect in all the systems is the lack of detailed chemical information. The formulations are simply supplied to NASA and Martin Marietta, the primary contractor, as components; Part A (isocyanate) and Part B (poly(s) and additives). Because of the lack of chemical information the performance behavior data for the current system, NASA sought the development of a non-proprietary room temperature curable foam insulation. Requirements for the developed system were that it should exhibit equal or better thermal stability both at elevated and cryogenic temperatures with better adhesion to aluminum as compared to the current system. Several formulations were developed that met these requirements, i.e., thermal stability, good pourability, and good bonding to aluminum.

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...

Acacia gum as modifier of thermal stability, solubility and emulsifying properties of α-lactalbumin.

PubMed

de Oliveira, Fabíola Cristina; Dos Reis Coimbra, Jane Sélia; de Oliveira, Eduardo Basílio; Rodrigues, Marina Quadrio Raposo Branco; Sabioni, Rachel Campos; de Souza, Bartolomeu Warlene Silva; Santos, Igor José Boggione

2015-03-30

Protein-polysaccharide conjugates often display improved techno-functional properties when compared to their individual involved biomolecules. α-Lactalbumin:acacia gum (α-la:AG) conjugates were prepared via Maillard reaction by the dry-heating method. Conjugate formation was confirmed using results of absorbance, o-phthalaldehyde test, sodium dodecyl sulfate-polyacrilamide gel electrophoresis (SDS-PAGE) and size exclusion chromatography. Techno-functional properties (emulsifying characteristics, solubility, and thermal stability) were evaluated for α-la, α-la/AG mixtures and α-la:AG conjugates. Conjugate thermal stability was improved compared to pure α-la treated at the same conditions of conjugate formation. Response surface methodology was used to establish models to predict solubility and emulsifying activity as functions of the salt concentration, pH and reaction time. α-la:AG conjugate solubility is affected in a complex manner by the three factors analyzed. Emulsifying activity index (EAI) of α-la is significantly affected by pH, while the α-la:AG EAI is affected by the three analyzed factors. Both solubility and EAI are maximized with pH 8.0, NaCl concentration of 0.3 mol L(-1) and two days of Maillard reaction. Copyright © 2014 Elsevier Ltd. All rights reserved.

The ring residue proline 8 is crucial for the thermal stability of the lasso peptide caulosegnin II.

PubMed

Hegemann, Julian D; Fage, Christopher D; Zhu, Shaozhou; Harms, Klaus; Di Leva, Francesco Saverio; Novellino, Ettore; Marinelli, Luciana; Marahiel, Mohamed A

2016-04-01

Lasso peptides are fascinating natural products with a unique structural fold that can exhibit tremendous thermal stability. Here, we investigate factors responsible for the thermal stability of caulosegnin II. By employing X-ray crystallography, mutational analysis and molecular dynamics simulations, the ring residue proline 8 was proven to be crucial for thermal stability.

Stabilization of Human Serum Albumin by the Binding of Phycocyanobilin, a Bioactive Chromophore of Blue-Green Alga Spirulina: Molecular Dynamics and Experimental Study

PubMed Central

Stanic-Vucinic, Dragana; Nikolic, Milan; Milcic, Milos; Cirkovic Velickovic, Tanja

2016-01-01

Phycocyanobilin (PCB) binds with high affinity (2.2 x 106 M-1 at 25°C) to human serum albumin (HSA) at sites located in IB and IIA subdomains. The aim of this study was to examine effects of PCB binding on protein conformation and stability. Using 300 ns molecular dynamics (MD) simulations, UV-VIS spectrophotometry, CD, FT-IR, spectrofluorimetry, thermal denaturation and susceptibility to trypsin digestion, we studied the effects of PCB binding on the stability and rigidity of HSA, as well as the conformational changes in PCB itself upon binding to the protein. MD simulation results demonstrated that HSA with PCB bound at any of the two sites showed greater rigidity and lower overall and individual domain flexibility compared to free HSA. Experimental data demonstrated an increase in the α-helical content of the protein and thermal and proteolytic stability upon ligand binding. PCB bound to HSA undergoes a conformational change to a more elongated conformation in the binding pockets of HSA. PCB binding to HSA stabilizes the structure of this flexible transport protein, making it more thermostable and resistant to proteolysis. The results from this work explain at molecular level, conformational changes and stabilization of HSA structure upon ligand binding. The resultant increased thermal and proteolytic stability of HSA may provide greater longevity to HSA in plasma. PMID:27959940

Structural control of side-chain chromophores to achieve highly efficient electro-optic activity.

PubMed

Yang, Yuhui; Chen, Zhuo; Liu, Jialei; Xiao, Hongyan; Zhen, Zhen; Liu, Xinhou; Jiang, Guohua

2017-05-10

A series of chromophores J1-J4 have been synthesized based on julolidine donors modified with different rigid steric hindrance groups. Compared with the chromophore (J1) without the isolation group, chromophores J2, J3 and J4 show better stability. Structural analysis and photophysical property measurements were carried out to compare the molecular mobility and steric hindrance effect of the different donor-modified chromophores. All of these chromophores with isolation groups showed superb thermal stabilities with high thermal decomposition temperatures above 250 °C. Furthermore, with rigid steric hindrance, chromophores J3 and J4 showed more enhanced thermal stabilities with thermal decomposition temperatures of 269 °C and 275 °C, respectively. Density functional theory was used to calculate the hyperpolarizability (β), and the high molecular hyperpolarizability of these chromophores can be effectively translated into large electro-optic coefficients. The electro-optic coefficients of poled films containing 20 wt% of these new chromophores doped in amorphous polycarbonate were 127, 266 and 209 pm V -1 at 1310 nm for chromophores J1-J3, respectively, while the film containing chromophore J4 showed the largest r 33 value of only 97 pm V -1 at 25 wt%. These results indicated that the introduced isolation group can reduce intermolecular electrostatic interactions, thus enhancing the macroscopic electro-optic activity, while the size of the isolation group should be suitable.

Comparison of Thermal Stability of Dry High-strength Concrete and Wet High-strength Concrete

NASA Astrophysics Data System (ADS)

Musorina, Tatiana; Katcay, Aleksandr; Selezneva, Anna; Kamskov, Victor

2018-03-01

High-strength concrete is a modern material, which occupies it`s own niche on the construction material market. It is applicable in a large-scale high-rise construction, particularly an underground construction is a frequently used solution for a space saving. Usually underground structure is related to a wet usage environment. Though not all properties of the high-strength concrete are investigated to the full extent. Under adverse climatic conditions of the Russian Federation one of the most important properties for constructional materials is a thermal capacity. Therefore, the main purpose of the paper is to compare a thermal capacity of the high-strength concrete in humid conditions and a thermal capacity of the high-strength concrete in dry operational condition. During the study dependency between thermal capacity and design wall thickness and ambient humidity has to be proven with two experiments. As a result the theoretical relation between thermal capacity characteristic - thermal inertia and wall thickness and ambient humidity was confirmed by the experimental data. The thermal capacity of a building is in direct ratio to the construction thickness. It follows from the experiments and calculations that wet high-strength concrete has less thermal stability.

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.

Thermal Stability of Oil Palm Empty Fruit Bunch (OPEFB) Nanocrystalline Cellulose: Effects of post-treatment of oven drying and solvent exchange techniques

NASA Astrophysics Data System (ADS)

Indarti, E.; Marwan; Wanrosli, W. D.

2015-06-01

Nanocrystallinecellulose (NCC) from biomass is a promising material with huge potentials in various applications. A big challenge in its utilization is the agglomeration of the NCC's during processing due to hydrogen bonding among the cellulose chains when in close proximity to each other. Obtaining NCC's in a non-agglomerated and non-aqueous condition is challenging. In the present work NCC's was isolated from oil palm empty fruit bunch (OPEFB) using TEMPO-oxidation reaction method. To obtain non-agglomerated and non-aqueous products, the NCC's underwent post-treatment using oven drying (OD) and solvent exchanged (SE) techniques. The thermal stability of all samples was determined from TGA and DTG profiles whilst FTIR was used to analyzethe chemical modifications that occurred under these conditions. NCC-SE has better thermal stability than the NCC-OD and its on-set degradation temperature and residue are also higher. FTIR analysis shows that NCC-SE has a slightly different chemical composition whereby the absorption band at 1300 cm-1 (due to C-O symmetric stretching) is absent as compared to NCC-OD indicating that in NCC-SE the carboxylate group is in acid form which contribute to its thermal stability

Rational design for the stability improvement of Armillariella tabescens β-mannanase MAN47 based on N-glycosylation modification.

PubMed

Hu, Weixiong; Liu, Xiaoyun; Li, Yufeng; Liu, Daling; Kuang, Zhihe; Qian, Chuiwen; Yao, Dongsheng

2017-02-01

β-Mannanase has been widely used in industries such as food and feed processing and thus has been a target enzyme for biotechnological development. In this study, we sought to improve the stability and protease resistance of a recombinant β-mannanase, MAN47 from Armillariella tabescens, through rationally designed N-glycosylation. Based on homology modeling, molecular docking, secondary structure analysis and glycosylation feasibility analysis, an enhanced aromatic sequon sequence was introduced into specific MAN47 loop regions to facilitate N-glycosylation. The mutant enzymes were expressed in Pichia pastoris SMD1168, and their thermal stability, pH stability, trypsin resistance and pepsin resistance were determined. Two mutant MAN47 enzymes, g-123 and g-347, were glycosylated as expected when expressed in yeast, and their thermal stability, pH stability, and protease resistance were significantly improved compared to the wild-type enzyme. An enzyme with multiple stability characterizations has broad prospects in practical applications, and the rational design N-glycosylation strategy may have applications in simultaneously improving several properties of other biotechnological targets. Copyright © 2016 Elsevier Inc. All rights reserved.

Charged black holes in quartic quasi-topological gravity

NASA Astrophysics Data System (ADS)

Ghanaatian, M.; Naeimipour, F.; Bazrafshan, A.; Abkar, M.

2018-05-01

In this paper, we construct exact solutions of charged black holes in the presence of quartic quasi-topological gravity. We obtain thermodynamics and conserved quantities of the solutions and check the first law of thermodynamics. In studying the physical properties of the solutions, we consider anti-de Sitter, de Sitter, and flat solutions of charged black holes in quartic quasi-topological gravity and compare them with Einstein and third-order quasi-topological gravities. We also investigate the thermal stability of the solutions and show that thermal stability is just for anti-de Sitter solutions, not for de Sitter and flat ones.

A Low-cost Environmental Control System for Precise Radial Velocity Spectrometers

NASA Astrophysics Data System (ADS)

Sliski, David H.; Blake, Cullen H.; Halverson, Samuel

2017-12-01

We present an environmental control system (ECS) designed to achieve milliKelvin (mK) level temperature stability for small-scale astronomical instruments. This ECS is inexpensive and is primarily built from commercially available components. The primary application for our ECS is the high-precision Doppler spectrometer MINERVA-Red, where the thermal variations of the optical components within the instrument represent a major source of systematic error. We demonstrate ±2 mK temperature stability within a 0.5 m3 thermal enclosure using resistive heaters in conjunction with a commercially available PID controller and off-the-shelf thermal sensors. The enclosure is maintained above ambient temperature, enabling rapid cooling through heat dissipation into the surrounding environment. We demonstrate peak-to-valley (PV) temperature stability of better than 5 mK within the MINERVA-Red vacuum chamber, which is located inside the thermal enclosure, despite large temperature swings in the ambient laboratory environment. During periods of stable laboratory conditions, the PV variations within the vacuum chamber are less than 3 mK. This temperature stability is comparable to the best stability demonstrated for Doppler spectrometers currently achieving m s-1 radial velocity precision. We discuss the challenges of using commercially available thermoelectrically cooled CCD cameras in a temperature-stabilized environment, and demonstrate that the effects of variable heat output from the CCD camera body can be mitigated using PID-controlled chilled water systems. The ECS presented here could potentially provide the stable operating environment required for future compact “astrophotonic” precise radial velocity (PRV) spectrometers to achieve high Doppler measurement precision with a modest budget.

The use of ionic salt dyes as amorphous, thermally stable emitting layers in organic light-emitting diodes

NASA Astrophysics Data System (ADS)

Chondroudis, Konstantinos; Mitzi, David B.

2000-01-01

The conversion of two neutral dye molecules (D) to ionic salts (H2N-D-NH2ṡ2HX) and their utilization as emitting layers in organic light-emitting diodes (OLEDs) is described. The dye salts, AEQTṡ2HCl and APTṡ2HCl, can be deposited as amorphous films using conventional evaporation techniques. X-ray diffraction and scanning electron microscopy analysis, coupled with thermal annealing studies, demonstrate the resistance of the films to crystallization. This stability is attributed to strong ionic forces between the relatively rigid molecules. OLEDs incorporating such salts for emitting layers exhibit better thermal stability compared with devices made from the corresponding neutral dyes (H2N-D-NH2). These results suggest that ionic salts may more generally enable the formation of thermally stable, amorphous emitting, and charge transporting layers.

Refractometric sensitivity and thermal stabilization of fluorescent core microcapillary sensors: theory and experiment.

PubMed

Lane, S; Marsiglio, F; Zhi, Y; Meldrum, A

2015-02-20

Fluorescent-core microcapillaries (FCMs) present a robust basis for the application of optical whispering gallery modes toward refractometric sensing. An important question concerns whether these devices can be rendered insensitive to local temperature fluctuations, which may otherwise limit their refractometric detection limits, mainly as a result of thermorefractive effects. Here, we first use a standard cylindrical cavity formalism to develop the refractometric and thermally limited detection limits for the FCM structure. We then measure the thermal response of a real device with different analytes in the channel and compare the result to the theory. Good stability against temperature fluctuations was obtained for an ethanol solvent, with a near-zero observed thermal shift for the transverse magnetic modes. Similarly good results could in principle be obtained for any other solvent (e.g., water), if the thickness of the fluorescent layer can be sufficiently well controlled.

Predictive Thermal Control Applied to HabEx

NASA Technical Reports Server (NTRS)

Brooks, Thomas E.

2017-01-01

Exoplanet science can be accomplished with a telescope that has an internal coronagraph or with an external starshade. An internal coronagraph architecture requires extreme wavefront stability (10 pm change/10 minutes for 10(exp -10) contrast), so every source of wavefront error (WFE) must be controlled. Analysis has been done to estimate the thermal stability required to meet the wavefront stability requirement. This paper illustrates the potential of a new thermal control method called predictive thermal control (PTC) to achieve the required thermal stability. A simple development test using PTC indicates that PTC may meet the thermal stability requirements. Further testing of the PTC method in flight-like environments will be conducted in the X-ray and Cryogenic Facility (XRCF) at Marshall Space Flight Center (MSFC).

Predictive thermal control applied to HabEx

NASA Astrophysics Data System (ADS)

Brooks, Thomas E.

2017-09-01

Exoplanet science can be accomplished with a telescope that has an internal coronagraph or with an external starshade. An internal coronagraph architecture requires extreme wavefront stability (10 pm change/10 minutes for 10-10 contrast), so every source of wavefront error (WFE) must be controlled. Analysis has been done to estimate the thermal stability required to meet the wavefront stability requirement. This paper illustrates the potential of a new thermal control method called predictive thermal control (PTC) to achieve the required thermal stability. A simple development test using PTC indicates that PTC may meet the thermal stability requirements. Further testing of the PTC method in flight-like environments will be conducted in the X-ray and Cryogenic Facility (XRCF) at Marshall Space Flight Center (MSFC).

Thermal optimum design for tracking primary mirror of Space Telescope

NASA Astrophysics Data System (ADS)

Pan, Hai-jun; Ruan, Ping; Li, Fu; Wang, Hong-Wei

2011-08-01

In the conventional method, the structural parameters of primary mirror are usually optimized just by the requirement of mechanical performance. Because the influences of structural parameters on thermal stability are not taken fully into account in this simple method, the lightweight optimum design of primary mirror usually brings the bad thermal stability, especially in the complex environment. In order to obtain better thermal stability, a new method about structure-thermal optimum design of tracking primary mirror is discussed. During the optimum process, both the lightweight ratio and thermal stability will be taken into account. The structure-thermal optimum is introduced into the analysis process and commenced after lightweight design as the secondary optimum. Using the engineering analysis of software ANSYS, a parameter finite element analysis (FEA) model of mirror is built. On the premise of appropriate lightweight ratio, the RMS of structure-thermal deformation of mirror surface and lightweight ratio are assigned to be state variables, and the maximal RMS of temperature gradient load to be object variable. The results show that certain structural parameters of tracking primary mirror have different influences on mechanical performance and thermal stability, even they are opposite. By structure-thermal optimizing, the optimized mirror model discussed in this paper has better thermal stability than the old one under the same thermal loads, which can drastically reduce difficulty in thermal control.

Self-adaptive thermal management - the fundamentals and applications in Li-polymer batteries

NASA Astrophysics Data System (ADS)

Geng, Xiaobao

The thermal management systems for electronic devices and their power sources are facing increasing challenge to accommodate the ever-changing environmental and operational conditions. The conventional thermal management systems, with a predominant focus on cooling, are often not sufficient in those cases. In addition, to support miniaturization, complex systems and broader applications (e.g., space and military), the thermal management system often needs to be compatible with smaller device and their fabrication processes, dissipate heat efficiently for localized heat spot, and meet the requirement of light weight and low power consumption. In order to address such issues, a self-adaptive thermal switch array (TSA) is proposed based on microelectromechanical systems (MEMS) technology which has the capability automatically change its thermal conductance according to the environmental and operational conditions. This TSA was actuated by low melting alloy (LMA) with neither control unit nor parasitic energy consumption. The idea has been first demonstrated by a prototype device with the stabilization temperatures under various power inputs investigated both experimentally and theoretically. When the power input was changed from 3.8W to 5.8W, the stabilization temperature of the device was increased only by 2.5°C due to the stabilization effect of TSA. The experimental data were found in good agreement with their theoretical value. Based on the theoretical model, two types of TSA, namely high-on and low-off, were further developed to increase on-state thermal conductance and decrease off-state thermal conductance, respectively. Compared with the low-off TSA, the high-on TSA can more efficiently cool the devices and stabilize their temperature at a value closer to the melting point of LMA even under higher power inputs. On the other hand, the startup time and energy consumption were significantly reduced with the low-off TSA design due to the enhanced off-state thermal insulation, making them more suitable for cold start applications. A few key design factors have been identified to increase the on-state thermal conductance, reduce the off-state thermal conductance and enhance their ratio (switching ratio). The TSAs were then applied to a Li-polymer battery stack to demonstrate the self-adaptive thermal management capability. When cold-started from -10°C, the TSA-regulated battery stack reached 20°C in ~10min. The operational temperature was sustained with a moderate discharge current until depletion, while maintaining a fairly uniform temperate distribution within the battery stack. Compared with the open-cooling case, the performance of the Li-polymer battery was significantly improved by TSA-regulated thermal management. The capacity and output energy were increased by 16% and 23%, respectively. With the low-off TSA, the cold-start time has been shortened to ~ 7min, while the capacity and output energy of battery stack were increased by 18% and 27%, respectively, as compared to open-cooling case. The promising results have also paved the way for improving the performance of self-adaptive thermal management through the key design parameters.

Electrochemical performance of a thermally rearranged polybenzoxazole nanocomposite membrane as a separator for lithium-ion batteries at elevated temperature

NASA Astrophysics Data System (ADS)

Lee, Moon Joo; Hwang, Jun-Ki; Kim, Ji Hoon; Lim, Hyung-Seok; Sun, Yang-Kook; Suh, Kyung-Do; Lee, Young Moo

2016-02-01

Shape-tunable hydroxyl copolyimide (HPI) nanoparticles are fabricated by a re-precipitation method and are coated onto electrospun HPI membranes, followed by heat treatment to prepare thermally rearranged polybenzoxazole (TR-PBO) composite membranes. The morphology of HPI nanoparticles consisted of sphere and sea-squirt structures, which is controlled by changing the concentration of the stabilizer. The morphological characteristics of TR-PBO nanoparticles convert from HPI nanoparticles by heat treatment and their composite membranes is confirmed by scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared spectroscopy (ATR-IR), thermogravimetric analysis (TGA) analysis, and contact angle measurements. TGA and DSC measurements confirm the excellent thermal stability compared to Celgard, a commercial PP separator for lithium-ion batteries (LIBs). Further, TR-PBO nano-composite membranes used in coin-cell type LIBs as a separator show excellent high power density performance as compared to Celgard. This is due to the fact that sea-squirt structured nanoparticles have better electrochemical properties than sphere structured nanoparticles at high temperature.

Production, thermal stability and immobilisation of inulinase from Fusarium oxysporum.

PubMed

Gupta, A K; Rathore, P; Kaur, N; Singh, R

1990-01-01

Fusarium oxysporum produced maximum extracellular inulinase after 9 days of its growth at 25 degrees C on a medium (pH 5.5) containing 3% fructan and 0.2% sodium nitrate. The level of this enzyme decreased on the addition of either glucose, fructose, galactose or sucrose to F. oxysporum already growing on a fructan-containing medium. A significant increase in invertase production which resulted in an increase of the invertase/inulinase (S/I) ratio, was observed on addition of inulin to this fungus growing on other carbon sources. Glycerol (10%) gave better protection to inulinase against thermal denaturation at 50 degrees C compared to ethylene glycol and sorbitol. Inulinase immobilised in polyacrylamide gel retained 45% of its original activity. The immobilised enzyme showed a higher optimum temperature (45 degrees C) compared to free enzyme (37 degrees C). The immobilised enzyme after storage at 25 degrees C for 96 h showed 58% activity. Thermal stability of entrapped inulinase increased in the presence of inulin.

Study of Selected Composites Copper Concentrate-Plastic Waste Using Thermal Analysis

NASA Astrophysics Data System (ADS)

Szyszka, Danuta

2017-12-01

The paper presents thermal analysis of selected composites (copper concentrate, plastic waste) in two stages. The first stage consisted in thermogravimetric analysis and differential thermal analysis on the applied plastic waste and copper concentrate, and subsequently, a comparative study has been carried out on products obtained, constituting composites of those materials. As a result of analyses, it was found that up to ca. 400 °C composites show high thermal stability, whereas above that temperature, a thermal decomposition of the composite occurs, resulting in emissions of organic compounds, i.e. hydrocarbon compounds and organic oxygenate derivatives.

Insight into destabilization mechanism of Mg-based hydrides interstitially co-doped with nonmetals: a DFT study

NASA Astrophysics Data System (ADS)

Wu, Zhen; Zhu, Luying; Yang, Fusheng; Zhang, Zaoxiao; Nyamsi, Serge N.

2018-04-01

Mg-based metal hydride is one of the most promising materials for hydrogen energy storage. However, the high thermal stability due to strong bonding effects between the atoms limits its practical application. In order to reduce the thermal stability, a method of doping double nonmetals into Mg-based system was proposed in this study. The density functional theory (DFT) calculation results showed that the thermal stabilities of both the B-N co-doped Mg-based alloy and its hydride are reduced compared with pure Mg-based system. The relative formation enthalpies of the alloy and its hydride are 0.323 and 0.595 eV atom-1, respectively. The values are much higher than those for either singly B- or N-doped Mg-based system. The more significant destabilization by doping double nonmetal elements than single element is mainly attributed to a dual effect in weakening Mg-Ni/NiH4 bonds, caused by criss-cross interactions between B-Ni and N-Mg bonds.

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.

Thermal stability analysis of the fine structure of solar prominences

NASA Technical Reports Server (NTRS)

Demoulin, Pascal; Malherbe, Jean-Marie; Schmieder, Brigitte; Raadu, Mickael A.

1986-01-01

The linear thermal stability of a 2D periodic structure (alternatively hot and cold) in a uniform magnetic field is analyzed. The energy equation includes wave heating (assumed proportional to density), radiative cooling and both conduction parallel and orthogonal to magnetic lines. The equilibrium is perturbed at constant gas pressure. With parallel conduction only, it is found to be unstable when the length scale 1// is greater than 45 Mn. In that case, orthogonal conduction becomes important and stabilizes the structure when the length scale is smaller than 5 km. On the other hand, when the length scale is greater than 5 km, the thermal equilibrium is unstable, and the corresponding time scale is about 10,000 s: this result may be compared to observations showing that the lifetime of the fine structure of solar prominences is about one hour; consequently, our computations suggest that the size of the unresolved threads could be of the order of 10 km only.

Sb7Te3/Ge multilayer films for low power and high speed phase-change memory

NASA Astrophysics Data System (ADS)

Chen, Shiyu; Wu, Weihua; Zhai, Jiwei; Song, Sannian; Song, Zhitang

2017-06-01

Phase-change memory has attracted enormous attention for its excellent properties as compared to flash memories due to their high speed, high density, better date retention and low power consumption. Here we present Sb7Te3/Ge multilayer films by using a magnetron sputtering method. The 10 years’ data retention temperature is significantly increased compared with pure Sb7Te3. When the annealing temperature is above 250 °C, the Sb7Te3/Ge multilayer thin films have better interface properties, which renders faster crystallization speed and high thermal stability. The decrease in density of ST/Ge multilayer films is only around 5%, which is very suitable for phase change materials. Moreover, the low RESET power benefits from high resistivity and better thermal stability in the PCM cells. This work demonstrates that the multilayer configuration thin films with tailored properties are beneficial for improving the stability and speed in phase change memory applications.

Organic microchemical performance of solvent resistant polycarbosilane based microreactor.

PubMed

Yoon, Tae-Ho; Jung, Sang-Hee; Kim, Dong-Pyo

2011-05-01

We report the successful fabrication of preceramic polymer allylhydridopolycarbosilane (AHPCS) derived microchannels with excellent organic solvent resistance and optical transparency via economic imprinting process, followed by UV and post thermal curing process at 160 degrees C for 3 h. The microchemical performance of the fabricated microreactors was evaluated by choosing two model micro chemical reactions under organic solvent conditions; syntheses of 2-aminothiazole in DMF and dimethylpyrazole in THF, and compared with glass-based microreactor having identical dimensions and batch system with analogy. It is clear that AHPCS derived microreactor showed excellent solvent resistance and chemical stability compare with glass derived microreactor made by high cost of photolithography and thermal bonding process. The novel preceramic polymer derived microreactors showed reliable mechanical and chemical stability and conversion yields compare with that of glass derived microreactors, which is very promising for developing an integrated microfluidics by adopting available microstructuring techniques of the polymers.

Production, Characterization, and Stability of Orange or Eucalyptus Essential Oil/β-Cyclodextrin Inclusion Complex.

PubMed

Kringel, Dianini Hüttner; Antunes, Mariana Dias; Klein, Bruna; Crizel, Rosane Lopes; Wagner, Roger; de Oliveira, Roberto Pedroso; Dias, Alvaro Renato Guerra; Zavareze, Elessandra da Rosa

2017-11-01

The aim of this study was to produce and characterize inclusion complexes (IC) between β-cyclodextrin (β-CD) and orange essential oil (OEO) or eucalyptus essential oil (EEO), and to compare these with their pure compounds and physical mixtures. The samples were evaluated by chemical composition, morphology, thermal stability, and volatile compounds by static headspace-gas chromatography (SH-GC). Comparing the free essential oil and physical mixture with the inclusion complex, of both essential oils (OEO and EEO), it was observed differences occurred in the chemical composition, thermal stability, and morphology. These differences show that there was the formation of the inclusion complex and demonstrate the necessity of the precipitation method used to guarantee the interaction between β-CD and essential oils. The slow loss of the volatile compounds from both essential oils, when complexed with β-CD, showed a higher stability when compared with their physical mixtures and free essential oils. Therefore, the results showed that the chemical composition, molecular size, and structure of the essential oils influence the characteristics of the inclusion complexes. The application of the β-CD in the formation of inclusion complexes with essential oils can expand the potential applications in foods. © 2017 Institute of Food Technologists®.

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

NASA Astrophysics Data System (ADS)

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

2004-01-01

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

Double-Layer Gadolinium Zirconate/Yttria-Stabilized Zirconia Thermal Barrier Coatings Deposited by the Solution Precursor Plasma Spray Process

NASA Astrophysics Data System (ADS)

Jiang, Chen; Jordan, Eric H.; Harris, Alan B.; Gell, Maurice; Roth, Jeffrey

2015-08-01

Advanced thermal barrier coatings (TBCs) with lower thermal conductivity, increased resistance to calcium-magnesium-aluminosilicate (CMAS), and improved high-temperature capability, compared to traditional yttria-stabilized zirconia (YSZ) TBCs, are essential to higher efficiency in next generation gas turbine engines. Double-layer rare-earth zirconate/YSZ TBCs are a promising solution. From a processing perspective, solution precursor plasma spray (SPPS) process with its unique and beneficial microstructural features can be an effective approach to obtaining the double-layer microstructure. Previously durable low-thermal-conductivity YSZ TBCs with optimized layered porosity, called the inter-pass boundaries (IPBs) were produced using the SPPS process. In this study, an SPPS gadolinium zirconate (GZO) protective surface layer was successfully added. These SPPS double-layer TBCs not only retained good cyclic durability and low thermal conductivity, but also demonstrated favorable phase stability and increased surface temperature capabilities. The CMAS resistance was evaluated with both accumulative and single applications of simulated CMAS in isothermal furnaces. The double-layer YSZ/GZO exhibited dramatic improvement in the single application, but not in the continuous one. In addition, to explore their potential application in integrated gasification combined cycle environments, double-layer TBCs were tested under high-temperature humidity and encouraging performance was recorded.

Thermal Performance Study of Composite Phase Change Material with Polyacrylicand Conformal Coating.

PubMed

Kee, Shin Yiing; Munusamy, Yamuna; Ong, Kok Seng; Cornelis Metselaar, Hendrik Simon; Chee, Swee Yong; Lai, Koon Chun

2017-07-28

The composite PCM was prepared by blending polymethyl methacrylate (PMMA) and myristic acid (MA) in different weight percentages. The MA and PMMA were selected as PCM and supporting material, respectively. As liquid MA may leak out during the phase transition, this study proposes the use of two coatings, namely a polyacrylic coating and a conformal coating to overcome the leakage problem. Both coatings were studied in terms of the leakage test, chemical compatibility, thermal stability, morphology, and reliability. No leakage was found in the PCMs with coatings compared to those without under the same proportions of MA/PMMA, thus justifying the use of coatings in the present study. The chemically compatibility was confirmed by FTIR spectra: the functional groups of PCMs were in accordance with those of coatings. DSC showed that the coatings did not significantly change the melting and freezing temperatures, however, they improved the thermal stability of composite PCMs as seen in TGA analysis. Furthermore, the composite PCMs demonstrated good thermal reliability after 1000 times thermal cycling. The latent heat of melting reduced by only 0.16% and 1.02% for the PCMs coated with conformal coating and polyacrylic coating, respectively. Therefore, the proposed coatings can be considered in preparing fatty acid/PMMA blends attributed to the good stability, compatibility and leakage prevention.

High Reynolds Number Thermal Stability Experiments

NASA Technical Reports Server (NTRS)

Emens, Jessica M.; Brown, Sarah P.; Frederick Robert A., Jr.; Wood, A. John

2004-01-01

This work represents preliminary thermal stability results for liquid hydrocarbon fuels. High Reynolds Number Thermal Stability experiments with Jet A and RP-1 resulted in a quantitative measurement of the thermal stability. Each fuel flowed through a heated capillary tube that held the outlet temperature at 290 C. An optical pyrometer measured the surface temperature of the tube at 12 locations as a function of time. The High Reynolds Number Thermal Stability number was then determined using standards published by the American Society for Testing and Materials. The results for Jet A showed lower thermal stability than similar tests conducted at another facility. The RP-1 results are the first reported using this technique. Because the temperature rise on the capillary tube during testing for the RP-1 fuels was not significant, a new standard for the testing conditions should be developed for these types of fuels.

Thermal properties of oil palm nano filler/kenaf reinforced epoxy hybrid nanocomposites

NASA Astrophysics Data System (ADS)

Saba, N.; Paridah, M. T.; Abdan, K.; Ibrahim, N. A.

2016-11-01

The aim of this research study was to fabricate nano oil palm empty fruit bunch (OPEFB)/kenaf/epoxy hybrid nanocomposites and to make comparative study on the thermal properties of nano OPEFB/kenaf/epoxy hybrid nanocomposites with the montmorillonite (MMT)/kenaf/epoxy hybrid nanocomposites and organically modified MMT (OMMT)/kenaf/epoxy hybrid nanocomposites. Epoxy based kenaf hybrid nanocomposites was prepared by dispersing the nano filler (nano OPEFB filler, MMT, OMMT) at 3% loading through high speed mechanical stirrer followed by hand lay-up technique. Thermal properties of hybrid nanocomposites were analyzed through thermogravimetry analyzer (TGA), and differential scanning calorimetry (DSC). Obtained results specified that addition of nano OPEFB filler improves the thermal stability and char yield of kenaf/epoxy composites. Furthermore, the increase in decomposition temperature by the nano OPEFB filler was quite comparable to the MMT/kenaf/epoxy but relatively less than OMMT/kenaf/epoxy hybrid nanocomposites. We concluded from overall consequences that the nano OPEFB filler can be used as the promising and innovative alternative of existing expensive nano filler, with relatively lesser impact on the environment having marked pronounced impact on the construction, automotive, aerospace, electronics and semiconducting sectors as future industries based on bio-wastes with satisfactory light weight and thermal stability on other side.

Li3PO4 surface coating on Ni-rich LiNi0.6Co0.2Mn0.2O2 by a citric acid assisted sol-gel method: Improved thermal stability and high-voltage performance

NASA Astrophysics Data System (ADS)

Lee, Suk-Woo; Kim, Myeong-Seong; Jeong, Jun Hui; Kim, Dong-Hyun; Chung, Kyung Yoon; Roh, Kwang Chul; Kim, Kwang-Bum

2017-08-01

A surface coating of Li3PO4 was applied to a Ni-rich LiNi0.6Co0.2Mn0.2O2 (NCM) material to improve its thermal stability and electrochemical properties via a citric acid assisted sol-gel method. The addition of citric acid effectively suppressed the instant formation of Li3PO4 in solution, resulting in successful coating of the NCM surface. The improved thermal stability of NCM after Li3PO4 surface coating was demonstrated by differential scanning calorimetry (DSC) analysis and in situ time-resolved X-ray diffraction (TR-XRD). In particular, the TR-XRD results showed that the improved thermal stability after Li3PO4 surface coating originates from suppression of the phase transition of charged NCM at high temperatures. Furthermore, the charge-discharge tests demonstrated that Li3PO4-coated LiNi0.6Co0.2Mn0.2O2 (LP-NCM) has excellent electrochemical properties. LP-NCM exhibited a specific capacity of 192.7 mAh g-1, a capacity retention of 44.1% at 10 C, and a capacity retention of 79.7% after 100 cycles at a high cut-off voltage of 4.7 V; these values represent remarkably improved electrochemical properties compared with those of bare NCM. These improved thermal and electrochemical properties were mainly attributed to the improvement of the structural stability of the material and the suppression of the interface reaction between the cathode and the electrolyte owing to the Li3PO4 coating.

Thermal Stability of Goethite-Bound Natural Organic Matter Is Impacted by Carbon Loading.

PubMed

Feng, Wenting; Klaminder, Jonatan; Boily, Jean-François

2015-12-24

Dissolved natural organic matter (NOM) sorption at mineral surfaces can significantly affect the persistence of organic carbon in soils and sediments. Consequently, determining the mechanisms that stabilize sorbed NOM is crucial for predicting the persistence of carbon in nature. This study determined the effects of loadings and pH on the thermal stability of NOM associated with synthetic goethite (α-FeOOH) particle surfaces, as a proxy for NOM-mineral interactions taking place in nature. NOM thermal stability was investigated using temperature-programmed desorption (TPD) in the 30-700 °C range to collect vibration spectra of thermally decomposing goethite-NOM assemblages, and to concomitantly analyze evolved gases using mass spectrometry. Results showed that NOM thermal stability, indicated by the range of temperatures in which CO2 evolved during thermal decomposition, was greatest in unbound NOM and lowest when NOM was bound to goethite. NOM thermal stability was also loading dependent. It decreased when loadings were in increased the 0.01 to 0.42 mg C m(-2) range, where the upper value corresponds to a Langmuirian adsorption maximum. Concomitant Fourier transform infrared (FTIR) spectroscopy measurement showed that these lowered stabilities could be ascribed to direct NOM-goethite interactions that dominated the NOM binding environment. Mineral surface interactions at larger loadings involved, on the contrary, a smaller fraction of the sorbed NOM, thus increasing thermal stability toward that of its unbound counterpart. This study thus identifies a sorption threshold below which NOM sorption to goethite decreases NOM thermal stability, and above which no strong effects are manifested. This should likely influence the fate of organic carbon exposed to thermal gradients in natural environments.

Lithium silicide nanocrystals: synthesis, chemical stability, thermal stability, and carbon encapsulation.

PubMed

Cloud, Jacqueline E; Wang, Yonglong; Li, Xuemin; Yoder, Tara S; Yang, Yuan; Yang, Yongan

2014-10-20

Lithium silicide (LixSi) is the lithiated form of silicon, one of the most promising anode materials for the next generation of lithium-ion batteries (LIBs). In contrast to silicon, LixSi has not been well studied. Herein we report a facile high-energy ball-milling-based synthesis of four phase-pure LixSi (x = 4.4, 3.75, 3.25, and 2.33), using hexane as the lubricant. Surprisingly, the obtained Li3.75Si phase shows significant downward shifts in all X-ray diffraction peak positions, compared with the standard. Our interpretation is that the high-energy ball-mill-synthesized Li3.75Si presents smaller internal pressures and larger lattice constants. The chemical-stability study reveals that only surface reactions occur after Li4.4Si and Li3.75Si are immersed in several battery-assembly-related chemicals. The thermal-stability study shows that Li4.4Si is stable up to 350 °C and Li3.75Si is stable up to 200 °C. This remarkable thermal stability of Li3.75Si is in stark contrast to the long-observed metastability for electrochemically synthesized Li3.75Si. The carbon encapsulation of Li4.4Si has also been studied for its potential applications in LIBs.

Use of thermal analysis techniques (TG-DSC) for the characterization of diverse organic municipal waste streams to predict biological stability prior to land application

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

Fernandez, Jose M., E-mail: joseman@sas.upenn.edu; Plaza, Cesar; Polo, Alfredo

2012-01-15

Highlights: Black-Right-Pointing-Pointer Thermal analysis was used to assess stability and composition of organic matter in three diverse municipal waste streams. Black-Right-Pointing-Pointer Results were compared with C mineralization during 90-day incubation, FTIR and {sup 13}C NMR. Black-Right-Pointing-Pointer Thermal analysis reflected the differences between the organic wastes before and after the incubation. Black-Right-Pointing-Pointer The calculated energy density showed a strong correlation with cumulative respiration. Black-Right-Pointing-Pointer Conventional and thermal methods provide complimentary means of characterizing organic wastes. - Abstract: The use of organic municipal wastes as soil amendments is an increasing practice that can divert significant amounts of waste from landfill, and providesmore » a potential source of nutrients and organic matter to ameliorate degraded soils. Due to the high heterogeneity of organic municipal waste streams, it is difficult to rapidly and cost-effectively establish their suitability as soil amendments using a single method. Thermal analysis has been proposed as an evolving technique to assess the stability and composition of the organic matter present in these wastes. In this study, three different organic municipal waste streams (i.e., a municipal waste compost (MC), a composted sewage sludge (CS) and a thermally dried sewage sludge (TS)) were characterized using conventional and thermal methods. The conventional methods used to test organic matter stability included laboratory incubation with measurement of respired C, and spectroscopic methods to characterize chemical composition. Carbon mineralization was measured during a 90-day incubation, and samples before and after incubation were analyzed by chemical (elemental analysis) and spectroscopic (infrared and nuclear magnetic resonance) methods. Results were compared with those obtained by thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. Total amounts of CO{sub 2} respired indicated that the organic matter in the TS was the least stable, while that in the CS was the most stable. This was confirmed by changes detected with the spectroscopic methods in the composition of the organic wastes due to C mineralization. Differences were especially pronounced for TS, which showed a remarkable loss of aliphatic and proteinaceous compounds during the incubation process. TG, and especially DSC analysis, clearly reflected these differences between the three organic wastes before and after the incubation. Furthermore, the calculated energy density, which represents the energy available per unit of organic matter, showed a strong correlation with cumulative respiration. Results obtained support the hypothesis of a potential link between the thermal and biological stability of the studied organic materials, and consequently the ability of thermal analysis to characterize the maturity of municipal organic wastes and composts.« less

Thermally Stabilized Transmit/Receive Modules

NASA Technical Reports Server (NTRS)

Hoffman, James; DelCastillo, Linda; Miller, Jennifer; Birur, Gaj

2011-01-01

RF-hybrid technologies enable smaller packaging and mass reduction in radar instruments, especially for subsystems with dense electronics, such as electronically steered arrays. We are designing thermally stabilized RF-hybrid T/R modules using new materials for improved thermal performance of electronics. We are combining advanced substrate and housing materials with a thermal reservoir material, and develop new packaging techniques to significantly improve thermal-cycling reliability and performance stability over temperature.

Development of polyisocyanurate pour foam formulation for space shuttle external tank thermal protection system. Final technical report, March 1986-October 1987

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

Harvey, J.A.; Butler, J.M.; Chartoff, R.P.

1988-08-01

Four commercially available polyisocyanurate polyurethane spray-foam insulation formulations are used to coat the external tank of the space shuttle. There are several problems associated with these formulations. For example, some do not perform well as pourable closeout/repair systems. Some do not perform well at cryogenic temperatures (poor adhesion to aluminum at liquid nitrogen temperatures). Their thermal stability at elevated temperatures is not adequate. A major defect in all the systems is the lack of detailed chemical information. The formulations are simply supplied to NASA and Martin Marietta, the primary contractor, as components; Part A (isocyanate) and Part B (poly(s) andmore » additives). Because of the lack of chemical information the performance behavior data for the current system, NASA sought the development of a non-proprietary room temperature curable foam insulation. Requirements for the developed system were that it should exhibit equal or better thermal stability both at elevated and cryogenic temperatures with better adhesion to aluminum as compared to the current system. Several formulations were developed that met these requirements, i.e., thermal stability, good pourability, and good bonding to aluminum.« less

Comparative study of the conformational lock, dissociative thermal inactivation and stability of euphorbia latex and lentil seedling amine oxidases.

PubMed

Amani, M; Moosavi-Movahedi, A A; Floris, G; Longu, S; Mura, A; Moosavi-Nejad, S Z; Saboury, A A; Ahmad, F

2005-04-01

The thermal stability of copper/quinone containing amine oxidases from Euphorbia characias latex (ELAO) and lentil seedlings (LSAO) was measured in 100 mM potassium phosphate buffer (pH 7.0) following changes in absorbance at 292 nm. ELAO was shown to be about 10 degrees C more stable than LSAO. The dissociative thermal inactivation of ELAO was studied using putrescine as substrate at different temperatures in the range 47-70 degrees C, and a "conformational lock" was developed using the theory pertaining to oligomeric enzyme. Moreover ELAO was shown to be more stable towards denaturants than LSAO, as confirmed by dodecyl trimethylammonium bromide denaturation curves. A comparison of the numbers of contact sites in inter-subunits of ELAO relative to LSAO led us to conclude that the higher stability of ELAO to temperature and towards denaturants was due to the presence of larger number of contact sites in the conformational lock of the enzyme. This study also gives a putative common mechanism for thermal inactivation of amine oxidases and explains the importance of C-terminal conserved amino acids residues in this class of enzymes.

Thermal-stability studies of electrode materials for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Jiang, Junwei

2005-07-01

The thermal stability of lithium-ion batteries has recently attracted attention for two major reasons. (1) Attempts to make large-size cells used in power tools, E-bikes and EVs. Large cells have lower surface area to volume ratios and hence heat dissipation is more problematic than 18650-size cells. Safety problems, therefore, for large cells are more serious. (2) Next generation high-capacity electrodes will increase the energy density of lithium-ion cells meaning even an 18650-size cell may face safety concerns. This thesis presents studies of the thermal stability of electrode materials in electrolytes to understand their reactivity. A search for new positive electrode materials with high thermal stability was made. The thermal stability of two common electrode materials (Li0.81 C6 and Li0.5CoO2) in lithium-ion cells was studied by Accelerating Rate Calorimeter (ARC). Li0.81C 6 has much lower reactivity with lithium bis(oxalato)borate (LiBOB) electrolyte compared to LiPF6 electrolyte. It is not the case, however, for Li0.5CoO2. Oven tests of full LiCoO 2/C 18650-size cells with LiBOB or LiPF6 electrolytes, confirmed the ARC results. ARC was then used to study the reactivity of existing electrode materials. The thermal stability of a negative electrode material was found to increase with the binding energy of Li atoms hosted in the material. Li0.5VO 2 (B) has a higher lithium binding energy (2.45 eV vs. Li) than Li 0.81C6 (0.1 eV vs. Li) and Li7Ti5O 12 (1.55 eV) and it shows the highest thermal stability in EC/DEC among the three materials. The reactivity of two existing positive electrode materials, LiMn2O4 and LiFePO4, was studied. Cell systems expected to be highly tolerant to thermal abuse were suggested: LiFePO 4/C or Li4Ti5O12 in LiBOB electrolytes. The system, x Li[Ni1/2Mn1/2]O2 • y LiCoO2 • z Li[Li1/3Mn2/3]O2 (x + y + z = 1), was explored for new positive electrode materials with large capacity and high thermal stability. Li[(Ni0.5Mn0.5) xCo1-x]O2 (0.4 ≤ x ≤ 0.7) samples have excellent electrochemical properties and thermal stability and are being commercialized by industry. Li[(Ni0.5Mn0.5)xCo y(Li1/3Mn2/3)z]O2 (1/12 ≤ y ≤ 1/4, 1/6 ≤ z ≤ 1/3) samples have high specific capacity (200 mA h g-1), excellent cycling performance, and are safer than LiCoO2. The materials are suggested for energy cells used in cell phones, laptops, and so on.

Analysis of curing process and thermal properties of phenol-urea-formaldehyde cocondensed resins

Treesearch

Bunchiro Tomita; Masahiko Ohyama; Atsushi Itoh; Kiyoto Doi; Chung-Yun Hse

1994-01-01

The curing processes of resols, urea-formaldehyde (UF) resins, their mechanical blends, and phenol-urea cocondensed resins, as well as the reaction of 2,4,6-trimethylolphenol with urea were investiiated with the torsional braid analysis method. The thermal stabilities of these resins after curing also were compared. The results were as follows: (1) In the curing...

Effect of polyethylene glycol conjugation on conformational and colloidal stability of a monoclonal antibody antigen-binding fragment (Fab').

PubMed

Roque, Cristopher; Sheung, Anthony; Rahman, Nausheen; Ausar, S Fernando

2015-02-02

We have investigated the effects of site specific "hinge" polyethylene glycol conjugation (PEGylation) on thermal, pH, and colloidal stability of a monoclonal antibody antigen-binding fragment (Fab') using a variety of biophysical techniques. The results obtained by circular dichroism (CD), ultraviolet (UV) absorbance, and fluorescence spectroscopy suggested that the physical stability of the Fab' is maximized at pH 6-7 with no apparent differences due to PEGylation. Temperature-induced aggregation experiments revealed that PEGylation was able to increase the transition temperature, as well as prevent the formation of visible and subvisible aggregates. Statistical comparison of the three-index empirical phase diagram (EPD) revealed significant differences in thermal and pH stability signatures between Fab' and PEG-Fab'. Upon mechanical stress, micro-flow imaging (MFI) and measurement of the optical density at 360 nm showed that the PEG-Fab' had significantly higher resistance to surface-induced aggregation compared to the Fab'. Analysis of the interaction parameter, kD, indicated repulsive intermolecular forces for PEG-Fab' and attractive forces for Fab'. In conclusion, PEGylation appears to protect Fab' against thermal and mechanical stress-induced aggregation, likely due to a steric hindrance mechanism.

Flexible, High-Wettability and Fire-Resistant Separators Based on Hydroxyapatite Nanowires for Advanced Lithium-Ion Batteries.

PubMed

Li, Heng; Wu, Dabei; Wu, Jin; Dong, Li-Ying; Zhu, Ying-Jie; Hu, Xianluo

2017-11-01

Separators play a pivotal role in the electrochemical performance and safety of lithium-ion batteries (LIBs). The commercial microporous polyolefin-based separators often suffer from inferior electrolyte wettability, low thermal stability, and severe safety concerns. Herein, a novel kind of highly flexible and porous separator based on hydroxyapatite nanowires (HAP NWs) with excellent thermal stability, fire resistance, and superior electrolyte wettability is reported. A hierarchical cross-linked network structure forms between HAP NWs and cellulose fibers (CFs) via hybridization, which endows the separator with high flexibility and robust mechanical strength. The high thermal stability of HAP NW networks enables the separator to preserve its structural integrity at temperatures as high as 700 °C, and the fire-resistant property of HAP NWs ensures high safety of the battery. In particular, benefiting from its unique composition and highly porous structure, the as-prepared HAP/CF separator exhibits near zero contact angle with the liquid electrolyte and high electrolyte uptake of 253%, indicating superior electrolyte wettability compared with the commercial polyolefin separator. The as-prepared HAP/CF separator has unique advantages of superior electrolyte wettability, mechanical robustness, high thermal stability, and fire resistance, thus, is promising as a new kind of separator for advanced LIBs with enhanced performance and high safety. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Trehalose delays the reversible but not the irreversible thermal denaturation of cutinase.

PubMed

Baptista, R P; Cabral, J M; Melo, E P

2000-12-20

The effect of trehalose (0.5 M) on the thermal stability of cutinase in the alkaline pH range was studied. The thermal unfolding induced by increasing temperature was analyzed in the absence and in the presence of trehalose according to a two-state model (which assumes that only the folded and unfolded states of cutinase were present). Trehalose delays the reversible unfolding. The midpoint temperature of the unfolding transition (Tm) increases by 4.0 degrees C and 2. 6 degrees C at pH 9.2 and 10.5, respectively, in the presence of trehalose. At pH 9.2 the thermal unfolding occurs at higher temperatures (Tm is 52.6 degrees C compared to 42.0 degrees C at pH 10.5) and a refolding yield of around 80% was obtained upon cooling. This pH value was chosen to study the irreversible inactivation (long-term stability) of cutinase. Temperatures in the transition range from folded to unfolded state were selected and the rate constants of irreversible inactivation determined. Inactivation followed first-order kinetics and trehalose reduced the observed rate constants of inactivation, pointing to a stabilizing effect on the irreversible inactivation step of thermal denaturation. However, if the contribution of reversible unfolding on the irreversible inactivation of cutinase was taken into account, i.e., considering the fraction of cutinase molecules in the reversible unfolded conformation, the intrinsic rate constants can be calculated. Based on the intrinsic rate constants it was concluded that trehalose does not delay the irreversible inactivation. This conclusion was further supported by comparing the activation energy of the irreversible inactivation in the absence and in the presence of trehalose. The apparent activation energy in the absence and in the presence of trehalose were 67 and 99 Kcal/mol, respectively. The activation energy calculated from intrinsic rate constants was higher in the absence (30 Kcal/mol) than in the presence of trehalose (16 Kcal/mol), showing that kinetics of the irreversible inactivation step increased in the presence of trehalose. In fact, trehalose stabilized only the reversible step of thermal denaturation of cutinase.

Formulation/cure technology for ultrahigh molecular weight silphenylene-siloxane polymers

NASA Technical Reports Server (NTRS)

Hundley, N. H.; Patterson, W. J.

1985-01-01

Molecular weights above one million were achieved for methylvinylsilphenylene-siloxane terpolymers using a two-stage polymerization technique which was successfully scaled up to 200 grams. The resulting polymer was vulcanized by two different formulations and compared to an identically formulated commercial methylvinyl silicone on the basis of ultimate strength, Young's modulus, percent elongation at failure, and tear strength. Relative thermal/oxidative stabilities of the elastomers were assessed by gradient and isothermal thermogravimetric analyses performed in both air and nitrogen. The experimental elastomer exhibited enhanced thermal/oxidative stability and possed equivalent or superior mechanical properties. The effect of variations in prepolymer molecular weight on mechanical properties was also investigated.

Effect of α-damage on fission-track annealing in zircon

USGS Publications Warehouse

Kasuya, Masao; Naeser, Charles W.

1988-01-01

The thermal stability of confined fission-track lengths in four zircon samples having different spontaneous track densities (i.e., different amounts of ??-damage) has been studied by one-hour isochronal annealing experiments. The thermal stability of spontaneous track lengths is independent of initial spontaneous track density. The thermal stability of induced track lengths in pre-annealed zircon, however, is significantly higher than that of spontaneous track lengths. The results indicate that the presence of ??-damage lowers the thermal stability of fission-tracks in zircon.

Molecular insights into the mechanism of thermal stability of actinomycete mannanase.

PubMed

Kumagai, Yuya; Uraji, Misugi; Wan, Kun; Okuyama, Masayuki; Kimura, Atsuo; Hatanaka, Tadashi

2016-09-01

Streptomyces thermolilacinus mannanase (StMan), which requires Ca(2+) for its enhanced thermal stability and hydrolysis activity, possesses two Ca(2+) -binding sites in loop6 and loop7. We evaluated the function of the Ca(2+) -binding site in loop7 and the hydrogen bond between residues Ser247 in loop6 and Asp279 in loop7. The Ca(2+) -binding in loop7 was involved only in thermal stability. Mutations of Ser247 or Asp279 retained the Ca(2+) -binding ability; however, mutants showed less thermal stability than StMan. Phylogenetic analysis indicated that most glycoside hydrolase family 5 subfamily 8 mannanases could be stabilized by Ca(2+) ; however, the mechanism of StMan thermal stability was found to be quite specific in some actinomycete mannanases. © 2016 Federation of European Biochemical Societies.

Effects of selective fusion on the thermal history of the Moon, Mars, and Venus

USGS Publications Warehouse

Lee, W.H.K.

1968-01-01

A comparative study on the thermal history of the Moon, Mars, and Venus was made by numerical solutions of the heat equation including and excluding selective fusion of silicates. Selective fusion was approximated by melting in a multicomponent system and redistribution of radioactive elements. Effects on selective fusion on the thermal models are (1) lowering (by several hundred degrees centigrade) and stabilizing the internal temperature distribution, and (2) increasing the surface heat-flow. ?? 1968.

Comparative evaluation of the stability of seven-transmembrane microbial rhodopsins to various physicochemical stimuli

NASA Astrophysics Data System (ADS)

Honda, Naoya; Tsukamoto, Takashi; Sudo, Yuki

2017-08-01

Rhodopsins are seven-transmembrane proteins that function as photoreceptors for a variety of biological processes. Their characteristic visible colors make rhodopsins a good model for membrane-embedded proteins. In this study, by utilizing their color changes, we performed comparative studies on the stability of five microbial rhodopsins using the same instruments, procedures and media. As denaturants, we employed four physicochemical stimuli: (i) thermal perturbation, (ii) the water-soluble reagent hydroxylamine, (iii) the detergent sodium dodecyl sulfate, and (iv) the organic solvent ethanol. On the basis of the results, models for stabilization mechanisms in rhodopsins against each stimulus is proposed.

SCD1 thermal design and test result analysis

NASA Technical Reports Server (NTRS)

Cardoso, Humberto Pontes; Muraoka, Issamu; Mantelli, Marcia Barbosa Henriques; Leite, Rosangela M. G.

1990-01-01

The SCD 01 (Satelite de Coleta de Dados 01) is a spin stabilized low Earth orbit satellite dedicated to the collection and distribution of environmental data. It was completely developed at the Brazilian Institute for Space Research (INPE) and is scheduled to be launched in 1992. The SCD 01 passive thermal control design configuration is presented and the thermal analysis results are compared with the temperatures obtained from a Thermal Balance Test. The correlation between the analytical and experimental results is considered very good. Numerical flight simulations show that the thermal control design can keep all the subsystem temperatures within their specified temperature range.

Characterization of nano-clay reinforced phytagel-modified soy protein concentrate resin.

PubMed

Huang, Xiaosong; Netravali, Anil N

2006-10-01

Phytagel and nano-clay particles were used to improve the mechanical and thermal properties and moisture resistance of soy protein concentrate (SPC) resin successfully. SPC and Phytagel were mixed together to form a cross-linked structure. The Phytagel-modified SPC resin (PH-SPC) showed improved tensile strength, modulus, moisture resistance, and thermal stability as compared to the unmodified SPC resin. The incorporation of 40% Phytagel and 20% glycerol led to an overall 340% increase in the tensile strength (over 50 MPa) and approximately 360% increase in the Young's modulus (over 710 MPa) of the SPC resin. Nano-clay was uniformly dispersed into PH-SPC resin to further improve the properties. The PH-SPC (40% Phytagel) resin modified with 7% clay nanoparticles (CPH-SPC) had a modulus of 2.1 GPa and a strength of 72.5 MPa. The dynamic mechanical properties such as storage modulus together with the glass transition temperature of the modified resins were also increased by the addition of clay nanoparticles. The moisture resistance of the CPH-SPC resin was higher as compared to both SPC and PH-SPC resins. The thermal stability of the CPH-SPC resin was seen to be higher as compared to the unmodified SPC.

On the impact of atmospheric thermal stability on the characteristics of nocturnal downslope flows

NASA Astrophysics Data System (ADS)

Ye, Z. J.; Garratt, J. R.; Segal, M.; Pielke, R. A.

1990-04-01

The impacts of background (or ambient) and local atmospheric thermal stabilities, and slope steepness, on nighttime thermally induced downslope flow in meso-β domains (i.e., 20 200 km horizontal extent) have been investigated using analytical and numerical model approaches. Good agreement between the analytical and numerical evaluations was found. It was concluded that: (i) as anticipated, the intensity of the downslope flow increases with increased slope steepness, although the depth of the downslope flow was found to be insensitive to slope steepness in the studied situations; (ii) the intensity of the downslope flow is generally independent of background atmospheric thermal stability; (iii) for given integrated nighttime cooling across the nocturnal boundary layer (NBL), Q s the local atmospheric thermal stability exerts a strong influence on downslope flow behavior: the downslope flow intensity increases when local atmospheric thermal stability increases; and (iv) the downslope flow intensity is proportional to Q s 1/2.

Enhancements in crystallinity, thermal stability, tensile modulus and strength of sisal fibres and their PP composites induced by the synergistic effects of alkali and high intensity ultrasound (HIU) treatments.

PubMed

Krishnaiah, Prakash; Ratnam, Chantara Thevy; Manickam, Sivakumar

2017-01-01

In this investigation, sisal fibres were treated with the combination of alkali and high intensity ultrasound (HIU) and their effects on the morphology, thermal properties of fibres and mechanical properties of their reinforced PP composites were studied. FTIR and FE-SEM results confirmed the removal of amorphous materials such as hemicellulose, lignin and other waxy materials after the combined treatments of alkali and ultrasound. X-ray diffraction analysis revealed an increase in the crystallinity of sisal fibres with an increase in the concentration of alkali. Thermogravimetric results revealed that the thermal stability of sisal fibres obtained with the combination of both alkali and ultrasound treatment was increased by 38.5°C as compared to the untreated fibres. Morphology of sisal fibre reinforced composites showed good interfacial interaction between fibres and matrix after the combined treatment. Tensile properties were increased for the combined treated sisal fibres reinforced PP composites as compared to the untreated and pure PP. Tensile modulus and strength increased by more than 50% and 10% respectively as compared to the untreated sisal fibre reinforced composite. It has been found that the combined treatment of alkali and ultrasound is effective and useful to remove the amorphous materials and hence to improve the mechanical and thermal properties. Copyright © 2016 Elsevier B.V. All rights reserved.

Dimensional stability tests over time and temperature for several low-expansion glass ceramics.

PubMed

Hall, D B

1996-04-01

The dimensional stabilities of five commercially available low-expansion glass ceramics have been measured between -40 °C and +90 °C. Materials tested include Zerodur, Zerodur M, Astrositall, Clearceram 55, and Clearceram 63. With the use of a standardized thermal testing procedure, the thermal expansion, isothermal shrinkage, and hysteresis behavior of the various materials are compared with one another. A detailed comparison of three separate melts of Astrositall, two separate melts of Zerodur, and one melt of Zerodur M indicates that between -40 °C and +90 °C the dimensional stability and uniformity characteristics of two of the melts of Astrositall are somewhat better than those of the other two materials. To my knowledge, this is the first published comparison of data from these glass ceramics taken with identical test procedures.

Thermal stability of gallium arsenide solar cells

NASA Astrophysics Data System (ADS)

Papež, Nikola; Škvarenina, Ľubomír.; Tofel, Pavel; Sobola, Dinara

2017-12-01

This article summarizes a measurement of gallium arsenide (GaAs) solar cells during their thermal processing. These solar cells compared to standard silicon cells have better efficiency and high thermal stability. However, their use is partly limited due to high acquisition costs. For these reasons, GaAs cells are deployed only in the most demanding applications where their features are needed, such as space applications. In this work, GaAs solar cells were studied in a high temperature range within 30-650 °C where their functionality and changes in surface topology were monitored. These changes were recorded using an electron microscope which determined the position of the defects; using an atomic force microscope we determined the roughness of the surface and an infrared camera that showed us the thermal radiated places of the defected parts of the cell. The electrical characteristics of the cells during processing were determined by its current-voltage characteristics. Despite the occurrence of subtle changes on the solar cell with newly created surface features after 300 °C thermal processing, its current-voltage characteristic remained without a significant change.

The effect of α-damage on fission-track annealing in zircon

USGS Publications Warehouse

Kasuya, M.; Naeser, C.W.

1988-01-01

The thermal stability of confined fission-track lengths in four zircon samples having different spontaneous track densities (i.e. different amounts of ??-damage) has been studied by one hour isochronal annealing experiments. The thermal stability of spontaneous track lengths is independent of initial spontaneous track density. The thermal stability of induced track lengths in pre-annealed zircon, however, is significantly higher than that of spontaneous track lengths. The results indicate that the presence of ??-damage lowers the thermal stability of fission-tracks in zircon. ?? 1988.

Structure and Mechanical Properties of Al-Cu-Fe-X Alloys with Excellent Thermal Stability.

PubMed

Školáková, Andrea; Novák, Pavel; Mejzlíková, Lucie; Průša, Filip; Salvetr, Pavel; Vojtěch, Dalibor

2017-11-05

In this work, the structure and mechanical properties of innovative Al-Cu-Fe based alloys were studied. We focused on preparation and characterization of rapidly solidified and hot extruded Al-Cu-Fe, Al-Cu-Fe-Ni and Al-Cu-Fe-Cr alloys. The content of transition metals affects mechanical properties and structure. For this reason, microstructure, phase composition, hardness and thermal stability have been investigated in this study. The results showed exceptional thermal stability of these alloys and very good values of mechanical properties. Alloying by chromium ensured the highest thermal stability, while nickel addition refined the structure of the consolidated alloy. High thermal stability of all tested alloys was described in context with the transformation of the quasicrystalline phases to other types of intermetallics.

Structure and Mechanical Properties of Al-Cu-Fe-X Alloys with Excellent Thermal Stability

PubMed Central

Školáková, Andrea; Novák, Pavel; Mejzlíková, Lucie; Průša, Filip; Salvetr, Pavel; Vojtěch, Dalibor

2017-01-01

In this work, the structure and mechanical properties of innovative Al-Cu-Fe based alloys were studied. We focused on preparation and characterization of rapidly solidified and hot extruded Al-Cu-Fe, Al-Cu-Fe-Ni and Al-Cu-Fe-Cr alloys. The content of transition metals affects mechanical properties and structure. For this reason, microstructure, phase composition, hardness and thermal stability have been investigated in this study. The results showed exceptional thermal stability of these alloys and very good values of mechanical properties. Alloying by chromium ensured the highest thermal stability, while nickel addition refined the structure of the consolidated alloy. High thermal stability of all tested alloys was described in context with the transformation of the quasicrystalline phases to other types of intermetallics. PMID:29113096

Low thermal budget annealing technique for high performance amorphous In-Ga-ZnO thin film transistors

NASA Astrophysics Data System (ADS)

Shin, Joong-Won; Cho, Won-Ju

2017-07-01

In this paper, we investigate a low thermal budget post-deposition-annealing (PDA) process for amorphous In-Ga-ZnO (a-IGZO) oxide semiconductor thin-film-transistors (TFTs). To evaluate the electrical characteristics and reliability of the TFTs after the PDA process, microwave annealing (MWA) and rapid thermal annealing (RTA) methods were applied, and the results were compared with those of the conventional annealing (CTA) method. The a-IGZO TFTs fabricated with as-deposited films exhibited poor electrical characteristics; however, their characteristics were improved by the proposed PDA process. The CTA-treated TFTs had excellent electrical properties and stability, but the CTA method required high temperatures and long processing times. In contrast, the fabricated RTA-treated TFTs benefited from the lower thermal budget due to the short process time; however, they exhibited poor stability. The MWA method uses a low temperature (100 °C) and short annealing time (2 min) because microwaves transfer energy directly to the substrate, and this method effectively removed the defects in the a-IGZO TFTs. Consequently, they had a higher mobility, higher on-off current ratio, lower hysteresis voltage, lower subthreshold swing, and higher interface trap density than TFTs treated with CTA or RTA, and exhibited excellent stability. Based on these results, low thermal budget MWA is a promising technology for use on various substrates in next generation displays.

Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb Sounder

NASA Technical Reports Server (NTRS)

Cofield, Richard E.; Kasl, Eldon P.

2011-01-01

The Scanning Microwave Limb Sounder (SMLS) is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission in [180,680] GHz. SMLS, planned for the NRC Decadal Survey's Global Atmospheric Composition Mission, uses a novel toric Cassegrain antenna to perform both elevation and azimuth scanning. This provides better horizontal and temporal resolution and coverage than were possible with elevation-only scanning in the two previous MLS satellite instruments. SMLS is diffraction-limited in the vertical plane but highly astigmatic in the horizontal (beam aspect ratio approx. 1:20). Nadir symmetry ensures that beam shape is nearly invariant over plus or minus 65 deg azimuth. A low-noise receiver FOV is swept over the reflector system by a small azimuth-scanning mirror. We describe the fabrication and thermal-stability test of a composite demonstration primary reflector, having full 4m height and 1/3 the width planned for flight. Using finite-element models of reflectors and structure, we evaluate thermal deformations and optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during soak tests in a chamber. The test temperature range exceeds predicted orbital ranges by large factors, implying in-orbit thermal stability of 0.21 micron rms (root mean square)/C, which meets SMLS requirements.

Glucose oxidase stabilization against thermal inactivation using high hydrostatic pressure and hydrophobic modification.

PubMed

Halalipour, Ali; Duff, Michael R; Howell, Elizabeth E; Reyes-De-Corcuera, José I

2017-03-01

High hydrostatic pressure (HHP) stabilized glucose oxidase (GOx) against thermal inactivation. The apparent first-order kinetics of inactivation of GOx were investigated at 0.1-300 MPa and 58.8-80.0°C. At 240 MPa and 74.5°C, GOx inactivated at a rate 50 times slower than at atmospheric pressure at the same temperature. The apparent activation energy of inactivation at 300 MPa was 281.0 ± 17.4 kJ mol -1 or 1.3-fold smaller than for the inactivation at atmospheric pressure (378.1 ± 25.6 kJ mol -1 ). The stabilizing effect of HHP was greatest at 74.5°C, where the activation volume of 57.0 ± 12.0 cm 3  mol -1 was highest compared to all other studied temperatures. Positive apparent activation volumes for all the treatment temperatures confirmed that HHP favors GOx stabilization. A second approach to increase GOx stability involved crosslinking with N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride (EDC) and either aniline or benzoate. The modified enzyme remained fully active with only slight increases in K M (1.3-1.9-fold increases for aniline and benzoate modification, respectively). The thermal stability of GOx increased by 8°C with aniline modification, while it decreased by 0.9°C upon modification with benzoate. Biotechnol. Bioeng. 2017;114: 516-525. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

Gelation and thermal characteristics of microwave extracted fish gelatin-natural gum composite gels.

PubMed

Binsi, P K; Nayak, Natasha; Sarkar, P C; Joshy, C G; Ninan, George; Ravishankar, C N

2017-02-01

In this study, the gelation and thermal characteristics of microwave extracted fish scale gelatin blended with natural gums such as gum arabic (AG), xanthan gum (XG), guar gum (GG), and tragacanth gum (TG) was evaluated. The nature of interaction and behavior of gelatin in presence of various gums was confirmed by particle size analysis, viscosity profile, FT-IR analysis and turbidity measurements. DSC data revealed that addition of AG, TG and GG remarkably improved the thermal stability of fish gelatin gel. The composite gels of TG, AG, and XG exhibited higher hardness and bloom strength values as compared to pure fish gelatin implying its textural synergy. Based on qualitative descriptive analysis, TG was found to be superior in improving the stability of fish gelatin gel, closely followed by AG. The results suggest that addition of these gums can reduce syneresis and retard melting of gelatin gels at ambient temperature, which are otherwise soft and thermally unstable.

Mechanical Properties of Layered La2Zr2O7 Thermal Barrier Coatings

NASA Astrophysics Data System (ADS)

Guo, Xingye; Li, Li; Park, Hyeon-Myeong; Knapp, James; Jung, Yeon-Gil; Zhang, Jing

2018-04-01

Lanthanum zirconate (La2Zr2O7) has been proposed as a promising thermal barrier coating (TBC) material due to its low thermal conductivity and high stability at high temperatures. In this work, both single and double-ceramic-layer (DCL) TBC systems of La2Zr2O7 and 8 wt.% yttria-stabilized zirconia (8YSZ) were prepared using air plasma spray (APS) technique. The thermomechanical properties and microstructure were investigated. Thermal gradient mechanical fatigue (TGMF) tests were applied to investigate the thermal cycling performance. The results showed that DCL La2Zr2O7 + 8YSZ TBC samples lasted fewer cycles compared with single-layered 8YSZ TBC samples in TGMF tests. This is because DCL La2Zr2O7 TBC samples had higher residual stress during the thermal cycling process, and their fracture toughness was lower than that of 8YSZ. Bond strength test results showed that 8YSZ TBC samples had higher bond strength compared with La2Zr2O7. The erosion rate of La2Zr2O7 TBC samples was higher than that of 8YSZ samples, due to the lower critical erodent velocity and fracture toughness of La2Zr2O7. DCL porous 8YSZ + La2Zr2O7 had a lower erosion rate than other SCL and DCL La2Zr2O7 coatings, suggesting that porous 8YSZ serves as a stress-relief buffer layer.

Fusion of an oligopeptide to the N terminus of an alkaline α-amylase from Alkalimonas amylolytica simultaneously improves the enzyme's catalytic efficiency, thermal stability, and resistance to oxidation.

PubMed

Yang, Haiquan; Lu, Xinyao; Liu, Long; Li, Jianghua; Shin, Hyun-dong; Chen, Rachel R; Du, Guocheng; Chen, Jian

2013-05-01

In this study, we constructed and expressed six fusion proteins composed of oligopeptides attached to the N terminus of the alkaline α-amylase (AmyK) from Alkalimonas amylolytica. The oligopeptides had various effects on the functional and structural characteristics of AmyK. AmyK-p1, the fusion protein containing peptide 1 (AEAEAKAKAEAEAKAK), exhibited improved specific activity, catalytic efficiency, alkaline stability, thermal stability, and oxidative stability compared with AmyK. Compared with AmyK, the specific activity and catalytic constant (kcat) of AmyK-p1 were increased by 4.1-fold and 3.5-fold, respectively. The following properties were also improved in AmyK-p1 compared with AmyK: kcat/Km increased from 1.8 liter/(g·min) to 9.7 liter/(g·min), stable pH range was extended from 7.0 to 11.0 to 7.0 to 12.0, optimal temperature increased from 50°C to 55°C, and the half-life at 60°C increased by ∼2-fold. Moreover, AmyK-p1 showed improved resistance to oxidation and retained 54% of its activity after incubation with H2O2, compared with 20% activity retained by AmyK. Finally, AmyK-p1 was more compatible than AmyK with the commercial solid detergents tested. The mechanisms responsible for these changes were analyzed by comparing the three-dimensional (3-D) structural models of AmyK and AmyK-p1. The significantly enhanced catalytic efficiency and stability of AmyK-p1 suggests its potential as a detergent ingredient. In addition, the oligopeptide fusion strategy described here may be useful for improving the catalytic efficiency and stability of other industrial enzymes.

Fusion of an Oligopeptide to the N Terminus of an Alkaline α-Amylase from Alkalimonas amylolytica Simultaneously Improves the Enzyme's Catalytic Efficiency, Thermal Stability, and Resistance to Oxidation

PubMed Central

Yang, Haiquan; Lu, Xinyao; Li, Jianghua; Shin, Hyun-dong; Chen, Rachel R.; Du, Guocheng

2013-01-01

In this study, we constructed and expressed six fusion proteins composed of oligopeptides attached to the N terminus of the alkaline α-amylase (AmyK) from Alkalimonas amylolytica. The oligopeptides had various effects on the functional and structural characteristics of AmyK. AmyK-p1, the fusion protein containing peptide 1 (AEAEAKAKAEAEAKAK), exhibited improved specific activity, catalytic efficiency, alkaline stability, thermal stability, and oxidative stability compared with AmyK. Compared with AmyK, the specific activity and catalytic constant (kcat) of AmyK-p1 were increased by 4.1-fold and 3.5-fold, respectively. The following properties were also improved in AmyK-p1 compared with AmyK: kcat/Km increased from 1.8 liter/(g·min) to 9.7 liter/(g·min), stable pH range was extended from 7.0 to 11.0 to 7.0 to 12.0, optimal temperature increased from 50°C to 55°C, and the half-life at 60°C increased by ∼2-fold. Moreover, AmyK-p1 showed improved resistance to oxidation and retained 54% of its activity after incubation with H2O2, compared with 20% activity retained by AmyK. Finally, AmyK-p1 was more compatible than AmyK with the commercial solid detergents tested. The mechanisms responsible for these changes were analyzed by comparing the three-dimensional (3-D) structural models of AmyK and AmyK-p1. The significantly enhanced catalytic efficiency and stability of AmyK-p1 suggests its potential as a detergent ingredient. In addition, the oligopeptide fusion strategy described here may be useful for improving the catalytic efficiency and stability of other industrial enzymes. PMID:23455344

Assessment of physical stability of an antibody drug conjugate by higher order structure analysis: impact of thiol- maleimide chemistry.

PubMed

Guo, Jianxin; Kumar, Sandeep; Prashad, Amarnauth; Starkey, Jason; Singh, Satish K

2014-07-01

To provide a systematic biophysical approach towards a better understanding of impact of conjugation chemistry on higher order structure and physical stability of an antibody drug conjugate (ADC). ADC was prepared using thiol-maleimide chemistry. Physical stabilities of ADC and its parent IgG1 mAb were compared using calorimetric, spectroscopic and molecular modeling techniques. ADC and mAb respond differently to thermal stress. Both the melting temperatures and heat capacities are substantially lower for the ADC. Spectroscopic experiments show that ADC and mAb have similar secondary and tertiary structures, but these are more easily destabilized by thermal stress on the ADC indicating reduced conformational stability. Molecular modeling calculations suggest a substantial decrease in the conformational energy of the mAb upon conjugation. The local surface around the conjugation sites also becomes more hydrophobic in the ADC, explaining the lower colloidal stability and greater tendency of the ADC to aggregate. Computational and biophysical analyses of an ADC and its parent mAb have provided insights into impact of conjugation on physical stability and pinpointed reasons behind lower structural stability and increased aggregation propensity of the ADC. This knowledge can be used to design appropriate formulations to stabilize the ADC.

Optoelectronic oscillator with improved phase noise and frequency stability

NASA Astrophysics Data System (ADS)

Eliyahu, Danny; Sariri, Kouros; Taylor, Joseph; Maleki, Lute

2003-07-01

In this paper we report on recent improvements in phase noise and frequency stability of a 10 GHz opto-electronic oscillator. In our OEO loop, the high Q elements (the optical fiber and the narrow bandpass microwave filter) are thermally stabilized using resistive heaters and temperature controllers, keeping their temperature above ambient. The thermally stabilized free running OEO demonstrates a short-term frequency stability of 0.02 ppm (over several hours) and frequency vs. temperature slope of -0.1 ppm/°C (compared to -8.3 ppm/°C for non thermally stabilized OEO). We obtained an exceptional spectral purity with phase noise level of -143 dBc/Hz at 10 kHz of offset frequency. We also describe the multi-loop configuration that reduces dramatically the spurious level at offset frequencies related to the loop round trip harmonic frequency. The multi-loop configuration has stronger mode selectivity due to interference between signals having different cavity lengths. A drop of the spurious level below -90 dBc was demonstrated. The effect of the oscillator aging on the frequency stability was studied as well by recording the oscillator frequency (in a chamber) over several weeks. We observed reversal in aging direction with logarithmic behavior of A ln(B t+1)-C ln(D t+1), where t is the time and A, B, C, D are constants. Initially, in the first several days, the positive aging dominates. However, later the negative aging mechanism dominates. We have concluded that the long-term aging behavioral model is consistent with the experimental results.

Kinetics and thermodynamics of the thermal inactivation and chaperone assisted folding of zebrafish dihydrofolate reductase.

PubMed

Thapliyal, Charu; Jain, Neha; Rashid, Naira; Chaudhuri Chattopadhyay, Pratima

2018-01-01

The maintenance of thermal stability is a major issue in protein engineering as many proteins tend to form inactive aggregates at higher temperatures. Zebrafish DHFR, an essential protein for the survival of cells, shows irreversible thermal unfolding transition. The protein exhibits complete unfolding and loss of activity at 50 °C as monitored by UV-Visible, fluorescence and far UV-CD spectroscopy. The heat induced inactivation of zDHFR follows first-order kinetics and Arrhenius law. The variation in the value of inactivation rate constant, k with increasing temperatures depicts faster inactivation at elevated temperatures. We have attempted to study the chaperoning ability of a shorter variant of GroEL (minichaperone) and compared it with that of conventional GroEL-GroES chaperone system. Both the chaperone system prevented the aggregation and assisted in refolding of zDHFR. The rate of thermal inactivation was significantly retarded in the presence of chaperones which indicate that it enhances the thermal stability of the enzyme. As minichaperone is less complex, and does not require high energy co-factors like ATP, for its function as compared to conventional GroEL-GroES system, it can act as a very good in vitro as well as in vivo chaperone model for monitoring assisted protein folding phenomenon. Copyright © 2017 Elsevier Inc. All rights reserved.

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.

Thermal stability and gel quality of myofibrillar protein as affected by soy protein isolates subjected to an acidic pH and mild heating.

PubMed

Niu, Haili; Xia, Xiufang; Wang, Chao; Kong, Baohua; Liu, Qian

2018-03-01

Thermal stability and gel quality of myofibrillar protein were evaluated with regard to the addition of native soy protein isolates (SPI) and SPI subjected to acidic pH and mild heating (modified SPI). Compared with the control, the addition of modified SPI increased the compression force of the protein gel and decreased water loss (P<0.05). Differential scanning calorimetry results showed that an addition of 0.75% native SPI decreased the first transition temperature (P<0.05), and addition of 0.5% and 0.75% modified SPI exhibited no appreciable changes on it (P>0.05), indicating that a higher concentration of modified SPI would not damage the protein thermal stability. Moreover, the addition of modified SPI enhanced hydrogen bonding and disulphide linkages. Atomic force microscopy analysis revealed that the addition of modified SPI decreased the roughness of the mixed myofibrillar protein gels. Overall, modified SPI has the potential to improve myofibrillar protein gel texture and water holding capacity. Copyright © 2017 Elsevier Ltd. All rights reserved.

Continuous synthesis of peralkylated imidazoles and their transformation into ionic liquids with improved (electro)chemical stabilities.

PubMed

Maton, Cedric; De Vos, Nils; Roman, Bart I; Vanecht, Evert; Brooks, Neil R; Binnemans, Koen; Schaltin, Stijn; Fransaer, Jan; Stevens, Christian V

2012-09-17

A versatile and efficient method to synthesize tetrasubstituted imidazoles via a one-pot modified Debus-Radziszewski reaction and their subsequent transformation into the corresponding imidazolium ionic liquids is reported. The tetrasubstituted imidazoles were also synthesized by means of a continuous flow process. This straightforward synthetic procedure allows for a fast and selective synthesis of tetrasubstituted imidazoles on a large scale. The completely substituted imidazolium dicyanamide and bis(trifluoromethylsulfonyl)imide salts were obtained via a metathesis reaction of the imidazolium iodide salts. The melting points and viscosities are of the same order of magnitude as for their non-substituted analogues. In addition to the superior chemical stability of these novel ionic liquids, which allows them to be applied in strong alkaline media, the improved thermal and electrochemical stabilities of these compounds compared with conventional imidazolium ionic liquids is also demonstrated by thermogravimetrical analysis (TGA) and cyclic voltammetry (CV). Although increased substitution of the ionic liquids does not further increase thermal stability, a definite increase in cathodic stability is observable. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Heat stability of strawberry anthocyanins in model solutions containing natural copigments extracted from rose (Rosa damascena Mill.) petals.

PubMed

Shikov, Vasil; Kammerer, Dietmar R; Mihalev, Kiril; Mollov, Plamen; Carle, Reinhold

2008-09-24

Thermal degradation and color changes of purified strawberry anthocyanins in model solutions were studied upon heating at 85 degrees C by HPLC-DAD analyses and CIELCh measurements, respectively. The anthocyanin half-life values increased significantly due to the addition of rose (Rosa damascena Mill.) petal extracts enriched in natural copigments. Correspondingly, the color stability increased as the total color difference values were smaller for anthocyanins upon copigment addition, especially after extended heating. Furthermore, the stabilizing effect of rose petal polyphenols was compared with that of well-known copigments such as isolated kaempferol, quercetin, and sinapic acid. The purified rose petal extract was found to be a most effective anthocyanin-stabilizing agent at a molar pigment/copigment ratio of 1:2. The results obtained demonstrate that the addition of rose petal polyphenols slows the thermal degradation of strawberry anthocyanins, thus resulting in improved color retention without affecting the gustatory quality of the product.

Comparison between rice husk ash grown in different regions for stabilizing fly ash from a solid waste incinerator.

PubMed

Benassi, L; Bosio, A; Dalipi, R; Borgese, L; Rodella, N; Pasquali, M; Depero, L E; Bergese, P; Bontempi, E

2015-08-15

The Stabilization of heavy metals from municipal solid waste incineration (MSWI) fly ash by rice husk ash (RHA) is under intense study as an effective strategy to recover and reuse industrial and agricultural waste together. We compare the metal entrapment performances of RHA from different Asian rice sources – namely from Japonica rice grown in Italy and Indica rice grown in India – Physicochemical and morphological characterization of the final stabilized material show that the same thermal treatment may result in marked structural differences in the silica contained in the two RHA. Remarkably, one of them displays a crystalline silica content, although obtained by a thermal treatment below 800 °C. We also find that the presence of an alkali metal ion (potassium) in the rice husk plays a crucial role in the attainment of the final silica phase. These physicochemical differences are mirrored by different stabilization yields by the two RHA. Copyright © 2015 Elsevier Ltd. All rights reserved.

The effect of copper, MDA, and accelerated aging on jet fuel thermal stability as measured by the gravimetric JFTOT

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

Pande, S.G.; Hardy, D.R.

1995-05-01

Thermally unstable jet fuels pose operational problems. In order to adequately identify such fuels, factors that realistically impact on thermal stability were examined. Evaluation was based on a quantitative method of measuring thermal stability, viz., NRL`s recently developed gravimetric JFTOT. This method gives a quantitative measurement of both the strip deposit and filterables formed. The pertinent factors examined, included the individual and interactive effects of: soluble copper, MDA (metal deactivator), and aging. The latter was accelerated to simulate field conditions of approximately six months aging at ambient temperature and pressure. The results indicate that the individual and interactive effects ofmore » copper, MDA, and accelerated aging appear to be fuel dependent. Based on the results, the three test fuels examined (one JP-8 and two JP-5s) were categorized as exhibiting very good, typical, and poor thermal stabilities, respectively. For both the very good and poor thermal stability fuels, the effect of copper in conjunction with accelerated aging did not significantly increase the total thermal deposits of the neat fuels. In contrast, for the typical thermal stability fuel, the combined effects of copper and accelerated aging, did. Furthermore, the addition of MDA prior to aging of the copper-doped, typical stability fuel significantly counteracted the adverse effect of copper and aging. A similar beneficial effect of MDA was not observed for the poor stability fuel. These results focus on the compositional differences among fuels and the need to elucidate these differences (physical and chemical) for a better understanding and prediction of their performance.« less

Fuels research: Fuel thermal stability overview

NASA Technical Reports Server (NTRS)

Cohen, S. M.

1980-01-01

Alternative fuels or crude supplies are examined with respect to satisfying aviation fuel needs for the next 50 years. The thermal stability of potential future fuels is discussed and the effects of these characteristics on aircraft fuel systems are examined. Advanced fuel system technology and design guidelines for future fuels with lower thermal stability are reported.

49 CFR 173.65 - Exceptions for Division 1.4G consumer fireworks.

Code of Federal Regulations, 2014 CFR

2014-10-01

...) The device must pass a thermal stability test. The test must be performed by maintaining the device... thermal stability test; (3) The manufacturer of the Division 1.4G consumer firework applies in writing to... thermal stability test; and (iv) Signed certification declaring that the device for which certification is...

49 CFR 173.65 - Exceptions for Division 1.4G consumer fireworks.

Code of Federal Regulations, 2013 CFR

2013-10-01

...) The device must pass a thermal stability test. The test must be performed by maintaining the device... thermal stability test; (3) The manufacturer of the Division 1.4G consumer firework applies in writing to... thermal stability test; and (iv) Signed certification declaring that the device for which certification is...

Effects of Thermal Variability on Broadband Seismometers: Controlled Experiments, Observations, and Implications

NASA Astrophysics Data System (ADS)

Doody, C.; Ringler, A. T.; Anthony, R. E.; Wilson, D.; Holland, A. A.; Hutt, C. R.; Sandoval, L. D.

2017-12-01

Although taking steps to isolate seismic instruments from temperature fluctuations is routine practice within the seismological community, the necessary level of thermal stability required in a broadband installation to avoid generating noise is largely unknown. In order to quantify the temperature sensitivity of seismometers over a broad range of frequencies, we artificially induced local temperature changes on three different models of seismometers to empirically measure the effect of thermal variations on seismometer output. We found that temperature changes above 0.002˚C per day show upwards of 10% change in broadband seismometer amplitude when compared to thermally stable reference measurements. We also find that rises in sensor incoherent self-noise increase with temperature variation; these increases in noise can be modeled as 1/f noise (pink noise). While seismometer output changes that correlate with temperature changes are likely correctable, this increase in 1/f noise is unlikely to be easily corrected for. These experimental results are also compared to data from Global Seismographic Network (GSN)-IRIS/USGS network station TUC (Tucson, Arizona) which is well instrumented with temperature sensors, as well as three different broadband sensors, each of which uses a different method of thermal isolation (i.e. Styrofoam box, 1.2m posthole within the pier, and water bricks). We show that isolating sensors with water bricks, as well as posthole and borehole installations, thermally isolate sensors well enough to remove any thermal variability that would affect their output. We find that better seismometer installations which provide thermal stability below 0.002 ˚C per day could help to improve long-period vertical seismic data across the GSN by decreasing temperature-driven 1/f noise.

Thermal stability of self-assembled peptide vaccine materials.

PubMed

Sun, Tao; Han, Huifang; Hudalla, Gregory A; Wen, Yi; Pompano, Rebecca R; Collier, Joel H

2016-01-01

The majority of current vaccines depend on a continuous "cold chain" of storage and handling between 2 and 8°C. Vaccines experiencing temperature excursions outside this range can suffer from reduced potency. This thermal sensitivity results in significant losses of vaccine material each year and risks the administration of vaccines with diminished protective ability, issues that are heightened in the developing world. Here, using peptide self-assemblies based on the fibril-forming peptide Q11 and containing the epitopes OVA323-339 from ovalbumin or ESAT651-70 from Mycobacterium tuberculosis, the chemical, conformational, and immunological stability of supramolecular peptide materials were investigated. It was expected that these materials would exhibit advantageous thermal stability owing to their adjuvant-free and fully synthetic construction. Neither chemical nor conformational changes were observed for either peptide when stored at 45°C for 7days. ESAT651-70-Q11 was strongly immunogenic whether it was stored as a dry powder or as aqueous nanofibers, showing undiminished immunogenicity even when stored as long as six months at 45°C. This result was in contrast to ESAT651-70 conjugated to a protein carrier and adjuvanted with alum, which demonstrated marked thermal sensitivity in these conditions. Antibody titers and affinities were undiminished in mice for OVA323-339-Q11 if it was stored as assembled nanofibers, yet some diminishment was observed for material stored as a dry powder. The OVA study was done in a different mouse strain and with a different prime/boost regimen, and so it should not be compared directly with the study for the ESAT epitope. This work indicates that peptide self-assemblies can possess attractive thermal stability properties in the context of vaccine development. Almost all current vaccines must be maintained within a tight and refrigerated temperature range, usually between 2 and 8°C. This presents significant challenges for their distribution, especially in the developing world. Here we report on the surprisingly robust thermal stability of a self-assembled peptide vaccine. In particular a self-assembled peptide vaccine containing a tuberculosis epitope maintained all of its potency in mice when exposed to an extreme thermal treatment of six months at 45°C. In a different mouse model, we investigated another model epitope and found some storage conditions where potency was diminished. Overall this study illustrates that some self-assembled peptide vaccines can have remarkable thermal stability. Copyright © 2015 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Spray drying egg using either maltodextrin or nopal mucilage as stabilizer agents.

PubMed

Medina-Torres, L; Calderas, F; Nuñez Ramírez, D M; Herrera-Valencia, E E; Bernad Bernad, M J; Manero, O

2017-12-01

In this work, a comparative study between spray drying (SD) of fresh egg by either maltodextrin (MD) or nopal-mucilage (MN) as stabilizing vectors was made. The powders obtained were characterized for drying performance, moisture content, chemical proximate analysis, thermal analysis (TGA), chemical composition (FTIR), microscopy (SEM) and rheology (viscoelasticity and steady state simple shear viscosity). Infrared analysis showed that MN has the effect of a thickening agent rather than an encapsulating one. Results indicated that SD egg with MN produced a high thermal and mechanical stable product and rendered the highest drying performance, producing a more uniform and defined sphere-shaped morphology in comparison to egg SD either alone and with MD.

Stability of Cholesterol, 7-Ketocholesterol and β-Sitosterol during Saponification: Ramifications for Artifact Monitoring of Sterol Oxide Products.

PubMed

Busch, T P; King, A J

2010-09-01

Cholesterol has been used to monitor artifact generation. Stability differences among cholesterol oxide products (COPs) and cholesterol in thermal and alkaline conditions are theorized. Thus, use of cholesterol may be unsuitable for detection of artifacts generated from COPs. Stability of cholesterol was compared to that of 7-ketocholesterol (7-keto) and β-sitosterol (βS) under various thermal and alkaline saponification conditions: 1 M methanolic KOH for 18 h at 24 °C (1 M18hr24°C, Control), 18 h at 37 °C (1M18hr37°C), 3 h at 45 °C (1M3hr45°C), and 3.6 M methanolic KOH for 3 h at 24 °C (3.6M3hr24°C). Trends indicated that cholesterol in solution was more stable than 7-keto under all conditions. Compared to βS, cholesterol was more stable under all conditions except for 1M18hr37°C for which stabilities were similar. Compounds were more labile in heat than alkalinity. Poor recoveries of 7-keto during cold saponification with high alkalinity were attributed to alkaline instability. 7-Keto, less stable than cholesterol, should be used to monitor artifact generation during screening of various methods that include thermal and alkaline conditions. In a preliminary analysis of turkey meat, more 3,5-7-one was generated from spiking with cholesterol than with 7-keto.

Stability of Cholesterol, 7-Ketocholesterol and β-Sitosterol during Saponification: Ramifications for Artifact Monitoring of Sterol Oxide Products

PubMed Central

Busch, T. P.

2010-01-01

Cholesterol has been used to monitor artifact generation. Stability differences among cholesterol oxide products (COPs) and cholesterol in thermal and alkaline conditions are theorized. Thus, use of cholesterol may be unsuitable for detection of artifacts generated from COPs. Stability of cholesterol was compared to that of 7-ketocholesterol (7-keto) and β-sitosterol (βS) under various thermal and alkaline saponification conditions: 1 M methanolic KOH for 18 h at 24 °C (1 M18hr24°C, Control), 18 h at 37 °C (1M18hr37°C), 3 h at 45 °C (1M3hr45°C), and 3.6 M methanolic KOH for 3 h at 24 °C (3.6M3hr24°C). Trends indicated that cholesterol in solution was more stable than 7-keto under all conditions. Compared to βS, cholesterol was more stable under all conditions except for 1M18hr37°C for which stabilities were similar. Compounds were more labile in heat than alkalinity. Poor recoveries of 7-keto during cold saponification with high alkalinity were attributed to alkaline instability. 7-Keto, less stable than cholesterol, should be used to monitor artifact generation during screening of various methods that include thermal and alkaline conditions. In a preliminary analysis of turkey meat, more 3,5-7-one was generated from spiking with cholesterol than with 7-keto. PMID:20835297

Thermal stability analysis and modelling of advanced perpendicular magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Van Beek, Simon; Martens, Koen; Roussel, Philippe; Wu, Yueh Chang; Kim, Woojin; Rao, Siddharth; Swerts, Johan; Crotti, Davide; Linten, Dimitri; Kar, Gouri Sankar; Groeseneken, Guido

2018-05-01

STT-MRAM is a promising non-volatile memory for high speed applications. The thermal stability factor (Δ = Eb/kT) is a measure for the information retention time, and an accurate determination of the thermal stability is crucial. Recent studies show that a significant error is made using the conventional methods for Δ extraction. We investigate the origin of the low accuracy. To reduce the error down to 5%, 1000 cycles or multiple ramp rates are necessary. Furthermore, the thermal stabilities extracted from current switching and magnetic field switching appear to be uncorrelated and this cannot be explained by a macrospin model. Measurements at different temperatures show that self-heating together with a domain wall model can explain these uncorrelated Δ. Characterizing self-heating properties is therefore crucial to correctly determine the thermal stability.

Thermal design and test results for SUNLITE ultra-stable reference cavity

NASA Technical Reports Server (NTRS)

Amundsen, Ruth M.

1991-01-01

SUNLITE (Stanford University-NASA Laser In-Space Technology Experiment) is a space-based experiment which uses a reference cavity to provide a stable frequency reference for a terahertz laser oscillator. Thermal stability of the cavity is a key factor in attaining a stable narrow-linewidth laser beam. The mount which is used to support and align the cavity will provide thermal isolation from the environment. The baseline requirement for thermal stability of the cavity is 0.025 C/min, but the design is directed toward achieving stability well beyond this requirement to improve the science data gained. A prototype of the cavity mount was fabricated and tested to characterize the thermal performance. The thermal vacuum test involved stable high-resolution temperature measurements and stable baseplate temperature control over long durations. Based on test data, the cavity mount design satisfies the severe requirement for the cavity thermal stability.

Theoretical Design on a Series of Novel Bicyclic and Cage Nitramines as High Energy Density Compounds.

PubMed

Pan, Yong; Zhu, Weihua

2017-11-30

We designed four bicyclic nitramines and three cage nitramines by incorporating -N(NO 2 )-CH 2 -N(NO 2 )-, -N(NO 2 )-, and -O- linkages based on the HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocane) framework. Then, their electronic structure, heats of formation, energetic properties, strain energy, thermal stability, and impact sensitivity were systematically studied using density functional theory (DFT). Compared to the parent compound HMX, all the title compounds have much higher density, better detonation properties, and better oxygen balance. Among them, four compounds have extraordinary high detonation properties (D > 9.70 km/s and P > 44.30 GPa). Moreover, most of the title compounds exhibit better thermal stability and lower impact sensitivity than CL-20 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane) or HNHAA (hexanitrohexaazaadamantane). Thus, all of the seven new nitramine compounds are promising candidates for high energy density compounds. In particular, five compounds exhibit a best combination of better oxygen balance, good thermal stability, excellent detonation properties superior to or comparable to CL-20 or HNHAA, and lower impact sensitivity than CL-20 or HNHAA. The results indicate that our unusual design strategy that constructing bicyclic or cage nitramines based on the HMX framework by incorporating the intramolecular linkages is very useful for developing novel energetic compounds with excellent detonation performance and low sensitivity.

NASA space materials research

NASA Technical Reports Server (NTRS)

Tenney, D. R.; Tompkins, S. S.; Sykes, G. F.

1985-01-01

The effect of the space environment on: (1) thermal control coatings and thin polymer films; (2) radiation stability of 250 F and 350 F cured graphite/epoxy composites; and (3) the thermal mechanical stability of graphite/epoxy, graphite/glass composites are considered. Degradation in mechanical properties due to combined radiation and thermal cycling is highlighted. Damage mechanisms are presented and chemistry modifications to improve stability are suggested. The dimensional instabilities in graphite/epoxy composites associated with microcracking during thermal cycling is examined as well as the thermal strain hysteresis found in metal-matrix composites.

Purification and characterization of two fully deuterated enzymes

NASA Technical Reports Server (NTRS)

Crespi, H. L.; Katz, J. J.; Parmerter, S.; Rokop, S.

1969-01-01

Comparative data reveal little difference between kinetic and thermal stabilities of pure preparations of two ordinary enzymes and their fully deuterated counterparts. The effects of temperature on the enzymes proved to be consistent with earlier results.

Comparison and characterization of volatile compounds as markers of oils stability during frying by HS-SPME-GC/MS and Chemometric analysis.

PubMed

Ben Hammouda, Ibtissem; Freitas, Flavia; Ammar, Sonda; Da Silva, M D R Gomes; Bouaziz, Mohamed

2017-11-15

The formation and emission of volatile compounds, including the aldehydes and some toxic compounds of oil samples, ROPO pure (100%) and the blended ROPO/RCO (80-20%), were carried out during deep frying at 180°C. The volatile profile of both oil samples was evaluated by an optimized HS-SPME-GC/MS method, before and after 20, 40 and 60 successive sessions of deep-frying. Actually, from 100 detected compounds, aldehydes were found to be the main group formed. In addition, the oil degradation under thermal treatment regarding the volatile compounds were evaluated and compared. Consequently, the blended ROPO/RCO revealed fewer formations of unsaturated aldehydes, including toxic ones, such as acrolein, and showed a greater stability against oxidative thermal degradation compared to ROPO pure. Copyright © 2017 Elsevier B.V. All rights reserved.

Radiation crosslinking of styrene-butadiene rubber containing waste tire rubber and polyfunctional monomers

NASA Astrophysics Data System (ADS)

Yasin, Tariq; Khan, Sara; Shafiq, Muhammad; Gill, Rohama

2015-01-01

The objective of this study was to investigate the influence of polyfunctional monomers (PFMs) and absorbed dose on the final characteristics of styrene-butadiene rubber (SBR) mixed with waste tire rubber (WTR). A series of SBR/WTR blends were prepared by varying the ratios of WTR in the presence of PFMs, namely trimethylolpropane trimethacrylate (TMPTMA) and trimethylolpropane triacrylate (TMPTA) and crosslinked using gamma rays. The physicochemical characteristics of the prepared blends were investigated. It was observed that tensile strength, hardness and gel content of the blends increased with absorbed dose while the blends containing TMPTA showed higher tensile strength, gel content and thermal stability as compared to the blends containing TMPTMA. Higher thermal stability was observed in the blends which were crosslinked by radiation as compared to the blends crosslinked by sulfur. These blends exhibited higher rate of swelling in organic solvents, whereas negligible swelling was observed in acidic and basic environment.

Comparing blends and blocks: Synthesis of partially fluorinated diblock polythiophene copolymers to investigate the thermal stability of optical and morphological properties

PubMed Central

Boufflet, Pierre; Wood, Sebastian; Wade, Jessica; Fei, Zhuping; Kim, Ji-Seon

2016-01-01

Summary The microstructure of the active blend layer has been shown to be a critically important factor in the performance of organic solar devices. Block copolymers provide a potentially interesting avenue for controlling this active layer microstructure in solar cell blends. Here we explore the impact of backbone fluorination in block copolymers of poly(3-octyl-4-fluorothiophene)s and poly(3-octylthiophene) (F-P3OT-b-P3OT). Two block co-polymers with varying block lengths were prepared via sequential monomer addition under Kumada catalyst transfer polymerisation (KCTP) conditions. We compare the behavior of the block copolymer to that of the corresponding homopolymer blends. In both types of system, we find the fluorinated segments tend to dominate the UV–visible absorption and molecular vibrational spectral features, as well as the thermal behavior. In the block copolymer case, non-fluorinated segments appear to slightly frustrate the aggregation of the more fluorinated block. However, in situ temperature dependent Raman spectroscopy shows that the intramolecular order is more thermally stable in the block copolymer than in the corresponding blend, suggesting that such materials may be interesting for enhanced thermal stability of organic photovoltaic active layers based on similar systems. PMID:27829922

Effect of Boric Acid on Volatile Products of Thermooxidative Degradation of Epoxy Polymers

NASA Astrophysics Data System (ADS)

Nazarenko, O. B.; Bukhareva, P. B.; Melnikova, T. V.; Visakh, P. M.

2016-01-01

The polymeric materials are characterized by high flammability. The use of flame retardants in order to reduce the flammability of polymers can lead to the formation of toxic gaseous products under fire conditions. In this work we studied the effect of boric acid on the volatile products of thermooxidative degradation of epoxy polymers. The comparative investigations were carried out on the samples of the unfilled epoxy resin and epoxy resin filled with a boric acid at percentage 10 wt. %. The analysis of the volatile decomposition products and thermal stability of the samples under heating in an oxidizing medium was performed using a thermal mass-spectrometric analysis. It is found that the incorporation of boric acid into the polymer matrix increases the thermal stability of epoxy composites and leads to a reduction in the 2-2.7 times of toxic gaseous products

Study of phase transformation and microstructure of alcohol washed titania nanoparticles for thermal stability

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

Kaur, Manpreet, E-mail: manpreet.kaur@thapar.edu; Singh, Gaganjot; Bimbraw, Keshav

Nanostructured titania have been successfully synthesized by hydrolysis of alkoxide at calcination temperatures 500 °C, 600 °C and 700 °C. As the calcination temperature increases, alcohol washed samples show lesser rutile content as compared to water washed samples. Morphology and Particle sizes was determined by field emission scanning electron microscopy (FESEM), while thermogravimetric-differential scanning calorimetry (TG-DSC) was used to determine thermal stability. Alcohol washed samples undergo 30% weight loss whereas 16% in water washed samples was observed. The mean particle sizes were found to be increase from 37 nm to 100.9 nm and 35.3 nm to 55.2 nm for water and alcohol washed samplesmore » respectively. Hydrolysis of alkoxide was shown to be an effective means to prepare thermally stable titania by using alcohol washed samples as a precursor.« less

Influence of some DNA-alkylating drugs on thermal stability, acid and osmotic resistance of the membrane of whole human erythrocytes and their ghosts.

PubMed

Ivanov, I T; Gadjeva, V

2000-09-01

Human erythrocytes and their resealed ghosts were alkylated under identical conditions using three groups of alkylating antitumor agents: mustards, triazenes and chloroethyl nitrosoureas. Osmotic fragility, acid resistance and thermal stability of membranes were changed only in alkylated ghosts in proportion to the concentration of the alkylating agent. All the alkylating agents decreased acid resistance in ghosts. The clinically used drugs sarcolysine, dacarbazine and lomustine all decreased osmotic fragility and thermal stability of ghost membranes depending on their lipophilicity. DM-COOH did not decrease osmotic fragility and thermal stability of ghost membranes, while NEM increased thermal stability of membranes. The preliminary but not subsequent treatment of ghosts with DM-COOH fully abolished the alkylation-induced thermal labilization of ghost membrane proteins while NEM had a partial effect only. The present study gives direct evidence that alkylating agents, having a high therapeutic activity against malignant growth, bind covalently to proteins of cellular membranes.

Pulsational stabilities of a star in thermal imbalance - Comparison between the methods

NASA Technical Reports Server (NTRS)

Vemury, S. K.

1978-01-01

The stability coefficients for quasi-adiabatic pulsations for a model in thermal imbalance are evaluated using the dynamical energy (DE) approach, the total (kinetic plus potential) energy (TE) approach, and the small amplitude (SA) approaches. From a comparison among the methods, it is found that there can exist two distinct stability coefficients under conditions of thermal imbalance as pointed out by Demaret. It is shown that both the TE approaches lead to one stability coefficient, while both the SA approaches lead to another coefficient. The coefficient obtained through the energy approaches is identified as the one which determines the stability of the velocity amplitudes. For a prenova model with a thin hydrogen-burning shell in thermal imbalance, several radial modes are found to be unstable both for radial displacements and for velocity amplitudes. However, a new kind of pulsational instability also appears, viz., while the radial displacements are unstable, the velocity amplitudes may be stabilized through the thermal imbalance terms.

Comparative thermal and thermodynamic study of DNA chemically modified with antitumor drug cisplatin and its inactive analog transplatin.

PubMed

Lando, Dmitri Y; Chang, Chun-Ling; Fridman, Alexander S; Grigoryan, Inessa E; Galyuk, Elena N; Hsueh, Ya-Wei; Hu, Chin-Kun

2014-08-01

Antitumor activity of cisplatin is exerted by covalent binding to DNA. For comparison, studies of cisplatin-DNA complexes often employ the very similar but inactive transplatin. In this work, thermal and thermodynamic properties of DNA complexes with these compounds were studied using differential scanning calorimetry (DSC) and computer modeling. DSC demonstrates that cisplatin decreases thermal stability (melting temperature, Tm) of long DNA, and transplatin increases it. At the same time, both compounds decrease the enthalpy and entropy of the helix-coil transition, and the impact of transplatin is much higher. From Pt/nucleotide molar ratio rb=0.001, both compounds destroy the fine structure of DSC profile and increase the temperature melting range (ΔT). For cisplatin and transplatin, the dependences δTm vs rb differ in sign, while δΔT vs rb are positive for both compounds. The change in the parameter δΔT vs rb demonstrates the GC specificity in the location of DNA distortions. Our experimental results and calculations show that 1) in contrast to [Pt(dien)Cl]Cl, monofunctional adducts formed by transplatin decrease the thermal stability of long DNA at [Na(+)]>30mM; 2) interstrand crosslinks of cisplatin and transplatin only slightly increase Tm; 3) the difference in thermal stability of DNA complexes with cisplatin vs DNA complexes with transplatin mainly arises from the different thermodynamic properties of their intrastrand crosslinks. This type of crosslink appears to be responsible for the antitumor activity of cisplatin. At any [Na(+)] from interval 10-210mM, cisplatin and transplatin intrastrand crosslinks give rise to destabilization and stabilization, respectively. Copyright © 2014 Elsevier Inc. All rights reserved.

Heat Sinking, Cross Talk, and Temperature Stability for Large, Close-Packed Arrays of Microcalorimeters

NASA Technical Reports Server (NTRS)

Imoto, Naoko; Bandler, SImon; Brekosky, Regis; Chervenak, James; Figueroa-Felicano, Enectali; Finkbeiner, Frederick; Kelley, Richard; Kilbourne, Caroline; Porter, Frederick; Sadleir, Jack;

Plasticization effect of triacetin on structure and properties of starch ester film.

PubMed

Zhu, Jie; Li, Xiaoxi; Huang, Chen; Chen, Ling; Li, Lin

2013-05-15

The aim of this work was to evaluate the plasticizing effect of triacetin on the structure and properties of starch ester film and further establish the structure-property relationships. The presence of triacetin resulted in multiple structure changes of the film. The mobility of macromolecular chain was increased to form scattered crystallite during the film formation process. The amorphous region was enlarged to contain more triacetin squeezed from crystalline region. The plasticization of triacetin and restriction of crystallite oppositely influenced the mobility of macromolecular chains in different regions. The thermal stability of triacetin changed along with its fluctuant interaction with macromolecules. Comparatively, the enhanced ether bond and the restriction from crystalline regions on the mobility of the amorphous chain consequently improved the thermal stability of the film matrix. The interaction between triacetin and starch ester was essential to film forming but unexpectedly lowered the triacetin stability. Copyright © 2013 Elsevier Ltd. All rights reserved.

SS-mPEG chemical modification of recombinant phospholipase C for enhanced thermal stability and catalytic efficiency.

PubMed

Fang, Xian; Wang, Xueting; Li, Guiling; Zeng, Jun; Li, Jian; Liu, Jingwen

2018-05-01

PEGylation is one of the most promising and extensively studied strategies for improving the properties of proteins as well as enzymic physical and thermal stability. Phospholipase C, hydrolyzing the phospholipids offers tremendous applications in diverse fields. However, the poor thermal stability and higher cost of production have restricted its industrial application. This study focused on improving the stabilization of recombinant PLC by chemical modification with methoxypolyethylene glycol-Succinimidyl Succinate (SS-mPEG, MW 5000). PLC gene from isolate Bacillus cereus HSL3 was fused with SUMO, a novel small ubiquitin-related modifier expression vector and over expressed in Escherichia coli. The soluble fraction of SUMO-PLC reached 80% of the total recombinant protein. The enzyme exhibited maximum catalytic activity at 80 °C and was relatively thermostable at 40-70 °C. It showed extensive substrate specificity pattern and marked activity toward phosphatidylcholine, which made it a typical non-specific PLC for industrial purpose. SS-mPEG-PLC complex exhibited an enhanced thermal stability at 70-80 °C and the catalytic efficiency (K cat /K m ) had increased by 3.03 folds compared with free PLC. CD spectrum of SS-mPEG-PLC indicated a possible enzyme aggregation after chemical modification, which contributed to the higher thermostability of SS-mPEG-PLC. The increase of antiparallel β sheets in secondary structure also made it more stable than parallel β sheets. The presence of SS-mPEG chains on the enzyme molecule surface somewhat changed the binding rate of the substrates, leading to a significant improvement in catalytic efficiency. This study provided an insight into the addition of SS-mPEG for enhancing the industrial applications of phospholipase C at higher temperature. Copyright © 2018 Elsevier B.V. All rights reserved.

Physico-chemical and immunological examination of the thermal stability of tetanus toxoid conjugate vaccines.

PubMed

Ho, Mei M; Mawas, Fatme; Bolgiano, Barbara; Lemercinier, Xavier; Crane, Dennis T; Huskisson, Rachel; Corbel, Michael J

2002-10-04

The thermal stability of meningococcal C (MenC)- and Haemophilus influenzae b (Hib)-tetanus toxoid (TT) conjugate vaccines was investigated using spectroscopic and chromatographic techniques and immunogenicity assays in animal models. In this stability study, both the bulk concentrate and final fills were incubated at -20, 4, 23, 37 or 55 degrees C for 5 weeks or subjected to cycles of freeze-thawing. The structural stability, hydrodynamic size and molecular integrity of the treated vaccines were monitored by circular dichroism (CD), fluorescence and nuclear magnetic resonance (NMR) spectroscopic techniques, size exclusion chromatography (FPLC-SEC), and high performance anion exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). Only storage at 55 degrees C for 5 weeks caused some slight unfolding and modification in the tertiary structure of the carrier protein in the MenC-TT conjugate. Substantial loss of saccharide content from the MenC conjugates was observed at 37 and 55 degrees C. Unexpectedly, the experimental immunogenicity of MenC-TT vaccine adsorbed to Alhydrogel was significantly reduced only by repeated freeze-thawing, but not significantly decreased by thermal denaturation. Neither the molecular integrity nor the immunogenicity of the lyophilised Hib-TT vaccines was significantly affected by freeze-thawing or by storage at high temperature. In conclusion, the MenC- and Hib-TT conjugate vaccines were relatively stable when stored at higher temperatures, though when MenC-TT vaccine was adsorbed to Alhydrogel, it was more vulnerable to repeated freeze-thawing. When compared with CRM(197) conjugate vaccines studied previously using similar techniques, the tetanus toxoid conjugates were found to have higher relative thermal stability in that they retained immunogenicity following storage at elevated temperatures.

SiC-dopped MCM-41 materials with enhanced thermal and hydrothermal stabilities

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

Wang, Yingyong; Jin, Guoqiang; Tong, Xili

2011-11-15

Graphical abstract: Novel SiC-dopped MCM-41 materials were synthesized by adding silicon carbide suspension in the molecular sieve precursor solvent followed by in situ hydrothermal synthesis. The dopped materials have a wormhole-like mesoporous structure and exhibit enhanced thermal and hydrothermal stabilities. Highlights: {yields} SiC-dopped MCM-41 was synthesized by in situ hydrothermal synthesis of molecular sieve precursor combined with SiC. {yields} The dopped MCM-41 materials show a wormhole-like mesoporous structure. {yields} The thermal stability of the dopped materials have an increment of almost 100 {sup o}C compared with the pure MCM-41. {yields} The hydrothermal stability of the dopped materials is also bettermore » than that of the pure MCM-41. -- Abstract: SiC-dopped MCM-41 mesoporous materials were synthesized by the in situ hydrothermal synthesis, in which a small amount of SiC was added in the precursor solvent of molecular sieve before the hydrothermal treatment. The materials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N{sub 2} physical adsorption and thermogravimetric analysis, respectively. The results show that the thermal and hydrothermal stabilities of MCM-41 materials can be improved obviously by incorporating a small amount of SiC. The structure collapse temperature of SiC-dopped MCM-41 materials is 100 {sup o}C higher than that of pure MCM-41 according to the differential scanning calorimetry analysis. Hydrothermal treatment experiments also show that the pure MCM-41 will losses it's ordered mesoporous structure in boiling water for 24 h while the SiC-dopped MCM-41 materials still keep partial porous structure.« less

Protein substitution affects glass transition temperature and thermal stability.

PubMed

Budhavaram, Naresh K; Miller, Jonathan A; Shen, Ying; Barone, Justin R

2010-09-08

When proteins are removed from their native state they suffer from two deficiencies: (1) glassy behavior with glass transition temperatures (Tg) well above room temperature and (2) thermal instability. The glassy behavior originates in multiple hydrogen bonds between amino acids on adjacent protein molecules. Proteins, like most biopolymers, are thermally unstable. Substituting ovalbumin with linear and cyclic substituents using a facile nucleophilic addition reaction can affect Tg and thermal stability. More hydrophobic linear substituents lowered Tg by interrupting intermolecular interactions and increasing free volume. More hydrophilic and cyclic substituents increased thermal stability by increasing intermolecular interactions. In some cases, substituents instituted cross-linking between protein chains that enhanced thermal stability. Internal plasticization using covalent substitution and external plasticization using low molecular weight polar liquids show the same protein structural changes and a signature of plasticization is identified.

Thermal conductivity and viscosity measurements of ethylene glycol-based Al2O3 nanofluids

NASA Astrophysics Data System (ADS)

Pastoriza-Gallego, María José; Lugo, Luis; Legido, José Luis; Piñeiro, Manuel M.

2011-12-01

The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction. The thermal conductivity and viscosity were experimentally determined at temperatures ranging from 283.15 K to 323.15 K using an apparatus based on the hot-wire method and a rotational viscometer, respectively. It has been found that both thermal conductivity and viscosity increase with the concentration of nanoparticles, whereas when the temperature increases the viscosity diminishes and the thermal conductivity rises. Measured enhancements on thermal conductivity (up to 19%) compare well with literature values when available. New viscosity experimental data yield values more than twice larger than the base fluid. The influence of particle size on viscosity has been also studied, finding large differences that must be taken into account for any practical application. These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity.

Plasmonic thermal IR emitters based on nanoamorphous carbon

NASA Astrophysics Data System (ADS)

Tay, Savaş; Kropachev, Aleksandr; Araci, Ismail Emre; Skotheim, Terje; Norwood, Robert A.; Peyghambarian, N.

2009-02-01

The development of plasmonic narrow-band thermal mid-IR emitters made from a conducting amorphous carbon composite is shown. These IR emitters have greatly improved thermal and mechanical stability compared to metallic emitters as they can be operated at 600 °C in air without any degradation in performance. The emitted thermal radiation has a bandwidth of 0.5 μm and can be set to the desired wavelength from 3 to 15 μm by changing the surface periodicity. The periodically patterned devices have in-band emissivities significantly exceeding that of the non-patterned devices, constituting simple yet efficient radiation sources at this important wavelength range.

Improving the Mechanical Performance and Thermal Stability of a PVA-Clay Nanocomposite by Electron Beam Irradiation

NASA Astrophysics Data System (ADS)

Shokuhi Rad, A.; Ebrahimi, D.

2017-07-01

The effects of electron beam irradiation and presence of clay on the mechanical properties and thermal stability of montmorillonite clay-modified polyvinyl alcohol nanocomposites were studied. By using the X-ray diffraction (XRD) and transmission electron microscopy (TEM), the microstructure of the nanocomposites was investigated. The results obtained from TEM and XRD tests showed that montmorillonite clay nanoparticles were located in the polyvinyl alcohol phase. The XRD analysis confirmed the formation of an exfoliated structure in nanocomposites samples. Increasing the amount of clay to 20 wt.% increased the tensile strength and modulus of the nanocomposite. Irradiation up to an absorbed dose of 100 kGy increased its mechanical properties and thermal stability, but at higher irradiation levels, the mechanical strength and thermal stability declined. The sample with 20 wt.% of the nanofiller, exposed to 100 kGy, showed the highest mechanical strength and thermal stability.

Phase evolution and thermal properties of yttria-stabilized hafnia nano-coatings deposited on alumina

NASA Astrophysics Data System (ADS)

Rubio, Ernesto Javier

High-temperature coatings are critical to the future power-generation systems and industries. Thermal barrier coatings (TBCs), which are usually the ceramic materials applied as thin coatings, protect engine components and allow further increase in engine temperatures for higher efficiency. Thus, the durability and reliability of the coating systems have to be more robust compared to current natural gas based engines. While a near and mid-term target is to develop TBC architecture with a 1300 °C surface temperature tolerance, a deeper understanding of the structure evolution and thermal behavior of the TBC-bond coat interface, specifically the thermally grown oxide (TGO), is of primary importance. In the present work, attention is directed towards yttria-stabilized hafnia (YSH) coatings on alumina (α-Al2O 3) to simulate the TBC-TGO interface and understand the phase evolution, microstructure and thermal oxidation of the coatings. YSH coatings were grown on α-Al2O3 substrates by sputter deposition by varying coating thickness in a wide range ˜30-1000 nm. The effect of coating thickness on the structure, morphology and the residual stress has been investigated using X-ray diffraction (XRD) and high resolution scanning electron microscopy (SEM). Thermal oxidation behavior of the coatings has been evaluated using the isothermal oxidation measurements under static conditions. X-ray diffraction analyses revealed the existence of monoclinic hafnia phase for relatively thin coatings indicating that the interfacial phenomena are dominant in phase stabilization. The evolution towards pure stabilized cubic phase of hafnia with the increasing coating thickness is observed. The SEM results indicate the changes in morphology of the coatings; the average grain size increases from 15 to 500 nm with increasing thickness. Residual stress was calculated employing XRD using the variable ψ-angle. Relation between residual stress and structural change is also studied. The results obtained on the thermal oxidation behavior indicate that the YSH coatings exhibit initial mass gain in the first 6 hours and sustained structure for extended hours of thermal treatment.

Enhanced mechanical, thermal, and electric properties of graphene aerogels via supercritical ethanol drying and high-temperature thermal reduction.

PubMed

Cheng, Yehong; Zhou, Shanbao; Hu, Ping; Zhao, Guangdong; Li, Yongxia; Zhang, Xinghong; Han, Wenbo

2017-05-03

Graphene aerogels with high surface areas, ultra-low densities and thermal conductivities have been prepared to exploit their wide applications from pollution adsorption to energy storage, supercapacitor, and thermal insulation. However, the low mechanical properties, poor thermal stability and electric conductivity restrict these aerogels' applications. In this paper, we prepared mechanically strong graphene aerogels with large BET surface areas, low thermal conductivities, high thermal stability and electric conductivities via hydrothermal reduction and supercritical ethanol drying. Annealing at 1500 °C resulted in slightly increased thermal conductivity and further improvement in mechanical properties, oxidation temperature and electric conductivity of the graphene aerogel. The large BET surface areas, together with strong mechanical properties, low thermal conductivities, high thermal stability and electrical conductivities made these graphene aerogels feasible candidates for use in a number of fields covering from batteries to sensors, electrodes, lightweight conductor and insulation materials.

Thermo-analytical and physico-chemical characterisation of organoclays and polymer-clay nacomposites

NASA Astrophysics Data System (ADS)

Cunningham, Andrew

A variety of modified clay minerals have been screened to determine their effectiveness as agents for the production of polystyrene-clay nanocomposites. The n-alkylammonium and n-alkyltrimethylammonium surfactants employed to compatibilise the aluminosilicate layers of the minerals were shown to degrade through a series of stages and mechanisms to yield a hydrocarbon product mixture consisting of a homologous series of saturated and unsaturated hydrocarbons, also, the dehydrocyclisation (DHC) of fragmented alkyl chains was shown to lead to the production of various ring compounds which included substituted cycloalkenes, benzene and toluene.The thermal stability of various cation exchanged modification treatments have been analysed. These organoclays have been characterised by XRD, TGA and TG-MS. The evolved gas analysis conducted by TG-MS was employed to identify which products were being thermally desorbed under thermal events previously seen when using TGA. In particular attention was paid to the activity of these materials with respect to the formation of linear, branched and cyclic aliphatics and aromatics from the feedstock surfactants.Intra-series comparisons of different organoclays showed that as the alkyl chain length of the n-alkylammonium surfactants was increased the concentration of thermal desorption products at approximately 400 °C was also increased. However, characterisation of n-alkyltrimethylammonium exchanged MMT showed that the concentration of thermal desorption products at lower temperatures (approximately 250 °C) increased with alkyl chain length between C[n] = 8 - 16. TG-MS analysis showed that this was mostly due to the DHC of alkyl fragments. These compounds appear to have been largely overlooked in related literature.SWa-1, a clay containing greater concentrations of structural iron, showed higher T[max] values for n-alkylammonium surfactant thermal desorption than similarly exchanged SAz-1. This may be evidence of a current theory that structural iron acts as a radical trap. This is thought to significantly reduce the catalytic activity of the clay's acid sites until higher temperatures. The formulation of polystyrene-clay nanocomposites (PSCNs) by in-situ polymerisation led to various results pertaining to their thermal stability. The relative effectiveness of various initiator species for the production of the most thermally stable PSCNs was AIBN > BPO > SPS > APS > AIBA. Lower radical initiator and organic modifier concentrations led to the production of PSCNs with higher thermal stability. The relative effectiveness of these various organoclays for the production of more thermally stable PSCNs was MCBP-Cn > C15A > C20A " C10A. The preparation method was shown to be effective for producing exfoliated nanocomposites for up to 1 wt% of the various organoclays using AIBN and BPO as initiators. The MCBP-Cn PSCNs remained exfoliated up to 5 wt% , they also showed higher thermal stability when compared with the commercial products, which XRD results showed to remain stacked at organoclay loadings > 1 wt%.A novel one-pot synthesis method for the production of PSCN, by the in-situ polymerisation of PS in the presence of decanamide (an uncharged surfactant) and Na-MMT, was shown to be successful. Whereas, other novel PSCN formulations incorporating N-vinylformamide and the amphoteric surfactant foamtaine SCAB were shown to be encouraging but have, so far, had limited success.In contrast, the analysis of industrially produced unsaturated polyester-clay nanocomposites showed very little increase in the thermal stability of the material. Associated analyses indicated increased dimensional stability of the material, AFM analysis showed that imaging of the clay dispersal was possible by this macroscopic technique. Also, ATR-FTIR analysis of the UPR and UPCN, showed that although not exfoliated the silane modified-MMT had a good synergistic effect on the overall material by reducing the formation of combustion products.The thermal stability and associated studies of kaolin-phenylphosphonic acid (KPPA) complexes was also conducted. PPA was shown to intercalate the kaolin crystal structure forming an expanded phase that exhibited remarkable thermal stability (Tmax = 660 °C). 31P MAS NMR of all the KPPA samples showed three peaks (at +1.2, -3.7 and -7.3 ppm) which represented PPA existing in three non-equivalent bonding states at the kaolin surface. The high thermal stability of these hybrid materials was evident from these studies. This research into the use of covalently bound intercalates in nanocomposite manufacture signifies the necessity for further research.

A Novel, Aqueous Surface Treatment To Thermally Stabilize High Resolution Positive Photoresist Images*

NASA Astrophysics Data System (ADS)

Grunwald, John J.; Spencer, Allen C.

1986-07-01

The paper describes a new approach to thermally stabilize the already imaged profile of high resolution positive photoresists such as ULTRAMAC" PR-914. ***XD-4000, an aqueous emulsion of a blend of fluorine-bearing compounds is spun on top of the developed, positive photoresist-imaged wafer, and baked. This allows the photoresist to withstand temperatures up to at least 175 deg. C. while essentially maintaining vertical edge profiles. Also, adverse effects of "outgassing" in harsh environments, ie., plasma and ion implant are greatly minimized by allowing the high resolution imaged photoresist to be post-baked at "elevated" temperatures. Another type of product that accomplishes the same effect is ***XD-4005, an aqueous emulsion of a high temperature-resistant polymer. While the exact mechanism is yet to be identified, it is postulated that absorption of the "polymeric" species into the "skin" of the imaged resist forms a temperature resistant "envelope", thereby allowing high resolution photoresists to also serve in a "high temperature" mode, without reticulation, or other adverse effects due to thermal degradation. SEM's are presented showing imaged ULTRAMAC" PR-914 and ULTRAMAC" **EPA-914 geometries coated with XD-4000 or XD-4005 and followed by plasma etched oxide,polysilicon and aluminum. Selectivity ratios are compared with and without the novel treatment and are shown to be significantly better with the treatment. The surface-treated photoresist for thermal resistance remains easily strippable in solvent-based or plasma media, unlike photoresists that have undergone "PRIST" or other gaseous thermal stabilization methods.

Thermal Analysis and Microhardness Mapping in Hybrid Laser Welds in a Structural Steel

DTIC Science & Technology

2003-01-01

conditions. Via the keyhole the laser beam brings about easier ignition of the arc, stabilization of the arc welding process, and penetration of the...with respect to the conventional GMAW or GTAW processes without the need for very close fit-up. This paper will compare an autogenous laser weld to a...UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADP017864 TITLE: Thermal Analysis and Microhardness Mapping in Hybrid Laser

Jet Fuel Thermal Stability Investigations Using Ellipsometry

NASA Technical Reports Server (NTRS)

Nash, Leigh; Vasu, Subith S.; Klettlinger, Jennifer Lindsey

2017-01-01

Jet fuels are typically used for endothermic cooling in practical engines where their thermal stability is very important. In this work the thermal stability of Sasol IPK (a synthetic jet fuel) with varying levels of naphthalene has been studied on stainless steel substrates using spectroscopic ellipsometry in the temperature range 385-400 K. Ellipsometry is an optical technique that measures the changes in a light beam’s polarization and intensity after it reflects off of a thin film to determine the film’s thickness and optical properties. All of the tubes used were rated as thermally unstable by the color standard portion of the Jet Fuel Thermal Oxidation Test, and this was confirmed by the deposit thicknesses observed using ellipsometry. A new amorphous model on a stainless steel substrate was used to model the data and obtain the results. It was observed that, as would be expected, increasing the temperature of the tube increased the overall deposit amount for a constant concentration of naphthalene. The repeatability of these measurements was assessed using multiple trials of the same fuel at 385 K. Lastly, the effect of increasing the naphthalene concentration in the fuel at a constant temperature was found to increase the deposit thickness.In conclusion, ellipsometry was used to investigate the thermal stability of jet fuels on stainless steel substrate. The effects of increasing temperature and addition of naphthalene on stainless steel tubes with Sasol IPK fuel were investigated. It was found, as expected, that increasing temperature lead to an increase in deposit thickness. It wasAmerican Institute of Aeronautics and Astronautics6also found that increasing amounts of naphthalene increased the maximum deposit thickness. The repeatability of these measurements was investigated using multiple tests at the same conditions. The present work provides as a better quantitative tool compared to the widely used JFTOT technique. Future work will expand on the fuel types, temperature, and substrate materials.

Stabilization of molten salt materials using metal chlorides for solar thermal storage.

PubMed

Dunlop, T O; Jarvis, D J; Voice, W E; Sullivan, J H

2018-05-29

The effect of a variety of metal-chlorides additions on the melting behavior and thermal stability of commercially available salts was investigated. Ternary salts comprised of KNO 3, NaNO 2, and NaNO 3 were produced with additions of a variety of chlorides (KCl, LiCl, CaCl 2 , ZnCl 2 , NaCl and MgCl 2 ). Thermogravimetric analysis and weight loss experiments showed that the quaternary salt containing a 5 wt% addition of LiCl and KCl led to an increase in short term thermal stability compared to the ternary control salts. These additions allowed the salts to remain stable up to a temperature of 630 °C. Long term weight loss experiments showed an upper stability increase of 50 °C. A 5 wt% LiCl addition resulted in a weight loss of only 25% after 30 hours in comparison to a 61% loss for control ternary salts. Calorimetry showed that LiCl additions allow partial melting at 80 °C, in comparison to the 142 °C of ternary salts. This drop in melting point, combined with increased stability, provided a molten working range increase of almost 100 °C in total, in comparison to the control ternary salts. XRD analysis showed the oxidation effect of decomposing salts and the additional phase created with LiCl additions to allow melting point changes to occur.

Molecularly Engineered Azobenzene Derivatives for High Energy Density Solid-State Solar Thermal Fuels.

PubMed

Cho, Eugene N; Zhitomirsky, David; Han, Grace G D; Liu, Yun; Grossman, Jeffrey C

2017-03-15

Solar thermal fuels (STFs) harvest and store solar energy in a closed cycle system through conformational change of molecules and can release the energy in the form of heat on demand. With the aim of developing tunable and optimized STFs for solid-state applications, we designed three azobenzene derivatives functionalized with bulky aromatic groups (phenyl, biphenyl, and tert-butyl phenyl groups). In contrast to pristine azobenzene, which crystallizes and makes nonuniform films, the bulky azobenzene derivatives formed uniform amorphous films that can be charged and discharged with light and heat for many cycles. Thermal stability of the films, a critical metric for thermally triggerable STFs, was greatly increased by the bulky functionalization (up to 180 °C), and we were able to achieve record high energy density of 135 J/g for solid-state STFs, over a 30% improvement compared to previous solid-state reports. Furthermore, the chargeability in the solid state was improved, up to 80% charged from 40% charged in previous solid-state reports. Our results point toward molecular engineering as an effective method to increase energy storage in STFs, improve chargeability, and improve the thermal stability of the thin film.

Can zinc aluminate-titania composite be an alternative for alumina as microelectronic substrate?

PubMed Central

Roshni, Satheesh Babu; Sebastian, Mailadil Thomas; Surendran, Kuzhichalil Peethambharan

2017-01-01

Alumina, thanks to its superior thermal and dielectric properties, has been the leading substrate over several decades, for power and microelectronics circuits. However, alumina lacks thermal stability since its temperature coefficient of resonant frequency (τf) is far from zero (−60 ppmK−1). The present paper explores the potentiality of a ceramic composite 0.83ZnAl2O4-0.17TiO2 (in moles, abbreviated as ZAT) substrates for electronic applications over other commercially-used alumina-based substrates and synthesized using a non-aqueous tape casting method. The present substrate has τf of + 3.9 ppmK−1 and is a valuable addition to the group of thermo-stable substrates. The ZAT substrate shows a high thermal conductivity of 31.3 Wm−1K−1 (thermal conductivity of alumina is about 24.5 Wm−1K−1), along with promising mechanical, electrical and microwave dielectric properties comparable to that of alumina-based commercial substrates. Furthermore, the newly-developed substrate material shows exceptionally good thermal stability of dielectric constant, which cannot be met with any of the alumina-based HTCC substrates. PMID:28084459

Increased thermolability of benzodiazepine receptors in cerebral cortex of a baboon with spontaneous seizures: a case report.

PubMed

Squires, R; Naquet, R; Riche, D; Braestrup, C

1979-06-01

The benzodiazepine receptor in the cortex of 1 spontaneously epileptic baboon exhibited an increased rate of thermal inactivation at 65 degrees C when compared with those from 3 other baboons. In other respects (receptor concentration, affinities for flunitrazepam and diazepam, and response to changing pH), the benzodiazepine receptor from this animal was very similar to the receptors in the cortex of 3 other baboons. The 3H-QNB (muscarinic) and 3H-naloxone (opiate) binding sites in the brain of all 4 baboons appeared very similar with respect to all parameters studied (thermal stability, concentration, regional distribution, and affinities for respective ligands). An endogenous factor stabilizing the benzodiazepine receptor could be lacking in the spontaneously epileptic baboon.

Transparent and robust siloxane-based hybrid lamella film as a water vapor barrier coating.

PubMed

Tokudome, Yasuaki; Hara, Takaaki; Abe, Risa; Takahashi, Masahide

2014-11-12

Water vapor barriers are important in various application fields, such as food packaging and sealants in electronic devices. Polymer/clay composites are well-studied water vapor barrier materials, but their transparency and mechanical strength degrade with increasing clay loading. Herein, we demonstrate films with good water vapor barrier properties, high transparency, and mechanical/thermal stability. Water vapor barrier films were prepared by the solution crystallization of siloxane hybrid lamellae. The films consist of highly crystallized organic/inorganic hybrid lamellae, which provide high transparency, hardness, and thermal stability and inhibit the permeation of water vapor. The water permeability of a 6 μm thick hybrid film is comparable to that of a 200 μm thick silicon rubber film.

The glass-like thermal conductivity in ZrO2-Dy3TaO7 ceramic for promising thermal barrier coating application

NASA Astrophysics Data System (ADS)

Wu, Peng; Hu, Ming Yu; Chong, Xiao Yu; Feng, Jing

2018-03-01

Using the solid-state reaction method, the (ZrO2)x-(Dy3TaO7)1-x (x = 0, 0.02, 0.04, 0.06, 0.08, and 0.1) ceramics are synthesized in this work. The identification of the crystal structures indicates that the (ZrO2)x-(Dy3TaO7)1-x ceramics belong to the orthorhombic system, and the space group is C2221 in spite of the value of x increasing to 0.1. The thermal conductivities of the (ZrO2)x-(Dy3TaO7)1-x ceramics range from 1.3 W/(m K) to 1.8 W/(m K), and this value is much lower than that of 7-8 YSZ (yttria-stabilized zirconia). Besides, the (ZrO2)x-(Dy3TaO7)1-x ceramics possess the glass-like thermal conductivity caused by intrinsic oxygen vacancies existing in the lattice of Dy3TaO7. Moreover, the results of thermal expansion rates demonstrate that the (ZrO2)x-(Dy3TaO7)1-x ceramics possess excellent high temperature phase stability, and the thermal expansion coefficients [(9.7-11) × 10-6 K-1] are comparable to that of 7-8 YSZ.

Thermally stable, plastic-bonded explosives

DOEpatents

Benziger, Theodore M.

1979-01-01

By use of an appropriate thermoplastic rubber as the binder, the thermal stability and thermal stress characteristics of plastic-bonded explosives may be greatly improved. In particular, an HMX-based explosive composition using an oil-extended styrene-ethylenebutylene-styrene block copolymer as the binder exhibits high explosive energy and thermal stability and good handling safety and physical properties.

Thermal Stability of Nanocrystalline Alloys by Solute Additions and A Thermodynamic Modeling

NASA Astrophysics Data System (ADS)

Saber, Mostafa

Nanocrystalline alloys show superior properties due to their exceptional microstructure. Thermal stability of these materials is a critical aspect. It is well known that grain boundaries in nanocrystalline microstructures cause a significant increase in the total free energy of the system. A driving force provided to reduce this excess free energy can cause grain growth. The presence of a solute addition within a nanocrystalline alloy can lead to the thermal stability. Kinetic and thermodynamic stabilization are the two basic mechanisms with which stability of a nanoscale grain size can be achieved at high temperatures. The basis of this thesis is to study the effect of solute addition on thermal stability of nanocrystalline alloys. The objective is to determine the effect of Zr addition on the thermal stability of mechanically alloyed nanocrysatillne Fe-Cr and Fe-Ni alloys. In Fe-Cr-Zr alloy system, nanoscale grain size stabilization was maintained up to 900 °C by adding 2 at% Zr. Kinetic pinning by intermetallic particles in the nanoscale range was identified as a primary mechanism of thermal stabilization. In addition to the grain size strengthening, intermetallic particles also contribute to strengthening mechanisms. The analysis of microhardness, XRD data, and measured grain sizes from TEM micrographs suggested that both thermodynamic and kinetic mechanisms are possible mechanisms. It was found that alpha → gamma phase transformation in Fe-Cr-Zr system does not influence the grain size stabilization. In the Fe-Ni-Zr alloy system, it was shown that the grain growth in Fe-8Ni-1Zr alloy is much less than that of pure Fe and Fe-8Ni alloy at elevated temperatures. The microstructure of the ternary Fe-8Ni-1Zr alloy remains in the nanoscale range up to 700 °C. Using an in-situ TEM study, it was determined that drastic grain growth occurs when the alpha → gamma phase transformation occurs. Accordingly, there can be a synergistic relationship between grain growth and alpha → gamma phase transformation in Fe-Ni-Zr alloys. In addition to the experimental study of thermal stabilization of nanocrystalline Fe-Cr-Zr or Fe-Ni-Zr alloys, the thesis presented here developed a new predictive model, applicable to strongly segregating solutes, for thermodynamic stabilization of binary alloys. This model can serve as a benchmark for selecting solute and evaluating the possible contribution of stabilization. Following a regular solution model, both the chemical and elastic strain energy contributions are combined to obtain the mixing enthalpy. The total Gibbs free energy of mixing is then minimized with respect to simultaneous variations in the grain boundary volume fraction and the solute concentration in the grain boundary and the grain interior. The Lagrange multiplier method was used to obtained numerical solutions. Application are given for the temperature dependence of the grain size and the grain boundary solute excess for selected binary system where experimental results imply that thermodynamic stabilization could be operative. This thesis also extends the binary model to a new model for thermodynamic stabilization of ternary nanocrystalline alloys. It is applicable to strongly segregating size-misfit solutes and uses input data available in the literature. In a same manner as the binary model, this model is based on a regular solution approach such that the chemical and elastic strain energy contributions are incorporated into the mixing enthalpy DeltaHmix, and the mixing entropy DeltaSmix is obtained using the ideal solution approximation. The Gibbs mixing free energy Delta Gmix is then minimized with respect to simultaneous variations in grain growth and solute segregation parameters. The Lagrange multiplier method is similarly used to obtain numerical solutions for the minimum Delta Gmix. The temperature dependence of the nanocrystalline grain size and interfacial solute excess can be obtained for selected ternary systems. As an example, model predictions are compared to experimental results for Fe-Cr-Zr and Fe-Ni-Zr alloy systems. Consistency between the experimental results and the present model predictions provide a more rigorous criterion for investigating thermal stabilization. However, other possible contributions for grain growth stabilization should still be considered.

Mosaic-shaped cathode for highly durable solid oxide fuel cell under thermal stress

NASA Astrophysics Data System (ADS)

Joo, Jong Hoon; Jeong, Jaewon; Kim, Se Young; Yoo, Chung-Yul; Jung, Doh Won; Park, Hee Jung; Kwak, Chan; Yu, Ji Haeng

2014-02-01

In this study, we propose a novel "mosaic structure" for a SOFC (solid oxide fuel cell) cathode with high thermal expansion to improve the stability against thermal stress. Self-organizing mosaic-shaped cathode has been successfully achieved by controlling the amount of binder in the dip-coating solution. The anode-supported cell with mosaic-shaped cathode shows itself to be highly durable performance for rapid thermal cycles, however, the performance of the cell with a non-mosaic cathode exhibits severe deterioration originated from the delamination at the cathode/electrolyte interface after 7 thermal cycles. The thermal stability of an SOFC cathode can be evidently improved by controlling the surface morphology. In view of the importance of the thermal expansion properties of the cathode, the effects of cathode morphology on the thermal stress stability are discussed.

Effect of deposition temperature on thermal stabilities of copper-carbon films in barrier-less Cu metallization

NASA Astrophysics Data System (ADS)

Zhu, Huan; Fu, Zhiqiang; Xie, Qi; Yue, Wen; Wang, Chengbiao; Kang, Jiajie; Zhu, Lina

2018-01-01

Copper-carbon alloy films have been applied in barrier-less Cu metallization as seed layers for improving the thermal stabilities. The effect of the deposition temperature on the microstructure and properties of C-doped Cu films on Si substrates was investigated. The films were prepared by ion beam-assisted deposition at various deposition temperatures by co-sputtering of Cu and graphite targets. No inter-diffusion between Cu and Si was observed in Cu(C) films throughout this experiment, because XRD patterns corresponding to their deep-level reaction product, namely, Cu3Si, were not observed in XRD patterns and EDS results of Cu(C) films. Amorphous carbon layer and SiC layer were found in the interface of Cu(C) as-deposited films when deposition temperature rose to 100 °C by TEM, high-resolution image and Fourier transformation pattern. The Cu(C) films deposited at 100 °C had the best thermal stabilities and the lowest electrical resistivity of 4.44 μW cm after annealing at 400 °C for 1 h. Cu agglomeration was observed in Cu(C) alloy films with deposition temperatures of 200, 300 and 400 °C, and the most serious agglomeration occurred in Cu(C) films deposited at 200 °C. Undesired Cu agglomeration resulted in a sharp increase in the resistivity after annealing at 300 °C for 1 h. The deposition temperature of 100 °C reflected the superior thermal stabilities of Cu(C) seed layers compared with those of other layers.

Experimentation and Modeling of Jet A Thermal Stability in a Heated Tube

NASA Technical Reports Server (NTRS)

Khodabandeh, Julia W.

2005-01-01

High performance aircraft typically use hydrocarbon fuel to regeneratively cool the airframe and engine components. As the coolant temperatures increase, the fuel may react with dissolved oxygen forming deposits that limit the regenerative cooling system performance. This study investigates the deposition of Jet A using a thermal stability experiment and computational fluid dynamics (CFD) modeling. The experimental portion of this study is performed with a high Reynolds number thermal stability (HiRets) tester in which fuel passes though an electrically heated tube and the fuel outlet temperature is held constant. If the thermal stability temperature of the fuel is exceeded, deposits form and adhere to the inside of the tube creating an insulating layer between the tube and the fuel. The HiRets tester measures the tube outer wall temperatures near the fuel outlet to report the effect of deposition occurring inside the tube. Final deposits are also estimated with a carbon burn off analysis. The CFD model was developed and used to simulate the fluid dynamics, heat transfer, chemistry, and transport of the deposit precursors. The model is calibrated to the experiment temperature results and carbon burn-off deposition results. The model results show that the dominant factor in deposition is the heated wall temperature and that most of the deposits are formed in the laminar sublayer. The models predicted a 7.0E-6 kilograms per square meter-sec deposition rate, which compared well to the carbon burn-off analysis deposition rate of 1.0E-6 kilograms per square meter-sec.

Feasibility and process scale-up low cost alumina fibers for advanced Re-usable Surface Insulation (RSI)

NASA Technical Reports Server (NTRS)

Pearson, A.

1975-01-01

The objective of this program was to establish feasibility of a process to produce low cost aluminum oxide fibers having sufficient strength, flexibility, and thermal stability for multiple re-use at temperatures to 1480 C in advanced RSI type heat shields for reentry vehicles. Using bench-scale processing apparatus, the Alcoa 'Saphiber' process was successfully modified to produce nominally 8 microns diameter polycrystalline alpha-alumina fiber. Thermal stability was demonstrated in vacuum reheating tests to 1371 C and in atmospheric reheating to 1483 C. Individual fiber properties of strength, modulus, and flexibility were not determined because of friability and short length of the fiber. Rigidized tile produced from fiber of nominally 8, 20 and 40 micron diameter had thermal conductivities significantly higher than those of RSI SiO2 or mullite at relatively low temperature but became comparable above about 1000 C. Tile densities were high due to short fiber length, especially in the coarser diameter fiber. No significant effect of fiber diameter on thermal properties could be determined form the data. Mechanical properties of tiles deteriorated as fiber diameter increased.

Characterization of Chemically and Thermally Treated Oil-in-Water Heteroaggregates and Comparison to Conventional Emulsions.

PubMed

Maier, Christiane; Reichert, Corina L; Weiss, Jochen

2016-10-01

Heteroaggregated oil-in-water (O/W) emulsions formed by targeted combination of oppositely charged emulsion droplets were proposed to be used for the modulation of physical properties of food systems, ideally achieving the formation of a particulate 3-dimensional network at comparably low-fat content. In this study, rheological properties of Quillaja saponins (QS), sugar beet pectin (SBP), and whey protein isolate (WPI) stabilized conventional and heteroaggregated O/W emulsions at oil contents of 10% to 60% (w/w) were investigated. Selected systems having an oil content of 30% (w/w) and different particle sizes (d 43 ≤ 1.1 or ≥16.7 μm) were additionally subjected to chemical (genipin or glutaraldehyde) and thermal treatments, aiming to increase network stability. Subsequently, their rheological properties and stability were assessed. Yield stresses (τ 0 ) of both conventional and heteroaggregated O/W emulsions were found to depend on emulsifier type, oil content, and initial droplet size. For conventional emulsions, high yield stresses were only observed for SBP-based emulsions (τ 0 , SBP approximately 157 Pa). Highest yield stresses of heteroaggregates were observed when using small droplets stabilized by SBP/WPI (approximately 15.4 Pa), being higher than those of QS/WPI (approximately 1.6 Pa). Subsequent treatments led to significant alterations in rheological properties for SBP/WPI systems, with yield stresses increasing 29-fold (glutaraldehyde) and 2-fold (thermal treatment) compared to untreated heteroaggregates, thereby surpassing yield stresses of similarly treated conventional SBP emulsions. Genipin-driven treatments proved to be ineffective. Results should be of interest to food manufacturers wishing to design viscoelastic food emulsion based systems at lower oil droplet contents. © 2016 Institute of Food Technologists®.

Blended polybenzimidazole and melamine-co-formaldehyde thermosets

DOE PAGES

Klaehn, John R.; Orme, Christopher J.; Peterson, Eric S.

2016-05-11

Polybenzimidazole [PBI; poly-2,2’(m-phenylene)-5,5’-bibenzimidazole] is known to have excellent high temperature stability (up to 450 ºC) and superb H 2/CO 2 selectivity compared to most high performance (HP) polymers. But, PBI has issues in thin-film formation compared to other HP polymers, due to challenging processing techniques. In this work, new blended thermosets were made with PBI and poly(melamine co-formaldehyde) [PMF] to produce stable thin-films after thermal processing at 220-250 ºC. PBI film formation is difficult, and the film tends to fracture and fissure due to loss of processing aids and stabilizers (salt/acid additives) that are found in PBI solutions above10 wtmore » %. The PBI-PMF blended thermosets we report do not have stabilizers, and can be made into dense thin-films. It is remarkable that these thermally processed PBI-PMF films were stable in deionized water for extended periods, whereas many PBI films that contain additives are not. The PBI-PMF films were analyzed using pure and mixed gas permeability measurement techniques. At 250 °C, the data show H 2/CO 2 gas selectivities greater than 13. Also, from the gas permeation data, the energy of activation (Ep) of a mixed gas stream for PBI-PMF shows that hydrogen permeates more easily than the other gases, while the permeabilities for the larger kinetic diameter gases are greatly diminished. The FT-IR spectra show that the PBI-PMF films have changed from parent PBI after thermal processing, and PMF dominates the spectra even in minor percent compositions. Altogether, the reported PBI-PMF thermoset films show good stability which can be used for high temperature gas separation.« less

Blended polybenzimidazole and melamine-co-formaldehyde thermosets

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

Klaehn, John R.; Orme, Christopher J.; Peterson, Eric S.

Polybenzimidazole [PBI; poly-2,2’(m-phenylene)-5,5’-bibenzimidazole] is known to have excellent high temperature stability (up to 450 ºC) and superb H 2/CO 2 selectivity compared to most high performance (HP) polymers. But, PBI has issues in thin-film formation compared to other HP polymers, due to challenging processing techniques. In this work, new blended thermosets were made with PBI and poly(melamine co-formaldehyde) [PMF] to produce stable thin-films after thermal processing at 220-250 ºC. PBI film formation is difficult, and the film tends to fracture and fissure due to loss of processing aids and stabilizers (salt/acid additives) that are found in PBI solutions above10 wtmore » %. The PBI-PMF blended thermosets we report do not have stabilizers, and can be made into dense thin-films. It is remarkable that these thermally processed PBI-PMF films were stable in deionized water for extended periods, whereas many PBI films that contain additives are not. The PBI-PMF films were analyzed using pure and mixed gas permeability measurement techniques. At 250 °C, the data show H 2/CO 2 gas selectivities greater than 13. Also, from the gas permeation data, the energy of activation (Ep) of a mixed gas stream for PBI-PMF shows that hydrogen permeates more easily than the other gases, while the permeabilities for the larger kinetic diameter gases are greatly diminished. The FT-IR spectra show that the PBI-PMF films have changed from parent PBI after thermal processing, and PMF dominates the spectra even in minor percent compositions. Altogether, the reported PBI-PMF thermoset films show good stability which can be used for high temperature gas separation.« less

Stabilization of a tetrameric malate dehydrogenase by introduction of a disulfide bridge at the dimer-dimer interface.

PubMed

Bjørk, Alexandra; Dalhus, Bjørn; Mantzilas, Dimitrios; Eijsink, Vincent G H; Sirevåg, Reidun

2003-12-05

Malate dehydrogenase (MDH) from the moderately thermophilic bacterium Chloroflexus aurantiacus (CaMDH) is a tetrameric enzyme, while MDHs from mesophilic organisms usually are dimers. To investigate the potential contribution of the extra dimer-dimer interface in CaMDH with respect to thermal stability, we have engineered an intersubunit disulfide bridge designed to strengthen dimer-dimer interactions. The resulting mutant (T187C, containing two 187-187 disulfide bridges in the tetramer) showed a 200-fold increase in half-life at 75 degrees C and an increase of 15 deg. C in apparent melting temperature compared to the wild-type. The crystal structure of the mutant (solved at 1.75 A resolution) was essentially identical with that of the wild-type, with the exception of the added inter-dimer disulfide bridge and the loss of an aromatic intra-dimer contact. Remarkably, the mutant and the wild-type had similar temperature optima and activities at their temperature optima, thus providing a clear case of uncoupling of thermal stability and thermoactivity. The results show that tetramerization may contribute to MDH stability to an extent that depends strongly on the number of stabilizing interactions in the dimer-dimer interface.

Aqueous clay suspensions stabilized by alginate fluid gels for coal spontaneous combustion prevention and control.

PubMed

Qin, Botao; Ma, Dong; Li, Fanglei; Li, Yong

2017-11-01

We have developed aqueous clay suspensions stabilized by alginate fluid gels (AFG) for coal spontaneous combustion prevention and control. Specially, this study aimed to characterize the effect of AFG on the microstructure, static and dynamic stability, and coal fire inhibition performances of the prepared AFG-stabilized clay suspensions. Compared with aqueous clay suspensions, the AFG-stabilized clay suspensions manifest high static and dynamic stability, which can be ascribed to the formation of a robust three-dimensional gel network by AFG. The coal acceleration oxidation experimental results show that the prepared AFG-stabilized clay suspensions can improve the coal thermal stability and effectively inhibit the coal spontaneous oxidation process by increasing crossing point temperature (CPT) and reducing CO emission. The prepared low-cost and nontoxic AFG-stabilized clay suspensions, exhibiting excellent coal fire extinguishing performances, indicate great application potentials in coal spontaneous combustion prevention and control.

Stabilizing the Electrode/Electrolyte Interface of LiNi0.8Co0.15Al0.05O2 through Tailoring Aluminum Distribution in Microspheres as Long-Life, High-Rate, and Safe Cathode for Lithium-Ion Batteries.

PubMed

Hou, Peiyu; Zhang, Hongzhou; Deng, Xiaolong; Xu, Xijin; Zhang, Lianqi

2017-09-06

The unstable electrode/electrolyte interface of high-capacity LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) cathodes, especially at a highly delithiated state, usually leads to the transformation of layered to spinel and/or rock-salt phases, resulting in drastic capacity fade and poor thermal stability. Herein, the Al-increased and Ni-,Co-decreased electrode surface is fabricated through tailoring element distribution in micrometer-sized spherical NCA secondary particles via coprecipitation and solid-state reactions, aimed at stabilizing the electrode/electrolyte interface during continuous cycles. As expected, it shows much extended cycle life, 93.6% capacity retention within 100 cycles, compared with that of 78.5% for the normal NCA. It also delivers large reversible capacity of about 140 mAh g -1 even at 20 C, corresponding to energy density of around 480 Wh kg -1 , which is enhanced by 45% compared to that of the normal NCA (about 330 Wh kg -1 ). Besides, the delayed heat emission temperature and reduced heat generation mean remarkably improved thermal stability. These foregoing improvements are ascribed to the Al-increased spherical secondary particle surface that stabilizes the electrode/electrolyte interface by protecting inner components from directly contacting with electrolyte and suppressing the side reaction on electrode surface between high oxidizing Ni 4+ and electrolyte.

Effects of pH-Shift Processing and Microbial Transglutaminase on the Gel and Emulsion Characteristics of Porcine Myofibrillar System

PubMed Central

Hong, Geun-Pyo; Chun, Ji-Yeon; Jo, Yeon-Ji

2014-01-01

This study investigated the effects of microbial transglutaminase (MTGase) and pH-shift processing on the functional properties of porcine myofibrillar proteins (MP). The pH-shift processing was carried out by decreasing the pH of MP suspension to 3.0, followed by re-adjustment to pH 6.2. The native (CM) and pH-shifted MP (PM) was reacted with and without MTGase, and the gelling and emulsion characteristics were compared. To compare the pH-shifted MTGase-treated MP (PT), deamidation (DM) was conducted by reacting MTGase with MP at pH 3.0. Rigid thermal gel was produced by MTGase-treated native MP (CT) and PT. PM and DM showed the lowest storage modulus (G') at the end of thermal scanning. Both MTGase and pH-shifting produced harder MP gel, and the highest gel strength was obtained in PT. All treatments yielded lower than CM, and CT showed significantly higher yield than PM and DM treatments. For emulsion characteristics, pH-shifting improved the emulsifying ability of MP-stabilized emulsion, while the treatments had lower emulsion stability. PM-stabilized emulsion exhibited the lowest creaming stability among all treatments. The emulsion stability could be improved by the usage of MTGase. The results indicated that pH-shifting combined with MTGase had a potential application to modify or improve functional properties of MP in manufacturing of meat products. PMID:26760940

A C-Te-based binary OTS device exhibiting excellent performance and high thermal stability for selector application.

PubMed

Chekol, Solomon Amsalu; Yoo, Jongmyung; Park, Jaehyuk; Song, Jeonghwan; Sung, Changhyuck; Hwang, Hyunsang

2018-08-24

In this letter, we demonstrate a new binary ovonic threshold switching (OTS) selector device scalable down to ø30 nm based on C-Te. Our proposed selector device exhibits outstanding performance such as a high switching ratio (I on /I off  > 10 5 ), an extremely low off-current (∼1 nA), an extremely fast operating speed of <10 ns (transition time of <2 ns and delay time of <8 ns), high endurance (10 9 ), and high thermal stability (>450 °C). The observed high thermal stability is caused by the relatively small atomic size of C, compared to Te, which can effectively suppress the segregation and crystallization of Te in the OTS film. Furthermore, to confirm the functionality of the selector in a crossbar array, we evaluated a 1S-1R device by integrating our OTS device with a ReRAM (resistive random access memory) device. The 1S-1R integrated device exhibits a successful suppression of leakage current at the half-selected cell and shows an excellent read-out margin (>2 12 word lines) in a fast read operation.

Development of Eco-friendly Soy Protein Isolate Films with High Mechanical Properties through HNTs, PVA, and PTGE Synergism Effect

PubMed Central

Liu, Xiaorong; Song, Ruyuan; Zhang, Wei; Qi, Chusheng; Zhang, Shifeng; Li, Jianzhang

2017-01-01

This study was to develop novel soy protein isolate-based films for packaging using halloysite nanotubes (HNTs), poly-vinyl alcohol (PVA), and 1,2,3-propanetriol-diglycidyl-ether (PTGE). The structural, crystallinity, opacity, micromorphology, and thermal stability of the resultant SPI/HNTs/PVA/PTGE film were analyzed by the Attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), UV-Vis spectrophotometry, scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA). The SPI/HNTs/PVA/PTGE film illustrated that HNTs were uniformly dispersed in the SPI matrix and the thermal stability of the film was enhanced. Furthermore, the tensile strength (TS) of the SPI/HNTs/PVA/PTGE film was increased by 329.3% and the elongation at the break (EB) remained unchanged. The water absorption (WA) and the moisture content (MC) were decreased by 5.1% and 10.4%, respectively, compared to the unmodified film. The results highlighted the synergistic effects of SPI, HNTs, PVA, and PTGE on the mechanical properties, water resistance, and thermal stability of SPI films, which showed excellent strength and flexibility. In short, SPI films prepared from HNTs, PVA, and PTGE showed considerable potential as packaging materials. PMID:28281634

Nanostructured porous Si optical biosensors: effect of thermal oxidation on their performance and properties.

PubMed

Shtenberg, Giorgi; Massad-Ivanir, Naama; Fruk, Ljiljana; Segal, Ester

2014-09-24

The influence of thermal oxidation conditions on the performance of porous Si optical biosensors used for label-free and real-time monitoring of enzymatic activity is studied. We compare three oxidation temperatures (400, 600, and 800 °C) and their effect on the enzyme immobilization efficiency and the intrinsic stability of the resulting oxidized porous Si (PSiO2), Fabry-Pérot thin films. Importantly, we show that the thermal oxidation profoundly affects the biosensing performance in terms of greater optical sensitivity, by monitoring the catalytic activity of horseradish peroxidase and trypsin-immobilized PSiO2. Despite the significant decrease in porous volume and specific surface area (confirmed by nitrogen gas adsorption-desorption studies) with elevating the oxidation temperature, higher content and surface coverage of the immobilized enzymes is attained. This in turn leads to greater optical stability and sensitivity of PSiO2 nanostructures. Specifically, films produced at 800 °C exhibit stable optical readout in aqueous buffers combined with superior biosensing performance. Thus, by proper control of the oxide layer formation, we can eliminate the aging effect, thus achieving efficient immobilization of different biomolecules, optical signal stability, and sensitivity.

Development of Eco-friendly Soy Protein Isolate Films with High Mechanical Properties through HNTs, PVA, and PTGE Synergism Effect

NASA Astrophysics Data System (ADS)

Liu, Xiaorong; Song, Ruyuan; Zhang, Wei; Qi, Chusheng; Zhang, Shifeng; Li, Jianzhang

2017-03-01

This study was to develop novel soy protein isolate-based films for packaging using halloysite nanotubes (HNTs), poly-vinyl alcohol (PVA), and 1,2,3-propanetriol-diglycidyl-ether (PTGE). The structural, crystallinity, opacity, micromorphology, and thermal stability of the resultant SPI/HNTs/PVA/PTGE film were analyzed by the Attenuated total reflectance-Fourier transformed infrared (ATR-FTIR) spectroscopy, X-ray diffraction (XRD), UV-Vis spectrophotometry, scanning electron microscopy (SEM), and thermo-gravimetric analysis (TGA). The SPI/HNTs/PVA/PTGE film illustrated that HNTs were uniformly dispersed in the SPI matrix and the thermal stability of the film was enhanced. Furthermore, the tensile strength (TS) of the SPI/HNTs/PVA/PTGE film was increased by 329.3% and the elongation at the break (EB) remained unchanged. The water absorption (WA) and the moisture content (MC) were decreased by 5.1% and 10.4%, respectively, compared to the unmodified film. The results highlighted the synergistic effects of SPI, HNTs, PVA, and PTGE on the mechanical properties, water resistance, and thermal stability of SPI films, which showed excellent strength and flexibility. In short, SPI films prepared from HNTs, PVA, and PTGE showed considerable potential as packaging materials.

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

DOE PAGES

Fergus, Jeffrey W.

2014-04-12

One of the important applications of yttria stabilized zirconia is as a thermal barrier coating for gas turbine engines. While yttria stabilized zirconia performs well in this function, the need for increased operating temperatures to achieve higher energy conversion efficiencies, requires the development of improved materials. To meet this challenge, some rare-earth zirconates that form the cubic fluorite derived pyrochlore structure are being developed for use in thermal barrier coatings due to their low thermal conductivity, excellent chemical stability and other suitable properties. In this paper, the thermal conductivities of current and prospective oxides for use in thermal barrier coatingsmore » are reviewed. The factors affecting the variations and differences in the thermal conductivities and the degradation behaviors of these materials are discussed.« less

Comparative Analysis of the Effects of Severe Plastic Deformation and Thermomechanical Training on the Functional Stability of Ti50.5Ni24.5Pd25 High-Temperature Shape Memory Alloy

NASA Technical Reports Server (NTRS)

Atli, K. C.; Karaman, I.; Noebe, R. D.; Maier, H. J.

2010-01-01

We compare the effectiveness of a conventional thermomechanical training procedure and severe plastic deformation via equal channel angular extrusion to achieve improved functional stability in a Ti50.5Ni24.5Pd25 high-temperature shape memory alloy. Thermomechanical testing indicates that both methods result in enhanced shape memory characteristics, such as reduced irrecoverable strain and thermal hysteresis. The mechanisms responsible for the improvements are discussed in light of microstructural findings from transmission electron microscopy.

Accelerating Vaccine Formulation Development Using Design of Experiment Stability Studies.

PubMed

Ahl, Patrick L; Mensch, Christopher; Hu, Binghua; Pixley, Heidi; Zhang, Lan; Dieter, Lance; Russell, Ryann; Smith, William J; Przysiecki, Craig; Kosinski, Mike; Blue, Jeffrey T

2016-10-01

Vaccine drug product thermal stability often depends on formulation input factors and how they interact. Scientific understanding and professional experience typically allows vaccine formulators to accurately predict the thermal stability output based on formulation input factors such as pH, ionic strength, and excipients. Thermal stability predictions, however, are not enough for regulators. Stability claims must be supported by experimental data. The Quality by Design approach of Design of Experiment (DoE) is well suited to describe formulation outputs such as thermal stability in terms of formulation input factors. A DoE approach particularly at elevated temperatures that induce accelerated degradation can provide empirical understanding of how vaccine formulation input factors and interactions affect vaccine stability output performance. This is possible even when clear scientific understanding of particular formulation stability mechanisms are lacking. A DoE approach was used in an accelerated 37(°)C stability study of an aluminum adjuvant Neisseria meningitidis serogroup B vaccine. Formulation stability differences were identified after only 15 days into the study. We believe this study demonstrates the power of combining DoE methodology with accelerated stress stability studies to accelerate and improve vaccine formulation development programs particularly during the preformulation stage. Copyright © 2016 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.

Effect of whey protein isolate and β-cyclodextrin wall systems on stability of microencapsulated vanillin by spray-freeze drying method.

PubMed

Hundre, Swetank Y; Karthik, P; Anandharamakrishnan, C

2015-05-01

Vanillin flavour is highly volatile in nature and due to that application in food incorporation is limited; hence microencapsulation of vanillin is an ideal technique to increase its stability and functionality. In this study, vanillin was microencapsulated for the first time by non-thermal spray-freeze-drying (SFD) technique and its stability was compared with other conventional techniques such as spray drying (SD) and freeze-drying (FD). Different wall materials like β-cyclodextrin (β-cyd), whey protein isolate (WPI) and combinations of these wall materials (β-cyd + WPI) were used to encapsulate vanillin. SFD microencapsulated vanillin with WPI showed spherical shape with numerous fine pores on the surface, which in turn exhibited good rehydration ability. On the other hand, SD powder depicted spherical shape without pores and FD encapsulated powder yielded larger particle sizes with flaky structure. FTIR analysis confirmed that there was no interaction between vanillin and wall materials. Moreover, spray-freeze-dried vanillin + WPI sample exhibited better thermal stability than spray dried and freeze-dried microencapsulated samples. Copyright © 2014 Elsevier Ltd. All rights reserved.

Thermal Degradation Mechanism of a Thermostable Polyester Stabilized with an Open-Cage Oligomeric Silsesquioxane

PubMed Central

Gozalbo, Ana; Mestre, Sergio; Sanz, Vicente

2017-01-01

A polyester composite was prepared through the polymerization of an unsaturated ester resin with styrene and an open-cage oligomeric silsesquioxane with methacrylate groups. The effect of the open-cage oligomeric silsesquioxane on the thermal stability of the thermostable polyester was studied using both thermogravimetric analysis and differential thermal analysis. The results showed that the methacryl oligomeric silsesquioxane improved the thermal stability of the polyester. The decomposition mechanism of the polyester/oligomer silsesquioxane composite was proposed by Fourier transform infrared spectroscopy (FTIR) analysis of the volatiles. PMID:29295542

Investigation on Synthesis, Stability, and Thermal Conductivity Properties of Water-Based SnO2/Reduced Graphene Oxide Nanofluids

PubMed Central

Yu, Xiaofen; Wu, Qibai; Zhang, Haiyan; Zeng, Guoxun; Li, Wenwu; Qian, Yannan; Li, Yang; Yang, Guoqiang; Chen, Muyu

2017-01-01

With the rapid development of industry, heat removal and management is a major concern for any technology. Heat transfer plays a critically important role in many sectors of engineering; nowadays utilizing nanofluids is one of the relatively optimized techniques to enhance heat transfer. In the present work, a facile low-temperature solvothermal method was employed to fabricate the SnO2/reduced graphene oxide (rGO) nanocomposite. X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscope (XPS), Raman spectroscopy, and transmission electron microscopy (TEM) have been performed to characterize the SnO2/rGO nanocomposite. Numerous ultrasmall SnO2 nanoparticles with average diameters of 3–5 nm were anchored on the surface of rGO, which contain partial hydrophilic functional groups. Water-based SnO2/rGO nanofluids were prepared with various weight concentrations by using an ultrasonic probe without adding any surfactants. The zeta potential was measured to investigate the stability of the as-prepared nanofluid which exhibited great dispersion stability after quiescence for 60 days. A thermal properties analyzer was employed to measure thermal conductivity of water-based SnO2/rGO nanofluids, and the results showed that the enhancement of thermal conductivity could reach up to 31% at 60 °C under the mass fraction of 0.1 wt %, compared to deionized water. PMID:29280972

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.

Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb Sounder

NASA Technical Reports Server (NTRS)

Cofield, Richard; Kasl, Eldon P.

2010-01-01

We describe the fabrication and thermal-stability analysis and test of a composite demonstration model of the Scanning Microwave Limb Sounder (SMLS) primary reflector, having full 4m height and 1/3 the width planned for flight. SMLS is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission between 180 and 660 GHz. Current MLS instruments in low Earth orbit scan pencil-beam antennas (sized to resolve about one scale height) vertically over the atmospheric limb. SMLS, planned for the Global Atmospheric Composition Mission of the NRC Decadal Survey, adds azimuthal scanning for better horizontal and temporal resolution and coverage than typical orbit spacing provides. SMLS combines the wide scan range of the parabolic torus with unblocked offset Cassegrain optics. The resulting system is diffraction-limited in the vertical plane but highly astigmatic in the horizontal, having a beam aspect ratio [tilde operator]1:20. Symmetry about the nadir axis ensures that beam shape is nearly invariant over +/-65(white bullet) azimuth. The a feeds a low-noise SIS receiver whose FOV is swept over the reflector system by a small scanning mirror. Using finiteelement models of antenna reflectors and structure, we evaluate thermal deformations and the resulting optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during wide-range (ambient+[-97,+75](white bullet) C) thermal soak tests of the primary in a chamber. This range exceeds predicted orbital soak ranges by large factors, implying in-orbit thermal stability of 0.21(mu)m rms/(white bullet)C, which meets SMLS requirements.

Organic Heat Stabilizers for Polyvinyl Chloride (PVC): A Synergistic Behavior of Eugenol and Uracil Derivative

NASA Astrophysics Data System (ADS)

Asawakosinchai, Aran; Jubsilp, Chanchira; Mora, Phattarin; Rimdusit, Sarawut

2017-10-01

Recycling ability, mechanical, and thermal properties of PVC stabilized with organic heat stabilizers, i.e., uracil (DAU) and eugenol were investigated to substitute PVCs stabilized with commercial lead, Ca/Zn, and organic-based stabilizer for PVC pipe production. PVC stabilized with the DAU and the eugenol can be processable at 30 °C lower than that of the PVC stabilized with commercial heat stabilizers. The most remarkable short-term thermal stability belonged to the PVC stabilized with the DAU, and its original color can be maintained at least up to 3 processing cycles. Synergistic behavior in thermal stability of the PVC mixed with DAU and eugenol at mass ratios of 1.5:1.5 was observed. Mechanical properties of DAU- and eugenol-stabilized PVC were higher than the samples with other heat stabilizers. Glass transition temperature of the PVC stabilized with all heat stabilizers was determined to be 99 °C with the exception of the value of 89 °C for eugenol-stabilized PVC. Therefore, the DAU and the eugenol showed high potential to be used as an organic heat stabilizer for PVC because of their non-toxic and good heat resistance properties.

Novel green nano composites films fabricated by indigenously synthesized graphene oxide and chitosan.

PubMed

Khan, Younus H; Islam, Atif; Sarwar, Afsheen; Gull, Nafisa; Khan, Shahzad M; Munawar, Muhammad A; Zia, Saba; Sabir, Aneela; Shafiq, Muhammad; Jamil, Tahir

2016-08-01

Graphene oxide (GO) was indigenously synthesized from graphite using standard Hummers method. Chitosan-graphene oxide green composite films were fabricated by mixing aqueous solution of chitosan and GO using dilute acetic acid as a solvent for chitosan. Chitosan of different viscosity and calculated molecular weight was used keeping amount of GO constant in each composite film. The structural properties, thermal stability and mechanical properties of the composite films were investigated using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and tensile test. FTIR studies revealed the successful synthesis of GO from graphite powder and it was confirmed that homogenous blending of chitosan and GO was promising due to oxygenated functional groups on the surface of GO. XRD indicated effective conversion of graphite to GO as its strong peak observed at 11.06° as compared to pristine graphite which appeared at 26°. Moreover, mechanical analysis confirmed the effect of molecular weight on the mechanical properties of chitosan-GO composites showing that higher molecular weight chitosan composite (GOCC-1000) showed best strength (higher than 3GPa) compared to other composite films. Thermal stability of GOCC-1000 was enhanced for which residual content increased up to 56% as compared to the thermal stability of GOCC-200 whose residue was restricted to only 24%. The morphological analysis of the composites sheets by SEM was smooth having dense structure and showed excellent interaction, miscibility, compatibility and dispersion of GO with chitosan. The prepared composite films find their applications as biomaterials in different biomedical fields. Copyright © 2016 Elsevier Ltd. All rights reserved.

Thermal Stabilization of Biologics with Photoresponsive Hydrogels.

PubMed

Sridhar, Balaji V; Janczy, John R; Hatlevik, Øyvind; Wolfson, Gabriel; Anseth, Kristi S; Tibbitt, Mark W

2018-03-12

Modern medicine, biological research, and clinical diagnostics depend on the reliable supply and storage of complex biomolecules. However, biomolecules are inherently susceptible to thermal stress and the global distribution of value-added biologics, including vaccines, biotherapeutics, and Research Use Only (RUO) proteins, requires an integrated cold chain from point of manufacture to point of use. To mitigate reliance on the cold chain, formulations have been engineered to protect biologics from thermal stress, including materials-based strategies that impart thermal stability via direct encapsulation of the molecule. While direct encapsulation has demonstrated pronounced stabilization of proteins and complex biological fluids, no solution offers thermal stability while enabling facile and on-demand release from the encapsulating material, a critical feature for broad use. Here we show that direct encapsulation within synthetic, photoresponsive hydrogels protected biologics from thermal stress and afforded user-defined release at the point of use. The poly(ethylene glycol) (PEG)-based hydrogel was formed via a bioorthogonal, click reaction in the presence of biologics without impact on biologic activity. Cleavage of the installed photolabile moiety enabled subsequent dissolution of the network with light and release of the encapsulated biologic. Hydrogel encapsulation improved stability for encapsulated enzymes commonly used in molecular biology (β-galactosidase, alkaline phosphatase, and T4 DNA ligase) following thermal stress. β-galactosidase and alkaline phosphatase were stabilized for 4 weeks at temperatures up to 60 °C, and for 60 min at 85 °C for alkaline phosphatase. T4 DNA ligase, which loses activity rapidly at moderately elevated temperatures, was protected during thermal stress of 40 °C for 24 h and 60 °C for 30 min. These data demonstrate a general method to employ reversible polymer networks as robust excipients for thermal stability of complex biologics during storage and shipment that additionally enable on-demand release of active molecules at the point of use.

Statistical Design in Isothermal Aging of Polyimide Resins

NASA Technical Reports Server (NTRS)

Sutter, James K.; Jobe, Marcus; Crane, Elizabeth A.

1995-01-01

Recent developments in research on polyimides for high temperature applications have led to the synthesis of many new polymers. Among the criteria that determines their thermal oxidative stability, isothermal aging is one of the most important. Isothermal aging studies require that many experimental factors are controlled to provide accurate results. In this article we describe a statistical plan that compares the isothermal stability of several polyimide resins, while minimizing the variations inherent in high-temperature aging studies.

Influence of different temperatures on the thermal fatigue behavior and thermal stability of hot-work tool steel processed by a biomimetic couple laser technique

NASA Astrophysics Data System (ADS)

Meng, Chao; Zhou, Hong; Zhou, Ying; Gao, Ming; Tong, Xin; Cong, Dalong; Wang, Chuanwei; Chang, Fang; Ren, Luquan

2014-04-01

Three kinds of biomimetic non-smooth shapes (spot-shape, striation-shape and reticulation-shape) were fabricated on the surface of H13 hot-work tool steel by laser. We investigated the thermal fatigue behavior of biomimetic non-smooth samples with three kinds of shapes at different thermal cycle temperature. Moreover, the evolution of microstructure, as well as the variations of hardness of laser affected area and matrix were studied and compared. The results showed that biomimetic non-smooth samples had better thermal fatigue behavior compared to the untreated samples at different thermal cycle temperatures. For a given maximal temperature, the biomimetic non-smooth sample with reticulation-shape had the optimum thermal fatigue behavior, than with striation-shape which was better than that with the spot-shape. The microstructure observations indicated that at different thermal cycle temperatures the coarsening degrees of microstructures of laser affected area were different and the microstructures of laser affected area were still finer than that of the untreated samples. Although the resistance to thermal cycling softening of laser affected area was lower than that of the untreated sample, laser affected area had higher microhardness than the untreated sample at different thermal cycle temperature.

Phosphorus-Assisted Biomass Thermal Conversion: Reducing Carbon Loss and Improving Biochar Stability

PubMed Central

Zhao, Ling; Cao, Xinde; Zheng, Wei; Kan, Yue

2014-01-01

There is often over 50% carbon loss during the thermal conversion of biomass into biochar, leading to it controversy for the biochar formation as a carbon sequestration strategy. Sometimes the biochar also seems not to be stable enough due to physical, chemical, and biological reactions in soils. In this study, three phosphorus-bearing materials, H3PO4, phosphate rock tailing (PRT), and triple superphosphate (TSP), were used as additives to wheat straw with a ratio of 1: 0.4–0.8 for biochar production at 500°C, aiming to alleviate carbon loss during pyrolysis and to increase biochar-C stabilization. All these additives remarkably increased the biochar yield from 31.7% (unmodified biochar) to 46.9%–56.9% (modified biochars). Carbon loss during pyrolysis was reduced from 51.7% to 35.5%–47.7%. Thermogravimetric analysis curves showed that the additives had no effect on thermal stability of biochar but did enhance its oxidative stability. Microbial mineralization was obviously reduced in the modified biochar, especially in the TSP-BC, in which the total CO2 emission during 60-d incubation was reduced by 67.8%, compared to the unmodified biochar. Enhancement of carbon retention and biochar stability was probably due to the formation of meta-phosphate or C-O-PO3, which could either form a physical layer to hinder the contact of C with O2 and bacteria, or occupy the active sites of the C band. Our results indicate that pre-treating biomass with phosphors-bearing materials is effective for reducing carbon loss during pyrolysis and for increasing biochar stabilization, which provides a novel method by which biochar can be designed to improve the carbon sequestration capacity. PMID:25531111

In-situ micro-FTIR Study of Thermal Changes of Organics in Tagish Lake Meteorite: Behavior of Aliphatic Oxygenated Functions and Effects of Minerals

NASA Technical Reports Server (NTRS)

Kebukawa, Yoko; Nakashima, Satoru; Nakamura-Messenger, Keiko; Zolensky, Michael E.

2007-01-01

Systematic in-situ FTIR heating experiments of Tagish Lake meteorite grains have been performed in order to study thermal stability of chondritic organics. Some aliphatic model organic substances have also been used to elucidate effects of hydrous phyllosilicate minerals on the thermal stability of organics. The experimental results indicated that organic matter in the Tagish Lake meteorite might contain oxygenated aliphatic hydrocarbons which are thermally stable carbonyls such as ester and/or C=O in ring compounds. The presence of hydrous phyllosilicate minerals has a pronounced effect on the increase of the thermal stability of aliphatic and oxygenated functions. These oxygenated aliphatic organics in Tagish Lake can be formed during the aqueous alteration in the parent body and the formation temperature condition might be less than 200 C, based especially on the thermal stability of C-O components. The hydrous phyllosilicates might provide sites for organic globule formation and protected some organic decomposition

Engineering Interface Structures and Thermal Stabilities via SPD Processing in Bulk Nanostructured Metals

DOE PAGES

Zheng, Shijian; Carpenter, John S.; McCabe, Rodney J.; ...

2014-02-27

Nanostructured metals achieve extraordinary strength but suffer from low thermal stability, both a consequence of a high fraction of interfaces. Overcoming this tradeoff relies on making the interfaces themselves thermally stable. In this paper, we show that the atomic structures of bi-metal interfaces in macroscale nanomaterials suitable for engineering structures can be significantly altered via changing the severe plastic deformation (SPD) processing pathway. Two types of interfaces are formed, both exhibiting a regular atomic structure and providing for excellent thermal stability, up to more than half the melting temperature of one of the constituents. Most importantly, the thermal stability ofmore » one is found to be significantly better than the other, indicating the exciting potential to control and optimize macroscale robustness via atomic-scale bimetal interface tuning. As a result, we demonstrate an innovative way to engineer pristine bimetal interfaces for a new class of simultaneously strong and thermally stable materials.« less

Dielectric Coating Thermal Stabilization During GaAs-Based Laser Fabrication for Improved Device Yield

DTIC Science & Technology

2015-11-25

1 Dielectric coating thermal stabilization during GaAs-based laser fabrication for improved device yield 1 Michael K. Connors a, c), Jamal...side contact metal, underlying SiO2 dielectric coating, and semiconductor surface. A thermal-anneal procedure developed for the fabrication of GaAs...slab coupled optical waveguide (SCOW) ridge waveguide devices stabilizes the SiO2 dielectric coating, by means of outgassing and stress reduction

Low conductivity and sintering-resistant thermal barrier coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming (Inventor); Miller, Robert A. (Inventor)

2007-01-01

A thermal barrier coating composition is provided. The composition has a base oxide, a primary stabilizer, and at least two additional cationic oxide dopants. Preferably, a pair of group A and group B defect cluster-promoting oxides is used in conjunction with the base and primary stabilizer oxides. The new thermal barrier coating is found to have significantly lower thermal conductivity and better sintering resistance. In preferred embodiments, the base oxide is selected from zirconia and hafnia. The group A and group B cluster-promoting oxide dopants preferably are selected such that the group A dopant has a smaller cationic radius than the primary stabilizer oxide, and so that the primary stabilizer oxide has a small cationic radius than that of the group B dopant.

Low conductivity and sintering-resistant thermal barrier coatings

NASA Technical Reports Server (NTRS)

Zhu, Dongming (Inventor); Miller, Robert A. (Inventor)

2006-01-01

A thermal barrier coating composition is provided. The composition has a base oxide, a primary stabilizer, and at least two additional cationic oxide dopants. Preferably, a pair of group A and group B defect cluster-promoting oxides is used in conjunction with the base and primary stabilizer oxides. The new thermal barrier coating is found to have significantly lower thermal conductivity and better sintering resistance. In preferred embodiments, the base oxide is selected from zirconia and hafnia. The group A and group B cluster-promoting oxide dopants preferably are selected such that the group A dopant has a smaller cationic radius than the primary stabilizer oxide, and so that the primary stabilizer oxide has a small cationic radius than that of the group B dopant.

Plasma membrane aquaporins mediates vesicle stability in broccoli

PubMed Central

Martínez-Ballesta, Maria del Carmen; García-Gomez, Pablo; Yepes-Molina, Lucía; Guarnizo, Angel L.; Teruel, José A.

2018-01-01

The use of in vitro membrane vesicles is attractive because of possible applications in therapies. Here we aimed to compare the stability and functionality of plasma membrane vesicles extracted from control and salt-treated broccoli. The impact of the amount of aquaporins was related to plasma membrane osmotic water permeability and the stability of protein secondary structure. Here, we describe for first time an increase in plant aquaporins acetylation under high salinity. Higher osmotic water permeability in NaCl vesicles has been related to higher acetylation, upregulation of aquaporins, and a more stable environment to thermal denaturation. Based on our findings, we propose that aquaporins play an important role in vesicle stability. PMID:29420651

Thermal conductivity and viscosity measurements of ethylene glycol-based Al2O3 nanofluids

PubMed Central

2011-01-01

The dispersion and stability of nanofluids obtained by dispersing Al2O3 nanoparticles in ethylene glycol have been analyzed at several concentrations up to 25% in mass fraction. The thermal conductivity and viscosity were experimentally determined at temperatures ranging from 283.15 K to 323.15 K using an apparatus based on the hot-wire method and a rotational viscometer, respectively. It has been found that both thermal conductivity and viscosity increase with the concentration of nanoparticles, whereas when the temperature increases the viscosity diminishes and the thermal conductivity rises. Measured enhancements on thermal conductivity (up to 19%) compare well with literature values when available. New viscosity experimental data yield values more than twice larger than the base fluid. The influence of particle size on viscosity has been also studied, finding large differences that must be taken into account for any practical application. These experimental results were compared with some theoretical models, as those of Maxwell-Hamilton and Crosser for thermal conductivity and Krieger and Dougherty for viscosity. PMID:21711737

Effect of thermal barrier coating with various blends of pumpkin seed oil methyl ester in DI diesel engine

NASA Astrophysics Data System (ADS)

Karthickeyan, V.; Balamurugan, P.

2017-10-01

The rise in oil prices, dependency on fossil fuels, degradation of non-renewable energy resources and global warming strives to find a low-carbon content alternative fuel to the conventional fuel. In the present work, Partially Stabilized Zirconia (PSZ) was used as a thermal barrier coating in piston head, cylinder head and intake and exhaust valves using plasma spray technique, which provided a rise in combustion chamber temperature. With the present study, the effects of thermal barrier coating on the blends of Pumpkin Seed Oil Methyl Ester (PSOME) were observed in both the coated and uncoated engine. Performance and emission characteristics of the PSOME in coated and uncoated engines were observed and compared. Increased thermal efficiency and reduced fuel consumption were observed for B25 and diesel in coated and uncoated engine. On comparing with the other biodiesel samples, B25 exhibited lower HC, NOx and smoke emissions in thermally coated engine than uncoated engine. After 100 h of operation, no anamolies were found in the thermally coated components except minor cracks were identified in the edges of the piston head.

An atlas of thermal data for biomass and other fuels

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

Gaur, S.; Reed, T.B.

1995-06-01

Biomass is recognized as a major source of renewable energy. In order to convert biomass energy to more useful forms, it is necessary to have accurate scientific data on the thermal properties of biomass. This Atlas has been written to supply a uniform source of that information. In the last few decades Thermal analysis (TA) tools such as thermogravimetry, differential thermal analysis, thermo mechanical analysis, etc. have become more important. The data obtained from these techniques can provide useful information in terms of reaction mechanism, kinetic parameters, thermal stability, phase transformation, heat of reaction, etc. for gas-solid and gas-liquid systems.more » Unfortunately, there are no ASTM standards set for the collection of these types of data using TA techniques and therefore, different investigators use different conditions which suit their requirements for measuring this thermal data. As a result, the information obtained from different laboratories is not comparable. This Atlas provides the ability to compare new laboratory results with a wide variety of related data available in the literature and helps ensure consistency in using these data.« less

[Thermal stability of rhodopsins and opsins in warm- and cold-blooded vertebrates].

PubMed

Berman, A L; Suvorov, S A; Parnova, R G; Gracheva, O A; Rychkova, M P

1981-01-01

Thermal stability of rhodopsins and opsins has been studied in endothermic (sheep, cattle, pig, rat) and ectothermic (frog) animals under two different conditions -- in the intact photoreceptor membranes (PM) and after substitution of the lipid surrounding of rhodopsins by molecules of a detergent Triton X-100. Lipid composition of PM in these animals was also studied, as well as the effect of proteases (pronase and papaine) upon thermal stability of rhodopsins in PM and in 1% Triton X-100 solutions. The thermal resistance of rhodopsins in PM was found to vary in the animals used to a great extent. The maximal differences in thermal stability of rhodopsins in ecto- and endothermic animals were due to the properties of photoreceptor protein itself, whereas in ectothermic animals they resulted mainly from differences in the lipid composition of PM. PM of endothermic animals differ from those of ectothermic ones by a lower content of polyenoic fatty acids and by a higher amount of phosphatidyl ethanolamine. The thermal stability of rhodopsins is not due to rhodopsin molecule as a whole, and depends mainly on its part which is directly bound to 11-cis retinal, located in hydrophobic region of PM and inaccessible to protease attack.

The thermal stability of photoacid generators in phenolic matrices

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

Barclay, G.G.; Medeiros, D.R.; Sinta, R.F.

1993-12-31

The thermal stability of various photolabile sulfonate esters in phenolic matrices have been investigated by differential scanning calorimetry and thermogravimetric analysis. It was observed that the thermal stability of these photoacid generators is lowered in the presence of phenolic groups. As a result acid can be thermally generated, thereby reducing the selectivity of photoacid generation. The sulfonate esters investigated in phenolic matrices included nitrobenzyl tosylates, imino sulfonates, benzoin tosylate and 1,2,3-tris(methanesulfonyloxy)benzene. Also the effect of the thermal generation of acid from these photoacid generators on the temperature and rate of deprotection of partially t-butoxycarbonate blocked poly (vinylphenol) was studied bymore » thermogravimetric analysis and FTIR.« less

Diketopyrrolopyrrole-based polymer:fullerene nanoparticle films with thermally stable morphology for organic photovoltaic applications

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

Holmes, Natalie P.; Vaughan, Ben; Williams, Evan L.

Polymer:fullerene nanoparticles (NPs) offer two key advantages over bulk heterojunction (BHJ) films for organic photovoltaics (OPVs), water-processability and potentially superior morphological control. Once an optimal active layer morphology is reached, maintaining this morphology at OPV operating temperatures is key to the lifetime of a device. Here in this paper we study the morphology of the PDPP-TNT (poly{3,6-dithiophene-2-yl-2,5-di(2-octyldodecyl)-pyrrolo[3,4-c]pyrrole-1,4-dione-alt-naphthalene}):PC 71BM ([6,6]-phenyl C 71 butyric acid methyl ester) NP system and then compare the thermal stability of NP and BHJ films to the common poly(3-hexylthiophene) (P3HT): phenyl C 61 butyric acid methyl ester (PC 61BM) system. We find that material T g playsmore » a key role in the superior thermal stability of the PDPP-TNT:PC 71BM system; whereas for the P3HT:PC 61BM system, domain structure is critical.« less

Environmentally friendly ultrosound synthesis and antibacterial activity of cellulose/Ag/AgCl hybrids.

PubMed

Dong, Yan-Yan; Deng, Fu; Zhao, Jin-Jin; He, Jing; Ma, Ming-Guo; Xu, Feng; Sun, Run-Cang

2014-01-01

This study aims to investigate the fabrication and property of cellulose/Ag/AgCl hybrids. In this article, preparation of cellulose/Ag/AgCl hybrids was reported using the cellulose solution, AgNO₃, AlCl₃·6H₂O with ultrasound agitation method. The cellulose solution was synthesized by the dissolution of the microcrystalline cellulose in NaOH/urea aqueous solution. Influences of the experimental parameters of ultrasound treatment time and ultrasonic intermittent on the hybrids were investigated. The phase, microstructure, thermal stability, and morphology of the hybrids were characterized by X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectrometry, thermogravimetric analysis (TGA), differential thermal analysis (DTA), and scanning electron microscopy (SEM). Results showed the successful synthesis of cellulose/Ag/AgCl hybrids with good thermal stability. Moreover, the hybrids displayed desirable antimicrobial activities. Compared with other conventional methods, the rapid, green, and environmentally friendly ultrasound agitation method opens a new window to the high value-added applications of biomass. Copyright © 2013 Elsevier Ltd. All rights reserved.

Evaluation of mechanical and thermal properties of commonly used denture base resins.

PubMed

Phoenix, Rodney D; Mansueto, Michael A; Ackerman, Neal A; Jones, Robert E

2004-03-01

The purpose of this investigation was to evaluate and compare the mechanical and thermal properties of 6 commonly used polymethyl methacrylate denture base resins. Sorption, solubility, color stability, adaptation, flexural stiffness, and hardness were assessed to determine compliance with ADA Specification No. 12. Thermal assessments were performed using differential scanning calorimetry and dynamic mechanical analysis. Results were assessed using statistical and observational analyses. All materials satisfied ADA requirements for sorption, solubility, and color stability. Adaptation testing indicated that microwave-activated systems provided better adaptation to associated casts than conventional heat-activated resins. According to flexural testing results, microwaveable resins were relatively stiff, while rubber-modified resins were more flexible. Differential scanning calorimetry indicated that microwave-activated systems were more completely polymerized than conventional heat-activated materials. The microwaveable resins displayed better adaptation, greater stiffness, and greater surface hardness than other denture base resins included in this investigation. Elastomeric toughening agents yielded decreased stiffness, decreased surface hardness, and decreased glass transition temperatures.

Development of flax/carbon fibre hybrid composites for enhanced properties.

PubMed

Dhakal, H N; Zhang, Z Y; Guthrie, R; Macmullen, J; Bennett, N

2013-07-01

Uni-directional (UD) and cross-ply (CP) cellulosic flax fibre epoxy composites were produced by hybridising UD carbon fibre prepreg onto flax system. A compression moulding technique was used to produce both flax and carbon/flax hybridised laminates. The effect of carbon fibre hybridisation on the water absorption behaviour, thermal and mechanical properties of both UD and CP flax specimens were investigated by means of water absorption, tensile, thermogravemetric analysis and flexural testing. The results showed that water absorption behaviour of hybrid samples are markedly improved compared to those without hybridisation. Similarly, the thermal stability, tensile and flexural properties of the hybrid composites are significantly improved in comparison with UD and CP flax composites without hybridisation. The experimental results suggest that cellulosic flax fibre reinforcement contributed to improve the toughness properties by promoting crack propagation whereas the carbon fibre contributed in improving thermal stability, water absorption behaviour and the overall strength and the stiffness of the hybrid composites. Copyright © 2013 Elsevier Ltd. All rights reserved.

Infrared Radiative Properties of Yttria-Stabilized Zirconia Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Eldridge, Jeff I.; Spuckler, Charles M.; Street, Ken W.; Markham, Jim R.; Gray, Hugh R. (Technical Monitor)

2002-01-01

The infrared (IR) transmittance and reflectance of translucent thermal barrier coatings (TBCs) have important implications for both the performance of these coatings as radiation barriers and emitters as well as affecting measurements of TBC thermal conductivity, especially as TBCs are being pushed to higher temperatures. In this paper, the infrared spectral directional-hemispherical transmittance and reflectance of plasma-sprayed 8wt% yttria-stabilized zirconia (8YSZ) TBCs are reported. These measurements are compared to those for single crystal YSZ specimens to show the effects of the plasma-sprayed coating microstructure. It is shown that the coatings exhibit negligible absorption at wavelengths up to about 5 micrometers, and that internal scattering rather than surface reflections dominates the hemispherical reflectance. The translucent nature of the 8YSZ TBCs results in the absorptance/emittance and reflectance of TBC-coated substrates depending on the TBC thickness, microstructure, as well as the radiative properties of the underlying substrate. The effects of these properties on TBC measurements and performance are discussed.

Scalable graphene coatings for enhanced condensation heat transfer.

PubMed

Preston, Daniel J; Mafra, Daniela L; Miljkovic, Nenad; Kong, Jing; Wang, Evelyn N

2015-05-13

Water vapor condensation is commonly observed in nature and routinely used as an effective means of transferring heat with dropwise condensation on nonwetting surfaces exhibiting heat transfer improvement compared to filmwise condensation on wetting surfaces. However, state-of-the-art techniques to promote dropwise condensation rely on functional hydrophobic coatings that either have challenges with chemical stability or are so thick that any potential heat transfer improvement is negated due to the added thermal resistance of the coating. In this work, we show the effectiveness of ultrathin scalable chemical vapor deposited (CVD) graphene coatings to promote dropwise condensation while offering robust chemical stability and maintaining low thermal resistance. Heat transfer enhancements of 4× were demonstrated compared to filmwise condensation, and the robustness of these CVD coatings was superior to typical hydrophobic monolayer coatings. Our results indicate that graphene is a promising surface coating to promote dropwise condensation of water in industrial conditions with the potential for scalable application via CVD.

Porous cellulose diacetate-SiO2 composite coating on polyethylene separator for high-performance lithium-ion battery.

PubMed

Chen, Wenju; Shi, Liyi; Wang, Zhuyi; Zhu, Jiefang; Yang, Haijun; Mao, Xufeng; Chi, Mingming; Sun, Lining; Yuan, Shuai

2016-08-20

The developments of high-performance lithium ion battery are eager to the separators with high ionic conductivity and thermal stability. In this work, a new way to adjust the comprehensive properties of inorganic-organic composite separator was investigated. The cellulose diacetate (CDA)-SiO2 composite coating is beneficial for improving the electrolyte wettability and the thermal stability of separators. Interestingly, the pore structure of composite coating can be regulated by the weight ratio of SiO2 precursor tetraethoxysilane (TEOS) in the coating solution. The electronic performance of lithium ion batteries assembled with modified separators are improved compared with the pristine PE separator. When weight ratio of TEOS in the coating solution was 9.4%, the composite separator shows the best comprehensive performance. Compared with the pristine PE separator, its meltdown temperature and the break-elongation at elevated temperature increased. More importantly, the discharge capacity and the capacity retention improved significantly. Copyright © 2016 Elsevier Ltd. All rights reserved.

Aging effects on vertical graphene nanosheets and their thermal stability

NASA Astrophysics Data System (ADS)

Ghosh, S.; Polaki, S. R.; Ajikumar, P. K.; Krishna, N. G.; Kamruddin, M.

2018-03-01

The present study investigates environmental aging effects and thermal stability of vertical graphene nanosheets (VGN). Self-organized VGN is synthesized by plasma enhanced chemical vapor deposition and exposed to ambient conditions over 6-month period to examine its aging behavior. A systematic inspection is carried out on morphology, chemical structure, wettability and electrical property by scanning electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, water contact angle and four-probe resistivity measurements at regular intervals, respectively. Detailed microscopic and spectroscopic analysis substantiated the retention of graphitic quality and surface chemistry of VGN over the test period. An unchanged sheet resistance and hydrophobicity reveals its electrical and wetting stability over the time, respectively. Thermogravimetric analysis ensures an excellent thermal stability of VGN up to 575 °C in ambient atmosphere. These findings of long-term morphological, structural, wetting, electrical and thermal stability of VGN validate their potential utilization for the next-generation device applications.

Analysis of protein stability and ligand interactions by thermal shift assay.

PubMed

Huynh, Kathy; Partch, Carrie L

2015-02-02

Purification of recombinant proteins for biochemical assays and structural studies is time-consuming and presents inherent difficulties that depend on the optimization of protein stability. The use of dyes to monitor thermal denaturation of proteins with sensitive fluorescence detection enables rapid and inexpensive determination of protein stability using real-time PCR instruments. By screening a wide range of solution conditions and additives in a 96-well format, the thermal shift assay easily identifies conditions that significantly enhance the stability of recombinant proteins. The same approach can be used as an initial low-cost screen to discover new protein-ligand interactions by capitalizing on increases in protein stability that typically occur upon ligand binding. This unit presents a methodological workflow for small-scale, high-throughput thermal denaturation of recombinant proteins in the presence of SYPRO Orange dye. Copyright © 2015 John Wiley & Sons, Inc.

Effect of thermal expansion on the stability of two-reactant flames

NASA Technical Reports Server (NTRS)

Jackson, T. L.

1986-01-01

The full problem of flame stability for the two-reactant model, which takes into account thermal expansion effects for all disturbance wave lengths, is examined. It is found that the stability problem for the class of two-reactant flames is equivalent to the stability problem for the class of one-reactant flames with an appropriate interpretation of Lewis numbers.

A Physics-Based Temperature Stabilization Criterion for Thermal Testing

NASA Technical Reports Server (NTRS)

Rickman, Steven L.; Ungar, Eugene K.

2009-01-01

Spacecraft testing specifications differ greatly in the criteria they specify for stability in thermal balance tests. Some specify a required temperature stabilization rate (the change in temperature per unit time, dT/dt), some specify that the final steady-state temperature be approached to within a specified difference, delta T , and some specify a combination of the two. The particular values for temperature stabilization rate and final temperature difference also vary greatly between specification documents. A one-size-fits-all temperature stabilization rate requirement does not yield consistent results for all test configurations because of differences in thermal mass and heat transfer to the environment. Applying a steady-state temperature difference requirement is problematic because the final test temperature is not accurately known a priori, especially for powered configurations. In the present work, a simplified, lumped-mass analysis has been used to explore the applicability of these criteria. A new, user-friendly, physics-based approach is developed that allows the thermal engineer to determine when an acceptable level of temperature stabilization has been achieved. The stabilization criterion can be predicted pre-test but must be refined during test to allow verification that the defined level of temperature stabilization has been achieved.

Low temperature superplasticity and thermal stability of a nanostructured low-carbon microalloyed steel

PubMed Central

Hu, J.; Du, L.-X.; Sun, G.-S.; Xie, H.; Misra, R.D.K.

2015-01-01

We describe here for the first time the low temperature superplasticity of nanostructured low carbon steel (microalloyed with V, N, Mn, Al, Si, and Ni). Low carbon nanograined/ultrafine-grained (NG/UFG) bulk steel was processed using a combination of cold-rolling and annealing of martensite. The complex microstructure of NG/UFG ferrite and 50–80 nm cementite exhibited high thermal stability at 500 °C with low temperature elongation exceeding 100% (at less than 0.5 of the absolute melting point) as compared to the conventional fine-grained (FG) counterpart. The low temperature superplasticity is adequate to form complex components. Moreover, the low strength during hot processing is favorable for decreasing the spring back and minimize die loss. PMID:26687012

Radiation resistant polypropylene blended with mobilizer,. antioxidants and nucleating agent

NASA Astrophysics Data System (ADS)

Shamshad, A.; Basfar, A. A.

2000-03-01

Post-irradiation storage of medical disposables prepared from isotactic polypropylene renders them brittle due to degradation. To avoid this, isotactic polypropylene [(is)PP] was blended with a mobilizer, dioctyl pthallate (DOP), three antioxidants (hindered amines and a secondary antioxidant) and benzoic acid to obtain radiation-resistant, thermally-stable and transparent material. Different formulations prepared were subjected to gamma radiation to doses of 25 and 50 kGy. Tests of breakage on bending after ageing in an oven at 70°C up to 12 months have shown that the addition of DOP and the antioxidants imparts improved radiation and thermal stability as compared to (is)PP alone or its blend with DOP. All the formulations irradiated or otherwise demonstrated excellent colour stability even after accelerated ageing at 70°C for prolonged periods.

Sintering, thermal stability and mechanical properties of ZrO2-WC composites obtained by pulsed electric current sintering

NASA Astrophysics Data System (ADS)

Huang, Shuigen; Vanmeensel, Kim; van der Biest, Omer; Vleugels, Jozef

2011-03-01

ZrO2-WC composites exhibit comparable mechanical properties as traditional WC-Co materials, which provides an opportunity to partially replace WC-Co for some applications. In this study, 2 mol.% Y2O3 stabilized ZrO2 composites with 40 vol.% WC were consolidated in the 1150°C-1850°C range under a pressure of 60 MPa by pulsed electric current sintering (PECS). The densification behavior, microstructure and phase constitution of the composites were investigated to clarify the role of the sintering temperature on the grain growth, mechanical properties and thermal stability of ZrO2 and WC components. Analysis results indicated that the composites sintered at 1350°C and 1450°C exhibited the highest tetragonal ZrO2 phase transformability, maximum toughness, and hardness and an optimal flexural strength. Chemical reaction of ZrO2 and C, originating from the graphite die, was detected in the composite PECS for 20 min at 1850°C in vacuum.

Burnout Test of First- and Second-Generation HTS Tapes in Liquid-Nitrogen Bath Cooling

NASA Astrophysics Data System (ADS)

Young, M. A.; Demko, J. A.; Duckworth, R. C.; Lue, J. W.; Gouge, M. J.; Pace, M. O.

2004-06-01

A series of BSCCO-2223 and YBCO tapes were subjected to burnout tests in a liquid-nitrogen bath to observe operational stability limits when different layers of dielectric tape are added to the sample surface. In this study, the BSCCO tapes were composed of a silver/alloy sheath with nickel/copper plating, while the YBCO tapes had a 50-μm layer of copper attached to the silver surface. After attaching the tapes to a thermally insulated G-10 holder, the stability of the tapes was found by applying current greater than the critical current and holding it constant for up to 1 min. If the sample voltage increased rapidly during this period, the tape was considered unstable at this current. This was repeated at different layers of Cryoflex™, and the results were compared to a numerical simulation of the energy balance equation. This simulation was also utilized to investigate the effect of the layers on the stability limit and estimate the thermal conductivity of the Cryoflex™.

Development of cellulase-nanoconjugates with enhanced ionic liquid and thermal stability for in situ lignocellulose saccharification.

PubMed

Grewal, Jasneet; Ahmad, Razi; Khare, S K

2017-10-01

The present work aimed to improve catalytic efficiency of Trichoderma reesei cellulase for enhanced saccharification. The cellulase was immobilized on two nanomatrices i.e. magnetic and silica nanoparticles with immobilization efficiency of 85% and 76% respectively. The nanobioconjugates exhibited increase in V max , temperature optimum, pH and thermal stability as compared with free enzyme. These could be efficiently reused for five repeated cycles and were stable in 1-ethyl-3-methylimidazoliumacetate [EMIM][Ac], an ionic liquid. Ionic liquids (IL) are used as green solvents to dissolve lignocellulosic biomass and facilitate better saccharification. The cellulase immobilized on magnetic nanoparticles was used for in situ saccharification of [EMIM][Ac] pretreated sugarcane bagasse and wheat straw for two cycles. The structural deconstruction and decrease in biomass crystallinity was confirmed by SEM, XRD and FTIR. The high hydrolysis yields (∼89%) obtained in this one-pot process coupled with IL stability and recycled use of immobilized cellulase, potentiates its usefulness in biorefineries. Copyright © 2017 Elsevier Ltd. All rights reserved.

Chemical vapor deposition: Stable carbons from low-rank coals

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

Sharma, R.K.; Kulas, R.W.; Olson, E.S.

1996-12-31

A chemical vapor deposition (CVD) technique has been used to increase the oxidative stability of activated carbons. Activated carbons prepared from Gascoyne lignite (North Dakota) by thermal or potassium hydroxide activations were subjected to BCI, in helium at 727{degrees}C with or without benzene for a limited period of time, followed by annealing in helium at 900{degrees}C for three days. Untreated and acid-washed coal samples were used to assess the magnitude of the effect of mineral matter in the coal on the boron coating. The oxidative stability of the boron-modified carbons was determined from the decomposition curves obtained from the thermogravimetricmore » analysis. Modification of the as-received, KOH-treated carbon yielded oxidatively stable carbons up to an initial temperature of 520{degrees}C, compared to about 350{degrees}C for the starting material. Similar results were obtained for the carbonized Gascoyne lignite. Sulfurous acid washing of the Gascoyne significantly enhanced the thermal stability (600{degrees}C) of the boron-modified carbon.« less

Strained hybrid perovskite thin films and their impact on the intrinsic stability of perovskite solar cells

PubMed Central

Zhao, Jingjing; Deng, Yehao; Wei, Haotong; Zheng, Xiaopeng; Yu, Zhenhua; Shao, Yuchuan; Shield, Jeffrey E.; Huang, Jinsong

2017-01-01

Organic-inorganic hybrid perovskite (OIHP) solar cells have achieved comparable efficiencies to those of commercial solar cells, although their instability hinders their commercialization. Although encapsulation techniques have been developed to protect OIHP solar cells from external stimuli such as moisture, oxygen, and ultraviolet light, understanding of the origin of the intrinsic instability of perovskite films is needed to improve their stability. We show that the OIHP films fabricated by existing methods are strained and that strain is caused by mismatched thermal expansion of perovskite films and substrates during the thermal annealing process. The polycrystalline films have compressive strain in the out-of-plane direction and in-plane tensile strain. The strain accelerates degradation of perovskite films under illumination, which can be explained by increased ion migration in strained OIHP films. This study points out an avenue to enhance the intrinsic stability of perovskite films and solar cells by reducing residual strain in perovskite films. PMID:29159287

Tuning of Thermal Stability in Layered Li(NixMnyCoz)O2.

PubMed

Zheng, Jiaxin; Liu, Tongchao; Hu, Zongxiang; Wei, Yi; Song, Xiaohe; Ren, Yang; Wang, Weidong; Rao, Mumin; Lin, Yuan; Chen, Zonghai; Lu, Jun; Wang, Chongmin; Amine, Khalil; Pan, Feng

2016-10-12

Understanding and further designing new layered Li(Ni x Mn y Co z )O 2 (NMC) (x + y + z = 1) materials with optimized thermal stability is important to rechargeable Li batteries (LIBs) for electrical vehicles (EV). Using ab initio calculations combined with experiments, we clarified how the thermal stability of NMC materials can be tuned by the most unstable oxygen, which is determined by the local coordination structure unit (LCSU) of oxygen (TM(Ni, Mn, Co) 3 -O-Li 3-x' ): each O atom bonds with three transition metals (TM) from the TM-layer and three to zero Li from fully discharged to charged states from the Li-layer. Under this model, how the lithium content, valence states of Ni, contents of Ni, Mn, and Co, and Ni/Li disorder to tune the thermal stability of NMC materials by affecting the sites, content, and the release temperature of the most unstable oxygen is proposed. The synergistic effect between Li vacancies and raised valence state of Ni during delithiation process can aggravate instability of oxygen, and oxygen coordinated with more nickel (especially with high valence state) in LSCU becomes more unstable at a fixed delithiation state. The Ni/Li mixing would decrease the thermal stability of the "Ni═Mn" group NMC materials but benefit the thermal stability of "Ni-rich" group, because the Ni in the Li layer would form 180° Ni-O-Ni super exchange chains in "Ni-rich" NMC materials. Mn and Co doping can tune the initial valence state of Ni, local coordination environment of oxygen, and the Ni/Li disorder, thus to tune the thermal stability directly.

Tuning of Thermal Stability in Layered Li(Ni x Mn y Co z )O 2

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

Zheng, Jiaxin; Liu, Tongchao; Hu, Zongxiang

2016-09-19

Understanding and further designing new layered Li(Ni xMn yCo z)O 2 (NMC) (x + y + z = 1) materials with optimized thermal stability is important to rechargeable Li batteries (LIBs) for electrical vehicles (EV). Using ab initio calculations combined with experiments, we clarified how the thermal stability of NMC materials can be tuned by the most unstable oxygen, which is determined by the local coordination structure unit (LCSU) of oxygen (TM(Ni, Mn, Co) 3-O-Li 3-x'): each O atom bonds with three transition metals (TM) from the TM-layer and three to zero Li from fully discharged to charged states frommore » the Li-layer. Under this model, how the lithium content, valence states of Ni, contents of Ni, Mn, and Co, and Ni/Li disorder to tune the thermal stability of NMC materials by affecting the sites, content, and the release temperature of the most unstable oxygen is proposed. The synergistic effect between Li vacancies and raised valence state of Ni during delithiation process can aggravate instability of oxygen, and oxygen coordinated with more nickel (especially with high valence state) in LSCU becomes more unstable at a fixed delithiation state. The Ni/Li mixing would decrease the thermal stability of the “NiMn” group NMC materials but benefit the thermal stability of “Ni-rich” group, because the Ni in the Li layer would form 180° Ni-O-Ni super exchange chains in “Ni-rich” NMC materials. Mn and Co doping can tune the initial valence state of Ni, local coordination environment of oxygen, and the Ni/Li disorder, thus to tune the thermal stability directly.« less

Multilayer compressive seal for sealing in high temperature devices

DOEpatents

Chou, Yeong-Shyung [Richland, WA; Stevenson, Jeffry W [Richland, WA

2007-08-21

A mica based compressive seal has been developed exhibiting superior thermal cycle stability when compared to other compressive seals known in the art. The seal is composed of compliant glass or metal interlayers and a sealing (gasket) member layer composed of mica that is infiltrated with a glass forming material, which effectively reduces leaks within the seal. The compressive seal shows approximately a 100-fold reduction in leak rates compared with previously developed hybrid seals after from 10 to about 40 thermal cycles under a compressive stress of from 50 psi to 100 psi at temperatures in the range from 600.degree. C. to about 850.degree. C.

First-principles calculations of the thermal stability of Ti 3SiC 2(0001) surfaces

NASA Astrophysics Data System (ADS)

Orellana, Walter; Gutiérrez, Gonzalo

2011-12-01

The energetic, thermal stability and dynamical properties of the ternary layered ceramic Ti3SiC2(0001) surface are addressed by density-functional theory calculations and molecular dynamic (MD) simulations. The equilibrium surface energy at 0 K of all terminations is contrasted with thermal stability at high temperatures, which are investigated by ab initio MD simulations in the range of 800 to 1400 °C. We find that the toplayer (sublayer) surface configurations: Si(Ti2) and Ti2(Si) show the lowest surface energies with reconstruction features for Si(Ti2). However, at high temperatures they are unstable, forming disordered structures. On the contrary, Ti1(C) and Ti2(C) despite their higher surface energies, show a remarkable thermal stability at high temperatures preserving the crystalline structures up to 1400 °C. The less stable surfaces are those terminated in C atoms, C(Ti1) and C(Ti2), which at high temperatures show surface dissociation forming amorphous TiCx structures. Two possible atomic scale mechanisms involved in the thermal stability of Ti3SiC2(0001) are discussed.

Enhanced thermal stability of a polymer solar cell blend induced by electron beam irradiation in the transmission electron microscope.

PubMed

Bäcke, Olof; Lindqvist, Camilla; de Zerio Mendaza, Amaia Diaz; Gustafsson, Stefan; Wang, Ergang; Andersson, Mats R; Müller, Christian; Kristiansen, Per Magnus; Olsson, Eva

2017-05-01

We show by in situ microscopy that the effects of electron beam irradiation during transmission electron microscopy can be used to lock microstructural features and enhance the structural thermal stability of a nanostructured polymer:fullerene blend. Polymer:fullerene bulk-heterojunction thin films show great promise for use as active layers in organic solar cells but their low thermal stability is a hindrance. Lack of thermal stability complicates manufacturing and influences the lifetime of devices. To investigate how electron irradiation affects the thermal stability of polymer:fullerene films, a model bulk-heterojunction film based on a thiophene-quinoxaline copolymer and a fullerene derivative was heat-treated in-situ in a transmission electron microscope. In areas of the film that exposed to the electron beam the nanostructure of the film remained stable, while the nanostructure in areas not exposed to the electron beam underwent large phase separation and nucleation of fullerene crystals. UV-vis spectroscopy shows that the polymer:fullerene films are stable for electron doses up to 2000kGy. Copyright © 2016 Elsevier B.V. All rights reserved.

Enhanced thermal stability of a polymer solar cell blend induced by electron beam irradiation in the transmission electron microscope.

PubMed

Bäcke, Olof; Lindqvist, Camilla; de Zerio Mendaza, Amaia Diaz; Gustafsson, Stefan; Wang, Ergang; Andersson, Mats R; Müller, Christian; Kristiansen, Per Magnus; Olsson, Eva

2017-02-01

We show by in situ microscopy that the effects of electron beam irradiation during transmission electron microscopy can be used to lock microstructural features and enhance the structural thermal stability of a nanostructured polymer:fullerene blend. Polymer:fullerene bulk-heterojunction thin films show great promise for use as active layers in organic solar cells but their low thermal stability is a hindrance. Lack of thermal stability complicates manufacturing and influences the lifetime of devices. To investigate how electron irradiation affects the thermal stability of polymer:fullerene films, a model bulk-heterojunction film based on a thiophene-quinoxaline copolymer and a fullerene derivative was heat-treated in-situ in a transmission electron microscope. In areas of the film that exposed to the electron beam the nanostructure of the film remained stable, while the nanostructure in areas not exposed to the electron beam underwent large phase separation and nucleation of fullerene crystals. UV-vis spectroscopy shows that the polymer:fullerene films are stable for electron doses up to 2000kGy. Copyright © 2017 Elsevier B.V. All rights reserved.

Photochemical and Thermal Stability of Green and Blue Proteorhodopsins: Implications for Protein-Based Bioelectronic Devices

PubMed Central

Ranaghan, Matthew J.; Shima, Sumie; Ramos, Lavosier; Poulin, Daniel S.; Whited, Gregg; Rajasekaran, Sanguthevar; Stuart, Jeffery A.; Albert, Arlene D.; Birge, Robert R.

2010-01-01

The photochemical and thermal stability of the detergent solubilized blue- and green-absorbing proteorhodpsins, BPR and GPR respectively, are investigated to determine viability of these proteins for photonic device applications. Photochemical stability is studied by using pulsed laser excitation and differential uv-vis spectroscopy to assign the photocyclicity. GPR, with a cyclicity of 7×104 photocycles protein−1, is 4–5 times more stable than BPR (9×103 photocycles protein−1), but is less stable than native bacteriorhodopsin (9×105 photocycles protein−1) or the 4-keto-bacteriorhodopsin analog (1×105 photocycles protein−1). The thermal stabilities are assigned by using differential scanning calorimetry and thermal bleaching experiments. Both proteorhodopsins display excellent thermal stability, with melting temperatures above 85°C, and remain photochemically stable up to 75°C. The biological relevance of our results is also discussed. The lower cyclicity of BPR is found to be adequate for the long-term biological function of the host organism at ocean depths of 50 m or more. PMID:20964279

Effect of Nickel Concentration on Bias Reliability and Thermal Stability of Thin-Film Transistors Fabricated by Ni-Metal-Induced Crystallization

NASA Astrophysics Data System (ADS)

Lai, Ming-Hui; Sermon Wu, YewChung; Huang, Jung-Jie

2012-01-01

Ni-metal-induced crystallization (MIC) of amorphous Si (α-Si) has been employed to fabricate low-temperature polycrystalline silicon (poly-Si) thin-film transistors (TFTs). Although the high leakage current is a major issue in the performance of conventional MIC-TFTs since Ni contamination induces deep-level state traps, it can be greatly improved by using well-known technologies to reduce Ni contamination. However, for active-matrix organic light-emitting diode (AMOLED) display applications, the bias reliability and thermal stability are major concerns especially when devices are operated under a hot carrier condition and in a high-temperature environment. It will be interesting to determine how the bias reliability and thermal stability are affected by the reduction of Ni concentration. In the study, the effect of Ni concentration on bias reliability and thermal stability was investigated. We found that a device exhibited high immunity against hot-carrier stress and elevated temperatures. These findings demonstrated that reducing the Ni concentration in MIC films was also beneficial for bias reliability and thermal stability.

Nd-Fe-B/Sm-M/Nd-M (M = Fe, Co, Ti, Cu, Zr) hybrid magnets with improved thermal stability

NASA Astrophysics Data System (ADS)

Grigoras, M.; Lostun, M.; Urse, M.; Borza, F.; Chiriac, H.; Lupu, N.

2018-02-01

Hybrid magnets of Nd12Fe82B6(2:14:1-phase)/Nd9.4Fe59Co25.3Ti6.3(3:29-phase) and Nd12Fe82B6/Sm11.1Co65.8Fe8.9Cu10.7Zr3.5(2:17-phase) with different weight ratio have been prepared by spark plasma sintering pressing technique from ball-milled powders obtained from melt-spun ribbons. Influence of the ratio between the two phases on the magnetic properties and thermal stability of the hybrid magnets was studied. It has been found that the ratio has a remarkable influence, especially on the thermal stability of the bulk magnets. However, the magnetic properties of such type of hybrid magnets result not only from the type and ratio of components but also from the interaction between them. It was found that in NdFeB/3:29 hybrid magnets with 15% content of 3:29-phase, the temperature coefficients of remanence (α) and of coercivity (β) are improved from -0.095 to -0.082 (%/°C) and from -0.57 to -0.47 (%/°C), respectively, as compared to the Nd2Fe14B single-phase counterpart. While for the NdFeB/2:17 hybrid magnets the content of 2:17-phase is not significantly influencing the temperature coefficient of induction (α), the temperature coefficient of °C (β) increases up to -0.41 (%/°C) for 10% content of 2:17-phase. The increase in the reversible temperature coefficients of hybrid magnets indicate a remarkable improvement of their thermal stability.

RP-1 Thermal Stability and Copper Based Materials Compatibility Study

NASA Technical Reports Server (NTRS)

Stiegemeier, B. R.; Meyer, M. L.; Driscoll, E.

2005-01-01

A series of electrically heated tube tests was performed at the NASA Glenn Research Center s Heated Tube Facility to investigate the effect that sulfur content, test duration, and tube material play in the overall thermal stability and materials compatibility characteristics of RP-1. Scanning-electron microscopic (SEM) analysis in conjunction with energy dispersive spectroscopy (EDS) were used to characterize the condition of the tube inner wall surface and any carbon deposition or corrosion formed during these runs. Results of the parametric study indicate that tests with standard RP-1 (total sulfur -23 ppm) and pure copper tubing are characterized by a depostion/deposit shedding process producing local wall temperature swings as high as 500 F. The effect of this shedding is to keep total carbon deposition levels relatively constant for run times from 20 minutes up to 5 hours, though increasing tube pressure drops were observed in all runs. Reduction in the total sulfur content of the fuel from 23 ppm to less than 0.1 ppm resulted in the elimination of deposit shedding, local wall temperature variation, and the tube pressure drop increases that were observed in standard sulfur level RP-1 tests. The copper alloy GRCop-84, a copper alloy developed specifically for high heat flux applications, was found to exhibit higher carbon deposition levels compared to identical tests performed in pure copper tubes. Results of the study are consistent with previously published heated tube data which indicates that small changes in fuel total sulfur content can lead to significant differences in the thermal stability of kerosene type fuels and their compatibility with copper based materials. In conjunction with the existing thermal stability database, these findings give insight into the feasibility of cooling a long life, high performance, high-pressure liquid rocket combustor and nozzle with RP-1.

Enhanced quench propagation in 2G-HTS coils co-wound with stainless steel or anodised aluminium tapes

NASA Astrophysics Data System (ADS)

Núñez-Chico, A. B.; Martínez, E.; Angurel, L. A.; Navarro, R.

2016-08-01

Early quench detection and thermal stability of superconducting coils are of great relevance for practical applications. Magnets made with second generation high temperature superconducting (2G-HTS) tapes present low quench propagation velocities and therefore slow voltage development and high local temperature rises, which may cause irreversible damage. Since quench propagation depends on the anisotropy of the thermal conductivity, this may be used to achieve an improvement of the thermal stability and robustness of 2G-HTS coils. On pancake type coils, the thermal conductivity along the tapes (coil’s azimuthal direction) is mostly fixed by the 2G-HTS tape characteristics, so that the reduction of anisotropy relies on the improvement of the radial thermal conductivity, which depends on the used materials between superconducting tapes, as well as on the winding and impregnation processes. In this contribution, we have explored two possibilities for such anisotropy reduction: by using anodised aluminium or stainless steel tapes co-wound with the 2G-HTS tapes. For all the analysed coils, critical current distribution, minimum quench energy values and both tangential and radial quench propagation velocities at different temperatures and currents are reported and compared with the results of similar coils co-wound with polyimide (Kapton®) tapes.

Layered Crystal Structure, Color-Tunable Photoluminescence, and Excellent Thermal Stability of MgIn2P4O14 Phosphate-Based Phosphors.

PubMed

Zhang, Jing; Cai, Ge-Mei; Yang, Lv-Wei; Ma, Zhi-Yuan; Jin, Zhan-Peng

2017-11-06

Single-component white phosphors stand a good chance to serve in the next-generation high-power white light-emitting diodes. Because of low thermal stability and containing lanthanide ions with reduced valence state, most of reported phosphors usually suffer unstable color of lighting for practical packaging and comparably complex synthetic processes. In this work, we present a type of novel color-tunable blue-white-yellow-emitting MgIn 2 P 4 O 14 :Tm 3+ /Dy 3+ phosphor with high thermal stability, which can be easily fabricated in air. Under UV excitation, the MgIn 2 P 4 O 14 :Tm 0.02 Dy 0.03 white phosphor exhibits negligible thermal-quenching behavior, with a 99.5% intensity retention at 150 °C, relative to its initial value at room temperature. The phosphor host MgIn 2 P 4 O 14 was synthesized and reported for the first time. MgIn 2 P 4 O 14 crystallizes in the space group of C2/c (No. 15) with a novel layered structure built of alternate anionic and cationic layers. Its disordering structure, with Mg and In atoms co-occupying the same site, is believed to facilitate the energy transfer between rare-earth ions and benefit by sustaining the luminescence with increasing temperature. The measured absolute quantum yields of MgIn 2 P 4 O 14 :Dy 0.04 , MgIn 2 P 4 O 14 :Tm 0.01 Dy 0.04 , and MgIn 2 P 4 O 14 :Tm 0.02 Dy 0.03 phosphors under the excitation of 351 nm ultraviolet radiation are 70.50%, 53.24%, and 52.31%, respectively. Present work indicates that the novel layered MgIn 2 P 4 O 14 is a promising candidate as a single-component white phosphor host with an excellent thermal stability for near-UV-excited white-light-emitting diodes (wLEDs).

Thermomechanical Properties of Sb2O3-TeO2-V2O5 Glassy Systems: Thermal Stability, Glass Forming Tendency and Vickers Hardness

NASA Astrophysics Data System (ADS)

Souri, Dariush; Torkashvand, Ziba

2017-04-01

Three-component 40TeO2-(60- x)V2O5- xSb2O3 glasses with 0 ≤ x ≤ 10 (in mol.%) were obtained by the rapid melt-quenching method. These glasses were studied with respect to some mechanical properties with the goal of obtaining information about their structure. The Vickers hardness test was employed to obtain Vickers micro-hardness ( H V) at two different loads, which was within the range of 13.187-17.557 GPa for a typical 0.1 HV (0.9807 N) load. In addition, theoretical micro-hardness ( H) was investigated and compared with experimental H V, showing the elevating trend with increase of Sb2O3 content, as for H V. Furthermore, differential scanning calorimetry (DSC) was employed within the range of 150-500°C at heating rates of φ = 3 K/min, 6 K/min, 9 K/min, 10 K/min, and 13 K/min. In this work, thermal stability ( T s = T cr - T x) and glass forming tendency ( K gl) were measured and reported for these glasses to determine the relationship between the chemical composition and the thermal stability, in order to interpret the structure of glass. Generally, from the ascertained outputs [analysis of mechanical data, titration study, the values of reduced fraction of vanadium ions ( C V) and oxygen molar volume ( V_{{O}}^{*} )], it was found that the micro-hardness had an increasing trend with increasing the Sb2O3 content. Among the studied glasses, the sample with x = 8 had a higher average micro-hardness value, the highest average thermal stability and glass forming tendency with respect to the other samples, which makes it a useful material (owning very good resistance against thermal attacks) for device manufacturing.

Formability and thermal stability of phase in (Fe1-y Coy)-(B, C, N) films

NASA Astrophysics Data System (ADS)

Sunaga, K.; Kadowaki, S.; Tsunoda, M.; Takahashi, M.

2004-06-01

In order to find a way to obtain stable -Fe16X2 phase, the formability and thermal stability of (bct) phase were discussed. According to a rigid sphere model, we concluded that the less formability of B for the phase is due to its large atomic radius. We elucidated the difference of thermal stability of -Fe-X, taking into account their decomposition process. While, the decomposition of -Fe-N progresses only by the migration of N, without changing the bone structure of Fe lattice, the additional energy is needed to break the original α-Fe lattice in the cases of α-Fe-B and α-Fe-C. Therefore thermal stability of α-Fe-B and α-Fe-C is higher than that of α-Fe-N.

Linking measurements of biodegradability, thermal stability and chemical composition to evaluate the effects of management on soil organic matter

NASA Astrophysics Data System (ADS)

Gregorich, Ed; Gillespie, Adam; Beare, Mike; Curtin, Denis; Sanei, Hamed; Yanni, Sandra

2015-04-01

The stability of soil organic matter (SOM) as it relates to resistance to microbial degradation has important implications for nutrient cycling, emission of greenhouse gases, and C sequestration. Hence, there is interest in developing new ways to accurately quantify and characterise the labile and stable forms of soil organic C. Our objectives in this study were to evaluate and describe relationships among the biodegradability, thermal stability and chemistry of SOM in soil under widely contrasting management regimes. Samples from the same soil under permanent pasture, an arable cropping rotation, and chemical fallow were fractionated (sand: 2000-50 μm; silt: 50-5 μm, and clay: < 5 μm). Biodegradability of the SOM in size fractions and whole soils was assessed in a laboratory mineralization study. The chemical composition of SOM was characterized by X-ray absorption near-edge structure (XANES) spectroscopy at the K-edge and its thermal stability was determined by analytical pyrolysis using a Rock-Eval pyrolyser. The mineralization bioassay showed that whole soils and soil fractions under fallow were less susceptible to biodegradation than other managements and that sand-associated organic matter was significantly more susceptible than that in the silt or clay fractions. Analysis by XANES showed accumulation of carboxylates and strong depletion of amides (protein) and aromatics in the fallow whole soil. Moreover, protein depletion was most significant in the sand fraction of the fallow soil. Sand fractions in fallow and cropped soils were, however, enriched in plant-derived phenols, aromatics and carboxylates compared to the sand fraction of pasture soils. In contrast, ketones, which have been identified as products of microbially-processed organic matter, were slightly enriched in the silt fraction of the pasture soil. These data suggest reduced inputs and cropping restrict the decomposition of plant residues and, without supplemental N additions, protein-N in native SOM is significantly mineralized in fallow systems to meet microbial C mineralization demands. Analytical pyrolysis showed distinct differences in the thermal stability of SOM among the size fractions and management treatments; it also showed that the loss of SOM generally involved dehydrogenation. The temperature at which half of the C was pyrolyzed showed strong correlation with mineralizable C and thus provides solid evidence for a link between the biological and thermal stability of SOM.

Magnetic Fe3O4@MCM-41 core-shell nanoparticles functionalized with thiol silane for efficient l-asparaginase immobilization.

PubMed

Ulu, Ahmet; Noma, Samir Abbas Ali; Koytepe, Suleyman; Ates, Burhan

2018-06-06

l-Asparaginase (l-ASNase) is a vital enzyme for medical treatment and food industry. Here, we assessed the use of Fe 3 O 4 @Mobil Composition of Matter No. 41 (MCM-41) magnetic nanoparticles as carrier matrix for l-ASNase immobilization. In addition, surface of Fe 3 O 4 @MCM-41 magnetic nanoparticles was functionalized with 3-mercaptopropyltrimethoxysilane (MPTMS) to enhance stability of l-ASNase. The chemical structure, thermal properties, magnetic profile and morphology of the thiol-functionalized Fe 3 O 4 @MCM-41 magnetic nanoparticles were characterized with Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential thermal analysis (DTA), differential scanning calorimetry (DSC), vibrating sample magnetometer (VSM), scanning electron microscope (SEM), energy dispersive X-ray (EDX) spectroscopy and zeta-potential measurement. l-ASNase was covalently immobilized onto the thiol-functionalized Fe 3 O 4 @MCM-41 magnetic nanoparticles. The properties of the immobilized enzyme, including optimum pH, temperature, kinetic parameters, thermal stability, reusability and storage stability were investigated and compared to free one. Immobilized enzyme was found to be stable over a wide range of pH and temperature range than free enzyme. The immobilized l-ASNase also showed higher thermal stability after 180 min incubation at 50 °C. The immobilized enzyme still retained 63% of its original activity after 16 times of reuse. The Km value for the immobilized enzyme was 1.15-fold lower than the free enzyme, which indicates increased affinity for the substrate. Additionally, the immobilized enzyme was active over 65% and 53% after 30 days of storage at 4 °C and room temperature (∼25 °C), respectively. Thereby, the results confirmed that thiol-functionalized Fe 3 O 4 @MCM-41 magnetic nanoparticles had high efficiency for l-ASNase immobilization and improved stability of L-ASNase.

Alternative High Performance Polymers for Ablative Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Boghozian, Tane; Stackpoole, Mairead; Gonzales, Greg

2015-01-01

Ablative thermal protection systems are commonly used as protection from the intense heat during re-entry of a space vehicle and have been used successfully on many missions including Stardust and Mars Science Laboratory both of which used PICA - a phenolic based ablator. Historically, phenolic resin has served as the ablative polymer for many TPS systems. However, it has limitations in both processing and properties such as char yield, glass transition temperature and char stability. Therefore alternative high performance polymers are being considered including cyanate ester resin, polyimide, and polybenzoxazine. Thermal and mechanical properties of these resin systems were characterized and compared with phenolic resin.

Non-flammable polyphosphonate electrolytes

NASA Astrophysics Data System (ADS)

Dixon, Brian G.; Morris, R. Scott; Dallek, Steven

This research is directed towards the development of safe, and thermally stable polymeric electrolytes. Advanced electrolytes are described, including thermal test data, which are ionically highly conductive, and non-flammable. These novel multi-heteropolymer electrolytes represent a significant advance in the design of high-performance rechargeable lithium systems that possess superior safety and handling characteristics. Representative results are shown by the figures contained in this text. These DSC/TGA results compare a typical liquid carbonate-based electrolyte system, ethylene carbonate and ethyl methyl carbonate, with novel polyphosphonates as synthesized in this program. These tests were performed with the electrolytes in combination with lithium metal, and the impressive relative thermal stability of the phosphonates is apparent.

Research and application of high performance GPES rigid foam composite plastic insulation boards

NASA Astrophysics Data System (ADS)

sun, Hongming; xu, Hongsheng; Han, Feifei

2017-09-01

A new type of heat insulation board named GPES was prepared by several polymers and modified nano-graphite particles, injecting high-pressure supercritical CO2. Compared with the traditional thermal insulation material, GPES insulation board has higher roundness bubble and thinner bubble wall. Repeatability and reproducibility tests show that melting knot, dimensional stability, strength and other physical properties are significantly better than traditional organic heat insulation materials. Especially the lower and more stable thermal conductivity of GPES can significantly reduce thermal insulation layer thickness. Obviously GPES is the best choice of insulation materials with the implement of 75% and higher energy efficiency standard.

The effect of free radical inhibitor on the sensitized radiation crosslinking and thermal processing stabilization of polyurethane shape memory polymers.

PubMed

Hearon, Keith; Smith, Sarah E; Maher, Cameron A; Wilson, Thomas S; Maitland, Duncan J

2013-02-01

The effects of free radical inhibitor on the electron beam crosslinking and thermal processing stabilization of novel radiation crosslinkable polyurethane shape memory polymers (SMPs) blended with acrylic radiation sensitizers have been determined. The SMPs in this study possess novel processing capabilities-that is, the ability to be melt processed into complex geometries as thermoplastics and crosslinked in a secondary step using electron beam irradiation. To increase susceptibility to radiation crosslinking, the radiation sensitizer pentaerythritol triacrylate (PETA) was solution blended with thermoplastic polyurethane SMPs made from 2-butene-1,4-diol and trimethylhexamethylene diisocyanate (TMHDI). Because thermoplastic melt processing methods such as injection molding are often carried out at elevated temperatures, sensitizer thermal instability is a major processing concern. Free radical inhibitor can be added to provide thermal stabilization; however, inhibitor can also undesirably inhibit radiation crosslinking. In this study, we quantified both the thermal stabilization and radiation crosslinking inhibition effects of the inhibitor 1,4-benzoquinone (BQ) on polyurethane SMPs blended with PETA. Sol/gel analysis of irradiated samples showed that the inhibitor had little to no inverse effects on gel fraction at concentrations of 0-10,000 ppm, and dynamic mechanical analysis showed only a slight negative correlation between BQ composition and rubbery modulus. The 1,4-benzoquinone was also highly effective in thermally stabilizing the acrylic sensitizers. The polymer blends could be heated to 150°C for up to five hours or to 125°C for up to 24 hours if stabilized with 10,000 ppm BQ and could also be heated to 125°C for up to 5 hours if stabilized with 1000 ppm BQ without sensitizer reaction occurring. We believe this study provides significant insight into methods for manipulation of the competing mechanisms of radiation crosslinking and thermal stabilization of radiation sensitizers, thereby facilitating further development of radiation crosslinkable thermoplastic SMPs.

The effect of free radical inhibitor on the sensitized radiation crosslinking and thermal processing stabilization of polyurethane shape memory polymers

NASA Astrophysics Data System (ADS)

Hearon, Keith; Smith, Sarah E.; Maher, Cameron A.; Wilson, Thomas S.; Maitland, Duncan J.

2013-02-01

The effects of free radical inhibitor on the electron beam crosslinking and thermal processing stabilization of novel radiation crosslinkable polyurethane shape memory polymers (SMPs) blended with acrylic radiation sensitizers have been determined. The SMPs in this study possess novel processing capabilities—that is, the ability to be melt processed into complex geometries as thermoplastics and crosslinked in a secondary step using electron beam irradiation. To increase susceptibility to radiation crosslinking, the radiation sensitizer pentaerythritol triacrylate (PETA) was solution blended with thermoplastic polyurethane SMPs made from 2-butene-1,4-diol and trimethylhexamethylene diisocyanate (TMHDI). Because the thermoplastic melt processing methods such as injection molding are often carried out at elevated temperatures, sensitizer thermal instability is a major processing concern. Free radical inhibitor can be added to provide thermal stabilization; however, inhibitor can also undesirably inhibit radiation crosslinking. In this study, we quantified both the thermal stabilization and radiation crosslinking inhibition effects of the inhibitor 1,4-benzoquinone (BQ) on polyurethane SMPs blended with PETA. Sol/gel analysis of irradiated samples showed that the inhibitor had little to no inverse effects on gel fraction at concentrations of 0-10,000 ppm, and dynamic mechanical analysis showed only a slight negative correlation between BQ composition and rubbery modulus. The 1,4-benzoquinone was also highly effective in thermally stabilizing the acrylic sensitizers. The polymer blends could be heated to 150 °C for up to 5 h or to 125 °C for up to 24 h if stabilized with 10,000 ppm BQ and could also be heated to 125 °C for up to 5 h if stabilized with 1000 ppm BQ without sensitizer reaction occurring. We believe this study provides significant insight into methods for manipulation of the competing mechanisms of radiation crosslinking and thermal stabilization of radiation sensitizers, thereby facilitating further development of radiation crosslinkable thermoplastic SMPs.

Generation of fatty acids from 1,2-dipalmitoyl-sn-glycero-3-phosphocholine/cardiolipin liposomes that stabilize recombinant human serum albumin.

PubMed

Frahm, Grant E; Cameron, Brooke E; Smith, Jeffrey C; Johnston, Michael J W

2013-06-01

At elevated temperatures, studies have shown that serum albumin undergoes irreversible changes to its secondary structure. Anionic fatty acids and/or anionic surfactants have been shown to stabilize human serum albumin (HSA) against thermal denaturation through bridging hydrophobic domains and cationic amino acids residues of the protein. As albumin can readily interact with a variety of liposomes, this study proposes that cardiolipin delivered via 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes can improve the thermal stability of recombinant HSA produced in Saccharomyces cerevisiae (ScrHSA) in a similar manner to anionic fatty acids. Thermal stability and structure of ScrHSA in the absence and presence of DPPC/cardiolipin liposomes was assessed with U/V circular dichroism spectropolarimetry and protein thermal stability was confirmed with differential scanning calorimetry. Although freshly prepared DPPC/cardiolipin liposomes did not improve the stability of ScrHSA, DPPC/cardiolipin liposomes incubated at room temperature for 7 d (7dRT) dramatically improved the thermal stability of the protein. Mass spectrometry analysis identified the presence of fatty acids in the 7dRT liposomes, not identified in freshly prepared liposomes, to which the improved stability was attributed. The generation of fatty acids is attributed to either the chemical hydrolysis or oxidative cleavage of the unsaturated acyl chains of cardiolipin. By modulating the lipid composition through the introduction of lipids with higher acyl chain unsaturation, it may be possible to generate the stabilizing fatty acids in a more rapid manner.

Evaluating the effects of buffer conditions and extremolytes on thermostability of granulocyte colony-stimulating factor using high-throughput screening combined with design of experiments.

PubMed

Ablinger, Elisabeth; Hellweger, Monika; Leitgeb, Stefan; Zimmer, Andreas

2012-10-15

In this study, we combined a high-throughput screening method, differential scanning fluorimetry (DSF), with design of experiments (DoE) methodology to evaluate the effects of several formulation components on the thermostability of granulocyte colony stimulating factor (G-CSF). First we performed a primary buffer screening where we tested thermal stability of G-CSF in different buffers, pH values and buffer concentrations. The significance of each factor and the two-way interactions between them were studied by multivariable regression analysis. pH was identified as most critical factor regarding thermal stability. The most stabilizing buffer, sodium glutamate, and sodium acetate were determined for further investigations. Second we tested the effect of 6 naturally occurring extremolytes (trehalose, sucrose, ectoine, hydroxyectoine, sorbitol, mannitol) on the thermal stability of G-CSF, using a central composite circumscribed design. At low pH (3.8) and low buffer concentration (5 mM) all extremolytes led to a significant increase in thermal stability except the addition of ectoine which resulted in a strong destabilization of G-CSF. Increasing pH and buffer concentration led to an increase in thermal stability with all investigated extremolytes. The described systematic approach allowed to create a ranking of stabilizing extremolytes at different buffer conditions. Copyright © 2012. Published by Elsevier B.V.

Thermal and Mechanical Characteristics of Polymer Composites Based on Epoxy Resin, Aluminium Nanopowders and Boric Acid

NASA Astrophysics Data System (ADS)

Nazarenko, O. B.; Melnikova, T. V.; Visakh, P. M.

2016-01-01

The epoxy polymers are characterized by low thermal stability and high flammability. Nanoparticles are considered to be effective fillers of polymer composites for improving their thermal and functional properties. In this work, the epoxy composites were prepared using epoxy resin ED-20, polyethylene polyamine as a hardener, aluminum nanopowder and boric acid fine powder as flame-retardant filler. The thermal characteristics of the obtained samples were studied using thermogravimetric analysis and differential scanning calorimetry. The mechanical characteristics of epoxy composites were also studied. It was found that an addition of all fillers enhances the thermal stability and mechanical characteristics of the epoxy composites. The best thermal stability showed the epoxy composite filled with boric acid. The highest flexural properties showed the epoxy composite based on the combination of boric acid and aluminum nanopowder.

Comparative study of stability of soluble and cell wall invertase from Saccharomyces cerevisiae.

PubMed

Margetić, Aleksandra; Vujčić, Zoran

2017-03-16

Yeast Saccharomyces cerevisiae is the most significant source of enzyme invertase. It is mainly used in the food industry as a soluble or immobilized enzyme. The greatest amount of invertase is located in the periplasmic space in yeast. In this work, it was isolated into two forms of enzyme from yeast S. cerevisiae cell, soluble and cell wall invertase (CWI). Both forms of enzyme showed same temperature optimum (60°C), similar pH optimum, and kinetic parameters. The significant difference between these biocatalysts was observed in their thermal stability, stability in urea and methanol solution. At 60°C, CWI had 1.7 times longer half-life than soluble enzyme, while at 70°C CWI showed 8.7 times longer half-life than soluble enzyme. After 2-hr of incubation in 8 M urea solution, soluble invertase and CWI retained 10 and 60% of its initial activity, respectively. During 22 hr of incubation of both enzymes in 30 and 40% methanol, soluble invertase was completely inactivated, while CWI changed its activity within the experimental error. Therefore, soluble invertase and CWI have not shown any substantial difference, but CWI showed better thermal stability and stability in some of the typical protein-denaturing agents.

Effect of Thermal Treatments on Ni-Mn-Ga and Ni-Rich Ni-Ti-Hf/Zr High-Temperature Shape Memory Alloys

NASA Astrophysics Data System (ADS)

Santamarta, Ruben; Evirgen, Alper; Perez-Sierra, Aquilina M.; Pons, Jaume; Cesari, Eduard; Karaman, Ibrahim; Noebe, Ron D.

2015-11-01

Among all the promising high-temperature shape memory alloys (HTSMAs), the Ni-Mn-Ga and the Ni-Ti-Hf/Zr systems exhibit interesting shape memory and superelastic properties that may place them in a good position for potential applications. The present work shows that thermal treatments play a crucial role in controlling the martensitic phase transformation characteristics of both systems, but in different ways. On one hand, the equilibrium phase diagram of the Ni-Mn-Ga family allows selecting compositions with high transformation temperatures and outstanding thermal stability at relatively high temperatures in air, showing no significant changes in the transformation behavior for continuous aging up to ˜5 years at 500 °C. Moreover, the excellent thermal stability correlates with a good thermal cyclic stability and an exceptional oxidation resistance of the parent phase. On the other hand, precipitation processes controlled by thermal treatments are needed to manipulate the transformation temperatures, mechanical properties, and thermal stability of Ni-rich Ni-Ti-Hf/Zr alloys to become HTSMAs. These changes in the functional properties are a consequence of the competition between the mechanical and compositional effects of the precipitates on the martensitic transformation.

The strengthening mechanism of a nickel-based alloy after laser shock processing at high temperatures

PubMed Central

Li, Yinghong; Zhou, Liucheng; He, Weifeng; He, Guangyu; Wang, Xuede; Nie, Xiangfan; Wang, Bo; Luo, Sihai; Li, Yuqin

2013-01-01

We investigated the strengthening mechanism of laser shock processing (LSP) at high temperatures in the K417 nickel-based alloy. Using a laser-induced shock wave, residual compressive stresses and nanocrystals with a length of 30–200 nm and a thickness of 1 μm are produced on the surface of the nickel-based alloy K417. When the K417 alloy is subjected to heat treatment at 900 °C after LSP, most of the residual compressive stress relaxes while the microhardness retains good thermal stability; the nanocrystalline surface has not obviously grown after the 900 °C per 10 h heat treatment, which shows a comparatively good thermal stability. There are several reasons for the good thermal stability of the nanocrystalline surface, such as the low value of cold hardening of LSP, extreme high-density defects and the grain boundary pinning of an impure element. The results of the vibration fatigue experiments show that the fatigue strength of K417 alloy is enhanced and improved from 110 to 285 MPa after LSP. After the 900 °C per 10 h heat treatment, the fatigue strength is 225 MPa; the heat treatment has not significantly reduced the reinforcement effect. The feature of the LSP strengthening mechanism of nickel-based alloy at a high temperature is the co-working effect of the nanocrystalline surface and the residual compressive stress after thermal relaxation. PMID:27877617

Porphyrin-substrate binding to murine ferrochelatase: effect on the thermal stability of the enzyme

PubMed Central

2004-01-01

Ferrochelatase (EC 4.99.1.1), the terminal enzyme of the haem biosynthetic pathway, catalyses the chelation of Fe(II) into the protoporphyrin IX ring. The energetics of the binding between murine ferrochelatase and mesoporphyrin were determined using isothermal titration calorimetry, which revealed a stoichiometry of one molecule of mesoporphyrin bound per protein monomer. The binding is strongly exothermic, with a large intrinsic enthalpy (ΔH=−97.1 kJ · mol−1), and is associated with the uptake of two protons from the buffer. This proton transfer suggests that hydrogen bonding between ferrochelatase and mesoporphyrin is a key factor in the thermodynamics of the binding reaction. Differential scanning calorimetry thermograms indicated a co-operative two-state denaturation process with a single transition temperature of 56 °C for wild-type murine ferrochelatase. An increase in the thermal stability of ferrochelatase is dependent upon mesoporphyrin binding. Similarly, murine ferrochelatase variants, in which the active site Glu-289 was replaced by either glutamine or alanine and, when purified, contained specifically-bound protoporphyrin, exhibited enhanced protein stability when compared with wild-type ferrochelatase. However, in contrast with the wild-type enzyme, the thermal denaturation of ferrochelatase variants was best described as a non-co-operative denaturation process. PMID:15496139

Coherency strain engineered decomposition of unstable multilayer alloys for improved thermal stability

NASA Astrophysics Data System (ADS)

Forsén, R.; Ghafoor, N.; Odén, M.

2013-12-01

A concept to improve hardness and thermal stability of unstable multilayer alloys is presented based on control of the coherency strain such that the driving force for decomposition is favorably altered. Cathodic arc evaporated cubic TiCrAlN/Ti1-xCrxN multilayer coatings are used as demonstrators. Upon annealing, the coatings undergo spinodal decomposition into nanometer-sized coherent Ti- and Al-rich cubic domains which is affected by the coherency strain. In addition, the growth of the domains is restricted by the surrounding TiCrN layer compared to a non-layered TiCrAlN coating which together results in an improved thermal stability of the cubic structure. A significant hardness increase is seen during decomposition for the case with high coherency strain while a low coherency strain results in a hardness decrease for high annealing temperatures. The metal diffusion paths during the domain coarsening are affected by strain which in turn is controlled by the Cr-content (x) in the Ti1-xCrxN layers. For x = 0 the diffusion occurs both parallel and perpendicular to the growth direction but for x > =0.9 the diffusion occurs predominantly parallel to the growth direction. Altogether this study shows a structural tool to alter and fine-tune high temperature properties of multicomponent materials.

Isolation of thermally stable cellulose nanocrystals by phosphoric acid hydrolysis.

PubMed

Camarero Espinosa, Sandra; Kuhnt, Tobias; Foster, E Johan; Weder, Christoph

2013-04-08

On account of their intriguing mechanical properties, low cost, and renewable nature, high-aspect-ratio cellulose nanocrystals (CNCs) are an attractive component for many nanomaterials. Due to hydrogen bonding between their surface hydroxyl groups, unmodified CNCs (H-CNCs) aggregate easily and are often difficult to disperse. It is shown here that on account of ionic repulsion between charged surface groups, slightly phosphorylated CNCs (P-CNCs, average dimensions 31 ± 14 × 316 ± 127 nm, surface charge density = 10.8 ± 2.7 mmol/kg cellulose), prepared by controlled hydrolysis of cotton with phosphoric acid, are readily dispersible and form stable dispersions in polar solvents such as water, dimethyl sulfoxide, and dimethylformamide. Thermogravimetric analyses reveal that these P-CNCs exhibit a much higher thermal stability than partially sulfated CNCs (S-CNCs), which are frequently employed, but suffer from limited thermal stability. Nanocomposites of an ethylene oxide-epichlorohydrin copolymer and H-CNCs, S-CNCs, and P-CNCs were prepared, and their mechanical properties were studied by dynamic mechanical thermal analysis. The results show that P-CNCs offer a reinforcing capability that is comparable to that of H-CNCs or S-CNCs.

[Aging of silorane- and methacrylate-based composite resins: effects on color and translucency].

PubMed

Liu, Chang; Pan, Jie; Lin, Hong; Shen, Song

2015-10-01

To evaluate the color stability and translucency of silorane-based low shrinkage composite after in vitro aging procedures of thermal cycling and water storage respectively, and to compare with those of conventional methacrylate-based posterior composite. Three light-cured composite resins, dimethacrylate-based composite A (Filtek™ Z350), B (Filtek™ P60) and silorane-based composite C (Filtek™ P90), were tested in this study. Ten specimens (10 mm in diameter, 1 mm in height) of each composite were prepared. The ten specimens in each group were then divided into two subgroups (n = 5). One subgroup underwent thermal cycling [(5.0 ± 0.5)~(55.0 ± 1.0) °C, 10 000 cycles] and the other was stored in 37 C° distilled water for 180 days. With a spectrophotometer, the CIE L * a * b * parameters of the specimens were tested before and after artificial aging against white, medium grey and black backgrounds, respectively. △E, TP and △TP were calculated and data were analyzed using independent-samples t test and partial analysis (P < 0.05). With regard to color stability, silorane-based composite showed color alteration above the clinically acceptable levels (△E > 3.3), and also showed higher △E with a statistically significant difference in comparison with the other composites (B and C) (P < 0.05) after artificial aging. With regard to translucency, composite C showed more alteration compared with composite B (P < 0.05) after thermal cycling. It may be concluded that the silorane-based composite underwent greater alteration with regard to color stability and translucency.

Use of phosphoranimines to reduce organic carbonate content in Li-ion battery electrolytes

DOE PAGES

Dufek, Eric J.; Klaehn, John R.; McNally, Joshua S.; ...

2016-05-09

In this study, the use of phosphoranimines (PAs), a class of linear, monomeric phosphazenes, as electrolytes for Li-ion battery applications has been investigated as a route to improve safety and stability for Li-ion batteries. Of the potential PAs for use in battery applications, this work focuses on the initial synthetic preparation and analysis of N-trimethylsilyl-P,P-bis((2-methoxyethoxy)ethoxy)-P-ethylphosphoranimine (PA-5). PA-5 has high LiPF6 solubility in excess of 2 M, high thermal stability with a melting point below -80°C and high thermal stability as a neat compound to at least 250°C. As part of electrolyte blends, the inclusion of PA-5 shifts the onset ofmore » thermal degradation by close to 40°C at 35% loading and by 20°C at a 10% loading, improves the low temperature performance of the electrolyte, and when used as a primary solvent leads to increases in the flash point (by 20°C) when compared to more traditional EC:EMC blends. Cycling capabilities of full-coin cells with graphite negative electrodes and Li 1+w[Ni 0.5Mn 0.3Co 0.2] 1-wO 2 positive electrodes using PA-5:EC:EMC electrolyte blends are comparable with the performance seen for traditional EC:EMC blends. Analysis of the impact of the use of additives such as vinylene carbonate in PA-5:EC:EMC blended electrolyte results in enhanced capacity retention and improved coulombic efficiency.« less

Co-evaporation of fluoropolymer additives for improved thermal stability of organic semiconductors

NASA Astrophysics Data System (ADS)

Price, Jared S.; Wang, Baomin; Grede, Alex J.; Shen, Yufei; Giebink, Noel C.

2017-08-01

Reliability remains an ongoing challenge for organic light emitting diodes (OLEDs) as they expand in the marketplace. The ability to withstand operation and storage at elevated temperature is particularly important in this context, not only because of the inverse dependence of OLED lifetime on temperature, but also because high thermal stability is fundamentally important for high power/brightness operation as well as applications such as automotive lighting, where interior car temperatures often exceed the ambient by 50 °C or more. Here, we present a strategy to significantly increase the thermal stability of small molecule OLEDs by co-depositing an amorphous fluoropolymer, Teflon AF, to prevent catastrophic failure at elevated temperatures. Using this approach, we demonstrate that the thermal breakdown limit of common hole transport materials can be increased from typical temperatures of ˜100 °C to more than 200 °C while simultaneously improving their electrical transport properties. Similar thermal stability enhancements are demonstrated in simple bilayer OLEDs. These results point toward a general approach to engineer morphologically-stable organic electronic devices that are capable of operating or being stored in extreme thermal environments.

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.

Thermal stability increase in metallic nanoparticles-loaded cellulose nanocrystal nanocomposites.

PubMed

Goikuria, U; Larrañaga, A; Vilas, J L; Lizundia, E

2017-09-01

Due to the potential of CNC-based flexible materials for novel industrial applications, the aim of this work is to improve the thermal stability of cellulose nanocrystals (CNC) films through a straightforward and scalable method. Based of nanocomposite approach, five different metallic nanoparticles (ZnO, SiO 2 , TiO 2 , Al 2 O 3 and Fe 2 O 3 ) have been co-assembled in water with CNCs to obtain free-standing nanocomposite films. Thermogravimetric analysis (TGA) reveals an increased thermal stability upon nanoparticle. This increase in the thermal stability reaches a maximum of 75°C for the nanocomposites having 10wt% of Fe 2 O 3 and ZnO. The activation energies of thermodegradation process (E a ) determined according to Kissinger and Ozawa-Flynn-Wall methods further confirm the delayed degradation of CNC nanocomposites upon heating. Finally, the changes induced in the crystalline structure during thermodegradation were followed by wide angle X-ray diffraction (WAXD). It is also observed that thermal degradation proceeds at higher temperatures for nanocomposites having metallic nanoparticles. Overall, experimental findings here showed make nanocomposite approach a simple low-cost environmentally-friendly strategy to overcome the relatively poor thermal stability of CNCs when extracted via sulfuric acid assisted hydrolysis of cellulose. Copyright © 2017 Elsevier Ltd. All rights reserved.

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

Abdelaziz, Omar; Mallow, Anne; Graham, Samuel

Organic materials, such as paraffin wax, are sought as stable and environmentally friendly phase change materials (PCM) for thermal energy storage, but they suffer from low thermal conductivity which limits the rate at which thermal energy flows into and out of the material. A common method to improve the PCM thermal behavior is through loading with high thermal conductivity particulate fillers. However, the stability of these composites in the molten state is a concern as settling of the fillers will change the effective thermal conductivity. In this work, we investigate the stability of wax loaded with exfoliated graphite nanoplatelets eithermore » of 1 m (xGnP-1) or 15 m (xGnP-15) diameter. The effect of dispersants, oxidation of the wax, viscosity of the wax, mixing time, and hydrocarbon chain length on stability is reported. It was found that the addition of octadecylphosphonic acid (ODPA) is an effective dispersant for xGnP in paraffin and microcrystalline wax. In addition, mixing time, viscosity, and oxidation of the wax influence stability in the molten state. Overall, it was found that a mixing time of 24 hours for xGnP-15 along with ODPA mixed in a high viscosity, oxidized microcrystalline wax results in composite PCM systems with the greatest stability determined at 80 C in the molten state.« less

SU-E-T-410: Fringe Stability and Phase Shift Measurements in a Michelson Interferometer for Optical Calorimetry

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

Flores-Martinez, E; Malin, M; DeWerd, L

2014-06-01

Purpose: To identify the variables limiting the resolution of a Michelson interferometer used to measure phase shifts (PS) in water as part of a radiometric calorimeter. Methods: We investigated the output stability of a He-Ne laser and a laser diode. The short and long term stability of the fringe pattern in a Michelson interferometer was tested with different types of lasers, thermal insulation arrangements, damping systems and optical mounts to optimize system performance. PS were induced by electrically heating water in a 1 cm quartz cuvette located in one of the interferometer arms. The PS was calculated from fringe intensitymore » changes and compared to a calculated PS using thermocouple-measured temperature changes in the water. Results: The intensity of the laser diode is more stable, but the gas laser’s profile is more suitable for fringe analysis and has better temporal coherence. The laser requires a warm-up time of 4 hours before its output is stabilized (SNR>95). The fringe’s stability strongly depends on the thermal insulation. When the interferometer is exposed to ambient temperature swings of 0.7 K, it is not possible to stabilize the fringe pattern. Enclosing the system in a 2.5 cm-thick Styrofoam box improves the SNR, but further insulation will be needed to increase the SNR above 50. High frequency noise is significantly reduced by damping the system.Inducing a temperature rise in water, starting at 299 K, the average temperature increase for a 2π PS is 0.29 ± 0.02 K and the proportionality constant is -21.1 ± 0.8 radians/K. This is 5.8% lower than the calculated value using the thermocouple. Conclusion: Interferometric PS measurements of temperature may provide an alternative to thermistors for water calorimetry. The resolution of the current prototype is limited by ambient temperature stability. Calculated and measured thermally-induced PS in water agreed to within 5.8%.« less

Use of thermal analysis techniques (TG-DSC) for the characterization of diverse organic municipal waste streams to predict biological stability prior to land application.

PubMed

Fernández, José M; Plaza, César; Polo, Alfredo; Plante, Alain F

2012-01-01

The use of organic municipal wastes as soil amendments is an increasing practice that can divert significant amounts of waste from landfill, and provides a potential source of nutrients and organic matter to ameliorate degraded soils. Due to the high heterogeneity of organic municipal waste streams, it is difficult to rapidly and cost-effectively establish their suitability as soil amendments using a single method. Thermal analysis has been proposed as an evolving technique to assess the stability and composition of the organic matter present in these wastes. In this study, three different organic municipal waste streams (i.e., a municipal waste compost (MC), a composted sewage sludge (CS) and a thermally dried sewage sludge (TS)) were characterized using conventional and thermal methods. The conventional methods used to test organic matter stability included laboratory incubation with measurement of respired C, and spectroscopic methods to characterize chemical composition. Carbon mineralization was measured during a 90-day incubation, and samples before and after incubation were analyzed by chemical (elemental analysis) and spectroscopic (infrared and nuclear magnetic resonance) methods. Results were compared with those obtained by thermogravimetry (TG) and differential scanning calorimetry (DSC) techniques. Total amounts of CO(2) respired indicated that the organic matter in the TS was the least stable, while that in the CS was the most stable. This was confirmed by changes detected with the spectroscopic methods in the composition of the organic wastes due to C mineralization. Differences were especially pronounced for TS, which showed a remarkable loss of aliphatic and proteinaceous compounds during the incubation process. TG, and especially DSC analysis, clearly reflected these differences between the three organic wastes before and after the incubation. Furthermore, the calculated energy density, which represents the energy available per unit of organic matter, showed a strong correlation with cumulative respiration. Results obtained support the hypothesis of a potential link between the thermal and biological stability of the studied organic materials, and consequently the ability of thermal analysis to characterize the maturity of municipal organic wastes and composts. Copyright © 2011 Elsevier Ltd. All rights reserved.

Pressure-induced reversal between thermal contraction and expansion in ferroelectric PbTiO3.

PubMed

Zhu, Jinlong; Zhang, Jianzhong; Xu, Hongwu; Vogel, Sven C; Jin, Changqing; Frantti, Johannes; Zhao, Yusheng

2014-01-15

Materials with zero/near zero thermal expansion coefficients are technologically important for applications in thermal management and engineering. To date, this class of materials can only be produced by chemical routes, either by changing chemical compositions or by composting materials with positive and negative thermal expansion. Here, we report for the first time a physical route to achieve near zero thermal expansion through application of pressure. In the stability field of tetragonal PbTiO3 we observed pressure-induced reversals between thermal contraction and expansion between ambient pressure and 0.9 GPa. This hybrid behavior leads to a mathematically infinite number of crossover points in the pressure-volume-temperature space and near-zero thermal expansion coefficients comparable to or even smaller than those attained by chemical routes. The observed pressures for this unusual phenomenon are within a small range of 0.1-0.9 GPa, potentially feasible for designing stress-engineered materials, such as thin films and nano-crystals, for thermal management applications.

Stable spin domains in a nondegenerate ultracold gas

NASA Astrophysics Data System (ADS)

Graham, S. D.; Niroomand, D.; Ragan, R. J.; McGuirk, J. M.

2018-05-01

We study the stability of two-domain spin structures in an ultracold gas of magnetically trapped 87Rb atoms above quantum degeneracy. Adding a small effective magnetic field gradient stabilizes the domains via coherent collective spin rotation effects, despite negligibly perturbing the potential energy relative to the thermal energy. We demonstrate that domain stabilization is accomplished through decoupling the dynamics of longitudinal magnetization, which remains in time-independent domains, from transverse magnetization, which undergoes a purely transverse spin wave trapped within the domain wall. We explore the effect of temperature and density on the steady-state domains, and compare our results to a hydrodynamic solution to a quantum Boltzmann equation.

The Formation and Stability of Carbonic Acid on Outer Solar System Bodies

NASA Technical Reports Server (NTRS)

Peeters, Z.; Hudson, R. L.; Moore, M. H.; Lewis, Ariel

2009-01-01

The radiation chemistry, thermal stability, and vapor pressure of solid-phase carbonic acid (H2CO3) have been studied with mid-infrared spectroscopy. A new procedure for measuring this molecule's radiation stability has been used to obtain intrinsic IR band strengths and half-lives for radiolytic destruction. Results are compared to literature values. We report, for the first time, measurements of carbonic acid's vapor pressure and its heat of sublimation. We also report the first observation of a chemical reaction involving solid-phase carbonic acid. Possible applications of these findings are discussed, with an emphasis on the outer Solar System.

Effects of thermal variability on broadband seismometers: Controlled experiments, observations, and implications

USGS Publications Warehouse

Doody, Claire; Ringler, Adam; Anthony, Robert E.; Wilson, David; Holland, Austin; Hutt, Charles R.; Sandoval, Leo

2017-01-01

Isolating seismic instruments from temperature fluctuations is routine practice within the seismological community. However, the necessary degree of thermal stability required in broadband installations to avoid generating noise or compromising the fidelity in the seismic records is largely unknown and likely application dependent. To quantify the temperature sensitivity of seismometers over a broad range of frequencies, we artificially induced local temperature changes on three different models of seismometers to measure the effect of thermal variations on seismometer output. We found that diurnal temperature changes above 0.002°C root mean square (rms) showed significant changes in velocity and acceleration output in comparison to thermally stable reference measurements. We also found that sensor incoherent self‐noise increased with temperature variation; these increases in noise can be modeled as 1/f">1/f noise (pink noise), and are unlikely to be easily corrected for. These experimental results are compared with the data from Incorporated Research Institutions for Seismology (IRIS) U.S. Geological Survey (USGS) Global Seismographic Network (GSN) station TUC (Tucson, Arizona). This station is well instrumented with temperature sensors and has three different broadband seismometers, each of which uses a different method of thermal isolation. We show that the water bricks and borehole installations give ample temperature attenuation to thermally isolate seismometers from diurnal thermal variability that would compromise seismic data. We find that seismometer installations that provide thermal stability below 0.002°C rms could help to improve long‐period vertical seismic data across the GSN by decreasing temperature‐driven 1/f">1/f noise.

Thermal-inertial ratchet effects: negative mobility, resonant activation, noise-enhanced stability, and noise-weakened stability.

PubMed

Li, Jing-hui; Łuczka, Jerzy

2010-10-01

Transport properties of a Brownian particle in thermal-inertial ratchets subject to an external time-oscillatory drive and a constant bias force are investigated. Since the phenomena of negative mobility, resonant activation and noise-enhance stability were reported before, in the present paper, we report some additional aspects of negative mobility, resonant activation and noise-enhance stability, such as the ingredients for the appearances of these phenomena, multiple resonant activation peaks, current reversals, noise-weakened stability, and so on.

Examination of molecular mechanism for the enhanced thermal stability of anthocyanins by metal cations and polysaccharides.

PubMed

Tachibana, Noriko; Kimura, Yukihiro; Ohno, Takashi

2014-01-15

Anthocyanins exhibit colour variation over wide pH range but the colour stability is relatively low at the physiological pH. To improve the stability of anthocyanins in neutral to weakly acidic pH region, effects of metal cations and polysaccharides on the colour stability of cyanidin-3-glucoside (C3G) were examined by ultraviolet-visible and resonance Raman spectroscopies. C3G was thermally stabilized by the addition of Fe(3+) but formed aggregation. However, further addition of anionic polysaccharides enhanced the thermal stability of C3G without aggregation. Similar stabilisation was confirmed for delphinidin-3-glucoside (D3G) but not for pelargonidin-3-glucoside. The stability of anthocyanins considerably varied depending on pHs and kinds of metal cations, polysaccharides and buffer molecules. The characteristic resonance Raman bands of C3G-Fe(3+) and D3G-Fe(3+) complexes were significantly affected by the addition of alginate, (18)O/(16)O-isotope substitution, and Fe(2+)/Fe(3+)-replacement. These results suggest that alginate associates with C3G through Fe(3+) to form a stable complex, which enhances the thermal stability of C3G. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effect of unsaponifiable matter extracted from Pistacia khinjuk fruit oil on the oxidative stability of olive oil.

PubMed

Tavakoli, Javad; Estakhr, Parviz; Jelyani, Aniseh Zarei

2017-08-01

The present study was carried out to investigate the improvement of oxidative stability of refined olive oil using various concentrations of unsaponifiable matters extracted from Pistacia khinjuk fruit oil (UFO). For further elucidation of UFO antioxidative power, tertbutylhydroquinone (TBHQ) was used in an olive oil sample, too. Oxidative stability of olive oil samples without and with different levels of UFO (50, 100, 250, 500, 750 and 1000 ppm) and TBHQ (100 ppm) were studied via evaluation of conjugated diene value, carbonyl value, oil/oxidative stability index, acid value and total tocopherol (TT) contents through 8 h thermal process at 170 °C. Results obtained by oxidative stability assays revealed that the highest antioxidative activity of olive oil was obtained by 100 ppm of UFO, followed using 100, 250, 500, 750, and 1000 ppm of UFO and 100 ppm TBHQ, respectively. Evaluation of the relationship between oxidative stability indexes and TT changes indicated a strong correlation (R 2  = 0.9718) between mean relative resistance to oxidation and relative resistance to TT reduction during thermal process. By promotion of relative resistance to TT reduction, olive oil samples' relative resistance to oxidation was enhanced exponentially; implying importance of TT in promotion of oxidative stability of edible oils. The results obtained in this study showed that UFO has higher antioxidative activity compared to TBHQ; thus UFO can be considered as a natural antioxidant with ideal antioxidative activity.

Structural and biophysical characterization of the α-carbonic anhydrase from the gammaproteobacterium Thiomicrospira crunogena XCL-2: insights into engineering thermostable enzymes for CO2 sequestration.

PubMed

Díaz-Torres, Natalia A; Mahon, Brian P; Boone, Christopher D; Pinard, Melissa A; Tu, Chingkuang; Ng, Robert; Agbandje-McKenna, Mavis; Silverman, David; Scott, Kathleen; McKenna, Robert

2015-08-01

Biocatalytic CO2 sequestration to reduce greenhouse-gas emissions from industrial processes is an active area of research. Carbonic anhydrases (CAs) are attractive enzymes for this process. However, the most active CAs display limited thermal and pH stability, making them less than ideal. As a result, there is an ongoing effort to engineer and/or find a thermostable CA to fulfill these needs. Here, the kinetic and thermal characterization is presented of an α-CA recently discovered in the mesophilic hydrothermal vent-isolate extremophile Thiomicrospira crunogena XCL-2 (TcruCA), which has a significantly higher thermostability compared with human CA II (melting temperature of 71.9°C versus 59.5°C, respectively) but with a tenfold decrease in the catalytic efficiency. The X-ray crystallographic structure of the dimeric TcruCA shows that it has a highly conserved yet compact structure compared with other α-CAs. In addition, TcruCA contains an intramolecular disulfide bond that stabilizes the enzyme. These features are thought to contribute significantly to the thermostability and pH stability of the enzyme and may be exploited to engineer α-CAs for applications in industrial CO2 sequestration.

Analytic tests and their relation to jet fuel thermal stability

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

Heneghan, S.P.; Kauffman, R.E.

1995-05-01

The evaluation of jet fuel thermal stability (TS) by simple analytic procedures has long been a goal of fuels chemists. The reason is obvious: if the analytic chemist can determine which types of material cause his test to respond, the refiners will know which materials to remove to improve stability. Complicating this quest is the lack of an acceptable quantitative TS test with which to compare any analytic procedures. To circumvent this problem, we recently compiled the results of TS tests for 12 fuels using six separate test procedures. The results covering a range of flow and temperature conditions showmore » that TS is not as dependent on test conditions as previously thought. Also, comparing the results from these tests with several analytic procedures shows that either a measure of the number of phenols or the total sulfur present in jet fuels is strongly indicative of the TS. The phenols have been measured using a cyclic voltammetry technique and the polar material by gas chromatography (atomic emission detection) following a solid phase extraction on silica gel. The polar material has been identified as mainly phenols (by mass spectrometry identification). Measures of the total acid number or peroxide concentration have little correlation with TS.« less

Synthesis of thermal and chemical resistant oxygen barrier starch with reinforcement of nano silicon carbide.

PubMed

Dash, Satyabrata; Swain, Sarat K

2013-09-12

Starch/silicon carbide (starch/SiC) bionanocomposites were synthesized by solution method using different wt% of silicon carbide with starch matrix. The interaction between starch and silicon carbide was studied by Fourier transform infrared (FTIR) spectroscopy. The structure of the bionanocomposites was investigated by X-ray diffraction (XRD) and field emission scanning electron microscope (FESEM). Thermal property of starch/SiC bionanocomposites was measured and a significant enhancement of thermal resistance was noticed. The oxygen barrier property of the composites was studied and a substantial reduction in permeability was observed as compared to the virgin starch. The reduction of oxygen permeability with enhancement of thermal stability of prepared bionanocomposites may enable the materials suitable for thermal resistant packaging and adhesive applications. Copyright © 2013 Elsevier Ltd. All rights reserved.

Thermal Conductivity of Diamond Packed Electrospun PAN-Based Carbon Fibers Incorporated with Multi Wall Carbon Nanotubes.

PubMed

Dong, Qi; Lu, Chunyuan; Tulugan, Kelimu; Jin, Chunzi; Yoon, Soo Jong; Park, Yeong Min; Kim, Tae Gyu

2016-02-01

Multi wall carbon nanotubes (MWCNTs) and diamond are renowned as superlative material due to their relatively high thermal conductivity and hardness while comparing with any bulk materials. In this research, polyacrylonitrile (PAN) solution incorporated with MWCNTs at an alteration of mass fractions (0 wt%, 0.6 wt%, 1 wt%, 2 wt%) were fabricated via electrospinning under optimized parameters. Dried composite nanofibers were stabilized and carbonized, after which water base polytrafluorethylene (PTFE) mixed with nano diamond powder solution was spin coated on them. Scanning electron microscopy, Raman spectroscopy, X-ray scattering and Laserflash thermal conductivity were used to characterize the composite nanofiber sheets. The result shows that the thermal conductivity increased to 4.825 W/m K from 2.061 W/mK. The improvement of thermal conductivities is suggesting the incorporation of MWCNTs.

[THERMAL STABILITY AS A PROGNOSTIC INDICATOR OF CONSERVATION OF LIVE EMBRYONIC SMALLPOX VACCINE (TEOVAC) DURING STORAGE].

PubMed

Zhukov, V A; Kokorev, S V; Rogozhkina, S V; Melnikov, D G; Terentiev, A I; Kovalchuk, E A; Vakhnov, E Yu; Borisevich, S V

2016-01-01

Determination of values of coefficients of thermal stability of TEOVac for prognosis of conservation of the vaccine (specific biological activity) during the process of warranty period storage. TEOVac (masticatory tablets) in primary packaging was kept at increased temperature (accelerated and stress-tests) and at the conditions established by PAP for the preparation (long-term tests). Biological activity of the vaccine was determined by titration on 12-day chicken embryos. A correlation between the value of coefficients of thermal stability and conservation of the prepared series of the condition preparation at the final date of storage was experimentally established. Coefficients of thermal stability could be used as a prognostic indicator of quality of the produced pelleted formulation of the preparation for evaluation of conservation of the vaccine during warranty period storage.

The performance of thermal control coatings on LDEF and implications to future spacecraft

NASA Technical Reports Server (NTRS)

Wilkes, Donald R.; Miller, Edgar R.; Mell, Richard J.; Lemaster, Paul S.; Zwiener, James M.

1993-01-01

The stability of thermal control coatings over the lifetime of a satellite or space platform is crucial to the success of the mission. With the increasing size, complexity, and duration of future missions, the stability of these materials becomes even more important. The Long Duration Exposure Facility (LDEF) offered an excellent testbed to study the stability and interaction of thermal control coatings in the low-Earth orbit (LEO) space environment. Several experiments on LDEF exposed thermal control coatings to the space environment. This paper provides an overview of the different materials flown and their stability during the extended LDEF mission. The exposure conditions, exposure environment, and measurements of materials properties (both in-space and postflight) are described. The relevance of the results and the implications to the design and operation of future space vehicles are also discussed.

Effect of thermal aging on stability of transformer oil based temperature sensitive magnetic fluids

NASA Astrophysics Data System (ADS)

Kaur, Navjot; Chudasama, Bhupendra

2018-04-01

Synthesizing stable temperature sensitive magnetic fluids with tunable magnetic properties that can be used as coolant in transformers is of great interest, however not exploited commercially due to the lack of its stability at elevated temperatures in bulk quantities. The task is quite challenging as the performance parameters of magnetic fluids are strongly influenced by thermal aging. In this article, we report the effect of thermal aging on colloidal stability and magnetic properties of Mn1-xZnxFe2O4 magnetic fluids prepared in industrial grade transformer oil. As-synthesized magnetic fluids possess good dispersion stability and tunable magnetic properties. Effect of accelerated thermal aging on the dispersion stability and magnetic properties have been evaluated by photon correlation spectroscopy and vibration sample magnetometry, respectively. Magnetic fluids are stable under accelerated aging at elevated temperatures (from 50 °C to 125 °C), which is critical for their efficient performance in high power transformers.

Laser surface modification of Yttria Stabilized Zirconia (YSZ) thermal barrier coating on AISI H13 tool steel substrate

NASA Astrophysics Data System (ADS)

Reza, M. S.; Aqida, S. N.; Ismail, I.

2018-03-01

This paper presents laser surface modification of plasma sprayed yttria stabilized zirconia (YSZ) coating to seal porosity defect. Laser surface modification on plasma sprayed YSZ was conducted using 300W JK300HPS Nd: YAG laser at different operating parameters. Parameters varied were laser power and pulse frequency with constant residence time. The coating thickness was measured using IM7000 inverted optical microscope and surface roughness was analysed using two-dimensional Mitutoyo Surface Roughness Tester. Surface roughness of laser surface modification of YSZ H-13 tool steel decreased significantly with increasing laser power and decreasing pulse frequency. The re-melted YSZ coating showed higher hardness properties compared to as-sprayed coating surface. These findings were significant to enhance thermal barrier coating surface integrity for dies in semi-solid processing.

Opposing effects of two osmolytes--trehalose and glycerol--on thermal inactivation of rabbit muscle 6-phosphofructo-1-kinase.

PubMed

Faber-Barata, Joana; Sola-Penna, Mauro

2005-01-01

Trehalose and glycerol are known as good stabilizers of function and structure of several macromolecules against stress conditions. We previously reported that they have comparable effectiveness on protecting two yeast cytosolic enzymes against thermal inactivation. However, enzyme protection has always been associated to a decrease in catalytic activity at the stabilizing conditions i.e., the presence of the protective molecule. In the present study we tested trehalose and glycerol on thermal protection of the mammalian cytosolic enzyme phosphofructokinase. Here we found that trehalose was able to protect phosphofructokinase against thermal inactivation as well as to promote an activation of its catalytic activity. The enzyme incubated in the presence of 1 M trehalose did not present any significant inactivation within 2 h of incubation at 50 degrees C, contrasting to control experiments where the enzyme was fully inactivated during the same period exhibiting a t0.5 for thermal inactivation of 56+/-5 min. On the other hand, enzyme incubated in the presence of 37.5% (v/v) glycerol was not protected against incubation at 50 degrees C. Indeed, when phosphofructokinase was incubated for 45 min at 50 degrees C in the presence of lower concentrations of glycerol (7.5-25%, v/v), the remaining activity was 2-4 times lower than control. These data show that the compatibility of effects previously shown for trehalose and glycerol with some yeast cytosolic enzymes can not be extended to all globular enzyme system. In the case of phosphofructokinase, we believe that its property of shifting between several different complex oligomers configurations can be influenced by the physicochemical properties of the stabilizing molecules.

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.

Groundwork for integration of hot water extraction as a potential pre-process in a biorefinery for downstream conversion and nano-fibrillation

NASA Astrophysics Data System (ADS)

Zhu, Rui

The economic competitiveness of biofuels production is highly dependent on feedstock cost, which constitutes 35-50 % of the total biofuels production cost. Economically viable feedstock pre-process has a significant influence on all the subsequent downstream processes in the biorefinery supply chain. In this work, hot water extraction (HWE) was exploited as a pre-process to initially fractionate cell wall structure of softwood Douglas fir, which is considerably more recalcitrant compared to hardwoods and agricultural feedstocks. A response surface model was developed and the highest hemicellulose extraction yield (HEY) was obtained when the temperature is 180 °C and the time is 79 min. HWE process partially removed hemicelluloses, reduced the moisture absorption and improved the thermal stability of wood. To investigate the effects of HWE pre-process on sulfite pretreatment to overcome recalcitrance of lignocellulose (SPORL), a series of SPORL with reduced combined severity factor (CSF) were conducted using HWE treated Douglas fir. Sugar analysis after enzymatic hydrolysis indicated that SPORL can be conducted at lower temperature (145 °C), shorter time (80 min), and lower acid volume (3 %), while still maintaining considerably high enzymatic digestibility ( 55-60%). Deriving valuable co-products would increase the overall revenue and improve the economics of the biofuels supply chain. The feasibility of extracting cellulose nanofibrils (CNFs) from HWE treated Douglas fir by ultrasonication and CNFs' reinforcing potentials in nylon 6 matrix were evaluated. Morphology analysis indicated that finer fibrils can be obtained by increasing ultrasonication time and/or amplitude. CNFs was found to have higher crystallinity and maintained the thermal stability compared to untreated fiber. A method of fabricating nylon 6/CNFs as-spun nanocomposite filaments using a combination of extrusion, compounding and capillary rheometer to minimize thermal degradation of CNFs was demonstrated. It was found that the nanocomposite filaments have slightly lower thermal stability and crystallinity compared to neat nylon 6 filaments. However, the incorporation of CNFs increased the tenacity and hydrophilicity of the nanocomposite filaments, indicating a potential for their use as precursor materials for textile yarns.

PMR-15/Layered Silicate Nanocomposites For Improved Thermal Stability And Mechanical Properties

NASA Technical Reports Server (NTRS)

Campbell, Sandi; Scheiman, Daniel; Faile, Michael; Papadopoulos, Demetrios; Gray, Hugh R. (Technical Monitor)

2002-01-01

Montmorillonite clay was organically modified by co-exchange of an aromatic diamine and a primary alkyl amine. The clay was dispersed into a PMR (Polymerization of Monomer Reactants)-15 matrix and the glass transition temperature and thermal oxidative stability of the resulting nanocomposites were evaluated. PMR-15/ silicate nanocomposites were also investigated as a matrix material for carbon fabric reinforced composites. Dispersion of the organically modified silicate into the PMR-15 matrix enhanced the thermal oxidative stability, the flexural strength, flexural modulus, and interlaminar shear strength of the polymer matrix composite.

Thermal degradation of ternary blend films containing PVA/chitosan/vanillin

NASA Astrophysics Data System (ADS)

Kasai, Deepak; Chougale, Ravindra; Masti, Saraswati; Narasgoudar, Shivayogi

2018-05-01

The ternary chitosan/poly (vinyl alcohol)/vanillin blend films were prepared by solution casting method. The influence of equal weight percent of poly (vinyl alcohol) and vanillin on thermal stability of the chitosan blend films were investigated by using thermogravimetric analysis (TGA). The kinetic parameters such as enthalpy (ΔH*), entropy (ΔS*), and Gibbs free energy (ΔG*) in the first and second decomposition steps based on the thermogravimetric data were calculated. The thermal stabilities of the blend films were confirmed by thermodynamic parameters obtained in the activation energies, which indicated that increase in the equal weight percent of PVA/vanillin decreased the thermal stability of the chitosan film.

Effect of Filler Concentration on Thermal Stability of Vinyl Copolymer Elastomer (VCE) Composites

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

Yang, Dali; Hubbard, Kevin Mark; Devlin, David James

To study the thermal stability of vinyl copolymer elastomer (VCE) in its composite form, systematic TGA characterizations were conducted in both nonisothermal and isothermal modes. The effects of filler concentration on the aging behaviors of the VCE/filler composites were investigated under nitroplasticizer (NP) environment. FTIR characterization was used to probe the structural changes in the VCE polymer before and after the thermal treatments. This study suggests that the filler concentration significantly deteriorates the thermal stability of NP at a moderate temperature (< 70 °C). The degradation of NP, in turn, accelerates the aging process of the VCE polymer in itsmore » composite form.« less

Highly defective oxides as sinter resistant thermal barrier coating

DOEpatents

Subramanian, Ramesh

2005-08-16

A thermal barrier coating material formed of a highly defective cubic matrix structure having a concentration of a stabilizer sufficiently high that the oxygen vacancies created by the stabilizer interact within the matrix to form multi-vacancies, thereby improving the sintering resistance of the material. The concentration of stabilizer within the cubic matrix structure is greater than that concentration of stabilizer necessary to give the matrix a peak ionic conductivity value. The concentration of stabilizer may be at least 30 wt. %. Embodiments include a cubic matrix of zirconia stabilized by at least 30-50 wt. % yttria, and a cubic matrix of hafnia stabilized by at least 30-50 wt. % gadolinia.

Improvement of activity, thermo-stability and fruit juice clarification characteristics of fungal exo-polygalacturonase.

PubMed

Amin, Faiza; Bhatti, Haq Nawaz; Bilal, Muhammad; Asgher, Muhammad

2017-02-01

An extracellular exo-polygalacturonase (exo-PG) from Penicillium notatum was immobilized in sodium-alginate matrix through two different protocols, viz. covalent bonding and adsorption to enhance its catalytic activity, thermal stability and life-time properties for industrial applications. Covalent immobilization was more efficient in terms of high relative activity (45.89%) and immobilization yield (71.6%) as compared to adsorption. Immobilized exo-PG derivatives displayed maximum activities at pH 5.5 and 55°C as compared to free enzyme which showed its optimum activity at pH 6.0 and 50°C. The affinity of enzyme towards its substrate (K m(app) ) was reduced after immobilization and V max of covalently immobilized exo-PG decreased to 66.7% while the V max value of adsorbed enzyme increased up to 150% as compared to free counterpart. Both immobilization techniques greatly enhanced the thermal stability profile of the enzyme. At 60°C, immobilized exo-PGs retained more than 90% of their residual activities after 60min of heating, while free enzyme did not show any activity at the same temperature. Thermodynamic properties (i.e., Ea, ΔH*, ΔS*and ΔG*) of the free and immobilized enzymes were also investigated. Sodium-alginate covalently immobilized and adsorbed enzymes showed excellent recycling efficiencies and retained 50.0% and 41.0% of original activities, respectively after seven consecutive batch reactions. Moreover, the immobilized enzymes treatment achieved promising results in turbidity and viscosity reduction as well as clarity amelioration in various fruit juices. Altogether catalytic, thermo-stability and fruit juices clarification characteristics of the immobilized ex-PGs suggest a high potential for biotechnological exploitability. Copyright © 2016 Elsevier B.V. All rights reserved.

The effects of certain glycols, substituted glycols and related organic solvents on the thermal stability of soluble collagen

PubMed Central

Hart, G. J.; Russell, A. E.; Cooper, D. R.

1971-01-01

The effects of a number of related diols, substituted diols and glycerol on the thermal stability of acid-soluble calf skin collagen were investigated. Thermal transition temperatures were determined by optical rotation measurement. Short-chain diols with terminal hydroxyl groups, i.e. ethylene glycol and propane-1,3-diol, stabilized the protein at all accessible concentrations. Stabilization was also observed with glycerol and diethylene glycol. Higher homologues in the diol series produced various effects, as did hydroxyl-group positional isomerism. Monoalkyl substitution of diols progressively lowered the denaturation temperature of collagen. Results are discussed in relation to possible mechanisms of perturbant action. PMID:5169191

A multi-layer discrete-ordinate method for vector radiative transfer in a vertically-inhomogeneous, emitting and scattering atmosphere. I - Theory. II - Application

NASA Technical Reports Server (NTRS)

Weng, Fuzhong

1992-01-01

A theory is developed for discretizing the vector integro-differential radiative transfer equation including both solar and thermal radiation. A complete solution and boundary equations are obtained using the discrete-ordinate method. An efficient numerical procedure is presented for calculating the phase matrix and achieving computational stability. With natural light used as a beam source, the Stokes parameters from the model proposed here are compared with the analytical solutions of Chandrasekhar (1960) for a Rayleigh scattering atmosphere. The model is then applied to microwave frequencies with a thermal source, and the brightness temperatures are compared with those from Stamnes'(1988) radiative transfer model.

Prospect of Thermal Insulation by Silica Aerogel: A Brief Review

NASA Astrophysics Data System (ADS)

Hasan, Mohammed Adnan; Sangashetty, Rashmi; Esther, A. Carmel Mary; Patil, Sharanabasappa B.; Sherikar, Baburao N.; Dey, Arjun

2017-10-01

Silica aerogel is a unique ultra light weight nano porous material which offers superior thermal insulation property as compared to the conventional thermal insulating materials. It can be applied not only for ground and aerospace applications but also in low and high temperatures and pressure regimes. Aerogel granules and monolith are synthesized by the sol-gel route while aerogel based composites are fabricated by the reinforcement of fibers, particle and opacifiers. Due to the characteristic brittleness (i.e., poor mechanical properties) of monolith or bulk aerogel, it is restricted in several applications. To improve the mechanical integrity and flexibility, usually different fibers are reinforced with aerogel and hence it can be used as flexible thermal insulation blankets. Further, to achieve effective thermal insulation behaviour particularly at high temperature, often opacifiers are doped with silica aerogel. In the present brief review, the prospects of bulk aerogel and aerogel based composites are discussed for the application of thermal insulation and thermal stability.

Synthesis and photophysical characterizations of thermal-stable naphthalene benzimidazoles.

PubMed

Erten-Ela, Sule; Ozcelik, Serdar; Eren, Esin

2011-07-01

Microwave-assisted synthesis, photophysical and electrochemical properties of thermal-stable naphthalene benzimidazoles and naphthalimides are studied in this paper. Microwave-assisted synthesis of naphthalene benzimidazoles provide higher yields than the conventional thermal synthesis. Comparative photophysical properties of naphthalene benzimidazoles and naphthalimides are revealed that conjugation of electron-donating group onto naphthalimide moiety increases fluorescence quantum yields. Fluorophore-solvent interactions are also investigated using Lippert-Mataga equation for naphthalimides and naphthalene benzimidazoles. Thermal stabilities of naphthalene benzimidazoles are better than naphthalimides due to increased aromaticity. The experimental E(LUMO) levels of naphthalene benzimidazoles are found to be between 3.15 and 3.28 eV. Therefore, naphthalene benzimidazole derivatives consisting of anchoring groups are promising materials in organic dye sensitized solar cells. © Springer Science+Business Media, LLC 2011

Quantifying data retention of perpendicular spin-transfer-torque magnetic random access memory chips using an effective thermal stability factor method

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

Thomas, Luc, E-mail: luc.thomas@headway.com; Jan, Guenole; Le, Son

The thermal stability of perpendicular Spin-Transfer-Torque Magnetic Random Access Memory (STT-MRAM) devices is investigated at chip level. Experimental data are analyzed in the framework of the Néel-Brown model including distributions of the thermal stability factor Δ. We show that in the low error rate regime important for applications, the effect of distributions of Δ can be described by a single quantity, the effective thermal stability factor Δ{sub eff}, which encompasses both the median and the standard deviation of the distributions. Data retention of memory chips can be assessed accurately by measuring Δ{sub eff} as a function of device diameter andmore » temperature. We apply this method to show that 54 nm devices based on our perpendicular STT-MRAM design meet our 10 year data retention target up to 120 °C.« less

Scatterometer-Calibrated Stability Verification Method

NASA Technical Reports Server (NTRS)

McWatters, Dalia A.; Cheetham, Craig M.; Huang, Shouhua; Fischman, Mark A.; CHu, Anhua J.; Freedman, Adam P.

2011-01-01

The requirement for scatterometer-combined transmit-receive gain variation knowledge is typically addressed by sampling a portion of the transmit signal, attenuating it with a known-stable attenuation, and coupling it into the receiver chain. This way, the gain variations of the transmit and receive chains are represented by this loop-back calibration signal, and can be subtracted from the received remote radar echo. Certain challenges are presented by this process, such as transmit and receive components that are outside of this loop-back path and are not included in this calibration, as well as the impracticality for measuring the transmit and receive chains stability and post fabrication separately, without the resulting measurement errors from the test set up exceeding the requirement for the flight instrument. To cover the RF stability design challenge, the portions of the scatterometer that are not calibrated by the loop-back, (e.g., attenuators, switches, diplexers, couplers, and coaxial cables) are tightly thermally controlled, and have been characterized over temperature to contribute less than 0.05 dB of calibration error over worst-case thermal variation. To address the verification challenge, including the components that are not calibrated by the loop-back, a stable fiber optic delay line (FODL) was used to delay the transmitted pulse, and to route it into the receiver. In this way, the internal loopback signal amplitude variations can be compared to the full transmit/receive external path, while the flight hardware is in the worst-case thermal environment. The practical delay for implementing the FODL is 100 s. The scatterometer pulse width is 1 ms so a test mode was incorporated early in the design phase to scale the 1 ms pulse at 100-Hz pulse repetition interval (PRI), by a factor of 18, to be a 55 s pulse with 556 s PRI. This scaling maintains the duty cycle, thus maintaining a representative thermal state for the RF components. The FODL consists of an RF-modulated fiber-optic transmitter, 20 km SMF- 28 standard single-mode fiber, and a photodetector. Thermoelectric cooling and insulating packaging are used to achieve high thermal stability of the FODL components. The chassis was insulated with 1-in. (.2.5-cm) thermal isolation foam. Nylon rods support the Micarta plate, onto which are mounted four 5-km fiber spool boxes. A copper plate heat sink was mounted on top of the fiber boxes (with thermal grease layer) and screwed onto the thermoelectric cooler plate. Another thermal isolation layer in the middle separates the fiberoptics chamber from the RF electronics components, which are also mounted on a copper plate that is screwed onto another thermoelectric cooler. The scatterometer subsystem fs overall stability was successfully verified to be calibratable to within 0.1 dB error in thermal vacuum (TVAC) testing with the fiber-optic delay line, while the scatterometer temperature was ramped from 10 to 30 C, which is a much larger temperature range than the worst-case expected seasonal variations.

Demonstration of EnergyNest thermal energy storage (TES) technology

NASA Astrophysics Data System (ADS)

Hoivik, Nils; Greiner, Christopher; Tirado, Eva Bellido; Barragan, Juan; Bergan, Pâl; Skeie, Geir; Blanco, Pablo; Calvet, Nicolas

2017-06-01

This paper presents the experimental results from the EnergyNest 2 × 500 kWhth thermal energy storage (TES) pilot system installed at Masdar Institute of Science & Technology Solar Platform. Measured data are shown and compared to simulations using a specially developed computer program to verify the stability and performance of the TES. The TES is based on a solid-state concrete storage medium (HEATCRETE®) with integrated steel tube heat exchangers cast into the concrete. The unique concrete recipe used in the TES has been developed in collaboration with Heidelberg Cement; this material has significantly higher thermal conductivity compared to regular concrete implying very effective heat transfer, at the same time being chemically stable up to 450 °C. The demonstrated and measured performance of the TES matches the predictions based on simulations, and proves the operational feasibility of the EnergyNest concrete-based TES. A further case study is analyzed where a large-scale TES system presented in this article is compared to two-tank indirect molten salt technology.

Reducing Pumping Power in Hydronic Heating and Cooling Systems with Microencapsulated Phase Change Material Slurries

NASA Astrophysics Data System (ADS)

Karas, Kristoffer Jason

Phase change materials (PCMs) are being used increasingly in a variety of thermal transfer and thermal storage applications. This thesis presents the results of a laboratory study into the feasibility of improving the performance of hydronic heating and cooling systems by adding microcapsules filled with a PCM to the water used as heat transport media in these systems. Microencapsulated PCMs (MPCMs) increase the heat carrying capacity of heat transport liquids by absorbing or releasing heat at a constant temperature through a change of phase. Three sequences of tests and their results are presented: 1) Thermal cycling tests conducted to determine the melting temperatures and extent of supercooling associated with the MPCMs tested. 2) Hydronic performance tests in which MPCM slurries were pumped through a fin-and-tube, air-to-liquid heat exchanger and their thermal transfer performance compared against that of ordinary water. 3) Mechanical stability tests in which MPCM slurries were pumped in a continuous loop in order to gauge the extent of rupture due to pumping. It is shown that slurries consisting of water and MPCMs ˜ 14-24 mum in diameter improve thermal performance and offer the potential for power savings in the form of reduced pumping requirements. In addition, it is shown that while slurries of MPCMs 2-5 mum in diameter appear to exhibit better mechanical stability than slurries of larger diameter MPCMs, the smaller MPCMs appear to reduce the thermal performance of air-to-liquid heat exchangers.

Evaluation of Sc-Bearing Aluminum Alloy C557 for Aerospace Applications

NASA Technical Reports Server (NTRS)

Domack, Marcia S.; Dicus, Dennis L.

2002-01-01

The performance of the Al-Mg-Sc alloy C557 was evaluated to assess its potential for a broad range of aerospace applications, including airframe and launch vehicle structures. Of specific interest were mechanical properties at anticipated service temperatures and thermal stability of the alloy. Performance was compared with conventional airframe aluminum alloys and with other emerging aluminum alloys developed for specific service environments. Mechanical properties and metallurgical structure were evaluated for commercially rolled sheet in the as-received H116 condition and after thermal exposures at 107 C. Metallurgical analyses were performed to de.ne grain morphology and texture, strengthening precipitates, and to assess the effect of thermal exposure.

Evaluation of high temperature structural adhesives for extended service, phase 4

NASA Technical Reports Server (NTRS)

Hendricks, C. L.; Hill, S. G.; Hale, J. N.

1985-01-01

The evaluation of three phenylquinoxaline polymers as high temperature structural adhesives is presented. These included an experimental crisskubjabke oiktner (X-PQ) and two experimental materials (PPQ-2501) and (PPQ-HC). Lap shear, crack extension, and climing drum peel specimens were fabricated from all three polymers, and tested after thermal, combined thermal/humidity, and stressed Skydrol exposure. All three polymers generally performed well as adhesives at initial test temperatures from 219K (-67 F) to 505K (450 F) and after humidity exposure. The 644K (700 F) cured test specimens exhibited superior Skydrol resistance and thermal stability at 505K (450 F) when compared to the 602K (625 F) cured test specimens.

Melamine-formaldehyde microcapsules filled sappan dye modified polypropylene composites: encapsulation and thermal properties

NASA Astrophysics Data System (ADS)

Phanyawong, Suphitcha; Siengchin, Suchart; Parameswaranpillai, Jyotishkumar; Asawapirom, Udom; Polpanich, Duangporn

2018-01-01

Sappan dye, a natural dye extracted from sappan wood is widely used in cosmetics, textile dyeing and as food additives. However, it was recognized that natural dyes cannot withstand high temperature. In this study, a protective coating of melamine-formaldehyde shell material was applied over the sappan dye to improve its thermal stability. The percentage of sappan dye used in the microencapsulation was 30, 40, 50, 60 and 70 wt%. The color, shape, size, and thermal stability of sappan dye microcapsules were investigated. It was found that increasing amount of sappan dye content in the microcapsules decreased the particle size. Thermal analysis reveals that the melamine-formaldehyde resin served as an efficient protective shell for sappan dye. Besides, 30 wt% sappan dye microcapsules with different weight percent (1, 3 and 5 wt%) of sappan dye was used as modifier for polypropylene (PP). All the prepared composites are red in color which supports the thermal stability of the microcapsules. The changes in crystallinity and melting behavior of PP by the addition of microcapsules were studied in detail by differential scanning calorimetry. Thermogravimetric studies showed that the thermal stability of PP composites increased by the addition of microcapsules.

Enhanced thermal conductivity of form-stable phase change composite with single-walled carbon nanotubes for thermal energy storage.

PubMed

Qian, Tingting; Li, Jinhong; Feng, Wuwei; Nian, Hong'en

2017-03-16

A striking contrast in the thermal conductivities of polyethylene glycol (PEG)/diatomite form-stable phase change composite (fs-PCC) with single-walled carbon nanotubes (SWCNs) as nano-additive has been reported in our present study. Compared to the pure PEG, the thermal conductivity of the prepared fs-PCC has increased from 0.24 W/mK to 0.87 W/Mk with a small SWCNs loading of 2 wt%. SWCNs are decorated on the inner surface of diatomite pores whilst retaining its porous structure. Compared to PEG/diatomite fs-PCC, the melting and solidification time of the PEG/diatomite/SWCNs fs-PCC are respectively decreased by 54.7% and 51.1%, and its thermal conductivity is 2.8 times higher. The composite can contain PEG as high as 60 wt% and maintain its original shape perfectly without any PEG leakage after subjected to 200 melt-freeze cycles. DSC results indicates that the melting point of the PEG/diatomite/SWCNs fs-PCC shifts to a lower temperature while the solidification point shifts to a higher temperature due to the presence of SWCNs. Importantly, the use of SWCNs is found to have clear beneficial effects for enhancing the thermal conductivity and thermal storage/release rates, without affecting thermal properties, chemical compatibility and thermal stability. The prepared PEG/diatomite/SWCNs fs-PCC exhibits excellent chemical and thermal durability and has potential application in solar thermal energy storage and solar heating.

Enhanced thermal conductivity of form-stable phase change composite with single-walled carbon nanotubes for thermal energy storage

NASA Astrophysics Data System (ADS)

Qian, Tingting; Li, Jinhong; Feng, Wuwei; Nian, Hong'En

2017-03-01

A striking contrast in the thermal conductivities of polyethylene glycol (PEG)/diatomite form-stable phase change composite (fs-PCC) with single-walled carbon nanotubes (SWCNs) as nano-additive has been reported in our present study. Compared to the pure PEG, the thermal conductivity of the prepared fs-PCC has increased from 0.24 W/mK to 0.87 W/Mk with a small SWCNs loading of 2 wt%. SWCNs are decorated on the inner surface of diatomite pores whilst retaining its porous structure. Compared to PEG/diatomite fs-PCC, the melting and solidification time of the PEG/diatomite/SWCNs fs-PCC are respectively decreased by 54.7% and 51.1%, and its thermal conductivity is 2.8 times higher. The composite can contain PEG as high as 60 wt% and maintain its original shape perfectly without any PEG leakage after subjected to 200 melt-freeze cycles. DSC results indicates that the melting point of the PEG/diatomite/SWCNs fs-PCC shifts to a lower temperature while the solidification point shifts to a higher temperature due to the presence of SWCNs. Importantly, the use of SWCNs is found to have clear beneficial effects for enhancing the thermal conductivity and thermal storage/release rates, without affecting thermal properties, chemical compatibility and thermal stability. The prepared PEG/diatomite/SWCNs fs-PCC exhibits excellent chemical and thermal durability and has potential application in solar thermal energy storage and solar heating.

Enhanced thermal conductivity of form-stable phase change composite with single-walled carbon nanotubes for thermal energy storage

PubMed Central

Qian, Tingting; Li, Jinhong; Feng, Wuwei; Nian, Hong’en

2017-01-01

A striking contrast in the thermal conductivities of polyethylene glycol (PEG)/diatomite form-stable phase change composite (fs-PCC) with single-walled carbon nanotubes (SWCNs) as nano-additive has been reported in our present study. Compared to the pure PEG, the thermal conductivity of the prepared fs-PCC has increased from 0.24 W/mK to 0.87 W/Mk with a small SWCNs loading of 2 wt%. SWCNs are decorated on the inner surface of diatomite pores whilst retaining its porous structure. Compared to PEG/diatomite fs-PCC, the melting and solidification time of the PEG/diatomite/SWCNs fs-PCC are respectively decreased by 54.7% and 51.1%, and its thermal conductivity is 2.8 times higher. The composite can contain PEG as high as 60 wt% and maintain its original shape perfectly without any PEG leakage after subjected to 200 melt-freeze cycles. DSC results indicates that the melting point of the PEG/diatomite/SWCNs fs-PCC shifts to a lower temperature while the solidification point shifts to a higher temperature due to the presence of SWCNs. Importantly, the use of SWCNs is found to have clear beneficial effects for enhancing the thermal conductivity and thermal storage/release rates, without affecting thermal properties, chemical compatibility and thermal stability. The prepared PEG/diatomite/SWCNs fs-PCC exhibits excellent chemical and thermal durability and has potential application in solar thermal energy storage and solar heating. PMID:28300191

Examination of lignocellulosic fibers for chemical, thermal, and separations properties: Addressing thermo-chemical stability issues

NASA Astrophysics Data System (ADS)

Johnson, Carter David

Natural fiber-plastic composites incorporate thermoplastic resins with fibrous plant-based materials, sometimes referred to as biomass. Pine wood mill waste has been the traditional source of natural fibrous feedstock. In anticipation of a waste wood shortage other fibrous biomass materials are being investigated as potential supplements or replacements. Perennial grasses, agricultural wastes, and woody biomass are among the potential source materials. As these feedstocks share the basic chemical building blocks; cellulose, hemicellulose, and lignin, they are collectively called lignocellulosics. Initial investigation of a number of lignocellulosic materials, applied to fiber-plastic composite processing and material testing, resulted in varied results, particularly response to processing conditions. Less thermally stable lignocellulosic filler materials were physically changed in observable ways: darkened color and odor. The effect of biomass materials' chemical composition on thermal stability was investigated an experiment involving determination of the chemical composition of seven lignocellulosics: corn hull, corn stover, fescue, pine, soy hull, soy stover, and switchgrass. These materials were also evaluated for thermal stability by thermogravimetric analysis. The results of these determinations indicated that both chemical composition and pretreatment of lignocellulosic materials can have an effect on their thermal stability. A second study was performed to investigate what effect different pretreatment systems have on hybrid poplar, pine, and switchgrass. These materials were treated with hot water, ethanol, and a 2:1 benzene/ethanol mixture for extraction times of: 1, 3, 6, 12, and 24 hours. This factorial experiment demonstrated that both extraction time and medium have an effect on the weight percent of extractives removed from all three material types. The extracted materials generated in the above study were then subjected to an evaluation of thermal stability by thermogravimetric analysis in a subsequent experiment. Overlay plots, combining individual weight loss curves, demonstrate that the experimental factors, solvent system and extraction time, produce effects on the thermal stability of the treated biomass samples. These data also indicated that the individual lignocellulosic materials had unique responses to the type of solvent used for pretreatment. Increasing extraction time had either no correlation with or a positive effect on thermal stability of the biomass samples.

Thermal stability of Ag, Al, Sn, Pb, and Hg films reinforced by 2D (C, Si) crystals and the formation of interfacial fluid states in them upon heating. MD experiment

NASA Astrophysics Data System (ADS)

Polukhin, V. A.; Kurbanova, E. D.

2016-02-01

Molecular dynamics simulation is used to study the thermal stability of the interfacial states of metallic Al, Ag, Sn, Pb, and Hg films (i.e., the structural elements of superconductor composites and conducting electrodes) reinforced by 2D graphene and silicene crystals upon heating up to disordering and to analyze the formation of nonautonomous fluid pseudophases in interfaces. The effect of perforation defects in reinforcing 2D-C and 2D-Si planes with passivated edge covalent bonds on the atomic dynamics is investigated. As compared to Al and Ag, the diffusion coefficients in Pd and Hg films increase monotonically with temperature during thermally activated disordering processes, the interatomic distances decrease, the sizes decrease, drops form, and their density profile grows along the normal. The coagulation of Pb and Hg drops is accompanied by a decrease in the contact angle, the reduction of the interface contact with graphene, and the enhancement of its corrugation (waviness).

Performance evaluation of a non-woven lithium ion battery separator prepared through a paper-making process

NASA Astrophysics Data System (ADS)

Huang, Xiaosong

2014-06-01

Porous separator functions to electrically insulate the negative and positive electrodes yet communicate lithium ions between the two electrodes when infiltrated with a liquid electrolyte. The separator must fulfill numerous requirements (e.g. permeability, wettability, and thermal stability) in order to optimize the abuse tolerance and electrochemical performance of a battery. Non-woven mat separators have advantages such as high porosity and heat resistance. However, their applications in lithium ion batteries are very limited as their inadequate pore structures could cause accelerated battery performance degradation and even internal short. This work features the development of thermally stable non-woven composite separators using a low cost paper-making process. The composite separators offer significantly improved thermal dimensional stability and exhibit superior wettability by the liquid electrolyte compared to a conventional polypropylene separator. The open porous structures of the non-woven composite separators also resulted in high effective ionic conductivities. The electrochemical performance of the composite separators was tested in coin cells. Stable cycle performances and improved rate capabilities have been observed for the coin cells with these composite separators.

A Comprehensive Review of Semiconductor Ultraviolet Photodetectors: From Thin Film to One-Dimensional Nanostructures

PubMed Central

Sang, Liwen; Liao, Meiyong; Sumiya, Masatomo

2013-01-01

Ultraviolet (UV) photodetectors have drawn extensive attention owing to their applications in industrial, environmental and even biological fields. Compared to UV-enhanced Si photodetectors, a new generation of wide bandgap semiconductors, such as (Al, In) GaN, diamond, and SiC, have the advantages of high responsivity, high thermal stability, robust radiation hardness and high response speed. On the other hand, one-dimensional (1D) nanostructure semiconductors with a wide bandgap, such as β-Ga2O3, GaN, ZnO, or other metal-oxide nanostructures, also show their potential for high-efficiency UV photodetection. In some cases such as flame detection, high-temperature thermally stable detectors with high performance are required. This article provides a comprehensive review on the state-of-the-art research activities in the UV photodetection field, including not only semiconductor thin films, but also 1D nanostructured materials, which are attracting more and more attention in the detection field. A special focus is given on the thermal stability of the developed devices, which is one of the key characteristics for the real applications. PMID:23945739

TES development for a frequency selective bolometer camera.

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

Datesman, A. M.; Downes, T. P.; Perera, T. A.

2009-06-01

We discuss the development, at Argonne National Laboratory (ANL), of a four-pixel camera with four spectral channels centered at 150, 220, 270, and 360 GHz. The scientific motivation involves photometry of distant dusty galaxies located by Spitzer and SCUBA, as well as the study of other millimeter-wave sources such as ultra-luminous infrared galaxies, the Sunyaev-Zeldovich effect in clusters, and galactic dust. The camera incorporates Frequency Selective Bolometer (FSB) and superconducting Transition-Edge Sensor (TES) technology. The current generation of TES devices we examine utilizes proximity effect superconducting bilayers of Mo/Au, Ti, or Ti/Au as TESs, located along with frequency selective absorbingmore » structures on silicon nitride membranes. The detector incorporates lithographically patterned structures designed to address both TES device stability and detector thermal transport concerns. The membrane is not perforated, resulting in a detector which is comparatively robust mechanically. In this paper, we report on the development of the superconducting bilayer TES technology, the design and testing of the detector thermal transport and device stability control structures, optical and thermal test results, and the use of new materials.« less

Ambient curing fire resistant foams

NASA Technical Reports Server (NTRS)

Hamermesh, C. L.; Hogenson, P. A.; Tung, C. Y.; Sawko, P. M.; Riccitiello, S. R.

1979-01-01

The feasibility of development of an ambient curing foam is described. The thermal stability and flame spread index of the foams were found to be comparable to those of the high-temperature cured polyimide foams by Monsanto two-foot tunnel test and NASA T-3 Fire test. Adaptation of the material to spray in place applications is described

Poly(vinyl alcohol) films reinforced with nanofibrillated cellulose (NFC) isolated from corn husk by high intensity ultrasonication.

PubMed

Xiao, Shaoliang; Gao, Runan; Gao, LiKun; Li, Jian

2016-01-20

This work was aimed at fabricating and characterizing poly(vinyl alcohol) films that were reinforced by nanofibrillated corn husk celluloses using a combination of chemical pretreatments and ultrasonication. The obtained nanofibrillated celluloses (NFCs) possessed a narrow width ranging from 50 to 250 nm and a high aspect ratio (394). The crystalline type of NFC was cellulose I type. Compared with the original corn husks, the NCF crystallinity and thermal stability increased due to the removal of the hemicelluloses and lignin. PVA films containing different NFC concentrations (0.5%, 1%, 3%, 5%, 7% and 9%, w/w, dry basis) were examined. The 1% PVA/NFC reinforced films exhibited a highly visible light transmittance of 80%, and its tensile strength and the tensile strain at break were increased by 1.47 and 1.80 times compared to that of the pure PVA film, respectively. The NFC with high aspect ratio and high crystallinity is beneficial to the improvement of the mechanical strength and thermal stability. Copyright © 2015 Elsevier Ltd. All rights reserved.

Thermal Stability and Fire Properties of Salen and Metallosalens as Fire Retardants in Thermoplastic Polyurethane (TPU)

PubMed Central

Ramgobin, Aditya; Fontaine, Gaëlle; Penverne, Christophe; Bourbigot, Serge

2017-01-01

This study deals with the synthesis and evaluation of salen based derivatives as fire retardants in thermoplastic polyurethane. Salens, hydroxysalens and their first row transition metal complexes (salen-M) were synthesized (Copper, Manganese, Nickel and Zinc). They were then incorporated in thermoplastic polyurethane (TPU) with a loading as low as 10:1 weight ratio. The thermal stability as well as the fire properties of the formulations were evaluated. Thermogravimetric analysis (TGA) showed that different coordination metals on the salen could induce different decomposition pathways when mixed with TPU. The Pyrolysis Combustion Flow Calorimetry (PCFC) results showed that some M-salen have the ability to significantly decrease the peak heat release rate (−61% compared to neat TPU) and total heat released (−63% compared to neat TPU) when formulated at 10:1 wt % ratio in TPU. Mass Loss Cone Calorimetry (MLC) results have shown that some additives (salen-Cu and salen-Mn) exhibit very promising performance and they are good candidates as flame-retardants for TPU. PMID:28773025

Dynamic mechanical analysis of carbon nanotube-reinforced nanocomposites.

PubMed

Her, Shiuh-Chuan; Lin, Kuan-Yu

2017-06-16

To predict the mechanical properties of multiwalled carbon nanotube (MWCNT)-reinforced polymers, it is necessary to understand the role of the nanotube-polymer interface with regard to load transfer and the formation of the interphase region. The main objective of this study was to explore and attempt to clarify the reinforcement mechanisms of MWCNTs in epoxy matrix. Nanocomposites were fabricated by adding different amounts of MWCNTs to epoxy resin. Tensile test and dynamic mechanical analysis (DMA) were conducted to investigate the effect of MWCNT contents on the mechanical properties and thermal stability of nanocomposites. Compared with the neat epoxy, nanocomposite reinforced with 1 wt% of MWCNTs exhibited an increase of 152% and 54% in Young's modulus and tensile strength, respectively. Dynamic mechanical analysis demonstrates that both the storage modulus and glass transition temperature tend to increase with the addition of MWCNTs. Scanning electron microscopy (SEM) observations reveal that uniform dispersion and strong interfacial adhesion between the MWCNTs and epoxy are achieved, resulting in the improvement of mechanical properties and thermal stability as compared with neat epoxy.

Comparative Study of the Electrochemical, Biomedical, and Thermal Properties of Natural and Synthetic Nanomaterials

NASA Astrophysics Data System (ADS)

Ghaemi, Ferial; Abdullah, Luqman Chuah; Kargarzadeh, Hanieh; Abdi, Mahnaz M.; Azli, Nur Farhana Waheeda Mohd; Abbasian, Maryam

2018-04-01

In this research, natural nanomaterials including cellulose nanocrystal (CNC), nanofiber cellulose (NFC), and synthetic nanoparticles such as carbon nanofiber (CNF) and carbon nanotube (CNT) with different structures, sizes, and surface areas were produced and analyzed. The most significant contribution of this study is to evaluate and compare these nanomaterials based on the effects of their structures and morphologies on their electrochemical, biomedical, and thermal properties. Based on the obtained results, the natural nanomaterials with low dimension and surface area have zero cytotoxicity effects on the living cells at 12.5 and 3.125 μg/ml concentrations of NFC and CNC, respectively. Meanwhile, synthetic nanomaterials with the high surface area around 15.3-21.1 m2/g and significant thermal stability (480 °C-600 °C) enhance the output of electrode by creating a higher surface area and decreasing the current flow resistance.

Flammability, odor, offgassing, thermal vacuum stability, and compatibility with aerospace fluids of wire insulations

NASA Technical Reports Server (NTRS)

Hirsch, David; Johnson, Harry

1994-01-01

The NASA Lewis Research Center requested NASA Johnson Space Center White Sands Test Facility to conduct flammability, odor, offgassing, thermal vacuum stability, and compatibility tests with aerospace fluids of several wire insulations.

A 45-Amino-Acid Scaffold Mined from the PDB for High-Affinity Ligand Engineering.

PubMed

Kruziki, Max A; Bhatnagar, Sumit; Woldring, Daniel R; Duong, Vandon T; Hackel, Benjamin J

2015-07-23

Small protein ligands can provide superior physiological distribution compared with antibodies, and improved stability, production, and specific conjugation. Systematic evaluation of the PDB identified a scaffold to push the limits of small size and robust evolution of stable, high-affinity ligands: 45-residue T7 phage gene 2 protein (Gp2) contains an α helix opposite a β sheet with two adjacent loops amenable to mutation. De novo ligand discovery from 10(8) mutants and directed evolution toward four targets yielded target-specific binders with affinities as strong as 200 ± 100 pM, Tms from 65 °C ± 3 °C to 80°C ± 1 °C, and retained activity after thermal denaturation. For cancer targeting, a Gp2 domain for epidermal growth factor receptor was evolved with 18 ± 8 nM affinity, receptor-specific binding, and high thermal stability with refolding. The efficiency of evolving new binding function and the size, affinity, specificity, and stability of evolved domains render Gp2 a uniquely effective ligand scaffold. Copyright © 2015 Elsevier Ltd. All rights reserved.

Urease immobilized polymer hydrogel: Long-term stability and enhancement of enzymatic activity.

PubMed

Kutcherlapati, S N Raju; Yeole, Niranjan; Jana, Tushar

2016-02-01

A method has been developed in which an enzyme namely urease was immobilized inside hydrogel matrix to study the stability and enzymatic activity in room temperature (∼27-30°C). This urease coupled hydrogel (UCG) was obtained by amine-acid coupling reaction and this procedure is such that it ensured the wider opening of mobile flap of enzyme active site. A systematic comparison of urea-urease assay and the detailed kinetic data clearly revealed that the urease shows activity for more than a month when stored at ∼27-30°C in case of UCG whereas it becomes inactive in case of free urease (enzyme in buffer solution). The aqueous microenvironment inside the hydrogel, unusual morphological features and thermal behaviour were believed to be the reasons for unexpected behaviour. UCG displayed enzyme activity at basic pH and up to 60°C. UCG showed significant enhancement in activity against thermal degradation compared to free urease. In summary, this method is a suitable process to stabilize the biomacromolecules in standard room temperature for many practical uses. Copyright © 2015 Elsevier Inc. All rights reserved.

Comparison of Oxidation Stability and Quenchant Cooling Curve Performance of Soybean Oil and Palm Oil

NASA Astrophysics Data System (ADS)

Said, Diego; Belinato, Gabriela; Sarmiento, Gustavo S.; Otero, Rosa L. Simencio; Totten, George E.; Gastón, Analía; Canale, Lauralice C. F.

2013-07-01

The potential use of vegetable oil-derived industrial oils continues to be of great interest because vegetable oils are relatively non-toxic, biodegradable, and they are a renewable basestock alternative to petroleum oil. However, the fatty ester components containing conjugated double bonds of the triglyceride structure of vegetable oils typically produce considerably poorer thermal-oxidative stability than that achievable with petroleum basestocks under typical use conditions. Typically, these conditions involve furnace loads of hot steel (850 °C), which are rapidly immersed and cooled to bath temperatures of approximately 50-60 °C. This is especially true when a vegetable oil is held in an open tank with agitation and exposed to air at elevated temperatures for extended periods of time (months or years). This paper will describe the thermal-oxidative stability and quenching performance of soybean oil and palm oil and the resulting impact on the heat transfer coefficient. These results are compared to typical fully formulated, commercially available accelerated (fast) and an unaccelerated (slow) petroleum oil-based quenchants.

Enhancing thermal conductivity of fluids with graphite nanoparticles and carbon nanotube

DOEpatents

Zhang, Zhiqiang [Lexington, KY; Lockwood, Frances E [Georgetown, KY

2008-03-25

A fluid media such as oil or water, and a selected effective amount of carbon nanomaterials necessary to enhance the thermal conductivity of the fluid. One of the preferred carbon nanomaterials is a high thermal conductivity graphite, exceeding that of the neat fluid to be dispersed therein in thermal conductivity, and ground, milled, or naturally prepared with mean particle size less than 500 nm, and preferably less than 200 nm, and most preferably less than 100 nm. The graphite is dispersed in the fluid by one or more of various methods, including ultrasonication, milling, and chemical dispersion. Carbon nanotubes with graphitic structure is another preferred source of carbon nanomaterial, although other carbon nanomaterials are acceptable. To confer long term stability, the use of one or more chemical dispersants is preferred. The thermal conductivity enhancement, compared to the fluid without carbon nanomaterial, is proportional to the amount of carbon nanomaterials (carbon nanotubes and/or graphite) added.

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.

Comparative evaluation of different thermally modified wood samples finishing with UV-curable and waterborne coatings

NASA Astrophysics Data System (ADS)

Herrera, René; Muszyńska, Monika; Krystofiak, Tomasz; Labidi, Jalel

2015-12-01

Thermally modified wood has been developed as an industrial method to improve durability and dimensional stability of wood and thus extends the range of uses and service life of wood-based products. Despite the improvements gained by treatment, surface finishing using coatings prevents esthetical changes such as color degradation or occasional growth of mold adding protection in outdoor use and extending the service life of products. The wood finishing process was carried out with commercially available waterborne and UV-curable coatings on industrially modified at 192, 200, 212 °C and unmodified European ash (Fraxinus excelsior L.) wood, using an industrial rollers system and a laboratory brushing system. Changes caused by thermal treatment which could affect the surface finish were measured and compared with control samples, such as water uptake, wettability and acidity. Following the wood finishing, surface properties and esthetic changes were evaluated; as well as the coatings performance. Thermally modified wood presented improved adherence compared with unmodified wood with a significant improvement in samples modified at 212 °C, which also present the highest hardness when UV-cured. Finishes with UV-curing maintain the hydrophobic effect of thermally modified wood, whereas waterborne finishes increase the surface wettability. Thermal modification did not negatively influence on the elastic properties of the coated substrate and thus allows this material to be finished with different coating systems in the same conditions as unmodified wood.

Synthesis of a Novel Polyethoxysilsesquiazane and Thermal Conversion into Ternary Silicon Oxynitride Ceramics with Enhanced Thermal Stability.

PubMed

Iwase, Yoshiaki; Horie, Yoji; Daiko, Yusuke; Honda, Sawao; Iwamoto, Yuji

2017-12-05

A novel polyethoxysilsesquiazane ([EtOSi(NH) 1.5 ] n , EtOSZ) was synthesized by ammonolysis at -78 °C of ethoxytrichlorosilane (EtOSiCl₃), which was isolated by distillation as a reaction product of SiCl₄ and EtOH. Attenuated total reflection-infra red (ATR-IR), 13 C-, and 29 Si-nuclear magnetic resonance (NMR) spectroscopic analyses of the ammonolysis product resulted in the detection of Si-NH-Si linkage and EtO group. The simultaneous thermogravimetric and mass spectrometry analyses of the EtOSZ under helium revealed cleavage of oxygen-carbon bond of the EtO group to evolve ethylene as a main gaseous species formed in-situ, which lead to the formation at 800 °C of quaternary amorphous Si-C-N with an extremely low carbon content (1.1 wt %) when compared to the theoretical EtOSZ (25.1 wt %). Subsequent heat treatment up to 1400 °C in N₂ lead to the formation of X-ray amorphous ternary Si-O-N. Further heating to 1600 °C in N₂ promoted crystallization and phase partitioning to afford Si₂N₂O nanocrystallites identified by the XRD and TEM analyses. The thermal stability up to 1400 °C of the amorphous state achieved for the ternary Si-O-N was further studied by chemical composition analysis, as well as X-ray photoelectron spectroscopy (XPS) and 29 Si-NMR spectroscopic analyses, and the results were discussed aiming to develop a novel polymeric precursor for ternary amorphous Si-O-N ceramics with an enhanced thermal stability.

Experimental assessment of non-edible candlenut biodiesel and its blend characteristics as diesel engine fuel.

PubMed

Imdadul, H K; Zulkifli, N W M; Masjuki, H H; Kalam, M A; Kamruzzaman, M; Rashed, M M; Rashedul, H K; Alwi, Azham

2017-01-01

Exploring new renewable energy sources as a substitute of petroleum reserves is necessary due to fulfilling the oncoming energy needs for industry and transportation systems. In this quest, a lot of research is going on to expose different kinds of new biodiesel sources. The non-edible oil from candlenut possesses the potential as a feedstock for biodiesel production. The present study aims to produce biodiesel from crude candlenut oil by using two-step transesterification process, and 10%, 20%, and 30% of biodiesel were mixed with diesel fuel as test blends for engine testing. Fourier transform infrared (FTIR) and gas chromatography (GC) were performed and analyzed to characterize the biodiesel. Also, the fuel properties of biodiesel and its blends were measured and compared with the specified standards. The thermal stability of the fuel blends was measured by thermogravimetric analysis (TGA) and differential scan calorimetry (DSC) analysis. Engine characteristics were measured in a Yanmar TF120M single cylinder direct injection (DI) diesel engine. Biodiesel produced from candlenut oil contained 15% free fatty acid (FFA), and two-step esterification and transesterification were used. FTIR and GC remarked the biodiesels' existing functional groups and fatty acid methyl ester (FAME) composition. The thermal analysis of the biodiesel blends certified about the blends' stability regarding thermal degradation, melting and crystallization temperature, oxidative temperature, and storage stability. The brake power (BP), brake specific fuel consumption (BSFC), and brake thermal efficiency (BTE) of the biodiesel blends decreased slightly with an increasing pattern of nitric oxide (NO) emission. However, the hydrocarbon (HC) and carbon monoxides (CO) of biodiesel blends were found decreased.

Enhanced thermal stability of RuO2/polyimide interface for flexible device applications

NASA Astrophysics Data System (ADS)

Music, Denis; Schmidt, Paul; Chang, Keke

2017-09-01

We have studied the thermal stability of RuO2/polyimide (Kapton) interface using experimental and theoretical methods. Based on calorimetric and spectroscopic analyses, this inorganic-organic system does not exhibit any enthalpic peaks as well as all bonds in RuO2 and Kapton are preserved up to 500 °C. In addition, large-scale density functional theory based molecular dynamics, carried out in the same temperature range, validates the electronic structure and points out that numerous Ru-C and a few Ru-O covalent/ionic bonds form across the RuO2/Kapton interface. This indicates strong adhesion, but there is no evidence of Kapton degradation upon thermal excitation. Furthermore, RuO2 does not exhibit any interfacial bonds with N and H in Kapton, providing additional evidence for the thermal stability notion. It is suggested that the RuO2/Kapton interface is stable due to aromatic architecture of Kapton. This enhanced thermal stability renders Kapton an appropriate polymeric substrate for RuO2 containing systems in various applications, especially for flexible microelectronic and energy devices.

Polarization Stability of Amorphous Piezoelectric Polyimides

NASA Technical Reports Server (NTRS)

Park, C.; Ounaies, Z.; Su, J.; Smith, J. G., Jr.; Harrison, J. S.

2000-01-01

Amorphous polyimides containing polar functional groups have been synthesized and investigated for potential use as high temperature piezoelectric sensors. The thermal stability of the piezoelectric effect of one polyimide was evaluated as a function of various curing and poling conditions under dynamic and static thermal stimuli. First, the polymer samples were thermally cycled under strain by systematically increasing the maximum temperature from 50 C to 200 C while the piezoelectric strain coefficient was being measured. Second, the samples were isothermally aged at an elevated temperature in air, and the isothermal decay of the remanent polarization was measured at room temperature as a function of time. Both conventional and corona poling methods were evaluated. This material exhibited good thermal stability of the piezoelectric properties up to 100 C.

Electroless nickel – phosphorus coating on crab shell particles and its characterization

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

Arulvel, S., E-mail: gs.arulvel.research@gmail.com; Elayaperumal, A.; Jagatheeshwaran, M.S.

Being hydrophilic material, crab shell particles have only a limited number of applications. It is, therefore, necessary to modify the surface of the crab shell particles. To make them useful ever for the applications, the main theme we proposed in this article is to utilize crab shell particles (CSP) with the core coated with nickel phosphorus (NiP) as a shell using the electroless coating process. For dealing with serious environmental problems, utilization of waste bio-shells is always an important factor to be considered. Chelating ability of crab shell particles eliminates the surface activation in this work proceeding to the coatingmore » process. The functional group, phase structure, microstructure, chemical composition and thermal analysis of CSP and NiP/CSP were characterized using Fourier transform infra-red spectroscopy (FTIR), x-ray diffraction analyzer (XRD), scanning electron microscope (SEM), energy-dispersive x-ray spectroscopy (EDS), and thermogravimetric analysis (TGA). The combination of an amorphous and crystalline structure was exhibited by CSP and NiP/CSP. NiP/CSP has shown a better thermal stability when compared to uncoated CSP. Stability test, adsorption test, and conductivity test were conducted for the study of adsorption behavior and conductivity of the particles. CSP presented a hydrophilic property in contrast to hydrophobic NiP/CSP. NiP/CSP presented a conductivity of about 44% greater compared to the CSP without any fluctuations. - Highlights: • Utilization of crab shell waste is focused on. • NiP coating on crab shell particle is fabricated using electroless process. • Thermal analysis, stability test, adsorption test and conductivity test were done. • Organic matrix of crab shell particle favors the coating process. • Results demonstrate the characterization of CSP core – NiP shell structure.« less

Improvement of the thermal stability of nickel silicide using a ruthenium interlayer deposited via remote plasma atomic layer deposition

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

Lee, Inhye; Park, Jingyu; Jeon, Heeyoung

In this study, the effects of a thin Ru interlayer on the thermal and morphological stability of NiSi have been investigated. Ru and Ni thin films were deposited sequentially to form a Ni/Ru/Si bilayered structure, without breaking the vacuum, by remote plasma atomic layer deposition (RPALD) on a p-type Si wafer. After annealing at various temperatures, the thermal stabilities of the Ni/Ru/Si and Ni/Si structures were investigated by various analysis techniques. The results showed that the sheet resistance of the Ni/Ru/Si sample was consistently lower compared to the Ni/Si sample over the entire temperature range. Although both samples exhibited themore » formation of NiSi{sub 2} phases at an annealing temperature of 800 °C, as seen with glancing angle x-ray diffraction, the peaks of the Ni/Ru/Si sample were observed to have much weaker intensities than those obtained for the Ni/Si sample. Moreover, the NiSi film with a Ru interlayer exhibited a better interface and improved surface morphologies compared to the NiSi film without a Ru interlayer. These results show that the phase transformation of NiSi to NiSi{sub 2} was retarded and that the smooth NiSi/Si interface was retained due to the activation energy increment for NiSi{sub 2} nucleation that is caused by adding a Ru interlayer. Hence, it can be said that the Ru interlayer deposited by RPALD can be used to control the phase transformation and physical properties of nickel silicide phases.« less

Stability of Curcuma longa rhizome lectin: Role of N-linked glycosylation.

PubMed

Biswas, Himadri; Chattopadhyaya, Rajagopal

2016-04-01

Curcuma longa rhizome lectin, a mannose-binding protein of non-seed portions of turmeric, is known to have antifungal, antibacterial and α-glucosidase inhibitory activities. We studied the role of complex-type glycans attached to asparagine (Asn) 66 and Asn 110 to elucidate the role of carbohydrates in lectin activity and stability. Apart from the native lectin, the characteristics of a deglycosylated Escherichia coli expressed lectin, high-mannose oligosaccharides at both asparagines and its glycosylation mutants N66Q and N110Q expressed in Pichia pastoris, were compared to understand the relationship between glycosylation and activity. Far UV circular dichroism (CD) spectra, fluorescence emission maximum, hemagglutination assay show no change in secondary or tertiary structures or sugar-binding properties between wild-type and aforementioned recombinant lectins under physiological pH. But reduced agglutination activity and loss of tertiary structure are observed in the acidic pH range for the deglycosylated and the N110Q protein. In thermal and guanidine hydrochloride (GdnCl)-induced unfolding, the wild-type and high-mannose lectins possess higher stability compared with the deglycosylated recombinant lectin and both mutants, as measured by a higher Tm of denaturation or a greater free energy change, respectively. Reversibility experiments after thermal denaturation reveal that deglycosylated proteins tend to aggregate during thermal inactivation but the wild type shows a much greater recovery to the native state upon refolding. These results suggest that N-glycosylation in turmeric lectin is important for the maintenance of its proper folding upon changes in pH, and that the oligosaccharides help in maintaining the active conformation and prevent aggregation in unfolded or partially folded molecules. © The Author 2015. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Thermal stability enhancement of modified carboxymethyl cellulose films using SnO2 nanoparticles.

PubMed

Baniasad, Arezou; Ghorbani, Mohsen

2016-05-01

In this study, in-situ and ex-situ hydrothermal synthesis procedures were applied to synthesize novel CMC/porous SnO2 nanocomposites from rice husk extracted carboxymethyl cellulose (CMC) biopolymer. In addition, the effects of SnO2 nanoparticles on thermal stability of the prepared nanocomposite were specifically studied. Products were investigated in terms of morphology, particle size, chemical structure, crystallinity and thermal stability by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Presence of characteristic bands in the FTIR spectra of samples confirmed the successful formation of CMC and CMC/SnO2 nanocomposites. In addition, FESEM images revealed four different morphologies of porous SnO2 nanoparticles including nanospheres, microcubes, nanoflowers and olive-like nanoparticles with hollow cores which were formed on CMC. These nanoparticles possessed d-spacing values of 3.35Å. Thermal stability measurements revealed that introduction of SnO2 nanoparticles in the structure of CMC enhanced stability of CMC to 85%. Copyright © 2016 Elsevier B.V. All rights reserved.

Thermal stability of G-rich anti-parallel DNA triplexes upon insertion of LNA and α-L-LNA.

PubMed

Kosbar, Tamer R; Sofan, Mamdouh A; Abou-Zeid, Laila; Pedersen, Erik B

2015-05-14

G-rich anti-parallel DNA triplexes were modified with LNA or α-L-LNA in their Watson-Crick and TFO strands. The triplexes were formed by targeting a pyrimidine strand to a putative hairpin formed by Hoogsteen base pairing in order to use the UV melting method to evaluate the stability of the triplexes. Their thermal stability was reduced when the TFO strand was modified with LNA or α-L-LNA. The same trend was observed when the TFO strand and the purine Watson-Crick strand both were modified with LNA. When all triad components were modified with α-L-LNA and LNA in the middle of the triplex, the thermal melting was increased. When the pyrimidine sequence was modified with a single insertion of LNA or α-L-LNA the ΔTm increased. Moreover, increasing the number of α-L-LNA in the pyrimidine target sequence to six insertions, leads to a high increase in the thermal stability. The conformational S-type structure of α-L-LNA in anti-parallel triplexes is preferable for triplex stability.

Independent movement, dimerization and stability of tandem repeats of chicken brain alpha-spectrin

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

Kusunoki, H.; Minasov, G.; Macdonald, R.I.

Previous X-ray crystal structures have shown that linkers of five amino acid residues connecting pairs of chicken brain {alpha}-spectrin and human erythroid {beta}-spectrin repeats can undergo bending without losing their {alpha}-helical structure. To test whether bending at one linker can influence bending at an adjacent linker, the structures of two and three repeat fragments of chicken brain {alpha}-spectrin have been determined by X-ray crystallography. The structure of the three-repeat fragment clearly shows that bending at one linker can occur independently of bending at an adjacent linker. This observation increases the possible trajectories of modeled chains of spectrin repeats. Furthermore, themore » three-repeat molecule crystallized as an antiparallel dimer with a significantly smaller buried interfacial area than that of {alpha}-actinin, a spectrin-related molecule, but large enough and of a type indicating biological specificity. Comparison of the structures of the spectrin and {alpha}-actinin dimers supports weak association of the former, which could not be detected by analytical ultracentrifugation, versus strong association of the latter, which has been observed by others. To correlate features of the structure with solution properties and to test a previous model of stable spectrin and dystrophin repeats, the number of inter-helical interactions in each repeat of several spectrin structures were counted and compared to their thermal stabilities. Inter-helical interactions, but not all interactions, increased in parallel with measured thermal stabilities of each repeat and in agreement with the thermal stabilities of two and three repeats and also partial repeats of spectrin.« less

Structural stability of purified human CFTR is systematically improved by mutations in nucleotide binding domain 1.

PubMed

Yang, Zhengrong; Hildebrandt, Ellen; Jiang, Fan; Aleksandrov, Andrei A; Khazanov, Netaly; Zhou, Qingxian; An, Jianli; Mezzell, Andrew T; Xavier, Bala M; Ding, Haitao; Riordan, John R; Senderowitz, Hanoch; Kappes, John C; Brouillette, Christie G; Urbatsch, Ina L

2018-05-01

The Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) is an ABC transporter containing two transmembrane domains forming a chloride ion channel, and two nucleotide binding domains (NBD1 and NBD2). CFTR has presented a formidable challenge to obtain monodisperse, biophysically stable protein. Here we report a comprehensive study comparing effects of single and multiple NBD1 mutations on stability of both the NBD1 domain alone and on purified full length human CFTR. Single mutations S492P, A534P, I539T acted additively, and when combined with M470V, S495P, and R555K cumulatively yielded an NBD1 with highly improved structural stability. Strategic combinations of these mutations strongly stabilized the domain to attain a calorimetric T m  > 70 °C. Replica exchange molecular dynamics simulations on the most stable 6SS-NBD1 variant implicated fluctuations, electrostatic interactions and side chain packing as potential contributors to improved stability. Progressive stabilization of NBD1 directly correlated with enhanced structural stability of full-length CFTR protein. Thermal unfolding of the stabilized CFTR mutants, monitored by changes in intrinsic fluorescence, demonstrated that Tm could be shifted as high as 67.4 °C in 6SS-CFTR, more than 20 °C higher than wild-type. H1402S, an NBD2 mutation, conferred CFTR with additional thermal stability, possibly by stabilizing an NBD-dimerized conformation. CFTR variants with NBD1-stabilizing mutations were expressed at the cell surface in mammalian cells, exhibited ATPase and channel activity, and retained these functions to higher temperatures. The capability to produce enzymatically active CFTR with improved structural stability amenable to biophysical and structural studies will advance mechanistic investigations and future cystic fibrosis drug development. Copyright © 2018 Elsevier B.V. All rights reserved.

Nanowire Lasers of Formamidinium Lead Halide Perovskites and Their Stabilized Alloys with Improved Stability

DOE PAGES

Fu, Yongping; Zhu, Haiming; Schrader, Alex W.; ...

2016-01-04

The excellent intrinsic optoelectronic properties of methylammonium lead halide perovskites (MAPbX 3, X = Br, I), such as high photoluminescence quantum efficiency, long carrier lifetime, and high gain coupled with the facile solution growth of nanowires make them promising new materials for ultralow-threshold nanowire lasers. However, their photo and thermal stabilities need to be improved for practical applications. Herein, we report a low-temperature solution growth of single crystal nanowires of formamidinium lead halide perovskites (FAPbX 3) that feature red-shifted emission and better thermal stability compared to MAPbX 3. We demonstrate optically pumped room-temperature near-infrared (~820 nm) and green lasing (~560more » nm) from FAPbI 3 (and MABr-stabilized FAPbI 3) and FAPbBr 3 nanowires with low lasing thresholds of several microjoules per square centimeter and high quality factors of about 1500–2300. More remarkably, the FAPbI 3 and MABr-stabilized FAPbI 3 nanowires display durable room-temperature lasing under ~10 8 shots of sustained illumination of 402 nm pulsed laser excitation (150 fs, 250 kHz), substantially exceeding the stability of MAPbI 3 (~10 7 laser shots). We further demonstrate tunable nanowire lasers in wider wavelength region from FA-based lead halide perovskite alloys (FA,MA)PbI 3 and (FA,MA)Pb(I,Br) 3 through cation and anion substitutions. The results suggest that formamidinium lead halide perovskite nanostructures could be more promising and stable materials for the development of light-emitting diodes and continuous-wave lasers.« less

Nanowire Lasers of Formamidinium Lead Halide Perovskites and Their Stabilized Alloys with Improved Stability.

PubMed

Fu, Yongping; Zhu, Haiming; Schrader, Alex W; Liang, Dong; Ding, Qi; Joshi, Prakriti; Hwang, Leekyoung; Zhu, X-Y; Jin, Song

2016-02-10

The excellent intrinsic optoelectronic properties of methylammonium lead halide perovskites (MAPbX3, X = Br, I), such as high photoluminescence quantum efficiency, long carrier lifetime, and high gain coupled with the facile solution growth of nanowires make them promising new materials for ultralow-threshold nanowire lasers. However, their photo and thermal stabilities need to be improved for practical applications. Herein, we report a low-temperature solution growth of single crystal nanowires of formamidinium lead halide perovskites (FAPbX3) that feature red-shifted emission and better thermal stability compared to MAPbX3. We demonstrate optically pumped room-temperature near-infrared (∼820 nm) and green lasing (∼560 nm) from FAPbI3 (and MABr-stabilized FAPbI3) and FAPbBr3 nanowires with low lasing thresholds of several microjoules per square centimeter and high quality factors of about 1500-2300. More remarkably, the FAPbI3 and MABr-stabilized FAPbI3 nanowires display durable room-temperature lasing under ∼10(8) shots of sustained illumination of 402 nm pulsed laser excitation (150 fs, 250 kHz), substantially exceeding the stability of MAPbI3 (∼10(7) laser shots). We further demonstrate tunable nanowire lasers in wider wavelength region from FA-based lead halide perovskite alloys (FA,MA)PbI3 and (FA,MA)Pb(I,Br)3 through cation and anion substitutions. The results suggest that formamidinium lead halide perovskite nanostructures could be more promising and stable materials for the development of light-emitting diodes and continuous-wave lasers.

Thermal Noise Limit in Frequency Stabilization of Lasers with Rigid Cavities

NASA Technical Reports Server (NTRS)

Numata, Kenji; Kemery, Amy; Camp, Jordan

2005-01-01

We evaluated thermal noise (Brownian motion) in a rigid reference cavity Used for frequency stabilization of lasers, based on the mechanical loss of cavity materials and the numerical analysis of the mirror-spacer mechanics with the direct application of the fluctuation dissipation theorem. This noise sets a fundamental limit for the frequency stability achieved with a rigid frequency-reference cavity of order 1 Hz/rtHz at 10mHz at room temperature. This level coincides with the world-highest level stabilization results.

Probing the Complexities of Structural Changes in Layered Oxide Cathode Materials for Li-Ion Batteries during Fast Charge-Discharge Cycling and Heating.

PubMed

Hu, Enyuan; Wang, Xuelong; Yu, Xiqian; Yang, Xiao-Qing

2018-02-20

The rechargeable lithium-ion battery (LIB) is the most promising energy storage system to power electric vehicles with high energy density and long cycling life. However, in order to meet customers' demands for fast charging, the power performances of current LIBs need to be improved. From the cathode aspect, layer-structured cathode materials are widely used in today's market and will continue to play important roles in the near future. The high rate capability of layered cathode materials during charging and discharging is critical to the power performance of the whole cell and the thermal stability is closely related to the safety issues. Therefore, the in-depth understanding of structural changes of layered cathode materials during high rate charging/discharging and the thermal stability during heating are essential in developing new materials and improving current materials. Since structural changes take place from the atomic level to the whole electrode level, combination of characterization techniques covering multilength scales is quite important. In many cases, this means using comprehensive tools involving diffraction, spectroscopy, and imaging to differentiate the surface from the bulk and to obtain structural/chemical information with different levels of spatial resolution. For example, hard X-ray spectroscopy can yield the bulk information and soft X-ray spectroscopy can give the surface information; X-ray based imaging techniques can obtain spatial resolution of tens of nanometers, and electron-based microcopy can go to angstroms. In addition to challenges associated with different spatial resolution, the dynamic nature of structural changes during high rate cycling and heating requires characterization tools to have the capability of collecting high quality data in a time-resolved fashion. Thanks to the advancement in synchrotron based techniques and high-resolution electron microscopy, high temporal and spatial resolutions can now be achieved. In this Account, we focus on the recent works studying kinetic and thermal properties of layer-structured cathode materials, especially the structural changes during high rate cycling and the thermal stability during heating. Advanced characterization techniques relating to the rate capability and thermal stability will be introduced. The different structure evolution behavior of cathode materials cycled at high rate will be compared with that cycled at low rate. Different response of individual transition metals and the inhomogeneity in chemical distribution will be discussed. For the thermal stability, the relationship between structural changes and oxygen release will be emphatically pointed out. In all these studies being reviewed, advanced characterization techniques are critically applied to reveal complexities at multiscale in layer-structured cathode materials.

Thermal Stability of Microstructure and Microhardness of Heterophase BCC-Alloys After Torsional Deformation on Bridgman Anvils

NASA Astrophysics Data System (ADS)

Ditenberg, I. A.; Tyumentsev, A. N.

2018-03-01

The results of investigations of thermal stability of microstructure and microhardness of alloys of the V-4Ti-4Cr and Mo-47Re systems, subjected to torsional deformation by high quasi-hydrostatic pressure at room temperature, are reported. It is shown that submicrocrystalline and nanocrystalline states, and the respective high values of microhardness, persist up to the upper bound ( 0.4 Tmelt) of the temperature interval of their recovery and polygonization in a single-phase state. The main factors ensuring thermal stability of highlydefective states in heterophase alloys are discussed.

On the thermal stability of graphone

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

Podlivaev, A. I.; Openov, L. A., E-mail: LAOpenov@mephi.ru

2011-07-15

Molecular dynamics simulation is used to study thermally activated migration of hydrogen atoms in graphone, a magnetic semiconductor formed of a graphene monolayer with one side covered with hydrogen. The temperature dependence of the characteristic time of disordering of graphone via hopping of hydrogen atoms to neighboring carbon atoms is established directly. The activation energy of this process is determined at E{sub a} = (0.05 {+-} 0.01) eV. The small value of E{sub a} is indicative of the extremely low thermal stability of graphone. The low stability presents a serious handicap for practical use of the material in nanoelectronics.

Alternate-strand triple-helix formation by the 3'-3'-linked oligodeoxynucleotides with the intercalators at the junction point.

PubMed

Ueno, Y; Mikawa, M; Hoshika, S; Takeba, M; Kitade, Y; Matsuda, A

2001-01-01

3'-3'-Linked oligodeoxynucleotides (ODNs) with the anthraquinonyl group at the junction point were synthesized on a DNA synthesizer using a controlled pore glass (CPG), which has pentaerythritol carrying the intercalator at one of the four hydroxymethyl groups. Stability of the triplexes with the target duplexes was studied by thermal denaturation. The 3'-3'-linked ODNs with the anthraquinonyl group enhanced the thermal stability of the triplexes when compared with those without the intercalator and the unmodified nonamer. The inhibitory activity of the 3'-3'-linked ODNs against the cleavage of the target DNA by the restriction enzyme Hind III was tested. It was found that the 3'-3'-linked ODN with the anthraquinonyl group at the junction point inhibited the cleavage by the enzyme more effectively than the nonamer and the 3'-3'-linked ODN without the intercalator.

About Nano-JASMINE Satellite System and Project Status

NASA Astrophysics Data System (ADS)

Sako, Nobutada

Intelligent Space Systems Laboratory, The University of Tokyo (ISSL) and National Astronomical Observatory of Japan (NAO) have been developing a small infrared astrometry satellite named “Nano-JASMINE”. The satellite size is about 50cm cubic and 20kg, which plays a pre-cursor role of JASMINE Project which is programmed by NAO and JAXA. In addition, since there has been only one astrometry satellite HIPPARCOS by ESA in the past, Nano-JASMINE is also expected to achieve certain scientific results in the field of astrometry. In this project, ISSL aims to develop new advanced small satellite bus system whose performance is comparable to that of 100-500kg sized satellites, including attitude stability of 1 arc-second and thermal stability of the mission subsystem of 1 mK. This paper overviews the Nano-JASMINE bus system with emphasis on attitude and thermal control systems.

Improved thermal oxidation stability of solution-processable silver nanowire transparent electrode by reduced graphene oxide.

PubMed

Ahn, Yumi; Jeong, Youngjun; Lee, Youngu

2012-12-01

Solution-processable silver nanowire-reduced graphene oxide (AgNW-rGO) hybrid transparent electrode was prepared in order to replace conventional ITO transparent electrode. AgNW-rGO hybrid transparent electrode exhibited high optical transmittance and low sheet resistance, which is comparable to ITO transparent electrode. In addition, it was found that AgNW-rGO hybrid transparent electrode exhibited highly enhanced thermal oxidation and chemical stabilities due to excellent gas-barrier property of rGO passivation layer onto AgNW film. Furthermore, the organic solar cells with AgNW-rGO hybrid transparent electrode showed good photovoltaic behavior as much as solar cells with AgNW transparent electrode. It is expected that AgNW-rGO hybrid transparent electrode can be used as a key component in various optoelectronic application such as display panels, touch screen panels, and solar cells.

Structural and spectral comparisons between isomeric benzisothiazole and benzothiazole based aromatic heterocyclic dyes

NASA Astrophysics Data System (ADS)

Wang, Yin-Ge; Wang, Yue-Hua; Tao, Tao; Qian, Hui-Fen; Huang, Wei

2015-09-01

A pair of isomeric heterocyclic compounds, namely 3-amino-5-nitro-[2,1]-benzisothiazole and 2-amino-6-nitrobenzothiazole, are used as the diazonium components to couple with two N-substituted 4-aminobenzene derivatives. As a result, two pairs of isomeric aromatic heterocyclic azo dyes have been produced and they are structurally and spectrally characterized and compared including single-crystal structures, electronic spectra, solvatochromism and reversible acid-base discoloration, thermal stability and theoretically calculations. It is concluded that both benzisothiazole and benzothiazole based dyes show planar molecular structures and offset π-π stacking interactions, solvatochromism and reversible acid-base discoloration. Furthermore, benzisothiazole based aromatic heterocyclic dyes exhibit higher thermal stability, larger solvatochromic effects and maximum absorption wavelengths than corresponding benzothiazole based ones, which can be explained successfully by the differences of their calculated isomerization energy, dipole moment and molecular band gaps.

Thermal stability of Pt nanoclusters interacting to carbon sublattice

NASA Astrophysics Data System (ADS)

Baidyshev, V. S.; Gafner, Yu. Ya.; Gafner, S. L.; Redel, L. V.

2017-12-01

The catalytic activity of Pt clusters is dependent not only on the nanoparticle size and its composition, but also on its internal structure. To determine the real structure of the nanoparticles used in catalysis, the boundaries of the thermal structure stability of Pt clusters to 8.0 nm in diameter interacting with carbon substrates of two types: a fixed α-graphite plane and a mobile substrate with the diamond structure. The effect of a substrate on the processes melting of Pt nanoclusters is estimated. The role of the cooling rate in the formation of the internal structure of Pt clusters during crystallization is studied. The regularities obtained in the case of "free" Pt clusters and Pt clusters on a substrate are compared. It is concluded that platinum nanoparticles with diameter D ≤ 4.0 nm disposed on a carbon substrate conserve the initial fcc structure during cooling.

[In Situ Polymerization and Characterization of Hydroxyapatite/polyurethane Implanted Material].

PubMed

Gu, Muqing; Xiao, Fengjuan; Liang, Ye; Yue, Lin; Li, Song; Li, Lanlan; Feng, Feifei

2015-08-01

In order to improve the interfacial bonding strength of hydroxyapatite/polyurethane implanted material and dispersion of hydroxyapatite in the polyurethane matrix, we in the present study synthesized nano-hydroxyapatite/polyurethane composites by in situ polymerization. We then characterized and analyzed the fracture morphology, thermal stability, glass transition temperature and mechanical properties. We seeded MG63 cells on composites to evaluate the cytocompatibility of the composites. In situ polymerization could improve the interfacial bonding strength, ameliorate dispersion of hydroxyapatite in the properties of the composites. After adding 20 wt% hydroxyapatite into the polyurethane, the thermal stability was improved and the glass transition temperatures were increased. The tensile strength and maximum elongation were 6.83 MPa and 861.17%, respectively. Compared with those of pure polyurethane the tensile strength and maximum elongation increased by 236.45% and 143.30%, respectively. The composites were helpful for cell adhesion and proliferation in cultivation.

Thermorheological characteristics and comparison of shape memory polymers fabricated by novel 3D printing technique

NASA Astrophysics Data System (ADS)

Hassan, Rizwan Ul; Jo, Soohwan; Seok, Jongwon

The feasibility of fabrication of shape memory polymers (SMPs) was investigated using a customized 3-dimensional (3D) printing technique with an excellent resolution that could be less than 100 microns. The thermorheological effects of SMPs were adjusted by contact and non-contact triggering, which led to the respective excellent shape recoveries of 100% and 99.89%. Thermogravimetric analyses of SMPs resulted in a minor weight loss, thereby revealing good thermal stability at higher temperatures. The viscoelastic properties of SMPs were measured using dynamic mechanical analyses, exhibiting increased viscous and elastic characteristics. Mechanical strength, thermal stability and viscoelastic properties, of the two SMPs were compared [di(ethylene) glycol dimethacrylate (DEGDMA) and poly (ethylene glycol) dimethacrylate (PEGDMA)] to investigate the shape memory behavior. This novel 3D printing technique can be used as a promising method for fabricating smart materials with increased accuracy in a cost-effective manner.

Factors affecting the thermal shock behavior of yttria stabilized hafnia based graphite and tungsten composites.

NASA Technical Reports Server (NTRS)

Lineback, L. D.; Manning, C. R.

1971-01-01

Hafnia-based composites containing either graphite or tungsten were investigated as rocket nozzle throat inserts in solid propellant rocket engines. The thermal shock resistance of these materials is considered in terms of macroscopic thermal conductivity, thermal expansion, modulus of elasticity, and compressive fracture stress. The effect of degree of hafnia stabilization, density, and graphite or tungsten content upon these parameters is discussed. The variation of the ratio of elastic modulus to compressive fracture stress with density and its effect upon thermal shock resistance of these materials are discussed in detail.

Ionic conductivity and thermal stability of magnetron-sputtered nanocrystalline yttria-stabilized zirconia

NASA Astrophysics Data System (ADS)

Sillassen, M.; Eklund, P.; Sridharan, M.; Pryds, N.; Bonanos, N.; Bøttiger, J.

2009-05-01

Thermally stable, stoichiometric, cubic yttria-stabilized zirconia (YSZ) thin-film electrolytes have been synthesized by reactive pulsed dc magnetron sputtering from a Zr-Y (80/20 at. %) alloy target. Films deposited at floating potential had a ⟨111⟩ texture. Single-line profile analysis of the 111 x-ray diffraction peak yielded a grain size of ˜20 nm and a microstrain of ˜2% regardless of deposition temperature. Films deposited at 400 °C and selected bias voltages in the range from -70 to -200 V showed a reduced grain size for higher bias voltages, yielding a grain size of ˜6 nm and a microstrain of ˜2.5% at bias voltages of -175 and -200 V with additional incorporation of argon. The films were thermally stable; very limited grain coarsening was observed up to an annealing temperature of 800 °C. Temperature-dependent impedance spectroscopy analysis of the YSZ films with Ag electrodes showed that the in-plane ionic conductivity was within one order of magnitude higher in films deposited with substrate bias corresponding to a decrease in grain size compared to films deposited at floating potential. This suggests that there is a significant contribution to the ionic conductivity from grain boundaries. The activation energy for oxygen ion migration was determined to be between 1.14 and 1.30 eV.

Intrinsic Flame-Retardant and Thermally Stable Epoxy Endowed by a Highly Efficient, Multifunctional Curing Agent

PubMed Central

Dong, Chunlei; Wirasaputra, Alvianto; Luo, Qinqin; Liu, Shumei; Yuan, Yanchao; Zhao, Jianqing; Fu, Yi

2016-01-01

It is difficult to realize flame retardancy of epoxy without suffering much detriment in thermal stability. To solve the problem, a super-efficient phosphorus-nitrogen-containing reactive-type flame retardant, 10-(hydroxy(4-hydroxyphenyl)methyl)-5,10-dihydrophenophosphazinine-10-oxide (HB-DPPA) is synthesized and characterized. When it is used as a co-curing agent of 4,4′-methylenedianiline (DDM) for curing diglycidyl ether of bisphenol A (DGEBA), the cured epoxy achieves UL-94 V-0 rating with the limiting oxygen index of 29.3%. In this case, the phosphorus content in the system is exceptionally low (0.18 wt %). To the best of our knowledge, it currently has the highest efficiency among similar epoxy systems. Such excellent flame retardancy originates from the exclusive chemical structure of the phenophosphazine moiety, in which the phosphorus element is stabilized by the two adjacent aromatic rings. The action in the condensed phase is enhanced and followed by pressurization of the pyrolytic gases that induces the blowing-out effect during combustion. The cone calorimeter result reveals the formation of a unique intumescent char structure with five discernible layers. Owing to the super-efficient flame retardancy and the rigid molecular structure of HB-DPPA, the flame-retardant epoxy acquires high thermal stability and its initial decomposition temperature only decreases by 4.6 °C as compared with the unmodified one. PMID:28774127

Improvement of Polylactide Properties through Cellulose Nanocrystals Embedded in Poly(Vinyl Alcohol) Electrospun Nanofibers.

PubMed

López de Dicastillo, Carol; Garrido, Luan; Alvarado, Nancy; Romero, Julio; Palma, Juan Luis; Galotto, Maria Jose

2017-05-11

Electrospun nanofibers of poly (vinyl alcohol) (PV) were obtained to improve dispersion of cellulose nanocrystals (CNC) within hydrophobic biopolymeric matrices, such as poly(lactic acid) (PLA). Electrospun nanofibers (PV/CNC) n were successfully obtained with a final concentration of 23% ( w / w ) of CNC. Morphological, structural and thermal properties of developed CNC and electrospun nanofibers were characterized. X-ray diffraction and thermal analysis revealed that the crystallinity of PV was reduced by the electrospinning process, and the incorporation of CNC increased the thermal stability of biodegradable nanofibers. Interactions between CNC and PV polymer also enhanced the thermal stability of CNC and improved the dispersion of CNC within the PLA matrix. PLA materials with CNC lyophilized were also casted in order to compare the properties with materials based on CNC containing nanofibers. Nanofibers and CNC were incorporated into PLA at three concentrations: 0.5%, 1% and 3% (CNC respect to polymer weight) and nanocomposites were fully characterized. Overall, nanofibers containing CNC positively modified the physical properties of PLA materials, such as the crystallinity degree of PLA which was greatly enhanced. Specifically, materials with 1% nanofiber 1PLA(PV/CNC) n presented highest improvements related to mechanical and barrier properties; elongation at break was enhanced almost four times and the permeation of oxygen was reduced by approximately 30%.

Are thermal barriers "higher" in deep sea turtle nests?

PubMed

Santidrián Tomillo, Pilar; Fonseca, Luis; Paladino, Frank V; Spotila, James R; Oro, Daniel

2017-01-01

Thermal tolerances are affected by the range of temperatures that species encounter in their habitat. Daniel Janzen hypothesized in his "Why mountain passes are higher in the tropics" that temperature gradients were effective barriers to animal movements where climatic uniformity was high. Sea turtles bury their eggs providing some thermal stability that varies with depth. We assessed the relationship between thermal uniformity and thermal tolerance in nests of three species of sea turtles. We considered that barriers were "high" when small thermal changes had comparatively large effects and "low" when the effects were small. Mean temperature was lower and fluctuated less in species that dig deeper nests. Thermal barriers were comparatively "higher" in leatherback turtle (Dermochelys coriacea) nests, which were the deepest, as embryo mortality increased at lower "high" temperatures than in olive ridley (Lepidochelys olivacea) and green turtle (Chelonia mydas) nests. Sea turtles have temperature-dependent sex determination (TSD) and embryo mortality increased as temperature approached the upper end of the transitional range of temperatures (TRT) that produces both sexes (temperature producing 100% female offspring) in leatherback and olive ridley turtles. As thermal barriers are "higher" in some species than in others, the effects of climate warming on embryo mortality is likely to vary among sea turtles. Population resilience to climate warming may also depend on the balance between temperatures that produce female offspring and those that reduce embryo survival.

Cryomilled Aluminum with Diamantane: Thermal Characterization by DSC and Effects of Magnesium

NASA Astrophysics Data System (ADS)

Arnold, Michael Colin

Many structural applications require a material that is both lightweight and corrosion resistant, for which aluminum and its alloys may be considered for use if not for their relatively low strength. By improving strength of aluminum through the Hall-Petch mechanism, it could become a more suitable choice for many structural applications. Cryomilling is used as a production technique to strengthen aluminum by reduction of grain size to the 20-50 nm range. Although the powders produced by cryomilling are well within the nanocrystalline regime, the powders experience significant grain growth during consolidation to a solid body. Cryomilled powders have been shown to remain nanocrystalline by introducing a nano-diamond, diamantane to the grain boundaries. To better characterize the thermal stability of the cryomilled powder with diamantane, Differential Scanning Calorimetry (DSC) was used to measure the isothermal heat flow in the 0.6Tm to 0.9Tm range. A model was developed to correlate the isothermal DSC signal to a grain growth curve and grain growth parameters were elucidated by assuming variable boundary mobility with a sigmoidal form. The model revealed a tendency for boundary mobility to transition from an athermal grain growth mechanism to standard thermally activated grain growth. Grain growth parameters were compared to shed light on possible mechanisms of aluminum-diamantane involvement during grain growth. Powders and consolidated samples with very low concentrations of diamantane and with magnesium were observed by TEM, SEM and XRD, and compared both separately and together to characterize the how thermal stability is affected by diamantane concentration and the presence of magnesium.

Chemical modification of L-asparaginase from Cladosporium sp. for improved activity and thermal stability.

PubMed

Mohan Kumar, N S; Kishore, Vijay; Manonmani, H K

2014-01-01

L-Asparaginase (ASNase), an antileukemia enzyme, is facing problems with antigenicity in the blood. Modification of L-asparaginase from Cladosporium sp. was tried to obtain improved stability and improved functionality. In our experiment, modification of the enzyme was tried with bovine serum albumin, ovalbumin by crosslinking using glutaraldehyde, N-bromosuccinimide, and mono-methoxy polyethylene glycol. Modified enzymes were studied for activity, temperature stability, rate constants (kd), and protection to proteolytic digestion. Modification with ovalbumin resulted in improved enzyme activity that was 10-fold higher compared to native enzyme, while modification with bovine serum albumin through glutaraldehyde cross-linking resulted in high stability of L-asparaginase that was 8.5- and 7.62-fold more compared to native enzyme at 28°C and 37°C by the end of 24 hr. These effects were dependent on the quantity of conjugate formed. Modification also markedly prolonged L-asparaginase half-life and serum stability. N-Bromosuccinimide-modified ASNase presented greater stability with prolonged in vitro half-life of 144 hr to proteolytic digestion relative to unmodified enzyme (93 h). The present work could be seen as producing a modified L-asparaginase with improved activity and stability and can be a potential source for developing therapeutic agents for cancer treatment.

A Comparative Study on the Mechanical, Thermal and Morphological Characterization of Poly(lactic acid)/Epoxidized Palm Oil Blend

PubMed Central

Giita Silverajah, V. S.; Ibrahim, Nor Azowa; Yunus, Wan Md Zin Wan; Hassan, Hazimah Abu; Woei, Chieng Buong

2012-01-01

In this work, poly(lactic acid) (PLA) a fully biodegradable thermoplastic polymer matrix was melt blended with three different epoxidized palm oil (EPO). The aim of this research was to enhance the flexibility, mechanical and thermal properties of PLA. The blends were prepared at various EPO contents of 1, 2, 3, 4 and 5 wt% and characterized. The SEM analysis evidenced successful modification on the neat PLA brittle morphology. Tensile tests indicate that the addition of 1 wt% EPO is sufficient to improve the strength and flexibility compared to neat PLA. Additionally, the flexural and impact properties were also enhanced. Further, DSC analysis showed that the addition of EPO results in a decrease in Tg, which implies an increase in the PLA chain mobility. In the presence of 1 wt% EPO, TGA results revealed significant increase in the thermal stability by 27%. Among the three EPOs used, EPO(3) showed the best mechanical and thermal properties compared to the other EPO’s, with an optimum loading of 1 wt%. Conclusively, EPO showed a promising outcome to overcome the brittleness and improve the overall properties of neat PLA, thus can be considered as a potential plasticizer. PMID:22754338

A comparative study on the mechanical, thermal and morphological characterization of poly(lactic acid)/epoxidized Palm Oil blend.

PubMed

Giita Silverajah, V S; Ibrahim, Nor Azowa; Yunus, Wan Md Zin Wan; Hassan, Hazimah Abu; Woei, Chieng Buong

2012-01-01

In this work, poly(lactic acid) (PLA) a fully biodegradable thermoplastic polymer matrix was melt blended with three different epoxidized palm oil (EPO). The aim of this research was to enhance the flexibility, mechanical and thermal properties of PLA. The blends were prepared at various EPO contents of 1, 2, 3, 4 and 5 wt% and characterized. The SEM analysis evidenced successful modification on the neat PLA brittle morphology. Tensile tests indicate that the addition of 1 wt% EPO is sufficient to improve the strength and flexibility compared to neat PLA. Additionally, the flexural and impact properties were also enhanced. Further, DSC analysis showed that the addition of EPO results in a decrease in T(g), which implies an increase in the PLA chain mobility. In the presence of 1 wt% EPO, TGA results revealed significant increase in the thermal stability by 27%. Among the three EPOs used, EPO(3) showed the best mechanical and thermal properties compared to the other EPO's, with an optimum loading of 1 wt%. Conclusively, EPO showed a promising outcome to overcome the brittleness and improve the overall properties of neat PLA, thus can be considered as a potential plasticizer.

Enhancing the thermal stability of avidin. Introduction of disulfide bridges between subunit interfaces.

PubMed

Nordlund, Henri R; Laitinen, Olli H; Uotila, Sanna T H; Nyholm, Thomas; Hytönen, Vesa P; Slotte, J Peter; Kulomaa, Markku S

2003-01-24

In this study we showed that tetrameric chicken avidin can be stabilized by introducing intermonomeric disulfide bridges between its subunits. These covalent bonds had no major effects on the biotin binding properties of the respective mutants. Moreover, one of the mutants (Avd-ccci) maintained its tetrameric integrity even in denaturing conditions. The new avidin forms Avd-ci and Avd-ccci, which have native --> denatured transition midpoints (T(m)) of 98.6 and 94.7 degrees C, respectively, in the absence of biotin, will find use in applications where extreme stability or minimal leakage of subunits is required. Furthermore, we showed that the intramonomeric disulfide bridges found in the wild-type avidin affect its stability. The mutant Avd-nc, in which this bridge was removed, had a lower T(m) in the absence of biotin than the wild-type avidin but showed comparable stability in the presence of biotin.

Covalent functionalization of graphene by azobenzene with molecular hydrogen bonds for long-term solar thermal storage

NASA Astrophysics Data System (ADS)

Feng, Yiyu; Liu, Hongpo; Luo, Wen; Liu, Enzuo; Zhao, Naiqin; Yoshino, Katsumi; Feng, Wei

2013-11-01

Reduced graphene oxide-azobenzene (RGO-AZO) hybrids were prepared via covalent functionalization for long-term solar thermal storage. Thermal barrier (ΔEa) of cis to tran reversion and thermal storage (ΔH) were improved by molecular hydrogen bonds (H-bonds) through ortho- or para-substitution of AZO. Intramolecular H-bonds thermally stabilized cis-ortho-AZO on RGO with a long-term half-life of 5400 h (ΔEa = 1.2 eV), which was much longer than that of RGO-para-AZO (116 h). RGO-para-AZO with one intermolecular H-bond showed a high density of thermal storage up to 269.8 kJ kg-1 compared with RGO-ortho-AZO (149.6 kJ kg-1) with multiple intra- and intermolecular H-bonds of AZO according to relaxed stable structures. Thermal storage in experiment was the same order magnitude to theoretical data based on ΔH calculated by density functional theory and packing density. Photoactive RGO-AZO hybrid can be developed for high-performance solar thermal storage by optimizing molecular H-bonds.

Covalent functionalization of graphene by azobenzene with molecular hydrogen bonds for long-term solar thermal storage

PubMed Central

Feng, Yiyu; Liu, Hongpo; Luo, Wen; Liu, Enzuo; Zhao, Naiqin; Yoshino, Katsumi; Feng, Wei

2013-01-01

Reduced graphene oxide-azobenzene (RGO-AZO) hybrids were prepared via covalent functionalization for long-term solar thermal storage. Thermal barrier (ΔEa) of cis to tran reversion and thermal storage (ΔH) were improved by molecular hydrogen bonds (H-bonds) through ortho- or para-substitution of AZO. Intramolecular H-bonds thermally stabilized cis-ortho-AZO on RGO with a long-term half-life of 5400 h (ΔEa = 1.2 eV), which was much longer than that of RGO-para-AZO (116 h). RGO-para-AZO with one intermolecular H-bond showed a high density of thermal storage up to 269.8 kJ kg−1 compared with RGO-ortho-AZO (149.6 kJ kg−1) with multiple intra- and intermolecular H-bonds of AZO according to relaxed stable structures. Thermal storage in experiment was the same order magnitude to theoretical data based on ΔH calculated by density functional theory and packing density. Photoactive RGO-AZO hybrid can be developed for high-performance solar thermal storage by optimizing molecular H-bonds. PMID:24247355

Covalent functionalization of graphene by azobenzene with molecular hydrogen bonds for long-term solar thermal storage.

PubMed

Feng, Yiyu; Liu, Hongpo; Luo, Wen; Liu, Enzuo; Zhao, Naiqin; Yoshino, Katsumi; Feng, Wei

2013-11-19

Reduced graphene oxide-azobenzene (RGO-AZO) hybrids were prepared via covalent functionalization for long-term solar thermal storage. Thermal barrier (ΔEa) of cis to tran reversion and thermal storage (ΔH) were improved by molecular hydrogen bonds (H-bonds) through ortho- or para-substitution of AZO. Intramolecular H-bonds thermally stabilized cis-ortho-AZO on RGO with a long-term half-life of 5400 h (ΔEa = 1.2 eV), which was much longer than that of RGO-para-AZO (116 h). RGO-para-AZO with one intermolecular H-bond showed a high density of thermal storage up to 269.8 kJ kg(-1) compared with RGO-ortho-AZO (149.6 kJ kg(-1)) with multiple intra- and intermolecular H-bonds of AZO according to relaxed stable structures. Thermal storage in experiment was the same order magnitude to theoretical data based on ΔH calculated by density functional theory and packing density. Photoactive RGO-AZO hybrid can be developed for high-performance solar thermal storage by optimizing molecular H-bonds.

Study of working principle and thermal balance process of a double longitudinal-mode He-Ne laser

NASA Astrophysics Data System (ADS)

Wang, Li-qiang

2009-07-01

A double longitudinal mode He-Ne laser with frequency stabilization is proposed. Compared with general methods, such as Lamb dip, Zeeman splitting and molecule saturation absorption method, this design has some advantages, such as no piezocrystal or magnetic field, a short frequency-stabilized time, lower cost, and higher frequency stability and reproducibility. The metal wire is uniformly wrapped on the discharge tube of the laser. When the metal wire is heated up, the resonant cavity changes with the temperature field around the discharge tube to make the frequency of the laser to be tuned. The polarizations of the two longitudinal modes from the laser must be orthogonal. The parallelly polarized light and the vertically polarized light compete with each other, i. e., the parallelly polarized light generates a larger output power, while, the vertically polarized light correspondingly generates a smaller one, but an equal value is found at the reference frequencies by automatically adjusting the length of the resonant cavity, due to change of the temperature in the discharge tube. Consequently the frequencies of the laser are stabilized. In my experiment, an intracavity He-Ne laser whose length of the resonant cavity is larger than 50mm and smaller than 300mm is selected for the double longitudinal-mode laser. Influence factors of frequency stability of this laser is only change of the length of the resonant cavity. The laser includes three stages: mode hopping, transition stage, and modes stability from startup to laser stability. When this laser is in modes stability, the waveform of heating metal wire is observed to a pulse whose duty is almost 50%, and thermal balances of the resonant cavity mainly rely on discharge tube.

Zirconia and Pyrochlore Oxides for Thermal Barrier Coatings in Gas Turbine Engines

NASA Astrophysics Data System (ADS)

Fergus, Jeffrey W.

2014-06-01

One of the important applications of yttria-stabilized zirconia (YSZ) is as a thermal barrier coating for gas turbine engines. While YSZ performs well in this function, the need for increased operating temperatures to achieve higher energy conversion efficiencies, requires the development of improved materials. To meet this challenge, some rare-earth zirconates that form the cubic fluorite-derived pyrochlore structure are being developed for use in thermal barrier coatings due to their low thermal conductivity, excellent chemical stability, and other suitable properties. In this paper, the thermal conductivities of current and prospective oxides for use in thermal barrier coatings are reviewed. The factors affecting the variations and differences in the thermal conductivities and the degradation behaviors of these materials are discussed.

Influence of growth conditions on exchange bias of NiMn-based spin valves

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

Wienecke, Anja; Kruppe, Rahel; Rissing, Lutz

2015-05-07

As shown in previous investigations, a correlation between a NiMn-based spin valve's thermal stability and its inherent exchange bias exists, even if the blocking temperature of the antiferromagnet is clearly above the heating temperature and the reason for thermal degradation is mainly diffusion and not the loss of exchange bias. Samples with high exchange bias are thermally more stable than samples with low exchange bias. Those structures promoting a high exchange bias are seemingly the same suppressing thermally induced diffusion processes (A. Wienecke and L. Rissing, “Relationship between thermal stability and layer-stack/structure of NiMn-based GMR systems,” in IEEE Transaction onmore » Magnetic Conference (EMSA 2014)). Many investigations were carried out on the influence of the sputtering parameters as well as the layer thickness on the magnetoresistive effect. The influence of these parameters on the exchange bias and the sample's thermal stability, respectively, was hardly taken into account. The investigation described here concentrates on the last named issue. The focus lies on the influence of the sputtering parameters and layer thickness of the “starting layers” in the stack and the layers forming the (synthetic) antiferromagnet. This paper includes a guideline for the evaluated sputtering conditions and layer thicknesses to realize a high exchange bias and presumably good thermal stability for NiMn-based spin valves with a synthetic antiferromagnet.« less

Tuneable enhancement of the salt and thermal stability of polymeric micelles by cyclized amphiphiles

PubMed Central

Honda, Satoshi; Yamamoto, Takuya; Tezuka, Yasuyuki

2013-01-01

Cyclic molecules provide better stability for their aggregates. Typically in nature, the unique cyclic cell membrane lipids allow thermophilic archaea to inhabit extreme conditions. By mimicking the biological design, the robustness of self-assembled synthetic nanostructures is expected to be improved. Here we report topology effects by cyclized polymeric amphiphiles against their linear counterparts, demonstrating a drastic enhancement in the thermal, as well as salt stability of self-assembled micelles. Furthermore, through coassembly of the linear and cyclic amphiphiles, the stability was successfully tuned for a wide range of temperatures and salt concentrations. The enhanced thermal/salt stability was exploited in a halogen exchange reaction to stimulate the catalytic activity. The mechanism for the enhancement was also investigated. These topology effects by the cyclic amphiphiles offer unprecedented opportunities in polymer materials design unattainable by traditional means. PMID:23481382

Thermally Stable Ni-rich Austenite Formed Utilizing Multistep Intercritical Heat Treatment in a Low-Carbon 10 Wt Pct Ni Martensitic Steel

NASA Astrophysics Data System (ADS)

Jain, Divya; Isheim, Dieter; Zhang, Xian J.; Ghosh, Gautam; Seidman, David N.

2017-08-01

Austenite reversion and its thermal stability attained during the transformation is key to enhanced toughness and blast resistance in transformation-induced-plasticity martensitic steels. We demonstrate that the thermal stability of Ni-stabilized austenite and kinetics of the transformation can be controlled by forming Ni-rich regions in proximity of pre-existing (retained) austenite. Atom probe tomography (APT) in conjunction with thermodynamic and kinetic modeling elucidates the role of Ni-rich regions in enhancing growth kinetics of thermally stable austenite, formed utilizing a multistep intercritical ( Quench- Lamellarization- Tempering (QLT)-type) heat treatment for a low-carbon 10 wt pct Ni steel. Direct evidence of austenite formation is provided by dilatometry, and the volume fraction is quantified by synchrotron X-ray diffraction. The results indicate the growth of nm-thick austenite layers during the second intercritical tempering treatment (T-step) at 863 K (590 °C), with austenite retained from first intercritical treatment (L-step) at 923 K (650 °C) acting as a nucleation template. For the first time, the thermal stability of austenite is quantified with respect to its compositional evolution during the multistep intercritical treatment of these steels. Austenite compositions measured by APT are used in combination with the thermodynamic and kinetic approach formulated by Ghosh and Olson to assess thermal stability and predict the martensite-start temperature. This approach is particularly useful as empirical relations cannot be extrapolated for the highly Ni-enriched austenite investigated in the present study.

Process margin enhancement for 0.25-μm metal etch process

NASA Astrophysics Data System (ADS)

Lee, Chung Y.; Ma, Wei Wen; Lim, Eng H.; Cheng, Alex T.; Joy, Raymond; Ross, Matthew F.; Wong, Selmer S.; Marlowe, Trey

2000-06-01

This study evaluates electron beam stabilization of UV6, a positive tone Deep-UV (DUV) resist from Shipley, for a 0.25 micrometer metal etch application. Results are compared between untreated resist and resist treated with different levels of electron beam stabilization. The electron beam processing was carried out in an ElectronCureTM flood electron beam exposure system from Honeywell International Inc., Electron Vision. The ElectronCureTM system utilizes a flood electron beam source which is larger in diameter than the substrate being processed, and is capable of variable energy so that the electron range is matched to the resist film thickness. Changes in the UV6 resist material as a result of the electron beam stabilization are monitored via spectroscopic ellipsometry for film thickness and index of refraction changes and FTIR for analysis of chemical changes. Thermal flow stability is evaluated by applying hot plate bakes of 150 degrees Celsius and 200 degrees Celsius, to patterned resist wafers with no treatment and with an electron beam dose level of 2000 (mu) C/cm2. A significant improvement in the thermal flow stability of the patterned UV6 resist features is achieved with the electron beam stabilization process. Etch process performance of the UV6 resist was evaluated by performing a metal pattern transfer process on wafers with untreated resist and comparing these with etch results on wafers with different levels of electron beam stabilization. The etch processing was carried out in an Applied Materials reactor with an etch chemistry including BCl3 and Cl2. All wafers were etched under the same conditions and the resist was treated after etch to prevent further erosion after etch but before SEM analysis. Post metal etch SEM cross-sections show the enhancement in etch resistance provided by the electron beam stabilization process. Enhanced process margin is achieved as a result of the improved etch resistance, and is observed in reduced resist side-wall angles after etch. Only a slight improvement is observed in the isolated to dense bias effects of the etch process. Improved CD control is also achieved by applying the electron beam process, as more consistent CDs are observed after etch.

Immobilization of Candida antarctica lipase B by adsorption to green coconut fiber.

PubMed

Brígida, Ana I S; Pinheiro, Alvaro D T; Ferreira, Andrea L O; Gonçalves, Luciana R B

2008-03-01

An agroindustrial residue, green coconut fiber, was evaluated as support for immobilization of Candida antarctica type B (CALB) lipase by physical adsorption. The influence of several parameters, such as contact time, amount of enzyme offered to immobilization, and pH of lipase solution was analyzed to select a suitable immobilization protocol. Kinetic constants of soluble and immobilized lipases were assayed. Thermal and operational stability of the immobilized enzyme, obtained after 2 h of contact between coconut fiber and enzyme solution, containing 40 U/ml in 25 mM sodium phosphate buffer pH 7, were determined. CALB immobilization by adsorption on coconut fiber promoted an increase in thermal stability at 50 and 60 degrees C, as half-lives (t (1/2)) of the immobilized enzyme were, respectively, 2- and 92-fold higher than the ones for soluble enzyme. Furthermore, operational stabilities of methyl butyrate hydrolysis and butyl butyrate synthesis were evaluated. After the third cycle of methyl butyrate hydrolysis, it retained less than 50% of the initial activity, while Novozyme 435 retained more than 70% after the tenth cycle. However, in the synthesis of butyl butyrate, CALB immobilized on coconut fiber showed a good operational stability when compared to Novozyme 435, retaining 80% of its initial activity after the sixth cycle of reaction.

Immobilization of Candida antarctica Lipase B by Adsorption to Green Coconut Fiber

NASA Astrophysics Data System (ADS)

Brígida, Ana I. S.; Pinheiro, Álvaro D. T.; Ferreira, Andrea L. O.; Gonçalves, Luciana R. B.

An agroindustrial residue, green coconut fiber, was evaluated as support for immobilization of Candida antarctica type B (CALB) lipase by physical adsorption. The influence of several parameters, such as contact time, amount of enzyme offered to immobilization, and pH of lipase solution was analyzed to select a suitable immobilization protocol. Kinetic constants of soluble and immobilized lipases were assayed. Thermal and operational stability of the immobilized enzyme, obtained after 2 h of contact between coconut fiber and enzyme solution, containing 40 U/ml in 25 mM sodium phosphate buffer pH 7, were determined. CALB immobilization by adsorption on coconut fiber promoted an increase in thermal stability at 50 and 60 °C, as half-lives (t 1/2) of the immobilized enzyme were, respectively, 2- and 92-fold higher than the ones for soluble enzyme. Furthermore, operational stabilities of methyl butyrate hydrolysis and butyl butyrate synthesis were evaluated. After the third cycle of methyl butyrate hydrolysis, it retained less than 50% of the initial activity, while Novozyme 435 retained more than 70% after the tenth cycle. However, in the synthesis of butyl butyrate, CALB immobilized on coconut fiber showed a good operational stability when compared to Novozyme 435, retaining 80% of its initial activity after the sixth cycle of reaction.

Towards ALD thin film stabilized single-atom Pd 1 catalysts

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

Piernavieja-Hermida, Mar; Lu, Zheng; White, Anderson

Supported precious metal single-atom catalysts have shown interesting activity and selectivity in recent studies. However, agglomeration of these highly mobile mononuclear surface species can eliminate their unique catalytic properties. In this paper, we study a strategy for synthesizing thin film stabilized single-atom Pd 1 catalysts using atomic layer deposition (ALD). The thermal stability of the Pd 1 catalysts is significantly enhanced by creating a nanocavity thin film structure. In situ infrared spectroscopy and Pd K-edge X-ray absorption spectroscopy (XAS) revealed that the Pd 1 was anchored on the surface through chlorine sites. The thin film stabilized Pd 1 catalysts weremore » thermally stable under both oxidation and reduction conditions. The catalytic performance in the methanol decomposition reaction is found to depend on the thickness of protecting layers. While Pd 1 catalysts showed promising activity at low temperature in a methanol decomposition reaction, 14 cycle TiO 2 protected Pd 1 was less active at high temperature. Pd L 3 edge XAS indicated that the low reactivity compared with Pd nanoparticles is due to the strong adsorption of carbon monoxide even at 250 °C. Lastly, these results clearly show that the ALD nanocavities provide a basis for future design of single-atom catalysts that are highly efficient and stable.« less

Towards ALD thin film stabilized single-atom Pd 1 catalysts

DOE PAGES

Piernavieja-Hermida, Mar; Lu, Zheng; White, Anderson; ...

2016-07-27

Supported precious metal single-atom catalysts have shown interesting activity and selectivity in recent studies. However, agglomeration of these highly mobile mononuclear surface species can eliminate their unique catalytic properties. In this paper, we study a strategy for synthesizing thin film stabilized single-atom Pd 1 catalysts using atomic layer deposition (ALD). The thermal stability of the Pd 1 catalysts is significantly enhanced by creating a nanocavity thin film structure. In situ infrared spectroscopy and Pd K-edge X-ray absorption spectroscopy (XAS) revealed that the Pd 1 was anchored on the surface through chlorine sites. The thin film stabilized Pd 1 catalysts weremore » thermally stable under both oxidation and reduction conditions. The catalytic performance in the methanol decomposition reaction is found to depend on the thickness of protecting layers. While Pd 1 catalysts showed promising activity at low temperature in a methanol decomposition reaction, 14 cycle TiO 2 protected Pd 1 was less active at high temperature. Pd L 3 edge XAS indicated that the low reactivity compared with Pd nanoparticles is due to the strong adsorption of carbon monoxide even at 250 °C. Lastly, these results clearly show that the ALD nanocavities provide a basis for future design of single-atom catalysts that are highly efficient and stable.« less

Calcium Binding and Disulfide Bonds Regulate the Stability of Secretagogin towards Thermal and Urea Denaturation

PubMed Central

Weiffert, Tanja; Ní Mhurchú, Niamh; O’Connell, David; Linse, Sara

2016-01-01

Secretagogin is a calcium-sensor protein with six EF-hands. It is widely expressed in neurons and neuro-endocrine cells of a broad range of vertebrates including mammals, fishes and amphibia. The protein plays a role in secretion and interacts with several vesicle-associated proteins. In this work, we have studied the contribution of calcium binding and disulfide-bond formation to the stability of the secretagogin structure towards thermal and urea denaturation. SDS-PAGE analysis of secretagogin in reducing and non-reducing conditions identified a tendency of the protein to form dimers in a redox-dependent manner. The denaturation of apo and Calcium-loaded secretagogin was studied by circular dichroism and fluorescence spectroscopy under conditions favoring monomer or dimer or a 1:1 monomer: dimer ratio. This analysis reveals significantly higher stability towards urea denaturation of Calcium-loaded secretagogin compared to the apo protein. The secondary and tertiary structure of the Calcium-loaded form is not completely denatured in the presence of 10 M urea. Reduced and Calcium-loaded secretagogin is found to refold reversibly after heating to 95°C, while both oxidized and reduced apo secretagogin is irreversibly denatured at this temperature. Thus, calcium binding greatly stabilizes the structure of secretagogin towards chemical and heat denaturation. PMID:27812162

Remarkably stable amorphous metal oxide grown on Zr-Cu-Be metallic glass

PubMed Central

Lim, Ka Ram; Kim, Chang Eun; Yun, Young Su; Kim, Won Tae; Soon, Aloysius; Kim, Do Hyang

2015-01-01

In the present study, we investigated the role of an aliovalent dopant upon stabilizing the amorphous oxide film. We added beryllium into the Zr50Cu50 metallic glass system, and found that the amorphous oxide layer of Be-rich phase can be stabilized even at elevated temperature above Tg of the glass matrix. The thermal stability of the amorphous oxide layer is substantially enhanced due to Be addition. As confirmed by high-temperature cross-section HR-TEM, fully disordered Be-added amorphous layer is observed, while the rapid crystallization is observed without Be. To understand the role of Be, we employed ab-initio molecular dynamics to compare the mobility of ions with/without Be dopant, and propose a disordered model where Be dopant occupies Zr vacancy and induces structural disorder to the amorphous phase. We find that the oxygen mobility is slightly suppressed due to Be dopant, and Be mobility is unexpectedly lower than that of oxygen, which we attribute to the aliovalent nature of Be dopant whose diffusion always accompany multiple counter-diffusion of other ions. Here, we explain the origin of superior thermal stability of amorphous oxide film in terms of enhanced structural disorder and suppressed ionic mobility due to the aliovalent dopant. PMID:26658671

Remarkably stable amorphous metal oxide grown on Zr-Cu-Be metallic glass.

PubMed

Lim, Ka Ram; Kim, Chang Eun; Yun, Young Su; Kim, Won Tae; Soon, Aloysius; Kim, Do Hyang

2015-12-14

In the present study, we investigated the role of an aliovalent dopant upon stabilizing the amorphous oxide film. We added beryllium into the Zr50Cu50 metallic glass system, and found that the amorphous oxide layer of Be-rich phase can be stabilized even at elevated temperature above Tg of the glass matrix. The thermal stability of the amorphous oxide layer is substantially enhanced due to Be addition. As confirmed by high-temperature cross-section HR-TEM, fully disordered Be-added amorphous layer is observed, while the rapid crystallization is observed without Be. To understand the role of Be, we employed ab-initio molecular dynamics to compare the mobility of ions with/without Be dopant, and propose a disordered model where Be dopant occupies Zr vacancy and induces structural disorder to the amorphous phase. We find that the oxygen mobility is slightly suppressed due to Be dopant, and Be mobility is unexpectedly lower than that of oxygen, which we attribute to the aliovalent nature of Be dopant whose diffusion always accompany multiple counter-diffusion of other ions. Here, we explain the origin of superior thermal stability of amorphous oxide film in terms of enhanced structural disorder and suppressed ionic mobility due to the aliovalent dopant.

Direct Room Temperature Welding and Chemical Protection of Silver Nanowire Thin Films for High Performance Transparent Conductors.

PubMed

Ge, Yongjie; Duan, Xidong; Zhang, Meng; Mei, Lin; Hu, Jiawen; Hu, Wei; Duan, Xiangfeng

2018-01-10

Silver nanowire (Ag-NW) thin films have emerged as a promising next-generation transparent electrode. However, the current Ag-NW thin films are often plagued by high NW-NW contact resistance and poor long-term stability, which can be largely attributed to the ill-defined polyvinylpyrrolidone (PVP) surface ligands and nonideal Ag-PVP-Ag contact at NW-NW junctions. Herein, we report a room temperature direct welding and chemical protection strategy to greatly improve the conductivity and stability of the Ag-NW thin films. Specifically, we use a sodium borohydride (NaBH 4 ) treatment process to thoroughly remove the PVP ligands and produce a clean Ag-Ag interface that allows direct welding of NW-NW junctions at room temperature, thus greatly improving the conductivity of the Ag-NW films, outperforming those obtained by thermal or plasmonic thermal treatment. We further show that, by decorating the as-formed Ag-NW thin film with a dense, hydrophobic dodecanethiol layer, the stability of the Ag-NW film can be greatly improved by 150-times compared with that of PVP-wrapped ones. Our studies demonstrate that a proper surface ligand design can effectively improve the conductivity and stability of Ag-NW thin films, marking an important step toward their applications in electronic and optoelectronic devices.

Thermal stability of the Mobil Five type metallosilicate molecular sieves-An in situ high temperature X-ray diffraction study

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

Bhange, D.S.; Ramaswamy, Veda

2007-05-03

We have carried out in situ high temperature X-ray diffraction (HTXRD) studies of silicalite-1 (S-1) and metallosilicate molecular sieves containing iron, titanium and zirconium having Mobil Five (MFI) structure (iron silicalite-1 (FeS-1), titanium silicalite-1 (TS-1) and zirconium silicalite-1 (ZrS-1), respectively) in order to study the thermal stability of these materials. Isomorphous substitution of Si{sup 4+} by metal atoms is confirmed by the expansion of unit cell volume by X-ray diffraction (XRD) and the presence of Si-O-M stretching band at {approx}960 cm{sup -1} by Fourier transform infrared (FTIR) spectroscopy. Appearance of cristobalite phase is seen at 1023 and 1173 K inmore » S-1 and FeS-1 samples. While the samples S-1 and FeS-1 decompose completely to cristobalite at 1173 and 1323 K, respectively, the other two samples are thermally stable upto 1623 K. This transformation is irreversible. Although all materials show a negative lattice thermal expansion, their lattice thermal expansion coefficients vary. The thermal expansion behavior in all samples is anisotropic with relative strength of contraction along 'a' axes is more than along 'b' and 'c' axes in S-1, TS-1, ZrS-1 and vice versa in FeS-1. Lattice thermal expansion coefficients ({alpha} {sub v}) in the temperature range 298-1023 K were -6.75 x 10{sup -6} K{sup -1} for S-1, -12.91 x 10{sup -6} K{sup -1} for FeS-1, -16.02 x 10{sup -6} K{sup -1} for TS-1 and -17.92 x 10{sup -6} K{sup -1} for ZrS-1. The highest lattice thermal expansion coefficients ({alpha} {sub v}) obtained were -11.53 x 10{sup -6} K{sup -1} for FeS-1 in temperature range 298-1173 K, -20.86 x 10{sup -6} K{sup -1} for TS-1 and -25.54 x 10{sup -6} K{sup -1} for ZrS-1, respectively, in the temperature range 298-1623 K. Tetravalent cation substitution for Si{sup 4+} in the lattice leads to a high thermal stability as compared to substitution by trivalent cations.« less

Multicomponent, Rare-Earth-Doped Thermal-Barrier Coatings

NASA Technical Reports Server (NTRS)

Miller, Robert A.; Zhu, Dongming

2005-01-01

Multicomponent, rare-earth-doped, perovskite-type thermal-barrier coating materials have been developed in an effort to obtain lower thermal conductivity, greater phase stability, and greater high-temperature capability, relative to those of the prior thermal-barrier coating material of choice, which is yttria-partially stabilized zirconia. As used here, "thermal-barrier coatings" (TBCs) denotes thin ceramic layers used to insulate air-cooled metallic components of heat engines (e.g., gas turbines) from hot gases. These layers are generally fabricated by plasma spraying or physical vapor deposition of the TBC materials onto the metal components. A TBC as deposited has some porosity, which is desirable in that it reduces the thermal conductivity below the intrinsic thermal conductivity of the fully dense form of the material. Undesirably, the thermal conductivity gradually increases because the porosity gradually decreases as a consequence of sintering during high-temperature service. Because of these and other considerations such as phase transformations, the maximum allowable service temperature for yttria-partially stabilized zirconia TBCs lies in the range of about 1,200 to 1,300 C. In contrast, the present multicomponent, rare-earth-doped, perovskite-type TBCs can withstand higher temperatures.

Thermal Conductivity and Stability of HfO2-Y2O3 and La2Zr2O7 Evaluated for 1650 Deg C Thermal/Environmental Barrier Coating Applications

NASA Technical Reports Server (NTRS)

Zhu, Dong-Ming; Bansal, Narottam P.; Miller, Robert A.

2003-01-01

HfO2-Y2O3 and La2Zr2O7 are candidate thermal and environmental barrier coating (T/EBC) materials for gas turbine ceramic matrix composite (CMC) combustor applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature stability of hot-pressed and plasma sprayed specimens with representative partially-stabilized and fully-cubic HfO2-Y2O3 compositions and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasmasprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC hexoloy or SiC/SiC CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermal/environmental barrier coating applications are also discussed.

Preparation and thermal stability of the spindle α-Fe{sub 2}O{sub 3}@SiO{sub 2} core–shell nanoparticles

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

Zhang, Xin; Niu, Yongan; Li, Yang

2014-03-15

The spindle α-Fe{sub 2}O{sub 3}@SiO{sub 2} core–shell nanoparticles (NPs) are prepared via hydrothermal synthesis and modified Stöber method. During these processes, shell thicknesses could be easily adjusted by the amount of tetraethylorthosilicate (TEOS), and the formation of core-free SiO{sub 2} could be effectively avoided. The structures and compositions of α-Fe{sub 2}O{sub 3}@SiO{sub 2} NPs are investigated by transmission electron microscope (TEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and ultraviolet–visible (UV–vis) absorption spectroscopy. These results reveal that the α-Fe{sub 2}O{sub 3}@SiO{sub 2} NPs with certain sizes are monodisperse and homogeneous. To estimate the thermal stability, the α-Fe{sub 2}O{submore » 3}, α-Fe{sub 2}O{sub 3}@SiO{sub 2} and SiO{sub 2} NPs are annealed at 600, 800 and 1000 °C for 1 h under air atmosphere, respectively. Furthermore, the stabilities of these NPs are confirmed by thermal analysis methods. The structure and shape stabilities of these as-prepared α-Fe{sub 2}O{sub 3}@SiO{sub 2} NPs are investigated by XRD and scanning electron microscope (SEM). -- Graphical abstract: Schematic of preparation of the monodisperse spindle α-Fe{sub 2}O{sub 3}@SiO{sub 2} nanoparticles (NPs). Highlights: • The spindle α-Fe{sub 2}O{sub 3}@SiO{sub 2} nanoparticles (NPs) are successfully prepared by hydrothermal synthesis and modified Stöber method. • Optical properties are estimated and calculated by UV vis absorption spectrum. • Thermal stability of the α-Fe{sub 2}O{sub 3}, α-Fe{sub 2}O{sub 3}@SiO{sub 2} and SiO{sub 2} NPs are compared and analyzed by the SEM technique. • The structural changes of α-Fe{sub 2}O{sub 3}@SiO{sub 2} NPs are measured by XRD measurement.« less

Development of a plasma sprayed ceramic gas path seal for high pressure turbine applications

NASA Technical Reports Server (NTRS)

Shiembob, L. T.

1977-01-01

The plasma sprayed graded layered yittria stabilized zirconia (ZrO2)/metal(CoCrAlY) seal system for gas turbine blade tip applications up to 1589 K (2400 F) seal temperatures was studied. Abradability, erosion, and thermal fatigue characteristics of the graded layered system were evaluated by rig tests. Satisfactory abradability and erosion resistance was demonstrated. Encouraging thermal fatigue tolerance was shown. Initial properties for the plasma sprayed materials in the graded, layered seal system was obtained, and thermal stress analyses were performed. Sprayed residual stresses were determined. Thermal stability of the sprayed layer materials was evaluated at estimated maximum operating temperatures in each layer. Anisotropic behavior in the layer thickness direction was demonstrated by all layers. Residual stresses and thermal stability effects were not included in the analyses. Analytical results correlated reasonably well with results of the thermal fatigue tests. Analytical application of the seal system to a typical gas turbine engine application predicted performance similar to rig specimen thermal fatigue performance. A model for predicting crack propagation in the sprayed ZrO2/CoCrAlY seal system was proposed, and recommendations for improving thermal fatigue resistance were made. Seal system layer thicknesses were analytically optimized to minimize thermal stresses in the abradability specimen during thermal fatigue testing. Rig tests on the optimized seal configuration demonstrated some improvement in thermal fatigue characteristics.

Synthesis and thermal stability of carborane containing phosphazenes

NASA Technical Reports Server (NTRS)

Fewell, L. L.; Basi, R. J.; Parker, J. A.

1983-01-01

Carborane substituted polyphosphazenes were prepared by the thermal polymerization of phenyl-carboranyl penta chlorocyclotriphosphazene. Successive isothermal vacuum pyrolyses were conducted on the polymer and examined for structural changes by infrared spectroscopy. The degradation products were ascertained by gas chromatography-mass spectrometric analysis. It was found that the presence of the carborane group improves the thermal stability of the polymer by retarding the ring chain equilibrium processes of decomposition.

An organic p-type dopant with high thermal stability for an organic semiconductor.

PubMed

Gao, Zhi Qiang; Mi, Bao Xiu; Xu, Gui Zhen; Wan, Yi Qian; Gong, Meng Lian; Cheah, Kok Wai; Chen, Chin H

2008-01-07

To overcome the thermal instability of a p-doped organic hole transporting layer using the state-of-the-art p-type dopant, 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, a potent electron accepter, 3,6-difluoro-2,5,7,7,8,8-hexacyanoquinodimethane, has been found to possess superior thermal stability and proved to be an excellent p-type dopant.

Improved thermal stability of oxide-supported naked gold nanoparticles by ligand-assisted pinning

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

Moreno, C; Divins, N. J.; Gazquez, Jaume

We report a method to improve the thermal stability, up to 900 C, of bare-metal (naked) gold nanoparticles supported on top of SiO{sub 2} and SrTiO{sub 3} substrates via ligand-assisted pinning. This approach leads to monodisperse naked gold nanoparticles without significant sintering after thermal annealing in air at 900 C. The ligand-assisted pinning mechanism is described.

Improved thermal-stability and mechanical properties of type I collagen by crosslinking with casein, keratin and soy protein isolate using transglutaminase.

PubMed

Wu, Xiaomeng; Liu, Yaowei; Liu, Anjun; Wang, Wenhang

2017-05-01

The inferior thermal- stability of collagen hinders its extensive application in food industry, including edible packaging. To improve the thermal- stability and mechanical properties of collagen, we attempted to crosslink collagen with some proteins possessing excellent thermal stability (i. e., casein, keratin and soy protein isolate (SPI)). Observed from the SDS- PAGE and particle size distribution, some complexes with higher molecule weight and relative bigger size particle occurred in the protein mixture, especially after TGase crosslinking. Importantly, the crosslinking greatly improved the thermal- stable property of protein complex, especially that of the collagen- casein complex judged from differential scanning calorimetric (DSC). Moreover, the crosslinking enhanced the mechanical properties of the combined films in terms of tensile strength (TS) and elongation at break (EAB). Also, some obvious differences in morphology of proteins before and after TGase crosslinking were observed by scanning electron microscopy (SEM). These impacts of TGase crosslinking with heat- resistant proteins on collagen features were associated with the conformational changes of the protein complex analyzed by Fourier transform infrared spectroscopy (FTIR). In conclusion, TGase crosslinking with higher thermally stable proteins could be an effective method to contribute to collagen' application in food packaging field. Copyright © 2017 Elsevier B.V. All rights reserved.

Steam reforming of n-hexane on pellet and monolithic catalyst beds. A comparative study on improvements due to heat transfer

NASA Technical Reports Server (NTRS)

1981-01-01

Monolithic catalysts with higher available active surface areas and better thermal conductivity than conventional pellets beds, making possible the steam reforming of fuels heavier than naphtha, were examined. Performance comparisons were made between conventional pellet beds and honeycomb monolith catalysts using n-hexane as the fuel. Metal-supported monoliths were examined. These offer higher structural stability and higher thermal conductivity than ceramic supports. Data from two metal monoliths of different nickel catalyst loadings were compared to pellets under the same operating conditions. Improved heat transfer and better conversion efficiencies were obtained with the monolith having higher catalyst loading. Surface-gas interaction was observed throughout the length of the monoliths.

Strategies to curb structural changes of lithium/transition metal oxide cathode materials & the changes' effects on thermal & cycling stability

DOE PAGES

Yu, Xiqian; Hu, Enyuan; Bak, Seongmin; ...

2015-12-07

Structural transformation behaviors of several typical oxide cathode materials during a heating process are reviewed in detail to provide in-depth understanding of the key factors governing the thermal stability of these materials. Furthermore, we also discuss applying the information about heat induced structural evolution in the study of electrochemically induced structural changes. All these discussions are expected to provide valuable insights for designing oxide cathode materials with significantly improved structural stability for safe, long-life lithium ion batteries, as the safety of lithium-ion batteries is a critical issue. As a result, it is widely accepted that the thermal instability of themore » cathodes is one of the most critical factors in thermal runaway and related safety problems.« less

Ambient effect on thermal stability of amorphous InGaZnO thin film transistors

NASA Astrophysics Data System (ADS)

Xu, Jianeng; Wu, Qi; Xu, Ling; Xie, Haiting; Liu, Guochao; Zhang, Lei; Dong, Chengyuan

2016-12-01

The thermal stability of amorphous InGaZnO thin film transistors (a-IGZO TFTs) with various ambient gases was investigated. The a-IGZO TFTs in air were more thermally stable than the devices in the ambient argon. Oxygen, rather than nitrogen and moisture, was responsible for this improvement. Furthermore, the thermal stability of the a-IGZO TFTs improved with the increasing oxygen content in the surrounding atmosphere. The related physical mechanism was examined, indicating that the higher ambient oxygen content induced more combinations of the oxygen vacancies and adsorbed oxygen ions in the a-IGZO, which resulted in the larger defect formation energy. This larger defect formation energy led to the smaller variation in the threshold voltage for the corresponding TFT devices.

Effect of some nitrogen compounds thermal stability of jet A

NASA Technical Reports Server (NTRS)

Antoine, A. C.

1982-01-01

The effect of known concentrations of some nitrogen containing compounds on the thermal stability of a conventional fuel, namely, Jet A was investigated. The concentration range from 0.01 to 0.1 wt% nitrogen was examined. Solutions were made containing, individually, pyrrole, indole, quinoline, pyridine, and 4 ethylpyridine at 0.01, 0.03, 0.06, and 0.1 wt% nitrogen concentrations in Jet A. The measurements were all made by using a standard ASTM test for evaluating fuel thermal oxidation behavior, namely, ASTM D3241, 'thermal oxidation stability of turbine fuels (JFTOT procedure).' Measurements were made at two temperature settings, and 'breakpoint temperatures' were determined. The results show that the pyrrole and indole solutions have breakpoint temperatures substantially lower than those of the Jet A used.

Thermal stability of liquid antioxidative extracts from pomegranate peel

USDA-ARS?s Scientific Manuscript database

This research was carried out to assess the potential of using the natural antioxidants in pomegranate peel extracts as replacement for synthetic antioxidants. As a result the thermal stability of pomegranate peel extract products during sterilization and storage, and its effect on industrial, color...

Thermal and storage characteristics of tomato seed oil

USDA-ARS?s Scientific Manuscript database

Thermal oxidative stability and effect of different storage conditions on quality characteristics of tomato seed oil have not been studied. The objectives of this research were to determine the changes in quality and oxidative stability of tomato seed oil, including color, antioxidant activity, per...

Application of FTIR spectroscopy to study the thermal stability of magnesium aspartate-arginine

NASA Astrophysics Data System (ADS)

Hacura, Andrzej; Marcoin, Wacława; Pasterny, Karol

2012-03-01

FTIR spectroscopy has been applied to study the thermal stability of magnesium aspartatearginine. An attempt has been made, using theoretically predicted IR spectra, to relate the changes in the experimental spectra with the decomposition process of the studied magnesium complex.

Durability of zirconia thermal-barrier ceramic coatings on air-cooled turbine blades in cyclic jet engine operation

NASA Technical Reports Server (NTRS)

Liebert, C. H.; Jacobs, R. E.; Stecura, S.; Morse, C. R.

1976-01-01

Thermal barrier ceramic coatings of stabilized zirconia over a bond coat of Ni Cr Al Y were tested for durability on air cooled turbine rotor blades in a research turbojet engine. Zirconia stabilized with either yttria, magnesia, or calcia was investigated. On the basis of durability and processing cost, the yttria stabilized zirconia was considered the best of the three coatings investigated.

Low-temperature technique for thick film resist stabilization and curing

NASA Astrophysics Data System (ADS)

Minter, Jason P.; Wong, Selmer S.; Marlowe, Trey; Ross, Matthew F.; Narcy, Mark E.; Livesay, William R.

1999-06-01

For a range of thick film photoresist applications, including MeV ion implant processing, thin film head manufacturing, and microelectromechanical systems processing, there is a need for a low-temperature method for resist stabilization and curing. Traditional methods of stabilizing or curing resist films have relied on thermal cycling, which may not be desirable due to device temperature limitations or thermally-induced distortion of the resist features.

Use of Encapsulated Zinc Particles in a Eutectic Chloride Salt to Enhance Thermal Energy Storage Capacity for Concentrated Solar Power

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

Cingarapu, Sreeram; Singh, Dileep; Timofeeva, Elena V.

2015-08-01

Concentrated Solar Power (CSP) is considered as a viable large-scale renewable energy source to produce electricity. However, current costs to produce electricity from CSP are not cost competitive as compared to the traditional energy generation technologies based on fossil fuels and nuclear. It is envisioned that development of high efficiency and high heat capacity thermal storage fluids will increase system efficiency, reduce structural storage volume, and hence, contribute to reducing costs. Particularly, with respect to CSP, current high temperature energy storage fluids, such as molten salts, are relatively limited in terms of their thermal energy storage capacity and thermal conductivity.more » The current work explores possibility of boosting the thermal storage capacity of molten salts through latent heat of added phase change materials. We studied the advantage Of adding coated Zn micron-sized particles to alkali chloride salt eutectic for enhanced thermal energy storage. Zinc particles (0.6 mu m and 5 mu m) obtained from commercial source were coated with an organo-phosphorus shell to improve chemical stability and to prevent individual particles from coalescing with one another during melt/freeze cycles. Thermal cycling tests (200 melt/freeze cycles) showed that coated Zn particles have good thermal stability and are chemically inert to alkali chloride salt eutectic in both N-2 and in air atmospheres. Elemental mapping of the cross-sectional view of coated Zn particles from the composite after thermal cycles showed no signs of oxidation, agglomeration or other type of particle degradation. The measured enhancement in volumetric thermal storage capacity of the composite with just similar to 10 vol% of coated Zn particles over the base chloride salt eutectic varies from 15% to 34% depending on cycling temperature range (Delta T = 50 degrees C -100 degrees C. (C) 2015 Elsevier Ltd. All rights reserved.« less

Novel formulations enhance the thermal stability of live-attenuated flavivirus vaccines

PubMed Central

Wiggan, O’Neil; Silengo, Shawn J.; Kinney, Richard M.; Osorio, Jorge E.; Huang, Claire Y.-H.; Stinchcomb, Dan T.

2011-01-01

Thermal stability is important for the manufacture, distribution and administration of vaccines, especially in tropical developing countries, where particularly adverse field conditions exist. Current live-attenuated flavivirus vaccines exhibit relatively poor liquid stability in clinical settings, and clinicians are instructed to discard the yellow fever vaccine 1h after reconstitution. We have identified novel combinations of excipients that greatly enhance the thermal stability of live-attenuated DEN-2 PDK-53-based flavivirus vaccine candidates. Liquid formulations comprising a sugar, albumin and a pluronic polymer minimized the loss of flavivirus infectious titer to less than 0.5log(10)pfu after storage for at least 8h at 37°C, 7 days at room temperature or at least 11 weeks at 4°C. Additionally, these formulations prevented reduction of viral infectivity after two freeze-thaw cycles of virus. Formulated candidate vaccines were readily lyophilized and reconstituted with minimal loss of viral titers. In mice, the formulations were safe and did not hinder the ability of the vaccine virus to generate a potent, protective immune response. These formulations provided significantly greater liquid-phase stability than has been reported previously for other flavivirus vaccine formulations. The enhanced thermal stability provided by the formulations described here will facilitate the effective distribution of flavivirus vaccines worldwide. PMID:21803103

Influence of Molecular Shape on the Thermal Stability and Molecular Orientation of Vapor-Deposited Organic Semiconductors

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

Walters, Diane M; Antony, Lucas; de Pablo, Juan

High thermal stability and anisotropic molecular orientation enhance the performance of vapor-deposited organic semiconductors, but controlling these properties is a challenge in amorphous materials. To understand the influence of molecular shape on these properties, vapor-deposited glasses of three disk-shaped molecules were prepared. For all three systems, enhanced thermal stability is observed for glasses prepared over a wide range of substrate temperatures and anisotropic molecular orientation is observed at lower substrate temperatures. For two of the disk-shaped molecules, atomistic simulations of thin films were also performed and anisotropic molecular orientation was observed at the equilibrium liquid surface. We find that themore » structure and thermal stability of these vapor-deposited glasses results from high surface mobility and partial equilibration toward the structure of the equilibrium liquid surface during the deposition process. For the three molecules studied, molecular shape is a dominant factor in determining the anisotropy of vapor-deposited glasses.« less

Honey bee odorant-binding protein 14: effects on thermal stability upon odorant binding revealed by FT-IR spectroscopy and CD measurements.

PubMed

Schwaighofer, Andreas; Kotlowski, Caroline; Araman, Can; Chu, Nam; Mastrogiacomo, Rosa; Becker, Christian; Pelosi, Paolo; Knoll, Wolfgang; Larisika, Melanie; Nowak, Christoph

2014-03-01

In the present work, we study the effect of odorant binding on the thermal stability of honey bee (Apis mellifera L.) odorant-binding protein 14. Thermal denaturation of the protein in the absence and presence of different odorant molecules was monitored by Fourier transform infrared spectroscopy (FT-IR) and circular dichroism (CD). FT-IR spectra show characteristic bands for intermolecular aggregation through the formation of intermolecular β-sheets during the heating process. Transition temperatures in the FT-IR spectra were evaluated using moving-window 2D correlation maps and confirmed by CD measurements. The obtained results reveal an increase of the denaturation temperature of the protein when bound to an odorant molecule. We could also discriminate between high- and low-affinity odorants by determining transition temperatures, as demonstrated independently by the two applied methodologies. The increased thermal stability in the presence of ligands is attributed to a stabilizing effect of non-covalent interactions between odorant-binding protein 14 and the odorant molecule.

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.

Characterisation of a new carbon nanotube detector coating for solar absolute radiometers

NASA Astrophysics Data System (ADS)

Remesal Oliva, A.; Finsterle, W.; Walter, B.; Schmutz, W.

2018-02-01

A new sprayable carbon nanotube coating for bolometric detectors aims to increase the absorptance compared to regular space qualified black paints. In collaboration with the National Institute of Standards and Technology (NIST), we have characterized the optical properties and mechanical and thermal stability of the carbon nanotube coating inside conical shaped cavity detectors.

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.

Ordering of Zn-centered porphyrin and phthalocyanine on TiO2(011): STM studies

PubMed Central

Godlewski, Szymon; Such, Bartosz; Pawlak, Rémy; Hinaut, Antoine; Jöhr, Res; Glatzel, Thilo; Meyer, Ernst; Szymonski, Marek

2017-01-01

Zn(II)phthalocyanine molecules (ZnPc) were thermally deposited on a rutile TiO2(011) surface and on Zn(II)meso-tetraphenylporphyrin (ZnTPP) wetting layers at room temperature and after elevated temperature thermal processing. The molecular homo- and heterostructures were characterized by high-resolution scanning tunneling microscopy (STM) at room temperature and their geometrical arrangement and degree of ordering are compared with the previously studied copper phthalocyanine (CuPc) and ZnTPP heterostructures. It was found that the central metal atom may play some role in ordering and growth of phthalocyanine/ZnTPP heterostructures, causing differences in stability of upright standing ZnPc versus CuPc molecular chains at given thermal annealing conditions. PMID:28144569

Effect of Functionalization of Graphene Nanoplatelets on the Mechanical and Thermal Properties of Silicone Rubber Composites

PubMed Central

Zhang, Guangwu; Wang, Fuzhong; Dai, Jing; Huang, Zhixiong

2016-01-01

This study investigated the effect of silane and surfactant treatments of graphene nanoplatelets (GnPs) on the mechanical and thermal properties of silicone rubber (SR) composites. GnPs were modified with aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), and Triton X-100, and then the pristine GnPs and functionalized GnPs were individually incorporated into the SR. Compared with the pristine GnP/SR composite, the composites reinforced with modified GnP showed better tensile strength, elongation at break, and thermal conductivity properties due to better dispersion of modified GnPs and stronger interfacial interactions between the modified GnPs and matrix. The mechanical properties and thermal conductivity of the VTMS-GnP/SR composite were comparable to the properties of the Triton-GnP counterpart, but better than that of the APTES-GnP/SR composite. In addition, the VTMS-GnP/SR composite demonstrated the highest thermal stability and crystallization temperature among the four types of composites. The remarkable improvement of mechanical and thermal properties of the VTMS-GnP/SR composite was mainly due to the covalent linkage of VTMS-GnP with SR. The VTMS treatment was a more appropriate modification of GnP particles to improve the multifunctional properties of SR. PMID:28787891

Effect of Functionalization of Graphene Nanoplatelets on the Mechanical and Thermal Properties of Silicone Rubber Composites.

PubMed

Zhang, Guangwu; Wang, Fuzhong; Dai, Jing; Huang, Zhixiong

2016-02-02

This study investigated the effect of silane and surfactant treatments of graphene nanoplatelets (GnPs) on the mechanical and thermal properties of silicone rubber (SR) composites. GnPs were modified with aminopropyltriethoxysilane (APTES), vinyltrimethoxysilane (VTMS), and Triton X-100, and then the pristine GnPs and functionalized GnPs were individually incorporated into the SR. Compared with the pristine GnP/SR composite, the composites reinforced with modified GnP showed better tensile strength, elongation at break, and thermal conductivity properties due to better dispersion of modified GnPs and stronger interfacial interactions between the modified GnPs and matrix. The mechanical properties and thermal conductivity of the VTMS-GnP/SR composite were comparable to the properties of the Triton-GnP counterpart, but better than that of the APTES-GnP/SR composite. In addition, the VTMS-GnP/SR composite demonstrated the highest thermal stability and crystallization temperature among the four types of composites. The remarkable improvement of mechanical and thermal properties of the VTMS-GnP/SR composite was mainly due to the covalent linkage of VTMS-GnP with SR. The VTMS treatment was a more appropriate modification of GnP particles to improve the multifunctional properties of SR.

NOx reduction in catalytically stabilized thermal burners. Annual report, pril 1, 1988-March 31, 1989

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

Pfefferle, L.D.

1989-09-01

Catalytically stabilized combustors can be designed to combine the high reaction rates of thermal combustors with low-NOx emissions. The objectives of the research are to understand why the CST burner has inherently low-NOx emissions and whether preexisting NOx can be reduced in-situ in the post-flame zone of a CST burner. Initial results indicate that reduced NOx emissions are, at least for some operating conditions, due to more than just the ability to stabilize combustion at low temperatures. The next phase of the investigation will focus on isothermal flow-tube kinetics studies to isolate catalytic and thermal effects.

Mechanical and thermal stability of graphene and graphene-based materials

NASA Astrophysics Data System (ADS)

Galashev, A. E.; Rakhmanova, O. R.

2014-10-01

Graphene has rapidly become one of the most popular materials for technological applications and a test material for new condensed matter ideas. This paper reviews the mechanical properties of graphene and effects related to them that have recently been discovered experimentally or predicted theoretically or by simulation. The topics discussed are of key importance for graphene's use in integrated electronics, thermal materials, and electromechanical devices and include the following: graphene transformation into other sp^2 hybridization forms; stability to stretching and compression; ion-beam-induced structural modifications; how defects and graphene edges affect the electronic properties and thermal stability of graphene and related composites.

Effect of nitrogenous bases on the thermal stability of jet fuels

NASA Technical Reports Server (NTRS)

Englin, B. A.; Alekseyeva, M. P.; Gasanova, Z. I.; Isaev, A. V.; Skovorodin, G. B.; Borisova, S. M.

1977-01-01

Fuels from naphthenic petroleums were evaluated, and it was found that they had more N bases than those paraffinic ones (0.00024 and 0.000009% N, respectively). The removal of the N bases improved significantly the thermal stability and reduced the residue formation during oxidation of the fuel. The improvement depended on both content and composition of the bases. Thus, fuels with similar content of N bases (0.00058% N) and thermal stability had oxidation residues of 17.5 and 5.6 and sol. gum of 13 and 1.5 mg/100 ml, before and after removing the N bases, respectively.

Comparison between polymerized ionic liquids synthesized using chain-growth and step-growth mechanisms used as stationary phase in gas chromatography.

PubMed

Roeleveld, Kevin; David, Frank; Lynen, Frédéric

2016-06-17

In this study the merits of polymerized imidazolium based ionic liquid (PIL) stationary phases obtained via condensation and free radical polymerizations are compared as stationary phases in gas chromatography (GC). Poly(1-vinyl-3-butyl-imidazolium - bis(trifluoromethane)sulfonamide) (poly(ViC4Im(+) NTf2(-))) was obtained via a chain-growth mechanism while poly(propylimidazolium-NTf2) (poly(C3Im(+) NTf2(-))) was synthesized via a step-growth polymerization. The thermal stability of both polymers was assessed using thermal gravimetric analysis and compared with bleeding profiles obtained from the statically coated GC columns (30m×0.25mm×0.25μm). The performance was compared to what could be obtained on commercially available 1,5-di(2,3-dimethylimidazolium)pentane(2+) 2NTf2(-) (SLB-IL111) ionic liquid based columns. It was observed that the step-growth polymer was more thermally stable, up to 325°C, while the chain-growth polymer showed initial degradation at 250°C. Both polymers allowed reaching minimal plate heights of 0.400-0.500mm for retained solutes such as benzaldehyde, acetophenone, 1-methylnaphthalene and aniline. Assessment of the McReynolds constants illustrated that the polarity of the step-growth polymer was similar to the SLB-IL111 column, while displaying improved column stability. The PIL phases and particularly the so far little studied condensation based polymer shows particular retention and satisfactory column performance for polar moieties such as esters, amine and carbonyl functionalities. Copyright © 2016 Elsevier B.V. All rights reserved.

Numerical investigation of CO{sub 2} emission and thermal stability of a convective and radiative stockpile of reactive material in a cylindrical pipe of variable thermal conductivity

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

Lebelo, Ramoshweu Solomon, E-mail: sollyl@vut.ac.za

In this paper the CO{sub 2} emission and thermal stability in a long cylindrical pipe of combustible reactive material with variable thermal conductivity are investigated. It is assumed that the cylindrical pipe loses heat by both convection and radiation at the surface. The nonlinear differential equations governing the problem are tackled numerically using Runge-Kutta-Fehlberg method coupled with shooting technique method. The effects of various thermophysical parameters on the temperature and carbon dioxide fields, together with critical conditions for thermal ignition are illustrated and discussed quantitatively.

High temperature polymers - A review of novel thermally stable hexafluoroisopropylidene-containing polymers

NASA Technical Reports Server (NTRS)

Kane, K. M.; Cassidy, P. E.; Tullos, G. L.; Reynolds, D. W.

1990-01-01

The synthesis and properties to date of several novel HFIP-containing polymers and copolymers are presented. Thermal analyses of polyether ketones (PEK), aromatic polyesters, and polymers from a novel 18F-diacid were performed on a thermal analyzer. All three polymer types exhibited enhanced solubility, thermal stability, and low dielectric constants that are predicted for polymers containing the HFIP moiety. The moderate thermal stability observed in the polymers derived from the 18F-diacid is attributed to the oxidatively weak methylene linkage between the HFIP groups and the phenyl rings. PEKs and polyarylates show potential as high emissivity coatings under conditions where atomic oxygen is present.

Thermal characterization and model free kinetics of aged epoxies and foams using TGA and DSC methods.

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

Cordaro, Joseph Gabriel; Kruizenga, Alan Michael; Nissen, April

2013-10-01

Two classes of materials, poly(methylene diphenyl diisocyanate) or PMDI foam, and cross-linked epoxy resins, were characterized using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC), to help understand the effects of aging and %E2%80%9Cbake-out%E2%80%9D. The materials were evaluated for mass loss and the onset of decomposition. In some experiments, volatile materials released during heating were analyzed via mass spectroscopy. In all, over twenty materials were evaluated to compare the mass loss and onset temperature for decomposition. Model free kinetic (MFK) measurements, acquired using variable heating rate TGA experiments, were used to calculate the apparent activation energy of thermal decomposition.more » From these compiled data the effects of aging, bake-out, and sample history on the thermal stability of materials were compared. No significant differences between aged and unaged materials were detected. Bake-out did slightly affect the onset temperature of decomposition but only at the highest bake-out temperatures. Finally, some recommendations for future handling are made.« less

Different thermostabilities of sarcoplasmic reticulum (Ca2+ + Mg2+)-ATPases from rabbit and trout muscles.

PubMed

de Toledo, F G; Albuquerque, M C; Goulart, B H; Chini, E N

1995-05-01

Trout and rabbit (Ca2+ + Mg2+)-ATPases from sarcoplasmic reticulum were compared for differences in thermal inactivation and susceptibility to trypsin digestion. The trout ATPase is more heat-sensitive than the rabbit ATPase and is stabilized by Ca2+, Na+, K+ and nucleotides. Solubilization of both ATPases shows that the two ATPases have different protein-intrinsic inactivation kinetics. When digested by trypsin, the two ATPases display different cleavage patterns. The present results indicate that the trout and rabbit ATPases have dissimilarities in protein structure that may explain the differences in thermal inactivation kinetics.

Scientific applications of frequency-stabilized laser technology in space

NASA Technical Reports Server (NTRS)

Schumaker, Bonny L.

1990-01-01

A synoptic investigation of the uses of frequency-stabilized lasers for scientific applications in space is presented. It begins by summarizing properties of lasers, characterizing their frequency stability, and describing limitations and techniques to achieve certain levels of frequency stability. Limits to precision set by laser frequency stability for various kinds of measurements are investigated and compared with other sources of error. These other sources include photon-counting statistics, scattered laser light, fluctuations in laser power, and intensity distribution across the beam, propagation effects, mechanical and thermal noise, and radiation pressure. Methods are explored to improve the sensitivity of laser-based interferometric and range-rate measurements. Several specific types of science experiments that rely on highly precise measurements made with lasers are analyzed, and anticipated errors and overall performance are discussed. Qualitative descriptions are given of a number of other possible science applications involving frequency-stabilized lasers and related laser technology in space. These applications will warrant more careful analysis as technology develops.

Stabilization of Phenylalanine Ammonia Lyase from Rhodotorula glutinis by Encapsulation in Polyethyleneimine-Mediated Biomimetic Silica.

PubMed

Cui, Jiandong; Liang, Longhao; Han, Cong; Lin Liu, Rong

2015-06-01

Phenylalanine ammonia lyase (PAL) from Rhodotorula glutinis was encapsulated within polyethyleneimine-mediated biomimetic silica. The main factors in the preparation of biomimetic silica were optimized by response surface methodology (RSM). Compared to free PAL (about 2 U), the encapsulated PAL retained more than 43 % of their initial activity after 1 h of incubation time at 60 °C, whereas free PAL lost most of activity in the same conditions. It was clearly indicated that the thermal stability of PAL was improved by encapsulation. Moreover, the encapsulated PAL exhibited the excellent stability of the enzyme against denaturants and storage stability, and pH stability was improved by encapsulation. Operational stability of 7 reaction cycles showed that the encapsulated PAL was stable. Nevertheless, the K m value of encapsulated PAL in biomimetic silica was higher than that of the free PAL due to lower total surface area and increased mass transfer resistance.

An investigation of the effects of radiation exposure on stability constraints in epitaxial SiGe strained layers

NASA Astrophysics Data System (ADS)

Chen, Tianbing; Sutton, Akil K.; Haugerud, Becca M.; Henderson, Walter; Gnana Prakash, A. P.; Cressler, John D.; Doolittle, Alan; Liu, Xuefeng; Joseph, Alvin; Marshall, Paul W.

2006-07-01

The thermodynamic stability of device-relevant epitaxial SiGe strained layers under proton irradiation is investigated using X-ray diffraction techniques, and compared with its stability constrain under high-temperature annealing. Irradiation with 63 MeV protons is found to introduce no significant microdefects into the SiGe thin films, regardless of starting stability condition of the SiGe film, and thus does not appear to be an issue for the use of SiGe HBT technology in emerging space systems. The strain relaxation of SiGe thin film under thermal annealing, however, is sensitive to the composition and thickness of the as-grown samples, as expected, with the subsequent lattice relaxation of the unstable samples occurring at a much higher rate than that of metastable samples.

Transient Thermal Stability of Polymer Nanocomposites

DTIC Science & Technology

2012-08-01

modified Montmorillonite, Nanocor masterbatch ) 1 wt % carbon black (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·nH2O Multiwalled Carbon Nanotubes (Nanocyl... masterbatch ) Twin screw extrusion (190C) Slow Heating Regime Thermogravimetric Analysis Nanospecies improve thermal stability as expected Laser

Study on immobilization of yeast alcohol dehydrogenase on nanocrystalline Ni-Co ferrites as magnetic support.

PubMed

Shakir, Mohammad; Nasir, Zeba; Khan, Mohd Shoeb; Lutfullah; Alam, Md Fazle; Younus, Hina; Al-Resayes, Saud Ibrahim

2015-01-01

The covalent binding of yeast alcohol dehydrogenase (YADH) enzyme complex in a series of magnetic crystalline Ni-Co nanoferrites, synthesized via sol-gel auto combustion technique was investigated. The structural analysis, morphology and magnetic properties of Ni-Co nanoferrites were determined by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), vibrating-sample magnetometer (VSM), high resolution transmission electron microscopy (HRTEM) and Fourier transform infrared spectroscopy (FTIR). The comparative analysis of the HRTEM micrographs of bare magnetic nanoferrite particles and particles immobilized with enzyme revealed an uniform distribution of the particles in both the cases without undergoing change in the size which was found to be in the range 20-30 nm. The binding of YADH to Ni-Co nanoferrites and the possible binding mechanism have been suggested by comparing the FTIR results. The binding properties of the immobilized YADH enzyme were also studied by kinetic parameters, optimum operational pH, temperature, thermal stability and reusability. The immobilized YADH exhibits enhanced thermal stability as compared to the free enzyme over a wide range of temperature and pH, and showed good durability after recovery by magnetic separation for repeated use. Copyright © 2014 Elsevier B.V. All rights reserved.

Failure Analysis of Multilayered Suspension Plasma-Sprayed Thermal Barrier Coatings for Gas Turbine Applications

NASA Astrophysics Data System (ADS)

Gupta, M.; Markocsan, N.; Rocchio-Heller, R.; Liu, J.; Li, X.-H.; Östergren, L.

2018-02-01

Improvement in the performance of thermal barrier coatings (TBCs) is one of the key objectives for further development of gas turbine applications. The material most commonly used as TBC topcoat is yttria-stabilized zirconia (YSZ). However, the usage of YSZ is limited by the operating temperature range which in turn restricts the engine efficiency. Materials such as pyrochlores, perovskites, rare earth garnets are suitable candidates which could replace YSZ as they exhibit lower thermal conductivity and higher phase stability at elevated temperatures. The objective of this work was to investigate different multilayered TBCs consisting of advanced topcoat materials fabricated by suspension plasma spraying (SPS). The investigated topcoat materials were YSZ, dysprosia-stabilized zirconia, gadolinium zirconate, and ceria-yttria-stabilized zirconia. All topcoats were deposited by TriplexPro-210TM plasma spray gun and radial injection of suspension. Lifetime of these samples was examined by thermal cyclic fatigue and thermal shock testing. Microstructure analysis of as-sprayed and failed specimens was performed with scanning electron microscope. The failure mechanisms in each case have been discussed in this article. The results show that SPS could be a promising route to produce multilayered TBCs for high-temperature applications.

Synthesis and Phase Stability of Scandia, Gadolinia, and Ytterbia Co-doped Zirconia for Thermal Barrier Coating Application

NASA Astrophysics Data System (ADS)

Li, Qi-Lian; Cui, Xiang-Zhong; Li, Shu-Qing; Yang, Wei-Hua; Wang, Chun; Cao, Qian

2015-01-01

Scandia, gadolinia, and ytterbia co-doped zirconia (SGYZ) ceramic powder was synthesized by chemical co-precipitation and calcination processes for application in thermal barrier coatings to promote the durability of gas turbines. The ceramic powder was agglomerated and sintered at 1150 °C for 2 h, and the powder exhibited good flowability and apparent density to be suitable for plasma spraying process. The microstructure, morphology and phase stability of the powder and plasma-sprayed SGYZ coatings were analyzed by means of scanning electron microscope and x-ray diffraction. Thermal conductivity of plasma-sprayed SGYZ coatings was measured. The results indicated that the SGYZ ceramic powder and the coating exhibit excellent stability to retain single non-transformable tetragonal zirconia even after high temperature (1400 °C) exposure for 500 h and do not undergo a tetragonal-to-monoclinic phase transition upon cooling. Furthermore, the plasma-sprayed SGYZ coating also exhibits lower thermal conductivity than yttria stabilized zirconia coating currently used in gas turbine engine industry. SGYZ can be explored as a candidate material of ultra-high temperature thermal barrier coating for advanced gas turbine engines.

Kinetic analysis of thermal stability of human low density lipoproteins: a model for LDL fusion in atherogenesis[S

PubMed Central

Lu, Mengxiao; Gantz, Donald L.; Herscovitz, Haya; Gursky, Olga

2012-01-01

Fusion of modified LDL in the arterial wall promotes atherogenesis. Earlier we showed that thermal denaturation mimics LDL remodeling and fusion, and revealed kinetic origin of LDL stability. Here we report the first quantitative analysis of LDL thermal stability. Turbidity data show sigmoidal kinetics of LDL heat denaturation, which is unique among lipoproteins, suggesting that fusion is preceded by other structural changes. High activation energy of denaturation, Ea = 100 ± 8 kcal/mol, indicates disruption of extensive packing interactions in LDL. Size-exclusion chromatography, nondenaturing gel electrophoresis, and negative-stain electron microscopy suggest that LDL dimerization is an early step in thermally induced fusion. Monoclonal antibody binding suggests possible involvement of apoB N-terminal domain in early stages of LDL fusion. LDL fusion accelerates at pH < 7, which may contribute to LDL retention in acidic atherosclerotic lesions. Fusion also accelerates upon increasing LDL concentration in near-physiologic range, which likely contributes to atherogenesis. Thermal stability of LDL decreases with increasing particle size, indicating that the pro-atherogenic properties of small dense LDL do not result from their enhanced fusion. Our work provides the first kinetic approach to measuring LDL stability and suggests that lipid-lowering therapies that reduce LDL concentration but increase the particle size may have opposite effects on LDL fusion. PMID:22855737

Kinetic analysis of thermal stability of human low density lipoproteins: a model for LDL fusion in atherogenesis.

PubMed

Lu, Mengxiao; Gantz, Donald L; Herscovitz, Haya; Gursky, Olga

2012-10-01

Fusion of modified LDL in the arterial wall promotes atherogenesis. Earlier we showed that thermal denaturation mimics LDL remodeling and fusion, and revealed kinetic origin of LDL stability. Here we report the first quantitative analysis of LDL thermal stability. Turbidity data show sigmoidal kinetics of LDL heat denaturation, which is unique among lipoproteins, suggesting that fusion is preceded by other structural changes. High activation energy of denaturation, E(a) = 100 ± 8 kcal/mol, indicates disruption of extensive packing interactions in LDL. Size-exclusion chromatography, nondenaturing gel electrophoresis, and negative-stain electron microscopy suggest that LDL dimerization is an early step in thermally induced fusion. Monoclonal antibody binding suggests possible involvement of apoB N-terminal domain in early stages of LDL fusion. LDL fusion accelerates at pH < 7, which may contribute to LDL retention in acidic atherosclerotic lesions. Fusion also accelerates upon increasing LDL concentration in near-physiologic range, which likely contributes to atherogenesis. Thermal stability of LDL decreases with increasing particle size, indicating that the pro-atherogenic properties of small dense LDL do not result from their enhanced fusion. Our work provides the first kinetic approach to measuring LDL stability and suggests that lipid-lowering therapies that reduce LDL concentration but increase the particle size may have opposite effects on LDL fusion.

Purification and Thermal Stability of Intact Bacillus subtilis Flagella

PubMed Central

Dimmitt, K.; Simon, M.

1971-01-01

Flagella were prepared and purified in a relatively intact form from bacterial lysates. Immunochemical tests showed that over 95% of the protein in the final preparation consisted of flagellar antigen. These flagella are more stable to thermal denaturation than flagella filaments obtained by shearing. Their thermal properties more closely resemble those of flagella in the native state on bacteria. The presence of the hook structure is responsible for this extra stability. Images PMID:4993323

Kinetics and thermal stability of the Ni62Nb38- x Ta x ( x=5, 10, 15, 20 and 25) bulk metallic glasses

NASA Astrophysics Data System (ADS)

He, MengKe; Zhang, Yi; Xia, Lei; Yu, Peng

2017-07-01

We studied thermal stability and its relationship to the glass-forming ability (GFA) of the Ni62Nb38- x Ta x ( x=5, 10, 15, 20, 25) bulk metallic glasses (BMG) from a kinetic point of view. By fitting the heating-rate dependence of glass transition temperature ( T g onset) and crystallization temperatures ( T x onset and T x peak) of the Ni62Nb38- x Ta x BMG using the Vogel-Fulcher-Tammann (VFT) equation, we obtained the ideal glass transition and crystallization temperatures ( T g 0 and T x 0) and the fragility parameter ( m), and also constructed continuous heating transition (CHT) diagrams for crystallization of the BMG. The CHT diagrams of the BMG indicate enhanced thermal stability by Ta addition; the T g 0 as well as the T x 0 also illustrates this improved stability limit. The compositional dependence of m, which agrees well with that of the reduced glass-transition temperature, indicates a strong correlation between liquid fragility and glass-forming ability in the present alloy system. These results provide new evidence for understanding thermal stability, liquid fragility, and GFA in BMG.

Evaluation of thermal stability in spectrally selective few-layer metallo-dielectric structures for solar thermophotovoltaics

NASA Astrophysics Data System (ADS)

Shimizu, Makoto; Kohiyama, Asaka; Yugami, Hiroo

2018-06-01

The thermal stability of spectrally selective few-layer metallo-dielectric structures is evaluated to analyze their potential as absorber and emitter materials in solar thermophotovoltaic (STPV) systems. High-efficiency (e.g., STPV) systems require materials with spectrally selective properties, especially at high temperatures (>1273 K). Aiming to develop such materials for high-temperature applications, we propose a few-layer structure composed of a refractory metal (i.e., Mo) nanometric film sandwiched between the layers of a dielectric material (i.e., hafnium oxide, HfO2) deposited on a Mo bulk substrate. In vacuum conditions (<5 × 10-2 Pa), the few-layer structure shows thermal stability at 1423 K for at least 1 h. At 1473 K, the spectral selectivity was degraded. This could have been caused by the oxidation of the Mo thin film by the residual oxygen through the grain boundaries of the upper HfO2 layer. This experiment showed the potential stability of few-layer structures for applications working at temperatures greater than 1273 K as well as the degradation mechanism of the few-layer structure. This characteristic is expected to help improve the thermal stability in few-layer structures further.

Minimizing Postsampling Degradation of Peptides by a Thermal Benchtop Tissue Stabilization Method

PubMed Central

Segerström, Lova; Gustavsson, Jenny

2016-01-01

Enzymatic degradation is a major concern in peptide analysis. Postmortem metabolism in biological samples entails considerable risk for measurements misrepresentative of true in vivo concentrations. It is therefore vital to find reliable, reproducible, and easy-to-use procedures to inhibit enzymatic activity in fresh tissues before subjecting them to qualitative and quantitative analyses. The aim of this study was to test a benchtop thermal stabilization method to optimize measurement of endogenous opioids in brain tissue. Endogenous opioid peptides are generated from precursor proteins through multiple enzymatic steps that include conversion of one bioactive peptide to another, often with a different function. Ex vivo metabolism may, therefore, lead to erroneous functional interpretations. The efficacy of heat stabilization was systematically evaluated in a number of postmortem handling procedures. Dynorphin B (DYNB), Leu-enkephalin-Arg6 (LARG), and Met-enkephalin-Arg6-Phe7 (MEAP) were measured by radioimmunoassay in rat hypothalamus, striatum (STR), and cingulate cortex (CCX). Also, simplified extraction protocols for stabilized tissue were tested. Stabilization affected all peptide levels to varying degrees compared to those prepared by standard dissection and tissue handling procedures. Stabilization increased DYNB in hypothalamus, but not STR or CCX, whereas LARG generally decreased. MEAP increased in hypothalamus after all stabilization procedures, whereas for STR and CCX, the effect was dependent on the time point for stabilization. The efficacy of stabilization allowed samples to be left for 2 hours in room temperature (20°C) without changes in peptide levels. This study shows that conductive heat transfer is an easy-to-use and efficient procedure for the preservation of the molecular composition in biological samples. Region- and peptide-specific critical steps were identified and stabilization enabled the optimization of tissue handling and opioid peptide analysis. The result is improved diagnostic and research value of the samples with great benefits for basic research and clinical work. PMID:27007059

A computational model for the dynamic stabilization of Rayleigh-Bénard convection in a cubic cavity.

PubMed

Carbo, Randy M; Smith, Robert W M; Poese, Matthew E

2014-02-01

The dynamic stability of Rayleigh-Bénard convection with vertical vibration in a cubic container is computationally modeled. Two parametric drives are considered (sinusoidal and rectangular), as well as two thermal boundary conditions on the sidewalls (insulating and conducting). The linearized equations are solved using a spectral Galerkin method and Floquet analysis. Both the synchronous and the subharmonic regions of instability are recovered. The conditions necessary for dynamic stability are reported for a range of Rayleigh numbers from critical to 10(7) and for Prandtl numbers in the range of 0.1-7. The linear model is compared to the data set available in the literature where the performance of an inverted pulse tube cryocooler is measured.

Thermally stable macromolecules.

NASA Technical Reports Server (NTRS)

Pezdirtz, G. F.; Johnston, N. J.

1972-01-01

Man-made polymers are compared with certain naturally occurring polymers which have long been used at elevated temperatures. The pyrolysis of model compounds is discussed together with aspects of thermogravimetric analysis, torsional braid analysis, and questions of chemical and radiation stability. Some structure-property relationships are examined, giving attention to asbestos, mica, graphite, and diamond. Questions of bond strengths are investigated along with the stability of ladder polymers and some fundamental concepts in the synthesis of aromatic and heteroaromatic polymers. The substances considered include aromatic single-strand polymers, heteroaromatic polymers, polymers obtained by addition polymerizations, and nonhydrogen-containing polymers. Future trends are also explored.

New class of thermosetting plastics has improved strength, thermal and chemical stability

NASA Technical Reports Server (NTRS)

Burns, E. A.; Dubrow, B.; Lubowitz, H. R.

1967-01-01

New class of thermosetting plastics has high hydrocarbon content, high stiffness, thermal stability, humidity resistance, and workability in the precured state. It is designated cyclized polydiene urethane, and is applicable as matrices to prepare chemically stable ablative materials for rocket nose cones of nozzles.

What the ultimate polymeric electro-optic materials will be: guest-host, crosslinked, or side-chain?

NASA Astrophysics Data System (ADS)

Zhang, Cheng; Zhang, Hua; Oh, Min-Cheol; Dalton, Larry R.; Steier, William H.

2003-07-01

Material processing and device fabrication of many different electro-optic (EO) polymers developed at USC are reviewed. Detailed discussion is given to guest-host CLD/APCs, crosslinking perfluorocyclobutane (PFCB) polymer CX1, and thermally stable side-chain polymers CX2 and CX3. Excellent EO performance (1.4V at 1.31 μm, 2.1 V at 1.55 μm) was achieved in CLD/APC Mach-Zehnder modulators (2-cm, push-pull). CLD/APCs also possess low optical losses (1.2 dB/cm in slab waveguides and in thick core channel waveguides). However, the guest-host materials only have limited thermal stability (110-132 °C in short term, <60 °C in long term) and require special techniques in device fabrication. The crosslinking polymer CX1 was able to provide long-term stability at 85 oC when fully cured. It also has a low optical loss (comparable to CLD/APCs) before curing and decent EO coefficient when poled at 180 °C. However, after the films were poled at the crosslinking temperatures (200 °C or above), the transmissions of the waveguides and EO activity became very poor due to poling-induced chromophore degradation. By judicial molecular design of both chromophore and monomer structures to suppress thermal motion of polymer segments, we were able to realize the same or even better thermal stability in side-chain polymers CX2 and CX3. Since no curing is needed, devices can be poled at their optimal poling temperatures, and all good properties can be obtained simultaneously. Despite the excellent solubility in chlorinated solvents, these side-chain polymers are resistant to some other organic solvents or solutions such as acetone, photoresist and various UV-curable liquids.

Effect of Surfactants on Mechanical, Thermal, and Photostability of a Monoclonal Antibody.

PubMed

Agarkhed, Meera; O'Dell, Courtney; Hsieh, Ming-Ching; Zhang, Jingming; Goldstein, Joel; Srivastava, Arvind

2018-01-01

The purpose of this work was to evaluate the effect of commonly used surfactants (at 0.01% w/v concentration) on mechanical, thermal, and photostability of a monoclonal antibody (MAb1) of IgG1 sub-class and to evaluate the minimum concentration of surfactant (Polysorbate 80) required in protecting MAb1 from mechanical stress. Surfactants evaluated were non-ionic surfactants, Polysorbate 80, Polysorbate 20, Pluronic F-68 (polyoxyethylene-polyoxypropylene block polymer), Brij 35 (polyoxyethylene lauryl ether), Triton X-100, and an anionic surfactant, Caprylic acid (1-Heptanecarboxylic acid). After evaluating effect of surfactants and determining stabilizing effect of Polysorbate 80 against mechanical stress without compromising thermal and photostability of MAb1, the minimum concentration of Polysorbate 80 required for mechanical stability was further examined. Polysorbate 80 concentration was varied from 0 to 0.02%. Mechanical stability was evaluated by agitation of MAb1 at 300 rotations per minute at room temperature for 72 h. Samples were analyzed for purity by SEC-HPLC, turbidity by absorbance at 350 nm, visible particles by visual inspection, and sub-visible particles by light obscuration technique on a particle analyzer. All non-ionic surfactants tested showed a similar effect in protecting against mechanical stress and did not exhibit any significant negative effect on thermal and photostability. However, Caprylic acid had a slightly negative effect on mechanical and photostability when compared to the non-ionic surfactants or sample without surfactant. This work demonstrated that polysorbate 80 is better than other surfactants tested and that a concentration of at least 0.005% (w/v) Polysorbate 80 is needed to protect MAb1 against mechanical stress.

Synthesis of a Novel Polyethoxysilsesquiazane and Thermal Conversion into Ternary Silicon Oxynitride Ceramics with Enhanced Thermal Stability

PubMed Central

Iwase, Yoshiaki; Horie, Yoji; Daiko, Yusuke; Honda, Sawao

2017-01-01

A novel polyethoxysilsesquiazane ([EtOSi(NH)1.5]n, EtOSZ) was synthesized by ammonolysis at −78 °C of ethoxytrichlorosilane (EtOSiCl3), which was isolated by distillation as a reaction product of SiCl4 and EtOH. Attenuated total reflection-infra red (ATR-IR), 13C-, and 29Si-nuclear magnetic resonance (NMR) spectroscopic analyses of the ammonolysis product resulted in the detection of Si–NH–Si linkage and EtO group. The simultaneous thermogravimetric and mass spectrometry analyses of the EtOSZ under helium revealed cleavage of oxygen-carbon bond of the EtO group to evolve ethylene as a main gaseous species formed in-situ, which lead to the formation at 800 °C of quaternary amorphous Si–C–N with an extremely low carbon content (1.1 wt %) when compared to the theoretical EtOSZ (25.1 wt %). Subsequent heat treatment up to 1400 °C in N2 lead to the formation of X-ray amorphous ternary Si–O–N. Further heating to 1600 °C in N2 promoted crystallization and phase partitioning to afford Si2N2O nanocrystallites identified by the XRD and TEM analyses. The thermal stability up to 1400 °C of the amorphous state achieved for the ternary Si-O-N was further studied by chemical composition analysis, as well as X-ray photoelectron spectroscopy (XPS) and 29Si-NMR spectroscopic analyses, and the results were discussed aiming to develop a novel polymeric precursor for ternary amorphous Si–O–N ceramics with an enhanced thermal stability. PMID:29206217

Thermal conductivity of cement stabilized earth bricks reinforced with date palm fiber

NASA Astrophysics Data System (ADS)

Berrehail, Tahar; Zemmouri, Noureddine; Agoudjil, Boudjemaa

2018-05-01

Recently, some cheap materials are available and adaptable to climate seem to meet current requirements. This paper investigates the thermal and mechanical properties of cement stabilized earth bricks(CSEB) reinforced with date palm fibers (DPF). The main goal is to develop and expand the field of use of these materials in the construction sector, and investigate the possibility of new bio composite as renewable, insulating building material with low cost, made of earth and reinforced with palm wood waste. In this study, a particular interest is brought to the thermal and mechanical characteristics, which constitute a decisive character for the choice of a building material. A series of earthen samples stabilized at 5% and reinforced with DPF of various fiber weight fractions, (5%, 10%), were manufactured and compacted applying two levels compacting, (5MPa and 10MPa). Compressive strength and thermal conductivity were experimentally studied; heating capacity and diffusivity were indirectly calculated. It was found that the fibrous reinforcement proved thermal conductivity and compressive strength. it also enhanced thermal performances. Thus, the results found allow us to investigate hygrothermal behaviour and its impact on occupants comfort.

Enhanced thermal properties of novel shape-stabilized PEG composite phase change materials with radial mesoporous silica sphere for thermal energy storage.

PubMed

Min, Xin; Fang, Minghao; Huang, Zhaohui; Liu, Yan'gai; Huang, Yaoting; Wen, Ruilong; Qian, Tingting; Wu, Xiaowen

2015-08-11

Radial mesoporous silica (RMS) sphere was tailor-made for further applications in producing shape-stabilized composite phase change materials (ss-CPCMs) through a facile self-assembly process using CTAB as the main template and TEOS as SiO2 precursor. Novel ss-CPCMs composed of polyethylene glycol (PEG) and RMS were prepared through vacuum impregnating method. Various techniques were employed to characterize the structural and thermal properties of the ss-CPCMs. The DSC results indicated that the PEG/RMS ss-CPCM was a promising candidate for building thermal energy storage applications due to its large latent heat, suitable phase change temperature, good thermal reliability, as well as the excellent chemical compatibility and thermal stability. Importantly, the possible formation mechanisms of both RMS sphere and PEG/RMS composite have also been proposed. The results also indicated that the properties of the PEG/RMS ss-CPCMs are influenced by the adsorption limitation of the PEG molecule from RMS sphere with mesoporous structure and the effect of RMS, as the impurities, on the perfect crystallization of PEG.

Enhanced thermal properties of novel shape-stabilized PEG composite phase change materials with radial mesoporous silica sphere for thermal energy storage

PubMed Central

Min, Xin; Fang, Minghao; Huang, Zhaohui; Liu, Yan’gai; Huang, Yaoting; Wen, Ruilong; Qian, Tingting; Wu, Xiaowen

2015-01-01

Radial mesoporous silica (RMS) sphere was tailor-made for further applications in producing shape-stabilized composite phase change materials (ss-CPCMs) through a facile self-assembly process using CTAB as the main template and TEOS as SiO2 precursor. Novel ss-CPCMs composed of polyethylene glycol (PEG) and RMS were prepared through vacuum impregnating method. Various techniques were employed to characterize the structural and thermal properties of the ss-CPCMs. The DSC results indicated that the PEG/RMS ss-CPCM was a promising candidate for building thermal energy storage applications due to its large latent heat, suitable phase change temperature, good thermal reliability, as well as the excellent chemical compatibility and thermal stability. Importantly, the possible formation mechanisms of both RMS sphere and PEG/RMS composite have also been proposed. The results also indicated that the properties of the PEG/RMS ss-CPCMs are influenced by the adsorption limitation of the PEG molecule from RMS sphere with mesoporous structure and the effect of RMS, as the impurities, on the perfect crystallization of PEG. PMID:26261089

Sequential events in the irreversible thermal denaturation of human brain-type creatine kinase by spectroscopic methods.

PubMed

Gao, Yan-Song; Su, Jing-Tan; Yan, Yong-Bin

2010-06-25

The non-cooperative or sequential events which occur during protein thermal denaturation are closely correlated with protein folding, stability, and physiological functions. In this research, the sequential events of human brain-type creatine kinase (hBBCK) thermal denaturation were studied by differential scanning calorimetry (DSC), CD, and intrinsic fluorescence spectroscopy. DSC experiments revealed that the thermal denaturation of hBBCK was calorimetrically irreversible. The existence of several endothermic peaks suggested that the denaturation involved stepwise conformational changes, which were further verified by the discrepancy in the transition curves obtained from various spectroscopic probes. During heating, the disruption of the active site structure occurred prior to the secondary and tertiary structural changes. The thermal unfolding and aggregation of hBBCK was found to occur through sequential events. This is quite different from that of muscle-type CK (MMCK). The results herein suggest that BBCK and MMCK undergo quite dissimilar thermal unfolding pathways, although they are highly conserved in the primary and tertiary structures. A minor difference in structure might endow the isoenzymes dissimilar local stabilities in structure, which further contribute to isoenzyme-specific thermal stabilities.

Chemical and thermal stability of N-heterocyclic ionic liquids in catalytic C-H activation reactions.

PubMed

Chen, Guanyi; Kang, Shujuan; Ma, Qisheng; Chen, Weiqun; Tang, Yongchun

2014-11-01

(1)H-NMR spectrum analyses are applied to study the chemical and thermal stability of selected N-heterocyclic ionic liquids within the reaction system that can highly efficiently activate a C-H bond of methane and convert it into the C-O bond in methanol. Our results indicate that under such reaction conditions involving using a powerful Pt-based catalyst and strong acidic solvent, the aromatic ring of an imidazolium cation becomes unstable generating an ammonium ion (NH(4)(+)). Our results also suggest that the instability of the imidazolium ring is more chemically (participation in reactions) than thermally based. Modifications of the aromatic ring structure such as pyrazolium and triazolium cations can increase the chemical/thermal stability of ionic liquids under these reaction conditions. Copyright © 2014 John Wiley & Sons, Ltd.

Novel Shape-Stabilized Phase Change Materials Composed of Polyethylene Glycol/Nonsurfactant-Templated Mesoporous Silica: Preparation and Thermal Properties

NASA Astrophysics Data System (ADS)

Chen, Yan; Zhu, Yingying; Wang, Jinbao; Lv, Mengjiao; Zhang, Xiongjie; Gao, Junkai; Zhang, Zijun; Lei, Hao

2017-12-01

A novel shape-stabilized phase change material (PEG/TAMS), fabricated using tannic acid-templated mesoporous silica (TAMS) as a support for polyethylene glycol, was developed for thermal energy storage. The method used to synthesize TAMS was simple, cost effective, environmentally friendly, and free of surfactant. The characterization results indicated that PEG was physically absorbed to TAMS and that TAMS had no influence on the crystal structure of PEG. According to the TGA thermograms, PEG/TAMS has excellent thermal stability and can be applied over a wide temperature range. Additionally, the differential scanning calorimetry results suggested that PEG/TAMS has good thermal properties and that its fusion and solidification enthalpies reached 114.7 J/g and 102.4 J/g, respectively. The results indicated that PEG/TAMS has great potential for practical applications.

High thermal stability and sluggish crystallization kinetics of high-entropy bulk metallic glasses

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

Yang, M.; Department of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon; Liu, X. J.

2016-06-28

Metallic glasses are metastable and their thermal stability is critical for practical applications, particularly at elevated temperatures. The conventional bulk metallic glasses (BMGs), though exhibiting high glass-forming ability (GFA), crystallize quickly when being heated to a temperature higher than their glass transition temperature. This problem may potentially be alleviated due to the recent developments of high-entropy (or multi-principle-element) bulk metallic glasses (HE-BMGs). In this work, we demonstrate that typical HE-BMGs, i.e., ZrTiHfCuNiBe and ZrTiCuNiBe, have higher kinetic stability, as compared with the benchmark glass Vitreoy1 (Zr{sub 41.2}Ti{sub 13.8}Cu{sub 12.5}Ni{sub 10}Be{sub 22.5}) with a similar chemical composition. The measured activation energymore » for glass transition and crystallization of the HE-BMGs is nearly twice that of Vitreloy 1. Moreover, the sluggish crystallization region ΔT{sub pl-pf}, defined as the temperature span between the last exothermic crystallization peak temperature T{sub pl} and the first crystallization exothermic peak temperature T{sub pf}, of all the HE-BMGs is much wider than that of Vitreloy 1. In addition, high-resolution transmission electron microscopy characterization of the crystallized products at different temperatures and the continuous heating transformation diagram which is proposed to estimate the lifetime at any temperature below the melting point further confirm high thermal stability of the HE-BMGs. Surprisingly, all the HE-BMGs show a small fragility value, which contradicts with their low GFA, suggesting that the underlying diffusion mechanism in the liquid and the solid of HE-BMGs is different.« less

Thermodynamic stability of carbonic anhydrase: measurements of binding affinity and stoichiometry using ThermoFluor.

PubMed

Matulis, Daumantas; Kranz, James K; Salemme, F Raymond; Todd, Matthew J

2005-04-05

ThermoFluor (a miniaturized high-throughput protein stability assay) was used to analyze the linkage between protein thermal stability and ligand binding. Equilibrium binding ligands increase protein thermal stability by an amount proportional to the concentration and affinity of the ligand. Binding constants (K(b)) were measured by examining the systematic effect of ligand concentration on protein stability. The precise ligand effects depend on the thermodynamics of protein stability: in particular, the unfolding enthalpy. An extension of current theoretical treatments was developed for tight binding inhibitors, where ligand effect on T(m) can also reveal binding stoichiometry. A thermodynamic analysis of carbonic anhydrase by differential scanning calorimetry (DSC) enabled a dissection of the Gibbs free energy of stability into enthalpic and entropic components. Under certain conditions, thermal stability increased by over 30 degrees C; the heat capacity of protein unfolding was estimated from the dependence of calorimetric enthalpy on T(m). The binding affinity of six sulfonamide inhibitors to two isozymes (human type 1 and bovine type 2) was analyzed by both ThermoFluor and isothermal titration calorimetry (ITC), resulting in a good correlation in the rank ordering of ligand affinity. This combined investigation by ThermoFluor, ITC, and DSC provides a detailed picture of the linkage between ligand binding and protein stability. The systematic effect of ligands on stability is shown to be a general tool to measure affinity.

Current Protocols in Protein Science

PubMed Central

Huynh, Kathy

2015-01-01

The purification of recombinant proteins for biochemical assays and structural studies is time-consuming and presents inherent difficulties that depend on the optimization of protein stability. The use of dyes to monitor thermal denaturation of proteins with sensitive fluorescence detection enables the rapid and inexpensive determination of protein stability using real-time PCR instruments. By screening a wide range of solution conditions and additives in 96-well format, the thermal shift assay easily identifies conditions that significantly enhance the stability of recombinant proteins. The same approach can be used as a low cost, initial screen to discover new protein:ligand interactions by capitalizing on increases in protein stability that typically occur upon ligand binding. This unit presents a methodological workflow for the small-scale, high-throughout thermal denaturation of recombinant proteins in the presence of SYPRO Orange dye. PMID:25640896

Highly transparent and thermal-stable silver nanowire conductive film covered with ZnMgO by atomic-layer-deposition

NASA Astrophysics Data System (ADS)

Wang, Lei; Huang, Dongchen; Li, Min; Xu, Hua; Zou, Jianhua; Tao, Hong; Peng, Junbiao; Xu, Miao

2017-12-01

Solution-processed silver nanowires (AgNWs) have been considered as a promising material for next generation flexible transparent conductive electrodes. However AgNWs films have several intrinsic drawbacks, such as thermal stability and storage stability. Herein, we demonstrate a laminated ZnO/MgO (ZnMgO, ZMO) as a protective layer on the AgNWs films using atomic layer deposition (ALD). The fabricated films exhibited a low sheet resistance of 16 Ω/sq with high transmittance of 91% at 550 nm, an excellent thermal stability and bending property. The ZMO film grows perpendicularly on the surface of the AgNWs, making a perfect coverage of bulk silver nanowires and junction, which can effectively prompt the electrical transport behavior and enhance stability of the silver nanowires network.

Molecular basis for polyol-induced protein stability revealed by molecular dynamics simulations

NASA Astrophysics Data System (ADS)

Liu, Fu-Feng; Ji, Luo; Zhang, Lin; Dong, Xiao-Yan; Sun, Yan

2010-06-01

Molecular dynamics simulations of chymotrypsin inhibitor 2 in different polyols (glycerol, xylitol, sorbitol, trehalose, and sucrose) at 363 K were performed to probe the molecular basis of the stabilizing effect, and the data in water, ethanol, and glycol were compared. It is found that protein protection by polyols is positively correlated with both the molecular volume and the fractional polar surface area, and the former contributes more significantly to the protein's stability. Polyol molecules have only a few direct hydrogen bonds with the protein, and the number of hydrogen bonds between a polyol and the protein is similar for different polyols. Thus, it is concluded that the direct interactions contribute little to the stabilizing effect. It is clarified that the preferential exclusion of the polyols is the origin of their protective effects, and it increases with increasing polyol size. Namely, there is preferential hydration on the protein surface (2 Å), and polyol molecules cluster around the protein at a distance of about 4 Å. The preferential exclusion of polyols leads to indirect interactions that prevent the protein from thermal unfolding. The water structure becomes more ordered with increasing the polyol size. So, the entropy of water in the first hydration shell decreases, and a larger extent of decrease is observed with increasing polyol size, leading to larger transfer free energy. The findings suggest that polyols protect the protein from thermal unfolding via indirect interactions. The work has thus elucidated the molecular mechanism of structural stability of the protein in polyol solutions.

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

Fu, Yongping; Zhu, Haiming; Schrader, Alex W.

The excellent intrinsic optoelectronic properties of methylammonium lead halide perovskites (MAPbX 3, X = Br, I), such as high photoluminescence quantum efficiency, long carrier lifetime, and high gain coupled with the facile solution growth of nanowires make them promising new materials for ultralow-threshold nanowire lasers. However, their photo and thermal stabilities need to be improved for practical applications. Herein, we report a low-temperature solution growth of single crystal nanowires of formamidinium lead halide perovskites (FAPbX 3) that feature red-shifted emission and better thermal stability compared to MAPbX 3. We demonstrate optically pumped room-temperature near-infrared (~820 nm) and green lasing (~560more » nm) from FAPbI 3 (and MABr-stabilized FAPbI 3) and FAPbBr 3 nanowires with low lasing thresholds of several microjoules per square centimeter and high quality factors of about 1500–2300. More remarkably, the FAPbI 3 and MABr-stabilized FAPbI 3 nanowires display durable room-temperature lasing under ~10 8 shots of sustained illumination of 402 nm pulsed laser excitation (150 fs, 250 kHz), substantially exceeding the stability of MAPbI 3 (~10 7 laser shots). We further demonstrate tunable nanowire lasers in wider wavelength region from FA-based lead halide perovskite alloys (FA,MA)PbI 3 and (FA,MA)Pb(I,Br) 3 through cation and anion substitutions. The results suggest that formamidinium lead halide perovskite nanostructures could be more promising and stable materials for the development of light-emitting diodes and continuous-wave lasers.« less

Thermoelectric properties and thermal stability of Bi-doped PbTe single crystal

NASA Astrophysics Data System (ADS)

Chen, Zhong; Li, Decong; Deng, Shuping; Tang, Yu; Sun, Luqi; Liu, Wenting; Shen, Lanxian; Yang, Peizhi; Deng, Shukang

2018-06-01

In this study, n-type Bi-doped single-crystal PbTe thermoelectric materials were prepared by melting and slow cooling method according to the stoichiometric ratio of Pb:Bi:Te = 1-x:x:1 (x = 0, 0.1, 0.15, 0.2, 0.25). The X-ray diffraction patterns of Pb1-xBixTe samples show that all main diffraction peaks are well matched with the PbTe matrix, which has a face-centered cubic structure with the space group Fm 3 bar m . Electron probe microanalysis reveals that Pb content decreases gradually, and Te content remains invariant basically with the increase of Bi content, indicating that Bi atoms are more likely to replace Pb atoms. Thermal analysis shows that the prepared samples possess relatively high thermal stability. Simultaneously, transmission electron microscopy and selected area electron diffraction pattern indicate that the prepared samples have typical single-crystal structures with good mechanical properties. Moreover, the electrical conductivity of the prepared samples improved significantly compared with that of the pure sample, and the maximum ZT value of 0.84 was obtained at 600 K by the sample with x = 0.2.

Utilizing environmental friendly iron as a substitution element in spinel structured cathode materials for safer high energy lithium-ion batteries

DOE PAGES

Hu, Enyuan; Bak, Seong -Min; Liu, Yijin; ...

2015-12-03

Suppressing oxygen release from lithium ion battery cathodes during heating is a critical issue for the improvement of the battery safety characteristics because oxygen can exothermically react with the flammable electrolyte and cause thermal runaway. Previous studies have shown that oxygen release can be reduced by the migration of transition metal cations from octahedral sites to tetrahedral sites during heating. Such site-preferred migration is determined by the electronic structure of cations. In addition, taking advantage of the unique electronic structure of the environmental friendly Fe, this is selected as substitution element in a high energy density material LiNi 0.5Mn 1.5Omore » 4 to improve the thermal stability. The optimized LiNi 0.33Mn 1.33Fe 0.33O 4 material shows significantly improved thermal stability compared with the unsubstituted one, demonstrated by no observed oxygen release at temperatures as high as 500°C. Due to the electrochemical contribution of Fe, the high energy density feature of LiNi 0.5Mn 1.5O 4 is well preserved.« less

Engineering glycoside hydrolase stability by the introduction of zinc binding

DOE PAGES

Ellinghaus, Thomas L.; Pereira, Jose H.; McAndrew, Ryan P.; ...

2018-06-27

The development of robust enzymes, in particular cellulases, is a key step in the success of biological routes to `second-generation' biofuels. The typical sources of the enzymes used to degrade biomass include mesophilic and thermophilic organisms. The endoglucanase J30 from glycoside hydrolase family 9 was originally identified through metagenomic analyses of compost-derived bacterial consortia. These studies, which were tailored to favor growth on targeted feedstocks, have already been shown to identify cellulases with considerable thermal tolerance. The amino-acid sequence of J30 shows comparably low identity to those of previously analyzed enzymes. As an enzyme that combines a well measurable activitymore » with a relatively low optimal temperature (50°C) and a modest thermal tolerance, it offers the potential for structural optimization aimed at increased stability. Here, the crystal structure of wild-type J30 is presented along with that of a designed triple-mutant variant with improved characteristics for industrial applications. Through the introduction of a structural Zn 2+ site, the thermal tolerance was increased by more than 10°C and was paralleled by an increase in the catalytic optimum temperature by more than 5°C.« less

Engineering glycoside hydrolase stability by the introduction of zinc binding

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

Ellinghaus, Thomas L.; Pereira, Jose H.; McAndrew, Ryan P.

The development of robust enzymes, in particular cellulases, is a key step in the success of biological routes to `second-generation' biofuels. The typical sources of the enzymes used to degrade biomass include mesophilic and thermophilic organisms. The endoglucanase J30 from glycoside hydrolase family 9 was originally identified through metagenomic analyses of compost-derived bacterial consortia. These studies, which were tailored to favor growth on targeted feedstocks, have already been shown to identify cellulases with considerable thermal tolerance. The amino-acid sequence of J30 shows comparably low identity to those of previously analyzed enzymes. As an enzyme that combines a well measurable activitymore » with a relatively low optimal temperature (50°C) and a modest thermal tolerance, it offers the potential for structural optimization aimed at increased stability. Here, the crystal structure of wild-type J30 is presented along with that of a designed triple-mutant variant with improved characteristics for industrial applications. Through the introduction of a structural Zn 2+ site, the thermal tolerance was increased by more than 10°C and was paralleled by an increase in the catalytic optimum temperature by more than 5°C.« less

Bifunctional role of leucine 300 of firefly luciferase in structural rigidity.

PubMed

Yousefi, Farzad; Ataei, Farangis; Mortazavi, Mojtaba; Hosseinkhani, Saman

2017-08-01

Firefly luciferase is susceptible to thermal inactivation, thereby its intracellular half-life decreased. Previous reports indicated that L 300 R mutation (LRR mutant) in E 354 R/Arg 356 double mutant (ERR mutant) from Lampyris turkestanicus luciferase has increased its thermal stability and rigidity through induction of some ionic bonds with Asp 270 and 271. Disruption of the deduced ionic bonds in an ultra-rigid mutant of firefly luciferase did not reverse the flexibility of the protein. In this study, we investigated the effects of this residue to find the truth behind an extraordinary increase in thermal stability and rigidity of luciferase after replacement of leucine 300 by arginine based on previous reports. For this purpose, L 300 R, L 300 K and L 300 E mutations were performed to compare the effects of these mutations on the native firefly luciferase. In spite of increase of intrinsic fluorescence of the mutants a slight increase in thermostability and retention of kinetic properties was observed. Based on our results, we can conclude that L 300 R mutation in LRR mutant accompanying with alteration in a flexible loop (352-359) increased thermostability and rigidity of luciferase. Copyright © 2017 Elsevier B.V. All rights reserved.

Physicochemical changes and microbial inactivation after high-intensity ultrasound processing of prebiotic whey beverage applying different ultrasonic power levels.

PubMed

Guimarães, Jonas T; Silva, Eric Keven; Alvarenga, Verônica O; Costa, Ana Letícia R; Cunha, Rosiane L; Sant'Ana, Anderson S; Freitas, Monica Q; Meireles, M Angela A; Cruz, Adriano G

2018-06-01

In this work, we investigated the effects of the ultrasonic power (0, 200, 400 and 600 W) on non-thermal processing of an inulin-enriched whey beverage. We studied the effects of high-intensity ultrasound (HIUS) on microbial inactivation (aerobic mesophilic heterotrophic bacteria (AMHB), total and thermotolerant coliforms and yeasts and molds), zeta potential, microstructure (optical microscopy, particle size distribution), rheology, kinetic stability and color. The non-thermal processing applying 600 W of ultrasonic power was comparable to high-temperature short-time (HTST) treatment (75 °C for 15 s) concerning the inactivation of AMHB and yeasts and molds (2 vs 2 log and 0.2 vs 0.4 log, respectively), although HIUS has reached a lower output temperature (53 ± 3 °C). The HIUS was better than HTST to improve beverage kinetic stability, avoiding phase separation, which was mainly attributed to the decrease of particles size, denaturation of whey proteins and gelation of polysaccharides (inulin and gellan gum). Thus, non-thermal processing by HIUS seems to be an interesting technology for prebiotic dairy beverages production. Copyright © 2018 Elsevier B.V. All rights reserved.

Enhanced Electrochemical and Thermal Transport Properties of Graphene/MoS2 Heterostructures for Energy Storage: Insights from Multiscale Modeling.

PubMed

Gong, Feng; Ding, Zhiwei; Fang, Yin; Tong, Chuan-Jia; Xia, Dawei; Lv, Yingying; Wang, Bin; Papavassiliou, Dimitrios V; Liao, Jiaxuan; Wu, Mengqiang

2018-05-02

Graphene has been combined with molybdenum disulfide (MoS 2 ) to ameliorate the poor cycling stability and rate performance of MoS 2 in lithium ion batteries, yet the underlying mechanisms remain less explored. Here, we develop multiscale modeling to investigate the enhanced electrochemical and thermal transport properties of graphene/MoS 2 heterostructures (GM-Hs) with a complex morphology. The calculated electronic structures demonstrate the greatly improved electrical conductivity of GM-Hs compared to MoS 2 . Increasing the graphene layers in GM-Hs not only improves the electrical conductivity but also stabilizes the intercalated Li atoms in GM-Hs. It is also found that GM-Hs with three graphene layers could achieve and maintain a high thermal conductivity of 85.5 W/(m·K) at a large temperature range (100-500 K), nearly 6 times that of pure MoS 2 [∼15 W/(m·K)], which may accelerate the heat conduction from electrodes to the ambient. Our quantitative findings may shed light on the enhanced battery performances of various graphene/transition-metal chalcogenide composites in energy storage devices.