WorldWideScience

Sample records for environmentally stable polyimides

  1. Polyimides: Thermally stable aerospace polymers

    Science.gov (United States)

    St.clair, A. K.

    1980-01-01

    An up to date review of available commercial and experimental high temperature polyimide resins which show potential for aerospace applications is presented. Current government research trends involving the use of polyimides as matrix resins for structural composites are discussed. Both the development of polyimides as adhesives for bonding metals and composites, and as films and coatings for use in an aerospace environment are reviewed. In addition, future trends for polyimides are proposed.

  2. Polyimide Cellulose Nanocrystal Composite Aerogels

    Science.gov (United States)

    Nguyen, Baochau N.; Meador, Mary Ann; Rowan, Stuart; Cudjoe, Elvis; Sandberg, Anna

    2014-01-01

    Polyimide (PI) aerogels are highly porous solids having low density, high porosity and low thermal conductivity with good mechanical properties. They are ideal for various applications including use in antenna and insulation such as inflatable decelerators used in entry, decent and landing operations. Recently, attention has been focused on stimuli responsive materials such as cellulose nano crystals (CNCs). CNCs are environmentally friendly, bio-renewable, commonly found in plants and the dermis of sea tunicates, and potentially low cost. This study is to examine the effects of CNC on the polyimide aerogels. The CNC used in this project are extracted from mantle of a sea creature called tunicates. A series of polyimide cellulose nanocrystal composite aerogels has been fabricated having 0-13 wt of CNC. Results will be discussed.

  3. Photosensitive Polyimides Having Aromatic Sulfonyoxyimide Groups in the Main Chain

    Energy Technology Data Exchange (ETDEWEB)

    Oh, S.Y.; Lee, J.Y. [Sogang University, Seoul (Korea); Cho, S.Y.; Chung, C.M. [Yonsei University, Wonju (Korea)

    2000-05-01

    Photosensitive polyimides having cyclobutane or phenyl and aromatic sulfonyloxyimide units in the main chain have been synthesized and the photodegradation behavior was investigated in relation with the polymer structure. The polyimides were prepared by condensation polymerization of N-hydroxyl and sulfonyl chloride. The prepared polyimides were stable up to 250 deg. C without thermal degradation. It has been found that the photodegradation of polyimides upon irradiation of 254 nm UV light results from scission of N-O bonds or ring opening of imides moiety by spectroscopic measurements. The polyimides were useful as positive working photodegradable polymers. Especially, the positive tone image of polyimide containing a pyromellitic diimide moiety exhibited high sensitivity and resolution. (author). 23 refs., 2 tabs., 8 figs.

  4. Synthesis and Characterization of Organosoluble, Thermal Stable and Hydrophobic Polyimides Derived from 4-(4-(1-pyrrolidinylphenyl-2,6-bis(4-(4-aminophenoxyphenylpyridine

    Directory of Open Access Journals (Sweden)

    Xiaohua Huang

    2017-10-01

    Full Text Available A novel aromatic diamine monomer, 4-(4-(1-pyrrolidinylphenyl-2,6-bis(4-(4-aminophenoxyphenylpyridine (PPAPP containing pyridine rings, pyrrolidine groups, and ether linkages, was successfully synthesized using 4-hydroxyacetophenone and 1-chloro-4-nitrobenzene as starting materials by three-step reactions, and then used to synthesize a series of polyimides by polycondensation with various aromatic dianhydrides via a two-step method. The structure of PPAPP was characterized by NMR, FT-IR, and mass spectrometry analysis methods. These polymers showed good solubility in common organic solvents (e.g., NMP, DMF, DMSO, and DMAc at room temperature or on heating. Moreover, they presented a high thermal stability with the glass transition temperature (Tgs exceeding 316 °C, as well as the temperature of 10% weight loss ranged from 552–580 °C with more than 67% residue at 800 °C under nitrogen. Furthermore, they also exhibited excellent hydrophobicity with a contact angle in the range of 85.6°–97.7°, and the results of Wide-Angle X-ray Diffraction (WAXD indicated that all of the polymers revealed an amorphous structure.

  5. The hydrolysis of polyimides

    Science.gov (United States)

    Hoagland, P. D.; Fox, S. W.

    1973-01-01

    Thermal polymerization of aspartic acid produces a polysuccinimide (I), a chain of aspartoyl residues. An investigation was made of the alkaline hydrolysis of the imide rings of (I) which converts the polyimide to a polypeptide. The alkaline hydrolysis of polyimides can be expected to be kinetically complex due to increasing negative charge generated by carboxylate groups. For this reason, a diimide, phthaloyl-DL-aspartoyl-beta-alanine (IIA) was synthesized for a progressive study of the hydrolysis of polyimides. In addition, this diimide (IIA) can be related to thalidomide and might be expected to exhibit similar reactivity during hydrolysis of the phthalimide ring.

  6. Polyimide Aerogel Thin Films

    Science.gov (United States)

    Meador, Mary Ann; Guo, Haiquan

    2012-01-01

    Polyimide aerogels have been crosslinked through multifunctional amines. This invention builds on "Polyimide Aerogels With Three-Dimensional Cross-Linked Structure," and may be considered as a continuation of that invention, which results in a polyimide aerogel with a flexible, formable form. Gels formed from polyamic acid solutions, end-capped with anhydrides, and cross-linked with the multifunctional amines, are chemically imidized and dried using supercritical CO2 extraction to give aerogels having density around 0.1 to 0.3 g/cubic cm. The aerogels are 80 to 95% porous, and have high surface areas (200 to 600 sq m/g) and low thermal conductivity (as low as 14 mW/m-K at room temperature). Notably, the cross-linked polyimide aerogels have higher modulus than polymer-reinforced silica aerogels of similar density, and can be fabricated as both monoliths and thin films.

  7. Environmental and biomedical applications of natural metal stable isotope variations

    Science.gov (United States)

    Bullen, T.D.; Walczyk, T.

    2009-01-01

    etal stable isotopes are now being used to trace metal contaminants in the environment and as indicators of human systemic function where metals play a role. Stable isotope abundance variations provide information about metal sources and the processes affecting metals in complex natural systems, complementing information gained from surrogate tracers, such as metal abundance ratios or biochemical markers of metal metabolism. The science is still in its infancy, but the results of initial studies confirm that metal stable isotopes can provide a powerful tool for forensic and biomedical investigations.

  8. Acetylene-Terminated Polyimide Siloxanes

    Science.gov (United States)

    St. Clair, Terry L.; Maudgal, Shubba

    1987-01-01

    Siloxane-containing addition polyimides yield toughened high-temperature adhesives and matrix resins. Addition polyimide made by reaction of aromatic tetracarboxylic acid dianhydride with aromatic diamine in presence of ethynyl-substituted aromatic monoamine. Acetylene-terminated siloxane imide cured by heating to yield acetylene-terminated polyimide siloxane.

  9. USE OF STABLE ISOTOPES IN ENVIRONMENTAL AND FORENSIC GEOCHEMISTRY STUDIES

    Science.gov (United States)

    Stable carbon and hydrogen isotopes have been used for many decades in the petroleum industry, but the development of combined gas chromatography-isotope ratio mass spectrometry (GCIRMS) has led to a virtual explosion in application of this technique not only in petroleum explora...

  10. Engineering Environmentally-Stable Proteases to Specifically Neutralize Protein Toxins

    Science.gov (United States)

    2013-10-01

    amplifying cascades. These include hydroxide (pH), fluoride, and nitrite. Nitrite is an indicator of many disease states, as it is a stable oxidation...6582-6598. (10) McPhalen, C. A., Schnebli, H. P., and James, M. N. (1985) Crystal and molecular structure of the inhibitor eglin from leeches in

  11. Lanthanide-containing polyimides

    Science.gov (United States)

    Stoakley, D. M.; St. Clair, Anne K.

    1987-01-01

    The preparation of a variety of lanthanide-containing polyimide films is described, and results of their characterization are presented. The properties investigated include the glass transition temperature, thermooxidative stability, magnetic susceptibility, and electrical conductivity of the polymer. Films containing lanthanide chlorides, fluorides, and sulfides are flexible, but those containing lanthanide nitrates are extremely brittle. The addition of lanthanide acetates and acetylacetonates caused immediate gelation of two of the synthesis-mixture ingredients. It was found that, in general, the addition of lanthanide to the polyimide increases the density and glass transition temperature of the polymer but slightly decreases the thermooxidative stability.

  12. Stable oligonucleotide-functionalized gold nanosensors for environmental biocontaminant monitoring.

    Science.gov (United States)

    Riquelme, Maria V; Leng, Weinan; Carzolio, Marcos; Pruden, Amy; Vikesland, Peter

    2017-12-01

    The global propagation of environmental biocontaminants such as antibiotic resistant pathogens and their antibiotic resistance genes (ARGs) is a public health concern that highlights the need for improved monitoring strategies. Here, we demonstrate the environmental stability and applicability of an oligonucleotide-functionalized gold nanosensor. The mecA ARG was targeted as model biocontaminant due to its presence in clinically-relevant pathogens and to its emergence as an environmental contaminant. mecA-specific nanosensors were tested for antibiotic resistance gene (ARG) detection in ARG-spiked effluent from four wastewater treatment plants (WWTPs). The mecA-specific nanosensors showed stability in environmental conditions and in high ionic strength ([MgCl2]<50mM), and high selectivity against mismatched targets. Spectrophotometric detection was reproducible with an LOD of 70pM (≈4×107genes/μL), even in the presence of interferences associated with non-target genomic DNA and complex WWTP effluent. This contribution supports the environmental applicability of a new line of cost-effective, field-deployable tools needed for wide-scale biocontaminant monitoring. Copyright © 2017. Published by Elsevier B.V.

  13. Identifying Seasonal Groundwater Recharge Using Environmental Stable Isotopes

    Directory of Open Access Journals (Sweden)

    Hsin-Fu Yeh

    2014-09-01

    Full Text Available In this study, the stable isotope values of oxygen and hydrogen were used to identify the seasonal contribution ratios of precipitation to groundwater recharge in the Hualien River basin of eastern Taiwan. The differences and correlations of isotopes in various water bodies were examined to evaluate the groundwater recharge sources for the Hualian River basin and the interrelations between groundwater and surface water. Proportions of recharge sources were calculated based on the results of the mass balance analysis of the isotope composition of hydrogen and oxygen in the basin. Mountain river water accounted for 83% and plain rainfall accounted for 17% of the groundwater recharge in the Huanlian River basin. Using the mean d-values, a comparison of d-values of precipitation and groundwater indicates the groundwater consists of 75.5% wet seasonal sources and 24.5% dry seasonal sources, representing a distinct seasonal variation of groundwater recharge in the study area. Comparisons between hydrogen and oxygen isotopes in rainwater showed that differences in the amount of rainfall resulted in depleted oxygen and hydrogen isotopes for precipitation in wet seasons as compared to dry seasons. The river water contained more depleted hydrogen and oxygen isotopes than was the case for precipitation, implying that the river water mainly came from the upstream catchment. In addition, the hydrogen and oxygen isotopes in the groundwater slightly deviated from the hydrogen and oxygen isotopic meteoric water line in Huanlian. Therefore, the groundwater in this basin might be a mixture of river water and precipitation, resulting in the effect of the river water recharge being greater than that of rainfall infiltration.

  14. Low Permeability Polyimide Insulation Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Resodyn Technologies proposes a new technology that enables the application of polyimide based cryogenic insulation with low hydrogen permeability. This effort...

  15. Recent developments in polyimide and bismaleimide adhesives

    Science.gov (United States)

    Politi, R. E.

    1985-01-01

    Research on high temperature resin systems has intensified. In the Aerospace Industry, the motivation for this increased activity has been to replace heat resistant alloys of aluminum, stainless steel and titanium by lighter weight glass and carbon fiber reinforced composites. Applications for these structures include: (1) engine nacelles involving long time exposure (thousands of hours) to temperatures in the 150 to 300 C range, (2) supersonic military aircraft involving moderately long exposure (hundreds of hours) to temperatures of 150 to 200 C, and (3) missile applications involving only brief exposure (seconds or minutes) to temperatures up to 500 C and above. Because of fatigue considerations, whenever possible, it is preferable to bond rather than mechanically fasten composite structures. For this reason, the increased usage of high temperature resin matrix systems for composites has necessitated the devlopment of compatible and equally heat stable adhesive systems. The performance of high temperature epoxy, epoxy phenolic and condensation polyimide adhesives is reviewed. This is followed by a discussion of three recently developed types of adhesives: (1) condensation reaction polyimides having improved processing characteristics; (2) addition reaction polyimides; and (3) bismaleimides.

  16. Organic light emitting diodes with environmentally and thermally stable doped graphene electrodes

    DEFF Research Database (Denmark)

    Kuruvila, Arun; Kidambi, Piran R.; Kling, Jens

    2014-01-01

    We present a comparative study of the environmental and thermal stability of graphene charge transfer doping using molybdenum– trioxide (MoO3), vanadium–pentoxide (V2O5) and tungsten–trioxide (WO3). Our results show that all these metal oxides allow a strong and stable p-type doping of graphene, ...

  17. Flexible polyimide fuel tank sealants

    Energy Technology Data Exchange (ETDEWEB)

    Jones, R.J.; Cassey, H.N.

    1978-01-01

    Requirements for elastomers or compliant polymers used as integral fuel tank sealant materials and as seals in high-performance military aircraft are examined, and a polyimide system with the appropriate properties is described. The system contains methylene dianiline, 4,4'-diaminostilbene, polyethyleneoxide diamine, and bis(4-(3,4-dicarboxyphenoxyl)phenyl) sulfone dianhydride. Development, preparation, and applications of the polyimide sealant are discussed.

  18. Winter environmental effects on dry-matter intake of stabled and unsheltered holstein cows

    Directory of Open Access Journals (Sweden)

    Antonio Cesar Alves Fagundes

    1995-03-01

    Full Text Available The purpose of this study was to verify the association of environment and feed intake and also to measure the variation on dry-matter intake of stabled and unsheltered holstein cows, as a function of temperature decrease, during the winter in humid subtropical climate. The experiment was developed in Santa Maria, State of Rio Grande do Sul, Brazil, during July and August, 1986. There were used 12 Holstein cows with ration based on corn silage fed for "ad libitum" consumption, distributed in two sets: stabled cows and cows maintened in padlots. The experimental design was completely randomized. The daily dry-matter intake of unsheltered cows (0.095 ± 0.006 kg/kg0.75, was significantly different (P< 0.01 from the stabled ones (0.077 ± 0.005 kg/kg0.75. There was significant correlation (P < 0.05 among dry-matter intake of unsheltered cows and environmental temperature, air humidity, wind velocity and precipitation, with coefficients varying from -0.58 to 0.51 while the feed intake of stabled cows was only correlated significantly (P < 0.05 with the environmental temperature at 7 a.m. with coefficient of -0.27. These results show that feed intake of Holstein cows kept in padlots was higher than in stabled cows, due to lower environmental temperatures, as high as 0.36 kgDM/cow for each unit of air temperature decrease and for each unit of increase of relative humidity and wind velocity at 7 a.m. and 9 p.m., simultaneously.

  19. Seasonal variation in stable carbon and nitrogen isotope values of bats reflect environmental baselines.

    Directory of Open Access Journals (Sweden)

    Ana G Popa-Lisseanu

    Full Text Available The stable carbon and nitrogen isotope composition of animal tissues is commonly used to trace wildlife diets and analyze food chains. Changes in an animal's isotopic values over time are generally assumed to indicate diet shifts or, less frequently, physiological changes. Although plant isotopic values are known to correlate with climatic seasonality, only a few studies restricted to aquatic environments have investigated whether temporal isotopic variation in consumers may also reflect environmental baselines through trophic propagation. We modeled the monthly variation in carbon and nitrogen isotope values in whole blood of four insectivorous bat species occupying different foraging niches in southern Spain. We found a common pattern of isotopic variation independent of feeding habits, with an overall change as large as or larger than one trophic step. Physiological changes related to reproduction or to fat deposition prior to hibernation had no effect on isotopic variation, but juvenile bats had higher δ13C and δ15N values than adults. Aridity was the factor that best explained isotopic variation: bat blood became enriched in both 13C and 15N after hotter and/or drier periods. Our study is the first to show that consumers in terrestrial ecosystems reflect seasonal environmental dynamics in their isotope values. We highlight the danger of misinterpreting stable isotope data when not accounting for seasonal isotopic baselines in food web studies. Understanding how environmental seasonality is integrated in animals' isotope values will be crucial for developing reliable methods to use stable isotopes as dietary tracers.

  20. PMR polyimide composites for aerospace applications

    Science.gov (United States)

    Serafini, T. T.

    1982-01-01

    Fiber reinforced PMR polyimides are finding increased acceptance as engineering materials for high performance structural applications. Prepreg materials based on this novel class of highly processable, high temperature resistant polyimides, are commercially available and the PMR concept was incorporated in several industrial applications. The status of PMR polyimides is reviewed. Emphasis is given to the chemistry, processing, and applications of the first generation PMR polyimides known as PMR-15.

  1. Polyimide resin composites via in situ polymerization of monomeric reactants

    Science.gov (United States)

    Cavano, P. J.

    1974-01-01

    Thermo-oxidatively stable polyimide/graphite-fiber composites were prepared using a unique in situ polymerization of monomeric reactants directly on reinforcing fibers. This was accomplished by using an aromatic diamine and two ester-acids in a methyl alcohol solvent, rather than a previously synthesized prepolymer varnish, as with other A-type polyimides. A die molding procedure was developed and a composite property characterization conducted with high modulus graphite fiber tow. Flexure, tensile, compressive, and shear tests were conducted at temperatures from 72 to 650 F on laminates before and after exposures at the given temperatures in an air environment for times up to 1000 hours. The composite material was determined to be oxidatively, thermally, and hydrolytically stable.

  2. Bonded polyimide fuel cell package

    Science.gov (United States)

    Morse, Jeffrey D.; Jankowski, Alan; Graff, Robert T.; Bettencourt, Kerry

    2010-06-08

    Described herein are processes for fabricating microfluidic fuel cell systems with embedded components in which micron-scale features are formed by bonding layers of DuPont Kapton.TM. polyimide laminate. A microfluidic fuel cell system fabricated using this process is also described.

  3. Engineering of air-stable Fe/C/Pd composite nanoparticles for environmental remediation applications

    Science.gov (United States)

    Haham, Hai; Grinblat, Judith; Sougrati, Moulay-Tahar; Stievano, Lorenzo; Margel, Shlomo

    2015-09-01

    The present manuscript presents a convenient method for the synthesis of iron/carbon (Fe/C) nanoparticles (NPs) coated with much smaller Pd NPs for the removal of halogenated organic pollutants. For this purpose, iron oxide/polyvinylpyrrolidone (IO/PVP) NPs were first prepared by the thermal decomposition of ferrocene mixed with PVP at 350 °C under an inert atmosphere. IO,Fe/C and Fe/C NPs coated with graphitic and amorphous carbon layers were then produced by annealing the IO/PVP NPs at 500 and 600 °C, respectively, under an inert atmosphere. The effect of the annealing temperature on the chemical composition, shape, crystallinity, surface area and magnetic properties of the IO/PVP, IO,Fe/C and Fe/C NPs has been elucidated. Air-stable Fe/C/Pd NPs were produced by mixing the precursor palladium acetate with the air-stable Fe/C NPs in ethanol. The obtained Fe/C/Pd NPs demonstrated significantly higher environmental activity than the Fe/C NPs on eosin Y, a model halogenated organic pollutant. The environmental activity of the Fe/C/Pd NPs also increased with their increasing Pd content.

  4. Engineering of air-stable Fe/C/Pd composite nanoparticles for environmental remediation applications

    Energy Technology Data Exchange (ETDEWEB)

    Haham, Hai; Grinblat, Judith [Institute of Nanotechnology and Advanced Materials, Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900 (Israel); Sougrati, Moulay-Tahar; Stievano, Lorenzo [Institute Charles Gerhardt (UMR 5253 CNRS), Université Montpellier 2, CC 1502, Place E. Bataillon, 34095 Montpellier, Cedex 5 (France); Margel, Shlomo, E-mail: shlomo.margel@mail.biu.ac.il [Institute of Nanotechnology and Advanced Materials, Department of Chemistry, Bar-Ilan University, Ramat-Gan 52900 (Israel)

    2015-09-01

    The present manuscript presents a convenient method for the synthesis of iron/carbon (Fe/C) nanoparticles (NPs) coated with much smaller Pd NPs for the removal of halogenated organic pollutants. For this purpose, iron oxide/polyvinylpyrrolidone (IO/PVP) NPs were first prepared by the thermal decomposition of ferrocene mixed with PVP at 350 °C under an inert atmosphere. IO,Fe/C and Fe/C NPs coated with graphitic and amorphous carbon layers were then produced by annealing the IO/PVP NPs at 500 and 600 °C, respectively, under an inert atmosphere. The effect of the annealing temperature on the chemical composition, shape, crystallinity, surface area and magnetic properties of the IO/PVP, IO,Fe/C and Fe/C NPs has been elucidated. Air-stable Fe/C/Pd NPs were produced by mixing the precursor palladium acetate with the air-stable Fe/C NPs in ethanol. The obtained Fe/C/Pd NPs demonstrated significantly higher environmental activity than the Fe/C NPs on eosin Y, a model halogenated organic pollutant. The environmental activity of the Fe/C/Pd NPs also increased with their increasing Pd content. - Highlights: • Fe/C NPs were produced by thermal annealing of iron oxide/PVP NPs under Ar atmosphere. • Fe/C NPs were coated with a thin layer of smaller Pd NPs by reduction of a Pd precursor. • The environmental activity of the Fe/C/Pd NPs was demonstrated.

  5. Metalized polyimide filters for x-ray astronomy and other applications

    Science.gov (United States)

    Powell, Forbes R.; Keski-Kuha, Ritva A.; Zombeck, Martin V.; Goddard, Richard E.; Chartas, George; Townsley, Leisa K.; Moebius, Eberhard; Davis, John M.; Mason, Glenn M.

    1997-07-01

    Filters fabricated from metalized polyimide have been specified for a number of x-ray astronomy missions, including the Advanced X-ray Astrophysics Facility (AXAF), the x-ray spectrometer (XRS) on Astro-E, the Advanced Composition Explorer (ACE), and the Geostationary Operational Environmental Satellite (GOES). Polyimide offers greater strength, improved temperature stability, and effectiveness in blocking unwanted ultraviolet radiation compared to polymeric films previously employed. This paper reviews the various x- ray astronomy missions and the particular challenges that were met with polyimide filters. The paper also reviews the development of free standing thin foils of polyimide with mechanical properties optimized for x-ray astronomy and other applications, such as synchrotron research.

  6. Polyimide/polyamideimide composites from different polyimide precursors

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.B. [Chonnam National University, Kwangju (Korea); Choi, Y.H. [Kumho Industry Ltd., Kwangju (Korea); Yim, B.T.; Park, J.S. [Kumho Petroleum Chemical Co., Taejeon (Korea)

    2001-03-01

    The various compositions of polyimide (PI)/polyamideimide (PAI) composites were prepared by heat treatment of the solvent cast PI precursors/PAI blends. The optical micrographs showed that a good compatibility was observed between poly(amic acid) (PAA) and PAI, but in the case of PAME/PAI mixtures, a phase separation apparently occurred due to the absence of ionic and/ or H{sub b}onding forces. Regardless of PI precursors, the similar tensile properties were observed. The tensile modulus of the composites were higher than that of the neat polyimide. The X-ray diffraction patterns of the composites showed that the chain rearrangement of PI was increased due to the plasticizing effect of PAI, which has lower glass transition temperature than that of PI, during thermal imidization process. (author)., 14 refs., 1 tab., 8 figs.

  7. Natural Gas Sweetening by Ultra-Microporous Polyimides Membranes

    KAUST Repository

    Alghunaimi, Fahd

    2017-05-01

    Most natural gas fields in Saudi Arabia contain around 10 mol.% carbon dioxide. The present technology to remove carbon dioxide is performed by chemical absorption, which has many drawbacks. Alternatively, membrane-based gas separation technology has attracted great interest in recent years due to: (i) simple modular design, (ii) potential cost effectiveness, (iii) ease of scale-up, and (iv) environmental friendliness. The state-of-the-art membrane materials for natural gas sweetening are glassy cellulose acetate and polyimide, which were introduced in the 1980s. In the near future, the kingdom is planning to boost its production of natural gas for power generation and increase the feedstock for new petrochemical plants. Therefore, the kingdom and worldwide market has an urgent need for better membrane materials to remove carbon dioxide from raw natural gas. The focus of this dissertation was to design new polyimide membrane materials for CO2/CH4 separation exhibiting high permeability and high selectivity relative to the standard commercial materials tested under realistic mixed-gas feed conditions. Furthermore, this study provided a fundamental understanding of structure/gas transport property relationships of triptycene-based PIM-polyimides. Optimally designed intrinsically microporous polyimide (PIM-PIs) membranes in this work exhibited drastically increased CO2/CH4 selectivities of up to ~75. In addition, a novel triptycene-based hydroxyl-containing polyimide (TDA1-APAF) showed 5-fold higher permeabilities over benchmark commercial materials such as cellulose acetate. Furthermore, this polyimide had a N2/CH4 selectivity of 2.3, thereby making it possible to simultaneously treat CO2- and N2-contaminated natural gas. Also, TDA1-APAF showed a CO2 permeability of 21 Barrer under binary 1:1 CO2/CH4 mixed-gas feed with a selectivity of 72 at a partial CO2 pressure of 10 bar which are significantly better than cellulose triacetate. These results suggest that TDA1

  8. Data-driven Approaches to Teaching Stable Isotopes in Hydrology and Environmental Geochemistry

    Science.gov (United States)

    Jefferson, A.; Merchant, W. R.; Dees, D.; Griffith, E. M.; Ortiz, J. D.

    2016-12-01

    Stable isotopes have revolutionized our understanding of watershed hydrology and other earth science processes. However, students may struggle to correctly interpret isotope ratios and few students understand how isotope measurements are made. New laser-based technologies lower the barrier to entry for giving students hands on experience with isotope measurements and data analysis. We hypothesizedthat integrating such activities into the curriculum would increase student content knowledge, perceptions, and motivation to learn. This project assessed the impact that different pedagogical approaches have on student learning of stable isotope concepts in upper-division geoscience courses. An isotope hydrograph separation module was developed and taught for a Watershed Hydrology course, and a Rayleigh distillation activity was developed and deployed for Environmental Geochemistry and Sedimentology/Stratigraphy classes. Groups of students were exposed to this content via (1) a lecture-only format; (2) a paper-based data analysis activity; and (3) hands-on data collection, sometimes including spectrometer analysis. Pre- and post-tests measured gains in content knowledge while approaches to learning and motivational questionnaires instruments were used to identify the effects of the classroom environment on learning approaches and motivation. Focus group interviews were also conducted to verify the quantitative data. All instructional styles appear to be equally effective at increasing student content knowledge of stable isotopes in the geosciences, but future studies need to move beyond "exam question" style assessment of learning. Our results may reflect that hands-on experiences are not new to upper-level geosciences students, because this is the way that many classes are taught in the geosciences (labs, field trips). Thus, active learning approaches may not have had the impact they would with other groups. The "messiness" of hands-on activities and authentic research

  9. A simple and stable method of tagging Agrobacterium fabrum C58 for environmental monitoring

    Directory of Open Access Journals (Sweden)

    Meriam BOURI

    2017-05-01

    Full Text Available Agrobacterium fabrum is one of the eleven Agrobacterium spp. complex species that has been observed to carry a Ti plasmid and induce crown gall, a disease causing significant damage to economically important perennial agricultural crops. Members of this species complex, including A. fabrum, are morphologically indistinguishable from one another on culture media and are known to grow together in soil and within host galls. Consequently, the tracking of this species in its natural environment requires a cautious approach to tagging strains without altering any of their ecologically important traits. A gentamicin resistant cassette (aacC1 was inserted, by homologous recombination, into a non-coding region of the A. fabrum C58 chromosome between the genes atu1182 and atu1183. The resultant strain did not show any significant in vitro growth differences compared to the wild-type strain, and the marker was stable in rich medium, both with and without selective pressure. The mutant/marked strain was indistinguishable from the parental strain for ability to induce galls, grow in bulk soil and colonize the rhizosphere of tomato plants. Easy, precise, safe and stable tagging of the A. fabrum C58 genome facilitates environmental population surveys by either simple selection or direct detection by PCR. This methodology provides understanding of the ecology of this species complex as an integral part of managing the soil microbiota for improved crown gall management.

  10. Optical waveguide components using fluorinated polyimides

    Science.gov (United States)

    Ishibashi, Shigeki; Takahara, Hideyuki

    1999-10-01

    Polyimides are widely used in electronics as heat-resistant organic materials and are now being studied for possible use in optical components. The fluorinated polyimides developed by NTT have high transparency at telecommunication wavelengths, a controllable index of refraction, and high thermal stability, making them suitable for use in optical communication systems. Here, optical components developed using fluorinated polyimides are reviewed, and the relationships between the material characteristics and the device parameters are discussed.

  11. PMR polyimides-review and update

    Science.gov (United States)

    Serafini, T. T.; Delvigs, P.; Alston, W. B.

    1982-01-01

    Fiber reinforced PMR polyimides are finding increased acceptance as engineering materials for high performance structural applications. Prepreg materials based on this novel class of highly processable, high temperature resistant polyimides are commercially available and the PMR concept is used by other investigators. The current status of first and second generation PMR polyimides were reviewed. Emphasis is given to the chemistry, processing and applications of the first generation material known as PMR-15.

  12. Gold recovery process from polyimide film

    Science.gov (United States)

    Houston, D. W.; Okamoto, G.

    1977-01-01

    Process economically separates gold from goldized polyimide film and other nonmetallic scrap without hazards of conventional processes. Technique uses nitric acid to destroy nonmetallic material, leaving gold intact.

  13. Use of polyimides in VLSI fabrication

    Science.gov (United States)

    Wilson, A. M.

    The functional requirements of overcoats and multilevel insulators for very large scale integrated circuits (VLSI) are outlined. The moisture barrier properties of polyimide films are reviewed. Polyimide performance vs plasma enhanced chemically vapor deposited (CVD) silicon nitride overcoats are compared. The topological and via forming advantages of polyimides vs plasma enhanced CVD silicon oxide as a multilevel insulator are cited. The temperature and voltage field induced electronic charge transport and trapping at oxide interfaces is cited as the most serious limitation to the use of polyimides as multilevel insulators on VLSI chips.

  14. Excimer laser etching of polyimide

    Science.gov (United States)

    Brannon, J. H.; Lankard, J. R.; Baise, A. I.; Burns, F.; Kaufman, J.

    1985-09-01

    It is reported that thin films of polyimide are efficiently etched in air at pulsed excimer laser wavelengths of 248, 308, and 351 nm. Etch rate versus incident fluence data are found to obey a Beer-Lambert etching relation. Sharp laser fluence thresholds for significant etching are found to correlate with the wavelength-dependent absorption coefficient. The absorbed energy density required to initiate significant etching is found, within experimental error, to be independent of the wavelengths examined. It is felt that this information demonstrates the predominantly thermal nature of the laser etching mechanism. Additionally, infrared spectroscopy and coupled gas chromatography/mass spectroscopy were used to identify several gases evolved during pulsed laser etching of polyimide in both air and vacuum.

  15. The effect of polyimide imidization conditions on adhesion strength of thin metal films on polyimide substrates

    CERN Document Server

    Yoo, S H

    1999-01-01

    The effects of Ar sup + RF plasma precleaning and polyimide curing conditions on the peel strength between Al thin films and polyimides have been studied. The BPDA-PDA polyimide precursor of PI-2611 (Du pont) was spin-coated and cured under various imidization conditions. The cured polyimide substrates were in-situ AR sup + RF plasma cleaned prior to metal deposition. Al-1 % Si-0.5 % Cu thin films were deposited onto the polyimide substrates by using DC magnetron sputtering. The peel strength was enhanced by Ar sup + RF plasma precleaning. The Al/modified PI specimen failed cohesively in the polyimide. The polyimide curing conditions strongly affect the peel strength in the Al/modified PI system.

  16. Polyimide-Foam/Aerogel Composites for Thermal Insulation

    Science.gov (United States)

    Williams, Martha; Fesmire, James; Sass, Jared; Smith, Trent; Weoser. Erol

    2009-01-01

    Composites of specific types of polymer foams and aerogel particles or blankets have been proposed to obtain thermal insulation performance superior to those of the neat polyimide foams. These composites have potential to also provide enhanced properties for vibration dampening or acoustic attenuation. The specific type of polymer foam is denoted "TEEK-H", signifying a series, denoted H, within a family of polyimide foams that were developed at NASA s Langley Research Center and are collectively denoted TEEK (an acronym of the inventors names). The specific types of aerogels include Nanogel aerogel particles from Cabot Corporation in Billerica, MA. and of Spaceloft aerogel blanket from Aspen Aerogels in Northborough, MA. The composites are inherently flame-retardant and exceptionally thermally stable. There are numerous potential uses for these composites, at temperatures from cryogenic to high temperatures, in diverse applications that include aerospace vehicles, aircraft, ocean vessels, buildings, and industrial process equipment. Some low-temperature applications, for example, include cryogenic storage and transfer or the transport of foods, medicines, and chemicals. Because of thermal cycling, aging, and weathering most polymer foams do not perform well at cryogenic temperatures and will undergo further cracking over time. The TEEK polyimides are among the few exceptions to this pattern, and the proposed composites are intended to have all the desirable properties of TEEK-H foams, plus improved thermal performance along with enhanced vibration or acoustic-attenuation performance. A composite panel as proposed would be fabricated by adding an appropriate amount of TEEK friable balloons into a mold to form a bottom layer. A piece of flexible aerogel blanket material, cut to the desired size and shape, would then be placed on the bottom TEEK layer and sandwiched between another top layer of polyimide friable balloons so that the aerogel blanket would become

  17. Sensitization of photoconductive polyimides for photovoltaic applications

    NARCIS (Netherlands)

    Mühlbacher, D.; Brabec, C.J.; Sariciftci, N.S.; Kotov, B.V.; Berendyaev, V.I.; Rumyantsev, B.M.; Hummelen, J.C.

    2001-01-01

    Soluble polyimides based on the N,N'-bis-(4-aminophenyl)-N,N'-diphenylbenzidine with a linkage between the phtalimide groups X = O, - , SO2, CO are investigated for their photovoltaic properties. Sensitization of these photoconductive polyimids with different small molecules like Rhodamine 6G as

  18. Coupled Environmental Processes in the Mojave Desert and Implications for ET Covers as Stable Landforms

    Energy Technology Data Exchange (ETDEWEB)

    D. Shafer; M. Y oung; S. Zitzer; E. McDonald; T. Caldwell

    2006-01-18

    Monolayer evapotranspiration (ET) covers are the baseline method for closure of disposal sites for low-level radioactive waste (LLW), mixed LLW, and transuranic (TRU) waste at the Nevada Test Site (NTS). The regulatory timeline is typically 1,000 years for LLW and 10,000 years for TRU waste. Covers for such waste have different technical considerations than those with shorter timelines because they are subject to environmental change for longer periods of time, and because the environmental processes are often coupled. To evaluate these changes, four analog sites (approximately 30, 1,000 to 2,000, 7,000 to 12,500, and 125,000 years in age) on the NTS were analyzed to address the early post-institutional control period (the youngest site), the 1,000-year compliance period for disposal of LLW, and the 10,000-year period for TRU waste. Tests included soil texture, structure, and morphology; surface soil infiltration and hydraulic conductivity; vegetation and faunal surveys; and literature reviews. Separate measurements were made in plant undercanopy and intercanopy areas. The results showed a progressive increase in silt and clay content of surface soils with age. Changes in soil texture and structure led to a fivefold decline in saturated hydraulic conductivity in intercanopy areas, but no change in undercanopies, which were subject to bioturbation. These changes may have been responsible for the reduction in total plant cover, most dramatically in intercanopy areas, primarily because more precipitation either runs off the site or is held nearer to the surface where plant roots are less common. The results suggest that covers may evolve over longer timeframes to stable landforms that minimize the need for active maintenance.

  19. Electro-optic side-chain polyimide system with large optical nonlinearity and high thermal stability

    Science.gov (United States)

    Sotoyama, Wataru; Tatsuura, Satoshi; Yoshimura, Tetsuzo

    1994-04-01

    We report electro-optic (EO) efficiency and thermal stability of a poled polyimide system with nonlinear optical dyes as side chains. The side-chain polyimide system is synthesized from a dianhydride containing azobenzene dye and a diamine. The dye in the polymer is chemically stable for temperatures below 250 °C. The polymer can be poled simultaneously with or after imidization of the polyamic acid. Our sample poled after imidization shows a large EO coefficient (r33=10.8 pm/V at λ=1.3 μm) and long-term thermal stability at 120 °C.

  20. PMR polyimide composites for aerospace applications. [Polymerization of Monomer Reactants

    Science.gov (United States)

    Serafini, T. T.

    1984-01-01

    A novel class of addition-type polyimides has been developed in response to the need for high temperature polymers with improved processability. The new plastic materials are known as PMR (for in situ polymerization of monomer reactants) polyimides. The highly processable PMR polyimides have made it possible to realize much of the potential of high temperature resistant polymers. Monomer reactant combinations for several PMR polyimides have been identified. The present investigation is concerned with a review of the current status of PMR polyimides. Attention is given to details of PMR polyimide chemistry, the processing of composites and their properties, and aerospace applications of PMR-15 polyimide composites.

  1. Potential uses of stable isotope ratios of Sr, Nd, and Pb in geological materials for environmental studies.

    Science.gov (United States)

    Nakano, Takanori

    2016-01-01

    The ratios of stable isotopes of certain elements in rocks and minerals have strong regional characteristics that are reflected in atmospheric components, in water, and in the living organisms that form Earth's surface environment as well as in agricultural and fishery products. Geologically derived stable isotope ratios can be used as a tracer for the source of many kinds of substances, with current geochemical techniques allowing the precise determination of numerous stable isotope ratios in both natural and manmade objects. This review presents examples of the use of stable isotopes as tracers within diverse dynamic ecosystems, focusing on Sr isotopes but also including examples of Nd and Pb isotopic analysis, and reviewing the potential of this technique for a wide range of environmental research, including determining the geographic origin of food and archeological materials.

  2. The development of aerospace polyimide adhesives

    Science.gov (United States)

    St.clair, A. K.; St.clair, T. L.

    1983-01-01

    Few materials are available which can be used as aerospace adhesives at temperatures in the range of 300 C. The Materials Division at NASA-Langley Research Center developed several high temperature polyimide adhesives to fulfill the stringent needs of current aerospace programs. These adhesives are the result of a decade of basic research studies on the structure property relationships of both linear and addition aromatic polyimides. The development of both in house and commercially available polyimides is reviewed with regards to their potential for use as aerospace adhesives.

  3. Optical polyimides for single-mode waveguides

    Science.gov (United States)

    Beuhler, Allyson J.; Wargowski, David A.; Kowalczyk, Tony C.; Singer, Kenneth D.

    1993-07-01

    The synthesis and optical characterization of fluorinated polyimide systems with potential use in passive waveguides and electro-optic devices is reported. The effect of fluorination on optical properties such as refractive index, birefringence, and near-infrared absorbance is reviewed in terms of optical performance requirements. Synthetic methods of tuning the refractive index in order to achieve appropriate core/cladding differentials is discussed. The relation between processing parameters and refractive index for several polyimide structures also is reported. We describe the microlithographic fabrication of a multilayer polyimide rib- type waveguide that is suitable for single mode guiding. The waveguide is fabricated using photosensitive polyimide systems via negative resist imaging. A comparison of wall profiles and resolution limits afforded by the wet-chemical patterning techniques is presented. Results on channel guide coupling, propagation, and loss are described, as well as progress in producing active guides.

  4. Applications of isotopes. [Need and cost of stable iotopes for use as tracers in biomedical and environmental studies

    Energy Technology Data Exchange (ETDEWEB)

    Kirby-Smith, J.S.

    1976-01-01

    Current and potential applications of stable isotopes as tracers in a number of biomedical and environmental areas are discussed. It is pointed out that a wide variety of problems exist in these fields whose solutions in principle are amenable to the isotopic approach. The number and diversity of these problems as well as the unique role stable isotopes can play in their solution illustrate the importance of achieving and maintaining a broad inventory of isotopic species. Experience has demonstrated unequivocally an additional overriding requirement for widespread exploration of stable isotopes by the scientific and technical community, i.e., the need for low cost availability of the materials in quantity. Some representative applications of /sup 12/C, /sup 13/C, /sup 14/N, /sup 15/N, /sup 16/O, /sup 17/O, and /sup 18/O are discussed.

  5. Slotted Polyimide-Aerogel-Filled-Waveguide Arrays

    Science.gov (United States)

    Rodriguez-Solis, Rafael A.; Pacheco, Hector L.; Miranda, Felix A.; Meador, Mary Ann B.

    2013-01-01

    This presentation discussed the potential advantages of developing Slotted Waveguide Arrays using polyimide aerogels. Polyimide (PI) aerogels offer great promise as an enabling technology for lightweight aerospace antenna systems. PI aerogels are highly porous solids possessing low density and low dielectric permittivity combined with good mechanical properties. For slotted waveguide array applications, there are significant advantages in mass that more than compensate for the slightly higher loss of the aerogel filled waveguide when compared to state of practice commercial waveguide.

  6. Mechanical property degradation of graphite/polyimide composites after exposure to moisture or shuttle orbiter fluids

    Science.gov (United States)

    Lisagor, W. B.

    1979-01-01

    The effects of moisture exposure on the mechanical properties of graphite polyimide systems are presented. The mechanism of the degradation and the magnitude of the affect associated with specific mechanical properties is investigated. An experimental effort involving exposure to selected environmental variables and subsequent mechanical property testing and analysis is included.

  7. Dianhydrides, polyimides, methods of making each, and methods of use

    KAUST Repository

    Ma, Xiaohua

    2015-01-08

    Embodiments of the present disclosure provide for an aromatic dianhydride, a method of making an aromatic dianhydride, an aromatic dianhydride-based polyimide, a method of making an aromatic dianhydride-based polyimide, and the like.

  8. Electrical conduction of polyimide films prepared from polyamic acid (PAA and pre-imidized polyimide (PI solution

    Directory of Open Access Journals (Sweden)

    2007-07-01

    Full Text Available Electrical conduction characteristics in two different polyimide films prepared by the imidization of polyamic acid (PAA and pre-imidized polyimide (PI solution were investigated. It is found that the current density of the polyimide film from PAA was higher than that of the polyimide film from PI at the same electric field, even though the conduction mechanism in both polyimide films follows the ionic hopping model. The hopping distance was calculated to be 2.8 nm for PAA type and 3.2 nm for PI type polyimide film. It is also found that the decay rate of the residual electrostatic charges on the polyimide films becomes faster in the PAA type than in the PI type polyimide film.

  9. Stable isotopic analysis of fossil chironomids as an approach to environmental reconstruction: state of development and future challenges

    Directory of Open Access Journals (Sweden)

    Oliver Heiri

    2012-10-01

    Full Text Available Remains of chironomid larvae, especially their strongly sclerotized head capsules, can be found abundantly and well preserved in most lake sediment records. These remains mainly consist of chitin and proteins and, since their chemical composition does not seem to be strongly affected by decompositional processes, they can be used to develop palaeoenvironmental reconstructions based on their stable isotopic composition. Here we review available stable isotope studies based on fossil chironomids and indicate future research necessary to further develop this still relatively new research approach. Efforts to produce stable isotope records based on fossil chironomids have mainly examined the elements H, N, C, and O. They have focussed on (1 developing the methodology for preparing samples for isotopic analysis, (2 laboratory studies cultivating chironomid larvae under controlled conditions to determine the factors affecting their stable isotopic composition, (3 ecosystem-scale studies relating stable isotopic measurements of fossil chironomid assemblages to environmental conditions, and (4 developing first down-core records describing past changes in the stable isotopic composition of chironomid assemblages. These studies have shown that chemical sample pretreatment may affect the isotopic composition for some elements. Laboratory runs suggest that the diet of the larvae influences their stable isotopic composition for H, N, C and O, whereas stable isotopes in the ambient water also strongly influence their oxygen and to a lesser extent hydrogen isotopic composition. These experiments also indicate only minor offsets between the nitrogen and carbon isotopic composition of chironomid soft tissue and the fossilizing head capsules, whereas for hydrogen and oxygen this offset remains to be explored. Though few datasets have been published, the available ecosystem studies and developed down-core sediment records indicate that stable isotopes in

  10. Fiber study involving a polyimide matrix

    Energy Technology Data Exchange (ETDEWEB)

    Cano, R.J. [NASA Langley Research Center, Hampton, VA (United States); Rommel, M. [Northop Grumman Corp., Pico Rivera, CA (United States); Hinkley, J.A.; Estes, E.D. [NASA Langley Research Center, Hampton, VA (United States)

    1996-12-31

    Mechanical properties are presented for eight different intermediate modulus carbon fiber/ polyimide matrix composites. Two unsized carbon fibers (Thornel T650-42 and Hercules IM9) and two sized carbon fibers (high temperature sized Thornel T650-42 HTS and epoxy sized Toray T1000) were prepregged on the NASA LaRC Multipurpose Tape Machine using the NASA LaRC developed polyimide resin matrix, LaRC{trademark}-PETI-5, and the DuPont developed Avitnid{reg_sign} R1-16. Composite panels fabricated from these prepregs were evaluated to determine their mechanical properties. The data show the effects of using sized fibers on the processing and mechanical properties of polyimide composites.

  11. Polyimides Derived from Novel Asymmetric Benzophenone Dianhydrides

    Science.gov (United States)

    Chuang, Chun-Hua (Inventor)

    2015-01-01

    This invention relates to the composition and processes for preparing thermoset polyimides derived from an asymmetric dianhydride, namely 2,3,3',4'-benzophenone dianhydride (a-BTDA) with at least one diamine, and a monofunctional terminal endcaps. The monofunctional terminating groups include 4-phenylethynylphthalic anhydride ester-acid derivatives, phenylethyl trimellitic anhydride (PETA) and its ester derivatives as well as 3-phenylethynylaniline. The process of polyimide composite comprises impregnating monomer reactants of dianhydride or its ester-acid derivatives, diamine and with monofunctional reactive endcaps into glass, carbon, quartz or synthetic fibers and fabrics, and then stack up into laminates and subsequently heated to between 150-375.degree. C. either at atmosphere or under pressure to promote the curing and crosslinking of the reactive endcaps to form a network of thermoset polyimides.

  12. Stable Tagging of Rhizobium meliloti with the Firefly Luciferase Gene for Environmental Monitoring

    Science.gov (United States)

    Cebolla, Angel; Ruiz-Berraquero, Francisco; Palomares, Antonio Jose

    1993-01-01

    A system for stable tagging of gram-negative bacteria with the firefly luciferase gene, luc, is described. A previously constructed fusion constitutively expressing luc from the λpR promoter was used. Stable integration into the bacterial genome was achieved by use of mini-Tn5 delivery vectors. The procedure developed was applied for tagging of representative gram-negative bacteria, such as Escherichia coli, Rhizobium meliloti, Pseudomonas putida, and Agrobacterium tumefaciens. The system permitted the detection of tagged R. meliloti in the presence of more than 105 CFU per plate without the use of any selective markers (such as antibiotic resistance genes). No significant differences in growth rates or soil survival were found between the marked strain and the wild-type strain. Studies of bioluminescent R. meliloti also revealed a good correlation between cell biomass and bioluminescence. The firefly luciferase tagging system is an easy, safe, and sensitive method for the detection and enumeration of bacteria in the environment. Images PMID:16349015

  13. HPLC for quality control of polyimides

    Science.gov (United States)

    Young, P. R.; Sykes, G. F.

    1979-01-01

    High Pressure Liquid Chromatography (HPLC) as a quality control tool for polyimide resins and prepregs are presented. A data base to help establish accept/reject criteria for these materials was developed. This work is intended to supplement, not replace, standard quality control tests normally conducted on incoming resins and prepregs. To help achieve these objectives, the HPLC separation of LARC-160 polyimide precursor resin was characterized. Room temperature resin aging effects were studied. Graphite reinforced composites made from fresh and aged resin were fabricated and tested to determine if changes observed by HPLC were significant.

  14. Are genetic and environmental influences on job satisfaction stable over time? A three-wave longitudinal twin study.

    Science.gov (United States)

    Li, Wen-Dong; Stanek, Kevin C; Zhang, Zhen; Ones, Deniz S; McGue, Matt

    2016-11-01

    Job satisfaction research has unfolded as an exemplary manifestation of the "person versus environment" debate in applied psychology. With the increasing recognition of the importance of time, it is informative to examine a question critical to the dispositional view of job satisfaction: Are genetic influences on job satisfaction stable across different time points? Drawing upon dispositional and situational perspectives on job satisfaction and recent research in developmental behavioral genetics, we examined whether the relative potency of genetic (i.e., the person) and environmental influences on job satisfaction changed over time in a 3-wave longitudinal twin study. Biometric behavioral genetics analyses showed that genetic influences accounted for 31.2% of the variance in job satisfaction measured at approximately Age 21, which was markedly greater than the 18.7% and 19.8% of variance explained by genetic factors at Age 25 and Age 30. Such genetic influences were mediated via positive affectivity and negative affectivity, but not via general mental ability. After partialing out genetic influences, environmental influences on job satisfaction were related to interpersonal conflict at work and occupational status, and these influences were relatively stable across the 3 time points. These results offer important implications for organizations and employees to better understand and implement practices to enhance job satisfaction. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

  15. Review of Polyimides Used in the Manufacturing of Micro Systems

    Science.gov (United States)

    Wilson, William C.; Atkinson, Gary M.

    2007-01-01

    Since their invention, polyimides have found numerous uses in MicroElectroMechanical Systems (MEMS) technology. Polyimides can act as photoresist, sacrificial layers, structural layers, and even as a replacement for silicon as the substrate during MEMS fabrication. They enable fabrication of both low and high aspect ratio devices. Polyimides have been used to fabricate expendable molds and reusable flexible molds. Development of a variety of devices that employ polyimides for sensor applications has occurred. Micro-robotic actuator applications include hinges, thermal actuators and residual stress actuators. Currently, polyimides are being used to create new sensors and devices for aerospace applications. This paper presents a review of some of the many uses of polyimides in the development of MEMS devices, including a new polyimide based MEMS fabrication process.

  16. Stable isotope signatures and element stoichiometry of Fucus vesiculosus as indicators for environmental conditions in the Kiel Bight, Baltic Sea

    Science.gov (United States)

    Winde, Vera; Mahler, Annika; Voss, Maren; Böttcher, Michael E.

    2014-05-01

    In the frame of the BMBF project BIOACID II we aim for an understanding of the natural distribution and variation of isotopic composition and C-N-S stoichiometry in Fucus vesiculosus growing around the coast line of the Kiel fjord (part of the Kiel bight). Environmental conditions (aquatic chemistry, temperature, salinity) were monitored, too. Some changes in aquatic chemistry are related to stress factors like human activity (e.g., waste input) and further factors leading to specific changes in the composition of Fucus vesiculosus. Sampling was carried out at different stations at the west and east coast of the Kiel Fjord. For each sampling station the aquatic chemistry (TA, pH, salinity, d13C(DIC), main and trace elements and nutrients) as well as the composition of the Fucus organic tissues (stoichiometry and stable isotope composition of carbon, nitrogen) are analysed. The Fucus tissue was sampled in three size classes (small, medium, large). It is shown, that Fucus vesiculosus indicates clear differences in the N contents and stable isotopes between the west and the east site of the Kiel Fjord. Stable nitrogen isotope signatures in Fucus vesiculosus, are useful proxies to identify the influence factors in the Fucus habitat. From the data it is obtained that the influence of human activity (wastewater treatment plant, harbour), small stream and drainage channels, which flow from the near coastal area into the bight, leads to different Fucus vesiculosus compositions. In future work, it is intended to extend the investigation to trace element signatures to further estimate environmental impacts.

  17. Fabrication of polyimide shells by vapor phase deposition for use as ICF targets

    Energy Technology Data Exchange (ETDEWEB)

    Alfonso, E.L.; Tsai, F.Y.; Chen, S.H.; Gram, R.Q.; Harding, D.R. [Univ. of Rochester, NY (United States). Lab. for Laser Energetics

    1999-03-01

    Hollow polyimide shells, for use as ICF targets, were fabricated by co-depositing monomer precursors from the vapor phase onto bounced spherical mandrels. The process involved two stages: first, the deposited monomers (pyromellitic dianhydride and 4,4{prime}-oxydianiline) reacted on the mandrel surface to form polyamic acid; second, the mandrel was heated to 300 C to imidize the polyamic acid and to decompose the mandrel. During this latter process the decomposed mandrel diffused through the thermally stable coating, leaving a polyimide shell. Depositions were performed under low ({approximately}10{sup {minus}3} Torr) and high ({approximately}10{sup {minus}6} Torr) vacuum. Also, flat witness films of polyimide deposited on Si wafers and NaCl allowed the mechanical properties and chemical composition of the film during the heating cycle to be measured. Polyimide shells with diameters ranging from 700 to 950 {micro}m and wall thicknesses ranging from 2 to 13 {micro}m were produced. The shell`s sphericity was greater than 99%. Burst and buckle pressure tests on these shells yielded the estimated mechanical strength properties. The elastic modulus and tensile strength were {approximately}15 GPa and {approximately}300 MPa, respectively. The permeability of D{sub 2} through polyamic acid at 25 C was 7.4 {times} 10{sup {minus}17} mol{center_dot}m/m{sup 2}{center_dot}Pa{center_dot}s and increased to 6.4 {times} 10{sup {minus}16} mol{center_dot}m/m{sup 2}{center_dot}Pa{center_dot}s at 25 C upon curing the shell to 150 C. The permeability of D{sub 2} at 25 C through vapor-deposited polyimide flat films was measured to be 240 times greater than through the as-deposited polyamic acid, and about 7 times greater than through commercially available solution-cast Kapton.

  18. Late Pleistocene ecological, environmental and climatic reconstruction based on megafauna stable isotopes from northwestern Chilean Patagonia

    Science.gov (United States)

    González-Guarda, Erwin; Domingo, Laura; Tornero, Carlos; Pino, Mario; Hernández Fernández, Manuel; Sevilla, Paloma; Villavicencio, Natalia; Agustí, Jordi

    2017-08-01

    Stable isotope analyses have been performed on the bioapatite (δ13C; δ18O) and collagen (δ13C; δ15N) of four late Pleistocene South American megafaunal taxa (Notiomastodon platensis, Equus andium, cf. Hemiauchenia paradoxa and Xenarthra indet.) to evaluate paleoclimatic and paleoenvironmental conditions as well as paleoecological features of this time period. The analyzed megafauna was found at several locations in the northwestern Chilean Patagonia (38°-42°S, 74°-71°W). The bioapatite δ13C values indicated the presence of C3 vegetation ranging from forestal to woodland areas. The collagen δ15N values pointed to temperate and humid ecosystems, and to the consumption of shrubs, trees, grasses and sedges. Mean annual temperatures estimated from bioapatite δ18OPO4 values show a similarity to modern temperatures and suggested that the megafauna under study may have lived during warm stages (interstadials) of the late Pleistocene. When comparing our results with those obtained from other South American regions, we find that the diet of this particular Chilean megafauna appears to have been more influenced by resource availability than by the potential dietary range of the taxa.

  19. Durability of polyimide to titanium bonds

    NARCIS (Netherlands)

    Akram, M.; Jansen, K.M.B.; Bhowmik, S.; Ernst, L.J.

    2012-01-01

    Titanium and its alloys are usually bonded together using a high temperature resistant polyimide or epoxy adhesives. Such adhesives can withstand temperatures from 200°C to300°C. Earlier research work indicates that Surface modification of titanium with mechanical treatment and atmospheric pressure

  20. Porous Cross-Linked Polyimide Networks

    Science.gov (United States)

    Meador, Mary Ann B. (Inventor); Guo, Haiquan (Inventor)

    2015-01-01

    Porous cross-linked polyimide networks are provided. The networks comprise an anhydride end-capped polyamic acid oligomer. The oligomer (i) comprises a repeating unit of a dianhydride and a diamine and terminal anhydride groups, (ii) has an average degree of polymerization of 10 to 50, (iii) has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups, and (iv) has been chemically imidized to yield the porous cross-linked polyimide network. Also provided are porous cross-linked polyimide aerogels comprising a cross-linked and imidized anhydride end-capped polyamic acid oligomer, wherein the oligomer comprises a repeating unit of a dianhydride and a diamine, and the aerogel has a density of 0.10 to 0.333 g/cm.sup.3 and a Young's modulus of 1.7 to 102 MPa. Also provided are thin films comprising aerogels, and methods of making porous cross-linked polyimide networks.

  1. Application of polyimide actuator rod seals

    Science.gov (United States)

    Watermann, A. W.; Gay, B. F.; Robinson, E. D.; Srinath, S. K.; Nelson, W. G.

    1972-01-01

    Development of polyimide two-stage hydraulic actuator rod seals for application in high-performance aircraft was accomplished. The significant portion of the effort was concentrated on optimization of the chevron and K-section second-stage seal geometries to satisfy the requirements for operation at 450 K (350 F) with dynamic pressure loads varying between 200 psig steady-state and 1500 psig impulse cycling. Particular significance was placed on reducing seal gland dimension by efficiently utilizing the fatigue allowables of polyimide materials. Other objectives included investigation of pressure balancing techniques for first-stage polyimide rod seals for 4000 psig 450 K(350 F) environment and fabrication of a modular retainer for the two-stage combination. Seals were fabricated in 0.0254 m (1.0in.) and 0.0635 m (2.5in.) sizes and tested for structural integrity, frictional resistance, and endurance life. Test results showed that carefully designed second stages using polyimides could be made to satisfy the dynamic return pressure requirements of applications in high-performance aircraft. High wear under full system pressure indicated that further research is necessary to obtain an acceptable first-stage design. The modular retainer was successfully tested and showed potential for new actuator applications.

  2. Crack-resistant polyimide coating for high-capacity battery anodes

    Science.gov (United States)

    Li, Yingshun; Wang, Shuo; Lee, Pui-Kit; He, Jieqing; Yu, Denis Y. W.

    2017-10-01

    Electrode cracking is a serious problem that hinders the application of many next-generation high-capacity anode materials for lithium-ion batteries. Even though nano-sizing the material can reduce fracturing of individual particles, capacity fading is still observed due to large volume change and loss of contact in the electrode during lithium insertion and extraction. In this study, we design a crack-resistant high-modulus polyimide coating with high compressive strength which can hold multiple particles together during charge and discharge to maintain contact. The effectiveness of the coating is demonstrated on tin dioxide, a high-capacity large-volume-change material that undergoes both alloy and conversion reactions. The polyimide coating improves capacity retention of SnO2 from 80% to 100% after 80 cycles at 250 mA g-1. Stable capacity of 585 mAh g-1 can be obtained even at 500 mA g-1 after 300 cycles. Scanning electron microscopy and in-situ dilatometry confirm that electrode cracking is suppressed and thickness change is reduced with the coating. In addition, the chemically-stable polyimide film can separate the surface from direct contact with electrolyte, improving coulombic efficiency to ∼100%. We expect the novel strategy of suppressing electrode degradation with a crack-resistant coating can also be used for other alloy and conversion-based anodes.

  3. Plant Water Use and Environmental Stress on Two Opposite Slopes: from Water and Carbon Stable Isotopic Perspective

    Science.gov (United States)

    Guan, H.; Xu, X.; Skrzypek, G.; Simmons, C. T.

    2014-12-01

    Climate-soil-vegetation dynamics are among key research focuses in the emerging ecohydrology discipline. Topographic relieves on landscapes provide various hydroclimatic conditions to examine vegetation functions and its responses to climate variation and changes in a short distance. In this study, we investigate ecohydrologic processes on two slopes of contrasting orientation and soil conditions in a native vegetation catchment with mean annual precipitation of 716 mm in South Australia, using water and carbon stable isotopes. Throughfall, soil water, twig water, and groundwater stable isotopes were measured and integrated into an isotope incorporated soil-plant-atmosphere model to examine different plant water use patterns on two slopes with different environmental conditions. The focuses are on how ecosystems on the two slopes receive, store, and use soil moisture in different manners. On these two slopes, trees are under different water stresses. Both leaf and soil 13C/12C ratio were measured for the two slopes to examine if δ13C can be used as an water stress indicator in this small catchment, and if the potential difference in δ13C can be observed in the soil organic matter. We monitored one-year leaf δ13C of two tree species, Eucalyptus leucoxylon and Acacia pycnantha. Our results indicate that leaf δ13C reflects different water stress conditions between slopes, seasons, and different locations on the slopes.

  4. Design Analysis and Thermo-Mechanical Fatigue of a Polyimide Composite for Combustion Chamber Support

    Science.gov (United States)

    Thesken, J. C.; Melis, M.; Shin, E.; Sutter, J.; Burke, Chris

    2004-01-01

    Polyimide composites are being evaluated for use in lightweight support structures designed to preserve the ideal flow geometry within thin shell combustion chambers of future space launch propulsion systems. Principles of lightweight design and innovative manufacturing techniques have yielded a sandwich structure with an outer face sheet of carbon fiber polyimide matrix composite. While the continuous carbon fiber enables laminated skin of high specific stiffness; the polyimide matrix materials ensure that the rigidity and durability is maintained at operation temperatures of 316 C. Significant weight savings over all metal support structures are expected. The protypical structure is the result of ongoing collaboration, between Boeing and NASA-GRC seeking to introduce polyimide composites to the harsh environmental and loads familiar to space launch propulsion systems. Design trade analyses were carried out using relevant closed form solutions, approximations for sandwich beams/panels and finite element analysis. Analyses confirm the significant thermal stresses exist when combining materials whose coefficients of thermal expansion (CTEs) differ by a factor of about 10 for materials such as a polymer composite and metallic structures. The ramifications on design and manufacturing alternatives are reviewed and discussed. Due to stringent durability and safety requirements, serious consideration is being given to the synergistic effects of temperature and mechanical loads. The candidate structure operates at 316 C, about 80% of the glass transition temperature T(sub g). Earlier thermomechanical fatigue (TMF) investigations of chopped fiber polyimide composites made this near to T(sub g), showed that cyclic temperature and stress promoted excessive creep damage and strain accumulation. Here it is important to verify that such response is limited in continuous fiber laminates.

  5. Sulfonated Polyimide-Clay Thin Films for Energy Application.

    Science.gov (United States)

    Ali, Farman; Saeed, Shaukat; Shah, Syed Sakhawat; Rahim, Fazal; Duclaux, Laurent; Levêque, Jean-Marc; Reinert, Laurence

    2016-01-01

    Sulfonated polyimides (SPIs) are considered as the promising alternatives to Nafion as membrane materials for the polymer electrolyte membrane (PEM). They generally exhibit high ionic conductivity, good mechanical properties, excellent thermal and chemical stabilities. The six-membered ring, naphthalenic anhydride-based SPIs, not only exhibit superior chemical and thermo-oxidative stabilities but are also more resistant to hydrolysis than their five-membered phthalic anhydride-based SPIs. The composites based on napthalenic polyimides are also significantly stable in high temperature environment and show better stability to hydrolysis. Incorporation of inorganic fillers into organic polymers has gained tremendous attention and these new materials are called organic-inorganic hybrids. Few patents related to the synthesis and performance PEM materials have been reviewed and cited. Keeping in view the importance of sulfonated polyimide based nanocomposites as potential membrane materials for PEM in fuel cell, we have synthesized SPIs clay based nanocomposite as potential membrane material. The objective of this work was to synthesize clay based SPIs thin films which could be used as membrane materials in PEM fuel cell for energy applications. Methods/Experimental: At the first step the nanometric sheets of vermiculite clay prepared via sonication was surface modified by grafting 3-APTES. Then the SPI was synthesized via one-step high temperature direct imidization method, which serve as a matrix material. The organo modified VMT was dispersed via sonication in the SPI matrix. Four different sets of organic-inorganic nanocomposite membranes thin films, having VMT contents in the range of 1 to 7 wt.% were prepared by casting, curing and acidification route. The synthesis of SPIs clay based thin films were carried out at three different steps and fully characterized. The synthesis of SPIs and SPIs clay based thin films were analyzed via different analytical techniques

  6. Environmental changes induced by human activities in the Northern Curonian Lagoon (Eastern Baltic: diatoms and stable isotope data

    Directory of Open Access Journals (Sweden)

    Giedrė Vaikutienė

    2017-05-01

    Full Text Available A sediment core collected from the northwestern part of the Curonian Lagoon, which was deposited approximately during 1800-2002, was analysed for several proxy records. Changes in diatom assemblages and carbon, nitrogen and oxygen stable isotopes (δ13C, δ15N and δ18O revealed two periods, which are characterized by differences in the sedimentation rate, sediment type and trophic state of the northern part of the Curonian Lagoon. Low δ15N values in organics and prevailing fresh-brackish benthic diatoms indicate low enrichment in the shallow, freshwater lagoon during the period 1800-1955. The eutrophic conditions in this shallow lagoon are reflected by a high abundance of planktonic diatoms common in nutrient-rich basins and increased d15N values in organics of the sediments since 1955. Starting approximately in the 1960s, decreased freshwater run-off and increased brackish-water inflow into the lagoon were observed. These changes were likely caused by the construction of the hydropower station (and a reservoir near the Nemunas River and the artificial deepening of the Klaipėda Strait during 1960-1962 and later, also by the rising sea level in the SE Baltic. The changed river run-off and the artificially deepened strait significantly influenced the fresh-brackish water circulation and environmental conditions in the northern part of the Curonian Lagoon in the last decades.

  7. Preparation and characterization of novel thermoset polyimide and polyimide-peo doped with LiCF3SO3

    Directory of Open Access Journals (Sweden)

    M. H. Ugur

    2014-02-01

    Full Text Available This paper deals with the synthesis and characterization of a new type of anhydrous ionic conducting lithium doped membranes consist of polyimide (PI, poly (ethylene oxide (PEO and lithium trifluoromethanesulfonate (LiCF3SO3 for solid polymer electrolyte (SPE. For this purpose, different molar ratios of lithium salt (Li-salt solution are added into poly (amic acid (PAA intermediate prepared from the reaction of 3,3',4,4'-benzophenon tetracarboxylic dianhydride (BTDA and 4,4'-oxydianiline (ODA. PEO is incorporated into PAA since it forms more stable complexes and possess high ionic conductivities. Then, Li-salt containing PAA solutions are imidized by thermal process. The effect of interaction between host polymer and Li-salt is characterized by FT-IR (Fourier Transform Infrared spectroscopy and SEM (scanning electron micrsocopy. The conductivities of Li-salt and PEO containing PI composite membranes are in the range of 10–7–10–5 S•cm–1. The conductivity increases with incorporation of PEO. Thermogravimetric analysis results reveal that the PI/PEO/LiCF3SO3 composite polymer electrolyte membranes are thermally stable up to 500°C.

  8. Acetylene (ethynyl) terminated polyimide siloxane and process for preparation thereof

    Science.gov (United States)

    Stclair, T. L.; ASI primers applied over ste (Inventor)

    1986-01-01

    Siloxane containing addition polyimides having improved physical property characteristics of flexibility, drape, tack, and toughness and the process for preparing and utilizing the same are disclosed. The novelty of this invention appears to reside in the composition and process of preparing addition type polyimides useful as structural adhesives as well as composite matrix materials and the process of preparing the same.

  9. Polyimides Containing Fluorine and Phosphorus for Potential Space Applications

    Science.gov (United States)

    Connell, John W.; Watson, Kent A.

    2000-01-01

    As part of an effort to develop low color, ultraviolet (UV) radiation and atomic oxygen resistant polyimides for potential space applications, a novel diamine containing fluorine and phosphorus was synthesized and used to prepare polyimides. The approach was to combine attributes from colorless, UV resistant polyimides and atomic oxygen (AO) resistant polymers into a single material. Preparation of colorless polyimides has focused on minimization of charge transfer complex formation by incorporation of bulky substituents and disrupting conjugation by using meta-catenated monomers. AO resistant polymer technology development has focused on placing phenylphosphine oxide groups into the backbone of aromatic polymers. However, polyimides prepared utilizing this approach thus far have all exhibited significant color. Thus in an attempt to combine these features in a polyimide a new diamine, bis(3-aminophenyl)-3,5-di(trifluoromethyl)phenylphosphine oxide (TFMDA) was synthesized and used to prepare polyimides. The polyimides were cast into films and characterized for physical and mechanical properties, optical transmission and AO and UV resistance.

  10. Polyimide Aerogels with Three-Dimensional Cross-Linked Structure

    Science.gov (United States)

    Meador, Mary Ann B. (Inventor)

    2016-01-01

    A method for creating a three dimensional cross-linked polyimide structure includes dissolving a diamine, a dianhydride, and a triamine in a solvent, imidizing a polyamic acid gel by heating the gel, extracting the gel in a second solvent, supercritically drying the gel, and removing the solvent to create a polyimide aerogel.

  11. High-performance membranes from polyimides with intrinsic microporosity.

    Science.gov (United States)

    Ghanem, Bader S; McKeown, Neil B; Budd, Peter M; Selbie, James D; Fritsch, Detlev

    2008-07-17

    Membranes with high permeability to gases are formed from polyimides with rigid backbones that incorporate a spiro-centre. A route to this new range of high-free-volume polyimides is demonstrated, and exceptional performance is obtained for a polymer containing a dimethyl binaphthyl unit. Copyright © 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Quantification of Gaseous Elemental Mercury Dry Deposition to Environmental Surfaces using Mercury Stable Isotopes in a Controlled Environment

    Science.gov (United States)

    Rutter, A. P.; Schauer, J. J.; Shafer, M. M.; Olson, M.; Robinson, M.; Vanderveer, P.; Creswell, J. E.; Parman, A.; Mallek, J.; Gorski, P.

    2009-12-01

    atmospheric turbulence and wind speed. GEM enriched in stable isotope 198 (GEM-198) was released into the room from source at elevated but environmentally relevant concentrations of GEM-198 for several days. Uptake of GEM-198 from deciduous and conifer trees, grass turf, 3 types of soil, sand, concrete, asphalt, and adsorbent coated deposition coupons were quantified over several days. Exposures were conducted between 10oC and 30oC, in dark and light conditions. Mercury was recovered from the samples using acidic digestions and surface leaches, and then analyzed for the content of GEM-198 by high resolution ICPMS. Experimental results demonstrated that uptake by White Ash, White Spruce, and Kentucky bluegrass were significantly higher than uptakes measured for two Wisconsin soils, peat, sand, concrete and asphalt at all of the conditions studied. Deposition resistances for surface transfer processes for were calculated for each of the substrates across the conditions studied for use in atmospheric model simulations.

  13. Improvement of mechanical property of polyimide blends with {sup 60}Co-irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Wang Zhen; Deng Pengyang; Sun Jiazhen; Ding Mengxian E-mail: mxding@ns.ciac.jl.cn

    2002-08-01

    Radiation effects on polyimide blends were studied at different irradiation temperatures and with different irradiation doses. The irradiation polyimides were the blends of linear polyimide (HQDPA/ODA) and 4-phenylethynyl phthalic anhydride end-capped oligomer polyimide. The tensile strength and the elongation at break of irradiated films were determined as the function of irradiation temperature and dose. Under proper conditions crosslinking reaction occurred when the polyimide blends were irradiated at high temperature. The mechanical properties of irradiated polyimide blends were found to be different from the linear polyimide.

  14. Titanium reinforced boron-polyimide composite

    Science.gov (United States)

    Clark, G. A.; Clayton, K. I.

    1969-01-01

    Processing techniques for boron polyimide prepreg were developed whereby composites could be molded under vacuum bag pressure only. A post-cure cycle was developed which resulted in no loss in room temperature mechanical properties of the composite at any time during up to 16 hours at 650 F. A design utilizing laminated titanium foil was developed to achieve a smooth transition of load from the titanium attachment points into the boron-reinforced body of the structure. The box beam test article was subjected to combined bending and torsional loads while exposed to 650 F. Loads were applied incrementally until failure occurred at 83% design limit load.

  15. The electrical conductivities of polyimide and polyimide/Li triflate composites: An a.c. impedance study

    Science.gov (United States)

    Aziz, Nor Diyana Abdul; Kamarulzaman, Norlida; Subban, Ri Hanum Yahaya; Hamzah, Ahmad Sazali; Ahmed, Azni Zain; Osman, Zurina; Rusdi, Roshidah; Kamarudin, Norashikin; Mohalid, Norhanim; Romli, Ahmad Zafir; Shaameri, Zurina

    2017-09-01

    Polymer electrolytes have been an essential area of research for many decades. One of the reasons was the need to find new electrolyte materials suitable for device applications like solid-state batteries, supercapacitors, fuel cells, etc. with enhanced characteristics. For more than 40 years, polyimide has been known as a super-engineering plastic due to its excellent thermal stability (Tg > 250 °C) and mechanical properties. Therefore, in an effort to develop new polymer electrolytes, polyimide as a polymer matrix was chosen. Composite films of the polymer doped with lithium salt, LiCF3SO3 was prepared. These PI based polymer electrolyte films were investigated by the alternating current (a.c.) impedance spectroscopy method in the temperature range from 300 K to 373 K. It was observed that conductivity increased with the increase of temperature and amount of doping salt. Alternatively, the activation energy (Ea) of the composite films decreased with the increase of the doping salt, LiCF3SO3.

  16. Novel reusable porous polyimide fibers for hot-oil adsorption.

    Science.gov (United States)

    Tian, Lidong; Zhang, Chongyin; He, Xiaowei; Guo, Yongqiang; Qiao, Mingtao; Gu, Junwei; Zhang, Qiuyu

    2017-10-15

    The development of oil sorbents with high thermal stability, adsorption capacity, reusability and recoverability is of great significance for hot oil leakage protection, especially for oil spillage of oil refinery, petrochemical industry and cars. In our work, highly efficient hot oil adsorption of polyimide (PI) fibers with excellent thermal stability was successfully prepared by a facile electrospinning method followed by post-treatment. The corresponding morphologies, structures and oil adsorption properties of as-prepared PI fibers at different temperatures were analyzed and characterized. Results showed that PI fibers presented a stable morphology and pore structure at 200°C. The oil adsorption capacity of porous PI fibers for hot motor oil (200°C) was about 57.4gg(-1), higher than that of PI fibers (32.7gg(-1)) with non-porous structure for the motor oil at room temperature. Even after ten adsorption cycles, porous PI fibers still maintained a comparable oil sorption capacity (oil retention of 4.2%). The obtained porous PI fibers exhibited excellent hot oil adsorption capacity, reusability and recoverability, which would broaden the application of electrospun fibers in oil spill cleanup and further provide a versatile platform for exploring the technologies of nanofibers in hot oil adsorption field. Copyright © 2017. Published by Elsevier B.V.

  17. Moisture absorption analysis of high performance polyimide adhesive

    NARCIS (Netherlands)

    Akram, M.; Jansen, K.M.B.; Bhowmik, S.; Ernst, L.J.

    2011-01-01

    The high temperature resistant polymers and metal composites are used widely in aviation, space, automotive and electronics industry. The high temperature resistant polymers and metals are joined together using high temperature adhesives. Polyimide and epoxy adhesives that can withstand high

  18. A continuum model for carbon nanotube-infused polyimides

    Science.gov (United States)

    Wilson, Heather; Banda, Sumanth; Smith, Ralph C.; Ounaies, Zoubeida

    2009-03-01

    Polyimides are presently being investigated for a wide range of aeronautic, aerospace and industrial applications due to the fact that they have good thermal and chemical resistance yet are flexible. Within the realm of aerospace applications, polyimides can be employed for deployment, positioning, and vibration attenuation of large structures including thin-film membrane mirrors and gossamer antennas. The inclusion of single wall carbon nanotubes raises the conductivity levels to permit electric discharge. Additionally, they augment the electromechanical coupling properties of piezoelectric polyimides to provide them with actuator capabilities. We present a temperature-dependent material model based on elasticity theory which characterizes stiffness through the material as a function of varying concentrations of single wall nanotubes (SWNT). We begin by investigating the temperature affects on the polyimide. We then discuss the effects of SWNT volume concentration on the composite storage modulus. The composite model takes into account the alignment, interphase, and geometry of the SWNTs.

  19. Surface Modification of Titanium and Polyimide Sheet for Adhesive Bonding

    NARCIS (Netherlands)

    Akram, M.

    2015-01-01

    Major industrial sectors like automotive, aerospace and others are increasingly using polymer composites in their structural parts. Polyimide sheet and adhesives, are high performance polymers. They are widely used in various engineering applications due to their excellent thermal, mechanical and

  20. Polyimide Aerogels with Three-Dimensional Cross-Linked Structure

    Science.gov (United States)

    Panek, John

    2010-01-01

    Polyimide aerogels with three-dimensional cross-linked structure are made using linear oligomeric segments of polyimide, and linked with one of the following into a 3D structure: trifunctional aliphatic or aromatic amines, latent reactive end caps such as nadic anhydride or phenylethynylphenyl amine, and silica or silsesquioxane cage structures decorated with amine. Drying the gels supercritically maintains the solid structure of the gel, creating a polyimide aerogel with improved mechanical properties over linear polyimide aerogels. Lightweight, low-density structures are desired for acoustic and thermal insulation for aerospace structures, habitats, astronaut equipment, and aeronautic applications. Aerogels are a unique material for providing such properties because of their extremely low density and small pore sizes. However, plain silica aerogels are brittle. Reinforcing the aerogel structure with a polymer (X-Aerogel) provides vast improvements in strength while maintaining low density and pore structure. However, degradation of polymers used in cross-linking tends to limit use temperatures to below 150 C. Organic aerogels made from linear polyimide have been demonstrated, but gels shrink substantially during supercritical fluid extraction and may have lower use temperature due to lower glass transition temperatures. The purpose of this innovation is to raise the glass transition temperature of all organic polyimide aerogel by use of tri-, tetra-, or poly-functional units in the structure to create a 3D covalently bonded network. Such cross-linked polyimides typically have higher glass transition temperatures in excess of 300 400 C. In addition, the reinforcement provided by a 3D network should improve mechanical stability, and prevent shrinkage on supercritical fluid extraction. The use of tri-functional aromatic or aliphatic amine groups in the polyimide backbone will provide such a 3D structure.

  1. Carbon fiber on polyimide ultra-microelectrodes

    Science.gov (United States)

    Gillis, Winthrop F.; Lissandrello, Charles A.; Shen, Jun; Pearre, Ben W.; Mertiri, Alket; Deku, Felix; Cogan, Stuart; Holinski, Bradley J.; Chew, Daniel J.; White, Alice E.; Otchy, Timothy M.; Gardner, Timothy J.

    2018-02-01

    Objective. Most preparations for making neural recordings degrade over time and eventually fail due to insertion trauma and reactive tissue response. The magnitudes of these responses are thought to be related to the electrode size (specifically, the cross-sectional area), the relative stiffness of the electrode, and the degree of tissue tolerance for the material. Flexible carbon fiber ultra-microelectrodes have a much smaller cross-section than traditional electrodes and low tissue reactivity, and thus may enable improved longevity of neural recordings in the central and peripheral nervous systems. Only two carbon fiber array designs have been described previously, each with limited channel densities due to limitations of the fabrication processes or interconnect strategies. Here, we describe a method for assembling carbon fiber electrodes on a flexible polyimide substrate that is expected to facilitate the construction of high-density recording and stimulating arrays. Approach. Individual carbon fibers were aligned using an alignment tool that was 3D-printed with sub-micron resolution using direct laser writing. Indium deposition on the carbon fibers, followed by low-temperature microsoldering, provided a robust and reliable method of electrical connection to the polyimide interconnect. Main results. Spontaneous multiunit activity and stimulation-evoked compound responses with SNR  >10 and  >120, respectively, were recorded from a small (125 µm) peripheral nerve. We also improved the typically poor charge injection capacity of small diameter carbon fibers by electrodepositing 100 nm-thick iridium oxide films, making the carbon fiber arrays usable for electrical stimulation as well as recording. Significance. Our innovations in fabrication technique pave the way for further miniaturization of carbon fiber ultra-microelectrode arrays. We believe these advances to be key steps to enable a shift from labor intensive, manual assembly to a more automated

  2. Carbon fiber on polyimide ultra-microelectrodes.

    Science.gov (United States)

    Gillis, Winthrop F; Lissandrello, Charles A; Shen, Jun; Pearre, Ben W; Mertiri, Alket; Deku, Felix; Cogan, Stuart; Holinski, Bradley J; Chew, Daniel J; White, Alice E; Otchy, Timothy M; Gardner, Timothy

    2017-09-14

    Objective. Most preparations for making neural recordings degrade over time and eventually fail due to insertion trauma and reactive tissue response. The magnitudes of these responses are thought to be related to the electrode size (specifically, the cross-sectional area), the relative stiffness of the electrode, and the degree of tissue tolerance for the material. Flexible carbon fiber ultra-microelectrodes have a much smaller cross-section than traditional electrodes and low tissue reactivity, and thus may enable improved longevity of neural recordings in the central and peripheral nervous systems. Only two carbon fiber array designs have been described previously, each with limited channel densities due to limitations of the fabrication processes or interconnect strategies. Here, we describe a method for assembling carbon fiber electrodes on a flexible polyimide substrate that is expected to facilitate the construction of high-density recording and stimulating arrays. Approach. Individual carbon fibers were aligned using an alignment tool that was 3D-printed with sub-micron resolution using direct laser writing. Indium deposition on the carbon fibers, followed by low-temperature microsoldering, provided a robust and reliable method of electrical connection to the polyimide interconnect. Main Results. Spontaneous multiunit activity and stimulation-evoked compound responses with SNR > 10 and > 120, respectively, were recorded from a small (125 µm) peripheral nerve. We also improved the typically poor charge injection capacity of small diameter carbon fibers by electrodepositing 100 nm thick iridium oxide films, making the carbon fiber arrays usable for electrical stimulation as well as recording. Significance. Our innovations in fabrication technique pave the way for further miniaturization of carbon fiber ultra-microelectrode arrays. We believe these advances to be key steps to enable a shift from labor intensive, manual assembly to a more automated

  3. Polyimide nanocomposites based on cubic zirconium tungstate

    Science.gov (United States)

    Ramasubramanian Sharma, Gayathri

    2009-12-01

    In this research, cubic zirconium tungstate (ZrW2O8) was used as a filler to reduce the CTE of polyimides (PI), and the effect of ZrW2O8 nanoparticles on the bulk polymer properties was studied. Polyimides are high performance polymers with exceptional thermal stability, and there is a need for PIs with low CTEs for high temperature applications. The nanofiller, cubic ZrW2O8, is well known for its isotropic negative thermal expansion (NTE) over a wide temperature range from -272.7 to 777°C. The preparation of nanocomposites involved the synthesis of ZrW 2O8 nanofiller, engineering the polymer-filler interface using linker groups and optimization of processing strategies to prepare free-standing PI nanocomposite films. A hydrothermal method was used to synthesize ZrW 2O8 nanoparticles. Polyimide-ZrW2O8 interface interaction was enhanced by covalently bonding linker moieties to the surface of ZrW2O8 nanoparticles. Specifically, ZrW 2O8 nanoparticles were functionalized with two different linker groups: (1) a short aliphatic silane, and (2) low molecular weight PI. The surface functionalization was confirmed using X-ray photoelectron spectroscopy and thermal gravimetric analysis (TGA). Reprecipitation blending was used to prepare the freestanding PI-ZrW2O8 nanocomposite films with up to 15 volume% filler loading. SEM images showed the improvements in polymer-filler wetting behavior achieved using interface engineering. SEM images indicated that there was better filler dispersion in the PI matrix using reprecipitation blending, compared to the filler dispersion achieved in the nanocomposites prepared using conventional blending technique. The structure-property relationships in PI-ZrW2O8 nanocomposites were investigated by studying the thermal degradation, glass transition, tensile and thermal expansion properties of the nanocomposites. The properties were studied as a function of filler loading and interface linker groups. Addition of ZrW2O8 nanoparticles did not

  4. Neurite outgrowth on fluorinated polyimide film micropatterned by ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Okuyama, Y.; Sato, M.; Nagaoka, S.; Kawakami, H. E-mail: kawakami-hiroyoshi@c.metro-u.ac.jp; Suzuki, Y.; Iwaki, M

    2003-05-01

    In this study, we investigated neurite outgrowth on a fluorinated polyimide film micropatterned by ion irradiation. We used the fluorinated polyimide because of its excellent thermal and mechanical properties and biocompatibility. Rattus norvegicus chromaphin (PC12) cells were used for in vitro studies. The polyimide films were irradiated with He{sup +}, Ne{sup +} or Kr{sup +} at 1 x 10{sup 14} ions/cm{sup 2} using an ion-beam mask. The lines in the mask were 120 and 160 {mu}m wide and 120-160 {mu}m apart. PC12 cells were selectively adhered on the polyimide film micropatterned by Kr{sup +}-irradiation. However, the neurite length on the film irradiated by Kr{sup +} was shorter than that determined in the film irradiated by He{sup +}. On the other hand, neurite outgrowth on the polyimide film micropatterned by He{sup +}-irradiation was at least 100 {mu}m in length. This initial study indicated the enhanced outgrowth of PC12 cells on the fluorinated polyimide film micropatterned by ion irradiation.

  5. Fatigue Characterization for Flexible Circuit with Polyimide on Adhesiveless Copper

    Science.gov (United States)

    Huang, Kuo-Hua; Duh, Jenq-Gong

    2015-10-01

    Adhesiveless materials are commonly used for electric or portable products that need high flexibility in operation. We studied a structure which included copper substrate and polyimide (PI) film without any resin to avoid residual resin issues during the manufacturing process. Life-time and fatigue characteristics require further study. Normally, the technique to measure life-time is by storing samples to monitor the changes over a long period, but this is time-consuming. An accelerated aging test is an alternative way to predict and evaluate the property shift in the short term; nevertheless, the test conditions will influence the results. Temperature and relative humidity are the major environmental parameters, and the conditions at 85°C/85% relative humidity (RH) and 150°C are discussed in this paper. A better prediction was found using accelerated testing at 85°C/85% RH after comparing with data from samples stored for 3 years, with errors <5%. Also, the copper grain microstructure affects the fatigue character and mechanical properties. The best flexibility is achieved when an appropriate copper and PI thickness has been identified.

  6. Use of carbon and nitrogen stable isotope ratios to assess the effects of environmental contaminants on aquatic food webs

    Energy Technology Data Exchange (ETDEWEB)

    Caquet, Thierry [Unite Mixte de Recherche 985 Institut National de la Recherche Agronomique, Agrocampus Rennes ' Ecobiologie et Qualite des Hydrosystemes Continentaux' , Equipe Ecotoxicologie et Qualite des Milieux aquatiques, 65 rue de Saint-Brieuc, F-35042 Rennes cedex (France)]. E-mail: Thierry.Caquet@rennes.inra.fr

    2006-05-15

    In this study, the value of carbon ({delta} {sup 13}C) and nitrogen ({delta} {sup 15}N) stable isotope ratios were determined in nymphs of a top-predator, the common backswimmer (Notonecta glauca L.), collected in 18 m{sup 3} outdoor freshwater mesocosms used to assess the fate and ecotoxicological effects of a diphenyl ether herbicide, fomesafen, applied alone or in combination with Agral 90[reg] (mixture of polyethoxylated derivatives of nonylphenol). Both treatments had a negative effect on {delta} {sup 13}C values which may reflect changes in carbon fluxes across food webs in the treated ponds associated with a shift in phytoplankton structure. A decrease in {delta} {sup 15}N values was observed in the nymphs collected in mixture-treated ponds, which was presumably due to an increase in the abundance of rotifers and Chironominae larvae in these ponds. These preliminary results indicate that stable isotope ratios may be used as shortcuts to detect qualitative or quantitative shifts in the structure of aquatic food webs caused by pollutants. - Carbon and nitrogen stable isotope ratios may be used to detect the impact of pollutants on aquatic food webs.

  7. The 3F condensation polyimides: Review and update

    Science.gov (United States)

    Alston, William B.; Gratz, Roy F.

    1989-01-01

    Nine new condensation polyimides containing the phenyltrifluoroethylidene (3F) linkage were synthesized by the amic-acid route. Several other polyimides, including some with hexafluoroisopropylidene (6F) linkage, were also prepared as controls. Amic-acid solutions were characterized by determining their inherent viscosities prior to thermal conversion into polyimide films. Glass transition temperatures (T sub g), thermogravimetric analysis (TGA), and isothermal weight loss data (at 316, 371, and 371 C under 0.5 MPa air pressure) were obtained for the films. The films were pulverized into molding powders which, in turn, were thermally processed under pressure into neat resin disks. The disks were also characterized by T sub g's and 316 and 371 C isothermal weight losses. The film study identified two new polyimides with T sub g's greater than 371 C and two new polyimides with low rates of weight loss. The resin disks exhibited the same overall trends in T sub g and weight loss as the respective films, however the weight loss per unit surface area was always greater, presumably due to molecular degradation induced during preparation of the molding powders. The overall results indicate that polyimides containing the 3F linkage have T sub g's and thermo-oxidative stability comparable to polyimides containing the 6F group. Alternate technology was also shown by the synthesis of two new polyalkyl substituted 3F diamines and five more new 3F polymers. Their potential as photoresists was demonstrated by T sub g advancement after ultraviolet exposure. Last, four U.S. patents on 3F monomers and polymers were issued and up to eight more are pending.

  8. Triptycene-based dianhydrides, polyimides, methods of making each, and methods of use

    KAUST Repository

    Ghanem, Bader

    2015-12-30

    A triptycene-based monomer, a method of making a triptycene-based monomer, a triptycene-based aromatic polyimide, a method of making a triptycene- based aromatic polyimide, methods of using triptycene-based aromatic polyimides, structures incorporating triptycene-based aromatic polyimides, and methods of gas separation are provided. Embodiments of the triptycene-based monomers and triptycene-based aromatic polyimides have high permeabilities and excellent selectivities. Embodiments of the triptycene-based aromatic polyimides have one or more of the following characteristics: intrinsic microporosity, good thermal stability, and enhanced solubility. In an exemplary embodiment, the triptycene-based aromatic polyimides are microporous and have a high BET surface area. In an exemplary embodiment, the triptycene-based aromatic polyimides can be used to form a gas separation membrane.

  9. Effect of Film Thickness and Physical Aging on “Intrinsic” Gas Permeation Properties of Microporous Ethanoanthracene-Based Polyimides

    KAUST Repository

    Ma, Xiaohua

    2018-01-31

    Two ethanoanthracene-based dianhydrides, 9,10-dimethylethanoanthracene-2,3,6,7-tetracarboxylic anhydride (EA-DA) and its more flexible dibenzodioxane-containing derivative (EAD-DA), were synthesized from the same starting material, 9,10-dimethyl-ethanoanthracene-2,3,6,7-tetraol, and used for the preparation of bicyclic intrinsically microporous polyimides (PIM-PIs) by one-pot polycondensation reaction with 3,3′-dimethylnaphthidine (DMN). The resulting organosoluble polyimides, EA-DMN and EAD-DMN, were thermally stable up to 300 °C and had good mechanical properties with tensile strength of 55 and 63 MPa and elongation at break of 15 and 30%, respectively. EA-DMN and EAD-DMN polyimides displayed Brunauer–Emmett–Teller (BET) surface areas of 720 and 800 m2 g–1, respectively. Fresh films showed promising gas separation performance with very high gas permeabilities and moderate gas-pair selectivities, which were both strongly dependent on film thickness. The results obtained in this study shed more light on the relative importance of film thickness and physical aging on faster attainment of the “intrinsic” gas transport properties of high free volume PIM-PIs.

  10. Aromatic Polyimide and Crosslinked Thermally Rearranged Poly(benzoxazole-co-imide) Membranes for Isopropanol Dehydration via Pervaporation

    KAUST Repository

    Ming Xu, Yi

    2015-10-31

    Novel crosslinked thermally rearranged polybenzoxazole (C-TR-PBO) membranes, which show impressive results for isopropanol dehydration, have been obtained via in-situ thermal conversion of hydroxyl-containing polyimide precursors. The polyimide precursors are synthesized by the polycondensation of three monomers; namely, 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA), 3,3′-dihydroxybenzidine diamine (HAB) and 3,5-diaminobenzoic acid (DABA). Due to the incorporation of the carboxylic-group containing diamine DABA into an ortho-hydroxypolyimide precursor, the thermal induced crosslinking reaction can be achieved together with the thermal rearrangement process. Consequently, a synergistic effect of high permeability and high selectivity can be realized in one step. The resultant C-TR-PBO membrane exhibits an unambiguous enhancement in permeation flux compared to their polyimide precursors. Moreover, the newly developed C-TR-PBO membrane displays stable isopropanol dehydration performance at 60 °C throughout the continuous 200 hours. The promising preliminary results achieved in this study may offer useful insights for the selection of membrane materials for pervaporation and new methods to molecularly design next-generation pervaporation membranes.

  11. Synthesis and Characterization of a Novel Microporous Dihydroxyl-Functionalized Triptycene-Diamine-Based Polyimide for Natural Gas Membrane Separation.

    Science.gov (United States)

    Alaslai, Nasser; Ma, Xiaohua; Ghanem, Bader; Wang, Yingge; Alghunaimi, Fahd; Pinnau, Ingo

    2017-09-01

    An intrinsically microporous polyimide is synthesized in m-cresol by a one-pot high-temperature condensation reaction of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and newly designed 2,6 (7)-dihydroxy-3,7(6)-diaminotriptycene (DAT1-OH). The 6FDA-DAT1-OH polyimide is thermally stable up to 440 °C, shows excellent solubility in polar solvents, and has moderately high Brunauer-Teller-Emmett (BET) surface area of 160 m 2 g -1 , as determined by nitrogen adsorption at -196 °C. Hydroxyl functionalization applied to the rigid 3D triptycene-based diamine building block results in a polyimide that exhibits moderate pure-gas CO 2 permeability of 70 Barrer combined with high CO 2 /CH 4 selectivity of 50. Mixed-gas permeation studies demonstrate excellent plasticization resistance of 6FDA-DAT1-OH with impressive performance as potential membrane material for natural gas sweetening with a CO 2 permeability of 50 Barrer and CO 2 /CH 4 selectivity of 40 at a typical natural gas well partial pressure of 10 atm. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Synthesis and Characterization of a Novel Microporous Dihydroxyl-Functionalized Triptycene-Diamine-Based Polyimide for Natural Gas Membrane Separation

    KAUST Repository

    Alaslai, Nasser Y.

    2017-07-10

    An intrinsically microporous polyimide is synthesized in m-cresol by a one-pot high-temperature condensation reaction of 4,4\\'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and newly designed 2,6 (7)-dihydroxy-3,7(6)-diaminotriptycene (DAT1-OH). The 6FDA-DAT1-OH polyimide is thermally stable up to 440 °C, shows excellent solubility in polar solvents, and has moderately high Brunauer-Teller-Emmett (BET) surface area of 160 m2 g-1 , as determined by nitrogen adsorption at -196 °C. Hydroxyl functionalization applied to the rigid 3D triptycene-based diamine building block results in a polyimide that exhibits moderate pure-gas CO2 permeability of 70 Barrer combined with high CO2 /CH4 selectivity of 50. Mixed-gas permeation studies demonstrate excellent plasticization resistance of 6FDA-DAT1-OH with impressive performance as potential membrane material for natural gas sweetening with a CO2 permeability of 50 Barrer and CO2 /CH4 selectivity of 40 at a typical natural gas well partial pressure of 10 atm.

  13. Synthesis and characterization of fluorinated polyaminoquinones and fluorinated polyimides

    Science.gov (United States)

    Vaccaro, Eleonora

    Phenolic and quinonoid compounds are widely studied in biological sciences because of their ability to chelate heavy metals like iron and copper and recently have found new applications in synthetic macromolecules. Amino- p-benzoquinone polymers, poly[(2,5-hexamethylenediamino)-1,4-benzoquinone] and poly {[2,5-(2,2'-bistrifluoromethyl)-4,4' -biphenylenediamino]1,4-benzoquinone}, were synthesized and evaluated as adhesion promoters for steel/epoxy joints. An improvement in the torsional shear strength of these joints was observed when these polymers were used as adhesion promoters. The durability of the adhesive bond was also improved after boiling water treatment, relative to untreated and silane treated joints. The improvement in adhesion could be attributed to the formation of a chelate between the polyaminoquinone (PAQ) and the iron surface and a chemical reaction between the PAQ and the epoxy resin. A low molecular weight model compound, bis[2,5-(4-methylanilido)]-1,4-benzoquinone was also used to study coupling between the epoxy adhesive and the steel surface. Electron spin resonance (ESR), atomic absorption spectroscopy and infrared spectroscopy were used to document the epoxy-coupling agent reaction and the chelate formation. Polyimides have acquired importance in the last twenty years as the most promising macromolecules for high technology applications in new materials. Their good thermo-oxidative stability is well known, as well as their high glass transition temperature. Polyimides are versatile polymers, which can be utilized for a wide range of applications: i.e., as matrices for high performance advanced composite materials, as thin films in electronic applications, as structural adhesives and sealants and as membranes for gas separation. A novel anhydride, 1,1,1-trifluoromethyl-1-pentafluorophenylethylidene-2,2-diphthalic anhydride, 8FDA, was synthesized. Five diamines were used in the synthesis of polyimides, namely p-phenylene diamine, 3

  14. Fabrication of optically-functionalized colorless polyimide patterns with high durability

    Science.gov (United States)

    Jun, Junho; Lee, Ji-Hyun; Choi, Hak-Jong; Moon, Sungjin; Kim, Il-Doo; Lee, Heon

    2017-11-01

    Colorless polyimide (CPI) is a promising material for flexible substrates because of its excellent mechanical hardness, chemical durability, thermal stability, and high optical transmittance. In particular, its superior durability under heating and mechanical forces compared with other polymeric materials makes polyimide compatible for industrial applications. Thus, it has been actively investigated for use in preparing flexible and transparent substrates for optical devices. Nevertheless, there is little research on the direct pattering of CPI to form structures with various optical functions. In this research, a simple and cost-effective process involving the patterning of optically functional structures and imidization via thermal nanoimprint lithography (NIL) was developed. CPI films patterned with structures such as nanoscale and microscale cones were fabricated by thermal NIL, and their optical functions, including their anti-reflection and high scattering properties, were demonstrated by UV-vis analysis. Moreover, the patterned CPI film has an excellent thermal stability and a mechanical hardness up to 1.12 GPa; this value was nearly maintained even at 400 °C. Therefore, nano- to microscale optical patterns of CPI were successfully formed, and these structures are stable towards mechanical damage and high temperatures.

  15. Reinforced Thermoplastic Polyimide with Dispersed Functionalized Single Wall Carbon Nanotubes

    Science.gov (United States)

    Lebron-Colon, Marisabel; Meador, Michael A.; Gaier, James R.; Sola, Francisco; Scheiman, Daniel A.; McCorkle, Linda S.

    2010-01-01

    Molecular pi-complexes were formed from pristine HiPCO single-wall carbon nanotubes (SWCNTs) and 1-pyrene- N-(4- N'-(5-norbornene-2,3-dicarboxyimido)phenyl butanamide, 1. Polyimide films were prepared with these complexes as well as uncomplexed SWCNTs and the effects of nanoadditive addition on mechanical, thermal, and electrical properties of these films were evaluated. Although these properties were enhanced by both nanoadditives, larger increases in tensile strength and thermal and electrical conductivities were obtained when the SWCNT/1 complexes were used. At a loading level of 5.5 wt %, the Tg of the polyimide increased from 169 to 197 C and the storage modulus increased 20-fold (from 142 to 3045 MPa). The addition of 3.5 wt % SWCNT/1 complexes increased the tensile strength of the polyimide from 61.4 to 129 MPa; higher loading levels led to embrittlement and lower tensile strengths. The electrical conductivities (DC surface) of the polyimides increased to 1 x 10(exp -4) Scm(exp -1) (SWCNT/1 complexes loading level of 9 wt %). Details of the preparation of these complexes and their effects on polyimide film properties are discussed.

  16. Use of Carbon and Nitrogen Stable Isotopes to Study Late Pleistocene to Holocene Environmental Change in the Waipaoa Sedimentary System, New Zealand

    Science.gov (United States)

    Childress, L. B.; Leithold, E. L.; Blair, N. E.; Brulet, B. R.

    2008-12-01

    The stable isotopic composition of organic matter in continental margin sediments provides a useful, long- term record of environmental change. The Waipaoa River watershed, New Zealand, represents a system of interest due to its very large sediment supply and well known, relatively recent history of anthropogenic disturbance. Three cores taken by the RV Marion Dufresne in January 2006 on the continental shelf offshore from the river mouth provide a record extending into the late Pleistocene, dating as far back as 14,000 years. Analyses of terrestrial sources, soil profiles, sedimentary rocks and riverine sediments from within the watershed create a more holistic understanding of the current and past source to sink relationships associated with the Waipaoa sedimentary system and its influence upon the marine isotopic record. Shoreline progradation, hillslope erosion and gully incision, and the capture of river tributaries are examples of terrestrial processes that are hypothesized to influence isotopic ratios and may leave identifiable imprints in the marine stratigraphic record. By coupling the carbon and nitrogen stable isotope records with radiocarbon data a timeline of environmental processes in the area is derived as well as more detailed source apportionments.

  17. Stable isotopes, ecological integration and environmental change: wolves record atmospheric carbon isotope trend better than tree rings.

    Science.gov (United States)

    Bump, Joseph K; Fox-Dobbs, Kena; Bada, Jeffrey L; Koch, Paul L; Peterson, Rolf O; Vucetich, John A

    2007-10-07

    Large-scale patterns of isotope ratios are detectable in the tissues of organisms, but the variability in these patterns often obscures detection of environmental trends. We show that plants and animals at lower trophic levels are relatively poor indicators of the temporal trend in atmospheric carbon isotope ratios (delta13C) when compared with animals at higher trophic levels. First, we tested how differences in atmospheric delta13C values were transferred across three trophic levels. Second, we compared contemporary delta13C trends (1961-2004) in atmospheric CO2 to delta13C patterns in a tree species (jack pine, Pinus banksiana), large herbivore (moose, Alces alces) and large carnivore (grey wolf, Canis lupus) from North America. Third, we compared palaeontological (approx. 30000 to 12000 14C years before present) atmospheric CO2 trends to delta13C patterns in a tree species (Pinus flexilis, Juniperus sp.), a megaherbivore (bison, Bison antiquus) and a large carnivore (dire wolf, Canis dirus) from the La Brea tar pits (southern California, USA) and Great Basin (western USA). Contrary to previous expectations, we found that the environmental isotope pattern is better represented with increasing trophic level. Our results indicate that museum specimens of large carnivores would best reflect large-scale spatial and temporal patterns of carbon isotopes in the palaeontological record because top predators can act as ecological integrators of environmental change.

  18. Structures and Performance of Graphene/Polyimide Composite Graphite Fibers

    Directory of Open Access Journals (Sweden)

    LI Na

    2017-09-01

    Full Text Available Dry-wet spinning process was used to gain graphene oxide/polyimide composite fibers, then graphene/polyimide composite carbon and graphite fibers were obtained through carbonized and graphitized. Different graphene oxide contents of the composite carbon and graphite fibers were measured by thermal gravimetric analysis, Raman, mechanical properties, electrical properties,SEM and so on. The results show that when the GO content is 0.3%(mass fraction,the same below, the thermal property of the graphene oxide/polyimide composite fibers is the best. The mechanical and electrical properties are obriously improved by the addition of GO, graphitization degree also increases. When the composite carbon fibers are treated at 2800℃, GO content increases to 2.0%, the thermal conductivity of the composite graphite fibers reaches 435.57W·m-1·K-1 and cross-section structures of carbon fibers are more compact.

  19. Measurement and improvement of the adhesion of copper to polyimide

    Energy Technology Data Exchange (ETDEWEB)

    Menezes, M. [Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois, Urbana, Illinois (United States); Robertson, I. M. [Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois, Urbana, Illinois (United States); Birnbaum, H. K. [Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois, Urbana, Illinois (United States)

    1999-10-01

    A contact angle measurement technique has been used to obtain an estimate of the interfacial energy and thermodynamic adhesive strength between copper and polyimide [pyromellitic dyanhydride oxydianalyn (PMDA-ODA) and p-phenylene biphenylteracarboinide (BPDA-PDA)]. Values of the strength of adhesion from these contact angle measurements are in reasonable agreement with values calculated using the Girifalco-Good-Fowkes nonpolar interfacial adhesion theory. Based on the surface energy it was predicted and experimentally observed that small copper clusters would embed into the polymer matrix if heated under ultrahigh vacuum conditions at temperatures near T{sub g} of the polymer. Controlled embedding of nanometer clusters was utilized to produce a textured interface, where the partially embedded clusters acted as ''nanonails'' to anchor a metal overlayer to the underlying polyimide substrate. These nanonails greatly increased the bonding between the copper overlayer and the polyimide, as demonstrated by mechanical debonding studies. (c) 1999 Materials Research Society.

  20. Fundamental aspects of polyimide dry film and composite lubrication: A review

    Science.gov (United States)

    Fusaro, R. L.

    1982-01-01

    The tribological properties of polyimide dry films and composites are reviewed. Friction coefficients, wear rates, transfer film characteristics, wear surface morphology, and possible wear mechanisms of several different polyimide films, polyimide-bonded solid lubricants, polyimide solid bodies, and polyimide composites are discussed. Such parameters as temperature, type of atmosphere, load, contact stress, and specimen configuration are investigated. Data from an accelerated test device (Pin-on-Disk) are compared to similar data obtained from an end use application test device (plain spherical bearing).

  1. Systems and methods for using a boehmite bond-coat with polyimide membranes for gas separation

    Science.gov (United States)

    Polishchuk, Kimberly Ann

    2013-03-05

    The subject matter disclosed herein relates to gas separation membranes and, more specifically, to polyimide gas separation membranes. In an embodiment, a gas separation membrane includes a porous substrate, a substantially continuous polyimide membrane layer, and one or more layers of boehmite nanoparticles disposed between the porous substrate and the polyimide membrane layer to form a bond-coat layer. The bond-coat layer is configured to improve the adhesion of the polyimide membrane layer to the porous substrate, and the polyimide membrane layer has a thickness approximately 100 nm or less.

  2. Development of autoclave moldable addition-type polyimides

    Science.gov (United States)

    Vaughan, R. W.; Jones, R. J.; Orell, M. K.; Zakrzewski, G. A.

    1976-01-01

    Chemistry and processing modifications of the poly(Diels Alder) polyimide (PDA) resin were performed to obtain structural composites suitable for 589 K (600 F) service. This work demonstrated that the PDA resin formulation is suitable for service at 589 K (600 F) for up to 125 hours when used in combination with Hercules HTS graphite fiber. Sandwich panels were autoclave molded using PDA/HTS skins and polyimide/glass honeycomb core. Excellent adhesion between honeycomb core and the facing skins was demonstrated. Fabrication ease was demonstrated by autoclave molding three-quarter scale YF-12 wing panels.

  3. Evaluation of Nanoclay Exfoliation Strategies for Thermoset Polyimide Nanocomposite Systems

    Science.gov (United States)

    Ginter, Michael J.; Jana, Sadhan C.; Miller, Sandi G.

    2007-01-01

    Prior works show exfoliated layered silicate reinforcement improves polymer composite properties. However, achieving full clay exfoliation in high performance thermoset polyimides remains a challenge. This study explores a new method of clay exfoliation, which includes clay intercalation by lower molecular weight PMR monomer under conditions of low and high shear and sonication, clay treatments by aliphatic and aromatic surfactants, and clay dispersion in primary, higher molecular weight PMR resin. Clay spacing, thermal, and mechanical properties were evaluated and compared with the best results available in literature for PMR polyimide systems.

  4. Stable isotope evidence for the environmental impact of a land-based fish farm in the western Mediterranean

    Energy Technology Data Exchange (ETDEWEB)

    Vizzini, Salvatrice; Mazzola, Antonio

    2004-07-01

    Isotopic examination ({delta}{sup 13}C and {delta}{sup 15}N) of organic matter sources and consumers was used to assess the impact and trace the dispersal of wastewater from a land-based fish farm in western Mediterranean. The results provide evidence of the non-negligible effect of aquaculture facilities on the natural stable isotopic composition of organisms. Aquaculture waste entered the food web, altering the natural isotopic composition of organic matter sources at the base and the upper trophic levels. Nitrogen-rich fish waste mainly affected {delta}{sup 15}N values, while {delta}{sup 13}C showed less alteration. Waste seemed to disperse widely enough to affect the isotopic composition at the study site about 500 m from the outfall, while sites at 1 and 2 km from the outfall showed values that were similar to each other and different from those of the impacted site. The impact was detected at different ecosystem levels, although primary producers were more affected by fish farm waste taking up aquaculture-derived nutrients.

  5. Environmental change and seasonal behavior of mastodons in the Great Lakes region inferred from stable isotope analysis

    Science.gov (United States)

    Metcalfe, Jessica Z.; Longstaffe, Fred J.

    2014-09-01

    We investigate seasonal variations in the diet and drinking water of four Great Lakes mastodon (Mammut americanum) specimens using stable isotope analysis of serially sampled inner-enamel bioapatite structural carbonate (δ13Csc, δ18Osc), and previously published bulk analyses. Isotopic analyses and thin section measurements showed that mastodon tooth enamel extension rates (~ 12-4 mm/yr, decreasing toward the cervix) were lower than those of mammoths or modern elephants. Mastodons had distinct and highly regular seasonal variations in δ13Csc and δ18Osc, which we interpret in the context of local glacial history and vegetation changes. Seasonal variations in δ18O were large but variations in δ13C were small, and may have been obscured if coarser sampling methods than our inner-enamel sampling approach were used. Thus, our approach may be particularly useful for understanding relatively small seasonal changes in δ13C within C3 environments. The seasonal patterns, though not entirely conclusive, suggest that the Ontario mastodons did not migrate over very long distances. Rather, the climate and seasonal dietary patterns of mastodons within the region changed over time, from ~ 12,400 to 10,400 14C yr BP (~ 15,000 - 12,000 cal yr BP). Insights gained using these methods can contribute to a better understanding of megafaunal extinctions and Paleoamerican lifeways.

  6. Influence of Surface Modified MWCNTs on the Mechanical, Electrical and Thermal Properties of Polyimide Nanocomposites

    Directory of Open Access Journals (Sweden)

    Singh Deepankar

    2008-01-01

    Full Text Available Abstract Polyamic acid, the precursor of polyimide, was used for the preparation of polyimide/multiwalled carbon nanotubes (MWCNTs nanocomposite films by solvent casting technique. In order to enhance the chemical compatibility between polyimide matrix and MWCNTs, the latter was surface modified by incorporating acidic and amide groups by chemical treatment with nitric acid and octadecylamine (C18H39N, respectively. While the amide-MWCNT/polyimide composite shows higher mechanical properties at low loadings (<3 wt%, the acid-MWCNT/polyimide composites perform better at higher loadings (5 wt%. The tensile strength (TS and the Young’s modulus (YM values of the acid-MWCNT/polyimide composites at 5 wt% MWCNT loadings was 151 and 3360 MPa, respectively, an improvement of 54% in TS and 35% in YM over the neat polyimide film (TS = 98 MPa; YM = 2492 MPa. These MWCNT-reinforced composites show remarkable improvement in terms of thermal stability as compared to that for pure polyimide film. The electrical conductivity of 5 wt% acid modified MWCNTs/polyimide nanocomposites improved to 0.94 S cm −1(6.67 × 10 −18 S cm−1for pure polyimide the maximum achieved so far for MWCNT-polyimide composites.

  7. Electrospun polyimide nanofiber-based nonwoven separators for lithium-ion batteries

    Science.gov (United States)

    Miao, Yue-E.; Zhu, Guan-Nan; Hou, Haoqing; Xia, Yong-Yao; Liu, Tianxi

    2013-03-01

    Polyimide (PI) nanofiber-based nonwovens have been fabricated via electrospinning for the separators of lithium-ion batteries (LIBs). Differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and hot oven tests show that the PI nanofiber-based nonwovens are thermally stable at a high temperature of 500 °C while the commercial Celgard membrane exhibits great shrinkage at 150 °C and even goes melting over 167 °C, indicating a superior thermal stability of PI nanofiber-based nonwovens than that of the Celgard membrane. Moreover, the PI nanofiber-based nonwovens exhibit better wettability for the polar electrolyte compared to the Celgard membrane. The PI nanofiber-based nonwoven separators are also evaluated to have higher capacity, lower resistance and higher rate capability compared to the Celgard membrane separator, which proves that they are ideal candidates for separators of high-performance rechargeable LIBs.

  8. Effect of Branching on Rod-coil Polyimides as Membrane Materials for Lithium Polymer Batteries

    Science.gov (United States)

    Meador, Mary Ann B.; Cubon, Valerie A.; Scheiman, Daniel A.; Bennett, William R.

    2003-01-01

    This paper describes a series of rod-coil block co-polymers that produce easy to fabricate, dimensionally stable films with good ionic conductivity down to room temperature for use as electrolytes for lithium polymer batteries. The polymers consist of short, rigid rod polyimide segments, alternating with flexible, polyalkylene oxide coil segments. The highly incompatible rods and coils should phase separate, especially in the presence of lithium ions. The coil phase would allow for conduction of lithium ions, while the rigid rod phase would provide a high degree of dimensional stability. An optimization study was carried out to study the effect of four variables (degree of branching, formulated molecular weight, polymerization solvent and lithium salt concentration) on ionic conductivity, glass transition temperature and dimensional stability in this system.

  9. Stable isotopes in yellow-bellied marmot (Marmota flaviventris) fossils reveal environmental stability in the late Quaternary of the Colorado Rocky Mountains

    Science.gov (United States)

    Reynard, Linda M.; Meltzer, David J.; Emslie, Steven D.; Tuross, Noreen

    2015-03-01

    High elevation plant and animal communities are considered extremely sensitive to environmental change. We investigated an exceptional fossil record of yellow-bellied marmot (Marmota flaviventris) specimens that was recovered from Cement Creek Cave (elev. 2860 m) and ranged in age from radiocarbon background circa 49.8 cal ka BP to ~ 1 cal ka BP. We coupled isotopic and radiocarbon measurements (δ18O, δD, δ15N, δ13C, and 14C) of bone collagen from individually-AMS dated specimens of marmots to assess ecological responses by this species to environmental change over time in a high elevation basin in the Rocky Mountains of southwestern Colorado, USA. We find little change in all four isotope ratios over time, demonstrating considerable environmental stability during periods when the marmots were present. The stable ecology and the apparent persistence of the small mammal community in the cave fauna throughout the late Quaternary are in marked contrast to the changes that occurred in the large mammal community, including local extirpation and extinction, at the end of the Pleistocene.

  10. Synthesis and properties of new polyimide/clay nanocomposite films

    Indian Academy of Sciences (India)

    789–798. c Indian Academy of Sciences. Synthesis and properties of new polyimide/clay nanocomposite films. YAGOUB MANSOORI. ∗. , SOMAYEH SHAH SANAEI, MOHAMMAD-REZA ZAMANLOO,. GHOLAMHASSAN IMANZADEH and SEYED VAHID ATGHIA. Department of Applied Chemistry, Faculty of Science, ...

  11. Low-void polyimide resins for autoclave processing

    Science.gov (United States)

    Jones, R. J.; Vaughan, R. W.

    1972-01-01

    Development of an advanced A-type polyimide, which can be used to produce autoclave molded, low-void content composites suitable for use at temperatures up to 316 C is reported. It consists of a mixture of methyl nadic anhydride, an 80:20 molar ratio of methylene dianaline and thiodianilene, and pyromellitic dianhydride.

  12. Synthesis and properties of new polyimide/clay nanocomposite films

    Indian Academy of Sciences (India)

    Nanocomposites exhibit higher glass transition temperature and improved thermal properties compared to neat polyimide due to the interaction between polymer matrix and organoclay particles. The results are also compared with data of a similar work. Morphology study with scanning electron microscopy showed that the ...

  13. Osmosis and pervaporation in polyimide submicron microfluidic channel structures

    NARCIS (Netherlands)

    Eijkel, Jan C.T.; Bomer, Johan G.; van den Berg, Albert

    2005-01-01

    Osmosis and pervaporation of water through the roof of all-polyimide channels of 500 nm height is described. The phenomena cause both a liquid flow in the channels and a concentration change of dissolved salt. Both effects are amplified due to the thin channel roof and the small channel height.

  14. Photopiezoelectric composites of azobenzene-functionalized polyimides and polyvinylidene fluoride.

    Science.gov (United States)

    Wie, Jeong Jae; Wang, David H; Tondiglia, Vincent P; Tabiryan, Nelson V; Vergara-Toloza, Rafael O; Tan, Loon-Seng; White, Timothy J

    2014-12-01

    Light is a readily available and sustainable energy source. Transduction of light into mechanical work or electricity in functional materials, composites, or systems has other potential advantages derived from the ability to remotely, spatially, and temporally control triggering by light. Toward this end, this work examines photoinduced piezoelectric (photopiezoelectric) effects in laminate composites prepared from photoresponsive polymeric materials and the piezoelectric polymer polyvinylidene fluoride (PVDF). In the geometry studied here, photopiezoelectric conversion is shown to strongly depend on the photomechanical properties inherent to the azobenzene-functionalized polyimides. Based on prior examinations of photomechanical effects in azobenzene-functionalized polyimides, this investigation focuses on amorphous materials and systematically varies the concentration of azobenzene in the copolymers. The baseline photomechanical response of the set of polyimides is characterized in cantilever deflection experiments. To improve the photomechanical response of the materials and enhance the electrical conversion, the polyimides are drawn to increase the magnitude of the deflection as well as photogenerated stress. In laminate composites, the photomechanical response of the materials in sequenced light exposure is shown to transduce light energy into electrical energy. The frequency of the photopiezoelectric response of the composite can match the frequency of the sequenced light exposing the films. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Commercialization of LARC (TradeMark) -SI Polyimide Technology

    Science.gov (United States)

    Bryant, Robert G.

    2011-01-01

    LARC(TradeMark)-SI, Langley Research Center- Soluble Imide, was developed in 1992, with the first patent issuing in 1997, and then subsequent patents issued in 1998 and 2000. Currently, this polymer has been successfully licensed by NASA, and has generated revenues, at the time of this reporting, in excess of $1.4 million. The success of this particular polymer has been due to many factors and many lessons learned to the point that the invention, while important, is the least significant part in the commercialization of this material. Commercial LARC(TradeMark)-SI is a polyimide composed of two molar equivalents of dianhydrides: 4,4 -oxydiphthalic anhydride (ODPA), and 3,3 ,4,4 -biphenyltetracarboxylic dianhydride (BPDA) and 3,4 -oxydianiline (3,4 -ODA) as the diamine. The unique feature of this aromatic polyimide is that it remains soluble after solution imidization in high-boiling, polar aprotic solvents, even at solids contents of 50-percent by weight. However, once isolated and heated above its T(sub g) of 240 C, it becomes insoluble and exhibits high-temperature thermoplastic melt-flow behavior. With these unique structure property characteristics, it was thought this would be an advantage to have an aromatic polyimide that is both solution and melt processable in the imide form. This could potentially lead to lower cost production as it was not as equipment- or labor-intensive as other high-performance polyimide materials that either precipitate or are intractable. This unique combination of properties allowed patents with broad claim coverage and potential commercialization. After the U.S. Patent applications were filed, a Small Business Innovation Research (SBIR) contract was awarded to Imtec, Inc. to develop and supply the polyimide to NASA and the general public. Some examples of demonstration parts made with LARC(TradeMark)-SI ranged from aircraft wire and multilayer printed-circuit boards, to gears, composite panels, supported adhesive tape, composite

  16. Superhydrophobic polyimide films with high thermal endurance via UV photo-oxidation

    Directory of Open Access Journals (Sweden)

    L. X. Song

    2014-08-01

    Full Text Available UV photo-oxidation was first applied to fabricate superhydrophobic polyimide (PI films in combination with fluoroalkylsilane (FAS modification. During prolonged UV irradiation, commercial flat PI films evolved to form unique micro/nanostructures. Meanwhile, the root mean square (RMS surface roughness increased from 1.74 to 53.70 nm, leading to a gradual increase of WCA from 105.1 to 159.2° after FAS treatment. After 72 h of UV radiation exposure, the micro/nano-structured and FAS-modified PI films exhibited superhydrophobicity with water contact angle (WCA larger than 150° and sliding angle (SA less than 5°. The superhydrophobicity remained even after annealing at 350°C, which enabled stable utilization under elevated temperature. Stable micro/nanostructures and chemical bonding of FAS were found to contribute to the high thermal endurance. Moreover, the formation mechanism of the superhydrophobic PI films was investigated. The proposed UV photo-oxidation method provides a new route for the industrial fabrication of thermally stable superhydrophobic PI films.

  17. Photochemical Cyclopolymerization of Polyimides in Ultraviolet Ridgidizing Composites for Use in Inflatable Structures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This innovation uses photochemical cyclopolymerization of polyimides to manufacture ultraviolet rigidizable composites for use in RIS (ridgidizing inflatable)...

  18. Radiation Abating Highly Flexible Multifunctional Polyimide Cryogenic and Thermal Insulation Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The development of highly flexible thermal insulation materials with multifunctional properties based in polyimide polymers and designed to provide significant...

  19. Principles and Application of Polyimide Fiber Bragg Gratings for Surface Strain Measurement

    Directory of Open Access Journals (Sweden)

    Yangyang Sun

    2017-09-01

    Full Text Available Although theoretical investigation has demonstrated that fewer strain transfer layers imply a greater strain transfer ratio, as well as increased accuracy, most researchers are still focused on investigating encapsulated Fiber Bragg gratings (FBGs in surface strain measurements. This is because, in a traditional view, bare FBGs are too fragile to be mounted on the substrate for measuring surface strain. Polyimide FBGs may provide a better balance point between accuracy and protection. A new method to measure surface strain with polyimide fiber Bragg gratings is proposed. Bare polyimide FBGs have a polyimide coating, but like regular non-coated FBGs. This gives polyimide FBGs a higher strain transfer ratio and response frequency. Bare polyimide FBGs can be considered as uncoated FBGs. The coupling of the matrix material of polyimide FBGs is improved as compared to FBGs without coating. In order to verify the capacity for surface strain measurement, polyimide FBGs are mounted to obtain the surface strain of a concrete specimen with SM130-700 interrogator from Micron Optics Incorporation (MOI with a sampling frequency maximum of 2000 Hz. The experiment demonstrates that polyimide FBGs work well even in dynamic surface strain measurements such as explosion measurement. Validation experiment in this paper also proposed that fewer strain transfer layers can increase dynamic response frequency and coupling between FBG and substrate.

  20. Latent synthesis of electrically conductive surface-silvered polyimide films.

    Science.gov (United States)

    Davis, Luke M; Abelt, Christopher J; Scott, Joseph L; Orlova, Evguenia; Thompson, David W

    2009-01-01

    A facile ambient temperature route to the fabrication of surface silver-metallized polyimide films is described. Silver(I) trifluoromethanesulfonate or silver(I) nitrate and a polyimide, derived from 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride and an equimolar amount of 4,4'-oxydianiline and 3,5-diaminobenzoic acid, were dissolved together in dimethylacetamide. Silver(I)-doped films were prepared at thicknesses of 25-40 microm and depleted of solvent by evaporation at ambient temperature and low humidity. The silver(I)-ion-containing films were then treated with aqueous solutions of the reducing agents hydrazine hydrate and hydroxylamine, which brought forth surface-silvered films exhibiting conductivity on the order of bulk polycrystalline silver accompanied by modest-to-high specular reflectivity.

  1. Polyimide and Metals MEMS Multi-User Processes

    KAUST Repository

    Arevalo, Arpys

    2016-11-01

    The development of a polyimide and metals multi-user surface micro-machining process for Micro-electro-mechanical Systems (MEMS) is presented. The process was designed to be as general as possible, and designed to be capable to fabricate different designs on a single silicon wafer. The process was not optimized with the purpose of fabricating any one specific device but can be tweaked to satisfy individual needs depending on the application. The fabrication process uses Polyimide as the structural material and three separated metallization layers that can be interconnected depending on the desired application. The technology allows the development of out-of-plane compliant mechanisms, which can be combined with six variations of different physical principles for actuation and sensing on a single processed silicon wafer. These variations are: electrostatic motion, thermal bimorph actuation, capacitive sensing, magnetic sensing, thermocouple-based sensing and radio frequency transmission and reception.

  2. Biogeochemistry Science and Education Part One: Using Non-Traditional Stable Isotopes as Environmental Tracers Part Two: Identifying and Measuring Undergraduate Misconceptions in Biogeochemistry

    Science.gov (United States)

    Mead, Chris

    This dissertation is presented in two sections. First, I explore two methods of using stable isotope analysis to trace environmental and biogeochemical processes. Second, I present two related studies investigating student understanding of the biogeochemical concepts that underlie part one. Fe and Hg are each biogeochemically important elements in their own way. Fe is a critical nutrient for phytoplankton, while Hg is detrimental to nearly all forms of life. Fe is often a limiting factor in marine phytoplankton growth. The largest source, by mass, of Fe to the open ocean is windblown mineral dust, but other more soluble sources are more bioavailable. To look for evidence of these non-soil dust sources of Fe to the open ocean, I measured the isotopic composition of aerosol samples collected on Bermuda. I found clear evidence in the fine size fraction of a non-soil dust Fe source, which I conclude is most likely from biomass burning. Widespread adoption of compact fluorescent lamps (CFL) has increased their importance as a source of environmental Hg. Isotope analysis would be a useful tool in quantifying this impact if the isotopic composition of Hg from CFL were known. My measurements show that CFL-Hg is isotopically fractionated, in a unique pattern, during normal operation. This fractionation is large and has a distinctive, mass-independent signature, such that CFL Hg can be uniquely identified from other sources. Misconceptions research in geology has been a very active area of research, but student thinking regarding the related field of biogeochemistry has not yet been studied in detail. From interviews with 40 undergraduates, I identified over 150 specific misconceptions. I also designed a multiple-choice survey (concept inventory) to measure understanding of these same biogeochemistry concepts. I present statistical evidence, based on the Rasch model, for the reliability and validity of this instrument. This instrument will allow teachers and researchers to

  3. Buckling and failure characteristics of graphite-polyimide shear panels

    Science.gov (United States)

    Shuart, M. J.; Hagaman, J. A.

    1983-01-01

    The buckling and failure characteristics of unstiffened, blade stiffened, and hat stiffened graphite-polyimide shear panels are described. The picture frame shear test is used to obtain shear stress-strain data at room temperature and at 316 deg C. The experimental results are compared with a linear buckling analysis, and the specimen failure modes are described. The effect of the 316 deg C test temperature on panel behavior are discussed.

  4. Inorganic Islands on a Highly Stretchable Polyimide Substrate

    OpenAIRE

    Vlassak, Joost J.; Sun, Jeong-Yun; Lu, Nanshu; Yoon, Juil; Oh, Kyu-Hwan; Suo, Zhigang

    2009-01-01

    For a flexible electronic device integrating inorganic materials on a polymer substrate, the polymer can deform substantially, but the inorganic materials usually fracture at small strains. This paper describes an approach to make such a device highly stretchable. A polyimide substrate is first coated with a thin layer of an elastomer, on top of which SiNx islands are fabricated. When the substrate is stretched to a large strain, the SiNx islands remain intact. Calculations confirm that th...

  5. Polyimide Aerogels Using Triisocyanate as Cross-linker.

    Science.gov (United States)

    Nguyen, Baochau N; Meador, Mary Ann B; Scheiman, Daniel; McCorkle, Linda

    2017-08-16

    A family of polyimide (PI)-based aerogels is produced using Desmodur N3300A, an inexpensive triisocyanate, as the cross-linker. The aerogels are prepared by cross-linking amine end-capped polyimide oligomers with the triisocyanate. The polyimide oligomers are formulated using 2,2'-dimethylbenzidine, 4,4'-oxydianiline, or mixtures of both diamines, combined with 3,3',4,4'-biphenyltetracarboxylic dianhydride, and are chemically imidized at room temperature. Depending on the backbone chemistry, chain length, and polymer concentration, density of the aerogels ranged from 0.06 to 0.14 g/cm(3) and Brunauer-Emmett-Teller surface areas ranged from 350 to 600 m(2)/g. Compressive moduli of these aerogels were as high as 225 MPa, which are comparable to, or higher than, those previously reported prepared with similar backbone structures but with other cross-linkers. Because of their lower cost and commercial availability as cross-linker, the aerogels may have further potential as insulation for building and construction, clothing, sporting goods, and automotive applications, although lower-temperature stability may limit their use in some aerospace applications.

  6. Microstructure and Thermomechanical Properties of Polyimide-Silica Nanocomposites

    Directory of Open Access Journals (Sweden)

    A. A. M. Ali

    2007-01-01

    Full Text Available Novel polyimide-silica nanocomposites with interphase chemical bonding have been prepared using the sol-gel process. The morphology, thermal and mechanical properties were studied as a function of silica content and compared with the similar composites having no interphase interaction. The polyimide precursors, polyamic acids (PAAs with or without pendant hydroxyl groups were prepared from the reaction of pyromellitic dianhydride with a mixture of oxydianiline and 1,3 phenylenediamine or 2,4-diminophenol in dimethylacetamide. The PAA with pendant hydroxyl groups was reacted with isocyanatopropyltriethoxysilane to produce alkoxy groups on the chain. The reinforcement of PAA matrices with or without alkoxy groups on the chain was carried out by mixing appropriate amount of tetraethoxysilane (TEOS and carrying out its hydrolysis and condensation in a sol-gel process. Thin hybrid films were imidized by successive heating up to 300C∘. The presence of alkoxy groups on the polymer chain and their cocondensation with TEOS developed the silica network which was interconnected chemically with the polyimide matrix. SEM studies show a drastic decrease in the silica particle size in the chemically bonded system. Higher thermal stability and mechanical strength, improved transparency, and low values of thermal coefficient of expansion were observed in case of chemically bonded composites.

  7. Determination of polymer chain orientation in rubbed polyimide films

    Science.gov (United States)

    Sands, James Matthew

    The mechanism by which small molecule liquid crystals are oriented on the surface of rubbed polyimide films has long been unexplained. Here, the surface and near surface orientation of polymer chains in rubbed films of BPDA-PDA polyimide is demonstrated and quantified by surface analysis. Grazing incidence X-ray scattering (GIXS) and near edge X-ray absorption spectroscopy (NEXAFS) are used to characterize the surface of rubbed and unrubbed polyimide films. In-plane, the polymer films, which are isotropic when unrubbed, become highly anisotropic when rubbed which is evidence for polymer chain orientation. GIXS analysis shows that the polyimide chains which are aligned perpendicular to the rub are affected to a great extent, while polymer chains aligned in the rubbing direction are largely unaffected. The surface anisotropy is, therefore, a result of a decrease in number of chains oriented perpendicular to the rubbing axis. The anisotropy is shown to depend upon the rubbing distance and the rubbing load. Again, GIXS demonstrates that the 1/e alignment load for the surface layer is 2.8 g/cmsp2, and the 1/e alignment distance is 60 cm. The rubbing affects only the polymer chains which are at the surface; the depth to which the chains are affected is measured to be 110 A by depth sensitive GIXS. NEXAFS results complement the GIXS analysis. NEXAFS results demonstrate that the near surface layer (10 A) orients under smaller rubbing loads (1/e alignment load is 1.2 g/cmsp2), but the 1/e alignment distance is the same (67 cm). Overall, the results point to a mechanism of polyimide chain orientation in the surface of rubbed films. The evidence demonstrates that the surface is yielding due to the applied stress. A review of the rubbing conditions demonstrates that the microscopic stress at the surface, even under small macroscopic loads, is considerably larger than the yield stress for the bulk film and is sufficient for the polymer surface to yield.

  8. Polyimide, dianhydride monomers, and polymers, methods of making and uses thereof

    KAUST Repository

    Pinnau, Ingo

    2017-11-16

    Embodiments of the present disclosure include, a dianhydride monomer, a polyimide, a method of making a dianhydride, a method of making a polyimide, and the like. Embodiments of the present disclosure can be used in membrane-based gas separation applications.

  9. 77 FR 62259 - Certain Polyimide Films, Products Containing Same, and Related Methods Commission Determination...

    Science.gov (United States)

    2012-10-12

    ... Polyimide Films, Products Containing Same, and Related Methods Commission Determination To Affirm the Final Initial Determination With Respect to the Issues on Review and To Terminate the Investigation AGENCY: U.S... after importation of certain polyimide films, products containing same, and related methods by reason of...

  10. Unpredictably Stable

    DEFF Research Database (Denmark)

    Failla, Virgilio; Melillo, Francesca; Reichstein, Toke

    2014-01-01

    Is entrepreneurship a more stable career choice for high employment turnover individuals? We find that a transition to entrepreneurship induces a shift towards stayer behavior and identify job matching, job satisfaction and lock-in effects as main drivers. These findings have major implications...

  11. Stable isotope

    African Journals Online (AJOL)

    Results of the study suggest that there are two main carbon pathways for plankton and nekton in the Kariega estuary, carbon derived from the eelgrass and its associated epiphytes and carbon which has its origins in the salt marsh riparian vegetation and zooplankton. Keywords: stable isotope analysis; temperate estuary; ...

  12. Low-melt Viscosity Polyimide Resins for Resin Transfer Molding (RTM) II

    Science.gov (United States)

    Chuang, Kathy C.; Criss, Jim M.; Mintz, Eric A.; Scheiman, Daniel A.; Nguyen, Baochau N.; McCorkle, Linda S.

    2007-01-01

    A series of polyimide resins with low-melt viscosities in the range of 10-30 poise and high glass transition temperatures (Tg s) of 330-370 C were developed for resin transfer molding (RTM) applications. These polyimide resins were formulated from 2,3,3 ,4 -biphenyltetracarboxylic dianhydride (a-BPDA) with 4-phenylethynylphthalic anhydride endcaps along with either 3,4 - oxyaniline (3,4 -ODA), 3,4 -methylenedianiline, (3,4 -MDA) or 3,3 -methylenedianiline (3,3 -MDA). These polyimides had pot lives of 30-60 minutes at 260-280 C, enabling the successful fabrication of T650-35 carbon fiber reinforced composites via RTM process. The viscosity profiles of the polyimide resins and the mechanical properties of the polyimide carbon fiber composites will be discussed.

  13. Process characterization of an aqueous developable photosensitive polyimide on a broadband stepper

    Science.gov (United States)

    Flack, Warren W.; Kulas, Scott; Franklin, Craig L.

    2000-06-01

    The number of lithographic applications that require the use of photosensitive polyimides is rapidly increasing. The major applications for photosensitive polyimides include flip chip bumping, advanced packaging, passivation stress buffer relief and interlevel dielectric films. The thickness requirements for these applications can vary from less than 1 micron to more than 20 microns. For processing simplicity and total cost of ownership, it is desirable to use an aqueous developable polyimide to maintain compatibility with standard photoresist processes. Optical steppers offer significant advantages for processing thick photosensitive polyimides due to the tighter overlay and improved critical dimension (CD) control possible with these lithography tools versus contact printers or full wafer scanners. A stepper has an additional advantage with thick polyimide structures since the focus can be adjusted at various levels into the film, which will result in improved wall angles and enhanced aspect ratios. For this study the performance of a commercially available, positive acting, aqueous developable polyimide is examined over a range of thicknesses using a novel broadband exposure system. This stepper exposes photosensitive films using the full mercury vapor spectrum output from 350 nm to 450 nm (g, h and i line) and allows rapid exposure of both broadband as well as narrow spectral sensitive films. The system has been optimized for thick photoresists and polyimides and uses a combination of low numerical aperture with maximum wafer level intensity to achieve well formed images in thick films yet offers the advantages of tighter CD control and tight overlay inherent in projection optics. Basic photoresist characterization techniques established for thin films in IC manufacturing are applied to the photosensitive polyimide films. Cross sectional SEM analysis, process linearity and process windows are used to establish relative lithographic capabilities for different

  14. Polyimide amplified piezoelectric scanner for endoscopic optical coherence tomography

    Science.gov (United States)

    Zara, Jason M.; Patterson, Paul E.

    2006-02-01

    We have modeled, fabricated, and tested polyimide amplified piezoelectric bimorph scanning mirrors for application in optical coherence tomography (OCT). These scanning mirrors are fabricated using photolithography using polyimide as a substrate. These devices use bimorph actuators to drive polyimide micromechanical structures at resonance. The forced vibration of these micromechanical structures causes polysilicon gold plated mirrors attached to two torsion hinges to tilt. Operating the device at resonance allows us to achieve very large displacements of the mirror at real-time imaging speeds. The large scan angles and fast imaging speeds give these novel scanning devices the potential to be used to image larger areas of tissue to search for diseases such as mucosal cancers and to guide interventional procedures such as laser ablations and biopsies in real time. The mirror and support structures were modeled using one-dimensional beam theory and fundamental vibration mechanics. The structures were also modeled and simulated using ANSYS, a finite element analysis package. The finite element modeling has also lead to the development of new methods to fabricate the entire devices on a single silicon wafer. Prototype scanning devices have demonstrated optical scan angles up to 97 degrees with applied voltages from 15-60 V at a resonant frequencies ranging from 12-60 Hz, appropriate for real time imaging. These amplified bimorph imaging probes have been integrated into the scanning arm of a Spectral Domain OCT (SD-OCT) imaging system and have been used to generate preliminary in vivo human skin images at frame rates of 25 frames per second.

  15. Characterization of Polyimide Foams for Ultra-Lightweight Space Structures

    Science.gov (United States)

    Meador, Michael (Technical Monitor); Hillman, Keithan; Veazie, David R.

    2003-01-01

    Ultra-lightweight materials have played a significant role in nearly every area of human activity ranging from magnetic tapes and artificial organs to atmospheric balloons and space inflatables. The application range of ultra-lightweight materials in past decades has expanded dramatically due to their unsurpassed efficiency in terms of low weight and high compliance properties. A new generation of ultra-lightweight materials involving advanced polymeric materials, such as TEEK (TM) polyimide foams, is beginning to emerge to produce novel performance from ultra-lightweight systems for space applications. As a result, they require that special conditions be fulfilled to ensure adequate structural performance, shape retention, and thermal stability. It is therefore important and essential to develop methodologies for predicting the complex properties of ultra-lightweight foams. To support NASA programs such as the Reusable Launch Vehicle (RLV), Clark Atlanta University, along with SORDAL, Inc., has initiated projects for commercial process development of polyimide foams for the proposed cryogenic tank integrated structure (see figure 1). Fabrication and characterization of high temperature, advanced aerospace-grade polyimide foams and filled foam sandwich composites for specified lifetimes in NASA space applications, as well as quantifying the lifetime of components, are immensely attractive goals. In order to improve the development, durability, safety, and life cycle performance of ultra-lightweight polymeric foams, test methods for the properties are constant concerns in terms of timeliness, reliability, and cost. A major challenge is to identify the mechanisms of failures (i.e., core failure, interfacial debonding, and crack development) that are reflected in the measured properties. The long-term goal of the this research is to develop the tools and capabilities necessary to successfully engineer ultra-lightweight polymeric foams. The desire is to reduce density

  16. Soluble Polyimides Bearing Long-Chain Alkyl Groups on Their Side Chain via Polymer Reaction

    Directory of Open Access Journals (Sweden)

    Yusuke Tsuda

    2012-01-01

    Full Text Available Novel soluble polyimides having long-chain alkyl groups on their side chain were synthesized via polymer reaction with the polyimides having phenolic OH groups and 3,4,5-tris(dodecyloxybenzoic acid (12GA using N,N′-dicyclohexylcarbodiimide (DCC as a dehydration reagent. The polyimides having phenolic OH groups were synthesized from the tetracarboxylic dianhydrides such as 5-(2,5-dioxotetrahydrofuryl-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride (cyclohexene-DA, 4,4′-hexafluoroisopropylidendi(phthalic anhydride (6FDA, and 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride (DSDA and aromatic diamines such as 4,4′-diamino-3,3′-dihydroxybiphenyl (HAB. The polymer reactions were carried out in NMP and the progresses of polymer reactions were quantitatively monitored by 1H NMR measurements (conversion; 12.2–98.7%. The obtained polyimides bearing long-chain alkyl groups have enough molecular weights, good film-forming ability, good solubility for various organic solvents, and enough thermal stability. The water contact angles of the polyimide films were investigated, and it is noted that the introduction of long-chain alkyl groups increases the hydrophobicity of polyimide surface. These polyimides are expected to be applicable as the functional materials for microelectronics such as the alignment layers of LCDs.

  17. Polyimide Nanocomposites Prepared from High-Temperature, Reduced Charge Organoclays

    Science.gov (United States)

    Delozier, D. M.; Orwoll, R. A.; Cahoon, J. F.; Ladislaw, J. S.; Smith, J. G., Jr.; Connell, J. W.

    2003-01-01

    Montmorillonite clays modified with the dihydrochloride salt of 1,3-bis(3-aminophenoxy)benzene (APB) were used in the preparation of polyimide/organoclay hybrid films. Organoclays with varying surface charge based upon APB were prepared and examined for their dispersion behavior in the polymer matrix. High molecular weight poly(amide acid) solutions were prepared in the presence of the organoclays. Films were cast and subsequently heated to 300C to cause imidization. The resulting nanocomposite films, containing 3 wt% of organoclay, were characterized by transmission electron microscopy and X-ray diffraction. The clay's cation exchange capacity (CEC) played a key role in determining the extent of dispersion in the polyimide matrix. Considerable dispersion was observed in some of the nanocomposite films. The most effective organoclay was found to have a CEC of 0.70 meq/g. Nanocomposite films prepared with 3-8 wt% of this organoclay were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), and thin-film tensile testing. High levels of clay dispersion could be achieved even at the higher clay loadings. Results from mechanical testing revealed that while the moduli of the nanocomposites increased with increasing clay loadings, both strength and elongation decreased.

  18. Thermal design of spacecraft solar arrays using a polyimide foam

    Science.gov (United States)

    Bianco, N.; Iasiello, M.; Naso, V.

    2015-11-01

    The design of the Thermal Control System (TCS) of spacecraft solar arrays plays a fundamental role. Indeed, the spacecraft components must operate within a certain range of temperature. If this doesn't occur, their performance is reduced and they may even break. Solar arrays, which are employed to recharge batteries, are directly exposed to the solar heat flux, and they need to be insulated from the earth's surface irradiation. Insulation is currently provided either with a white paint coating or with a Multi Layer Insulation (MLI) system [1]. A configuration based on an open-cell polyimide foam has also been recently proposed [2]. Using polyimide foams in TCSs looks very attractive in terms of costs, weight and assembling. An innovative thermal analysis of the above cited TCS configurations is carried out in this paper, by solving the porous media energy equation, under the assumption of Local Thermal Equilibrium (LTE) between the two phases. Radiation effects through the solar array are also considered by using the Rosseland approximation. Under a stationary daylight condition, temperature profiles are obtained by means of the finite-element based code COMSOL Multiphysics®. Finally, since the weight plays an important role in aerospace applications, weights of the three TCS configurations are compared.

  19. Polyimide/Glass Composite High-Temperature Insulation

    Science.gov (United States)

    Pater, Ruth H.; Vasquez, Peter; Chatlin, Richard L.; Smith, Donald L.; Skalski, Thomas J.; Johnson, Gary S.; Chu, Sang-Hyon

    2009-01-01

    Lightweight composites of RP46 polyimide and glass fibers have been found to be useful as extraordinarily fire-resistant electrical-insulation materials. RP46 is a polyimide of the polymerization of monomeric reactants (PMR) type, developed by NASA Langley Research Center. RP46 has properties that make it attractive for use in electrical insulation at high temperatures. These properties include high-temperature resistance, low relative permittivity, low dissipation factor, outstanding mechanical properties, and excellent resistance to moisture and chemicals. Moreover, RP46 contains no halogen or other toxic materials and when burned it does not produce toxic fume or gaseous materials. The U. S. Navy has been seeking lightweight, high-temperature-resistant electrical-insulation materials in a program directed toward reducing fire hazards and weights in ship electrical systems. To satisfy the requirements of this program, an electrical-insulation material must withstand a 3-hour gas-flame test at 1,600 F (about 871 C). Prior to the development reported here, RP46 was rated for use at temperatures from -150 to +700 F (about -101 to 371 C), and no polymeric product - not even RP46 - was expected to withstand the Navy 3-hour gas-flame test.

  20. Sulfonated polyimides containing triphenylphosphine oxide for proton exchange membranes

    Energy Technology Data Exchange (ETDEWEB)

    Mandal, Arun Kumar; Bera, Debaditya; Banerjee, Susanta, E-mail: susanta@matsc.iitkgp.ernet.in

    2016-09-15

    A series of sulfonated co-polyimides (co-SPI) were prepared by one pot polycondensation reaction of a combination of diamines namely; 4,4′-diaminostilbene-2,2′-disulfonic acid (DSDSA) and prepared non-sulfonated diamine (DATPPO) containing triphenylphosphine oxide with 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA). All these soluble co-SPI gave flexible membranes with high thermal stability and showed good mechanical property. Transmission electron microscopy (TEM) analysis revealed the microphase separated morphology with well-dispersed hydrophilic (cluster size in the range of 5–55 nm) domains. The co-SPI membranes showed high oxidative and hydrolytic stability with higher proton conductivity. All these co-SPI membranes exhibited low water uptake and swelling ratio. The co-SPI membrane TPPO-60 (60% degree of sulfonation) with IEC{sub W} = 1.84 mequiv g{sup −1} showed high proton conductivity (99 mS cm{sup −1} at 80 °C and 107 mS cm{sup −1} at 90 °C) in water with high oxidative (20 h) and hydrolytic stability (only 5% degradation in 24 h). - Highlights: • Triphenylphosphine oxide containing sulfonated polyimides (SPIs) was synthesized. • The SPIs showed good oxidative and hydrolytic stability and high proton conductivity. • TEM analysis revealed well separated morphology of the SPIs.

  1. Porous Cross-Linked Polyimide-Urea Networks

    Science.gov (United States)

    Meador, Mary Ann B. (Inventor); Nguyen, Baochau N. (Inventor)

    2015-01-01

    Porous cross-linked polyimide-urea networks are provided. The networks comprise a subunit comprising two anhydride end-capped polyamic acid oligomers in direct connection via a urea linkage. The oligomers (a) each comprise a repeating unit of a dianhydride and a diamine and a terminal anhydride group and (b) are formulated with 2 to 15 of the repeating units. The subunit was formed by reaction of the diamine and a diisocyanate to form a diamine-urea linkage-diamine group, followed by reaction of the diamine-urea linkage-diamine group with the dianhydride and the diamine to form the subunit. The subunit has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups. The subunit has been chemically imidized to yield the porous cross-linked polyimide-urea network. Also provided are wet gels, aerogels, and thin films comprising the networks, and methods of making the networks.

  2. Fabrication of nanochannels on polyimide films using dynamic plowing lithography

    Science.gov (United States)

    Stoica, Iuliana; Barzic, Andreea Irina; Hulubei, Camelia

    2017-12-01

    Three distinct polyimide films were analyzed from the point of view of their morphology in order to determine if their surface features can be adapted for applications where surface anisotropy is mandatory. Channels of nanometric dimensions were created on surface of the specimens by using a less common atomic force microscopy (AFM) method, namely Dynamic Plowing Lithography (DPL). The changes generated by DPL procedure were monitored through the surface texture and other functional parameters, denoting the surface orientation degree and also bearing and fluid retention properties. The results revealed that in the same nanolithography conditions, the diamine and dianhydride moieties have affected the characteristics of the nanochannels. This was explained based on the aliphatic/aromatic nature of the monomers and the backbone flexibility. The reported data are of great importance in designing custom nanostructures with enhanced anisotropy on surface of polyimide films for liquid crystal orientation or guided cell growth purposes. At the end, to track the effect of the nanolithography process on the tip sharpness, degradation and contamination, the blind tip reconstruction was performed on AFM probe, before and after lithography experiments, using TGT1 test grating AFM image.

  3. Molecular Modeling of the Poling of Piezoelectric Polyimides

    Science.gov (United States)

    Young, J. A.; Farmer, B. L.; Hinkley, J. A.

    1999-01-01

    The computational method described in this paper allows the calculation of the dielectric relaxation strength of an amorphous polymer based solely upon its chemical structure. The 4,4' oxydiphthalic anhydride (ODPA) dianhydride and bis-aminophenoxybenzene (APB) diamine based polyimides, (beta-CN) APB-ODPA and APB-ODPA were studied. Amorphous cells were constructed and then poled using molecular dynamics. Dielectric relaxation strengths of Delta(epsilon) = 17.8 for (beta-CN) APB-ODPA and Delta(epsilon) = 7.7 for APB-ODPA were predicted. These values are in excellent agreement with the experimental values. It was found that both the pendant nitrile dipole and the backbone anhydride residue dipole make significant contributions to the polyimides dielectric response. Specifically, it was shown that the difference in the magnitude of the dielectric relaxations is directly attributable to the nitrile dipole. The size of the relaxations indicate an absence of cooperative dipolar motions, The model was used to explain these results in terms of the average orientation of the nitrile and anhydride dipoles to within 51 deg. and 63 deg., respectively, of the applied electric field.

  4. SYNTHESIS AND CHARACTERIZATION OF POLYIMIDE-ZEOLITE MIXED MATRIX MEMBRANE

    Directory of Open Access Journals (Sweden)

    Budiyono Budiyono

    2012-02-01

    Full Text Available Biogas has become an attractive alternative energy source due to the limitation of energy from fossil. In this study, a new type of mixed matrix membrane (MMM consisting of polyimide-zeolite was synthesized and characterized for biogas purification. The MMM consists of medium concentration of polymer (20% wt polyimide, 80% N-Methyl-2-pyrrolidone (NMP and 25% zeolite 4A in total solid were prepared by a dry/wet phase inversion technique.  The fabricated MMM was characterized using SEM, DSC, TGA and gas permeation. Post treatment coating procedure was also conducted. The research showed that surface coating by 3% silicone rubber toward MMM PI 20% gave the significant effect to improve membrane selectivity. The ideal selectivity for CO2/CH4 separation increased from 0.99 for before coating to 7.9 after coating for PI-Zeolite MMM, respectively. The results suggest that PI-Zeolite MMM with good post treatment procedure will increase the membrane selectivity and permeability with more saver polymer requirement as well as energy saving due to low energy for mixing.

  5. Excimer laser ablation of polyimide: a 14-year IBM perspective

    Science.gov (United States)

    Brannon, James H.; Wassick, Thomas A.

    1997-05-01

    IBM introduced the first commercial high-end mainframe computer system incorporating laser ablation technology in 1991. This milestone was the culmination of nearly a decade of scientific, engineering, and manufacturing effort. Extensive research and development on 308 nm laser ablation of polyimide lead to the first IBM prototype ablation tool in 1987 for the production of via-holes in thin film packaging structures. This prototype, similar to step and repeat photolithography systems, evolved into full-scale manufacturing tools which utilize sophisticated beam shaping, beam homogenizing, and projection optics. But the maturity of this technology belies the fact that the scientific understanding of the laser ablation process is still far from complete. This paper briefly reviews the engineering and scientific accomplishments, both within and external to IBM, that lead to the commercial utilization of the laser ablation process. Current technical tissues are discussed, in addition to alternative IBM applications of polyimide ablation. The paper concludes by discussing the relative merits of excimer vs. solid-state lasers, and how each may impact future manufacturing technology.

  6. Effects of Supercritical CO 2 Conditioning on Cross-Linked Polyimide Membranes

    KAUST Repository

    Kratochvil, Adam M.

    2010-05-25

    The effects of supercritical CO2 (scCO2) conditioning on high-performance cross-linked polyimide membranes is examined through gas permeation and sorption experiments. Under supercritical conditions, the cross-linked polymers do not exhibit a structural reorganization of the polymer matrix that was observed in the non-cross-linkable, free acid polymer. Pure gas permeation isotherms and mixed gas permeabilities and selectivities show the cross-linked polymers to be much more stable to scCO2 conditioning than the free acid polymer. In fact, following scCO2 conditioning, the mixed gas CO2 permeabilities of the cross-linked polymers increased while the CO2/CH4 separation factors remained relatively unchanged. This response highlights the stability and high performance of these cross-linked membranes in aggressive environments. In addition, this response reveals the potential for the preconditioning of cross-linked polymer membranes to enhance productivity without sacrificing efficiency in practical applications which, in effect, provides another tool to \\'tune\\' membrane properties for a given separation. Finally, the dual mode model accurately describes the sorption and dilation characteristics of the cross-linked polymers. The changes in the dual mode sorption model parameters before and after the scCO2 exposure also provide insights into the alterations in the different glassy samples due to the cross-linking and scCO2 exposure. © 2010 American Chemical Society.

  7. Enhanced thermal stability of RuO2/polyimide interface for flexible device applications

    Science.gov (United States)

    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.

  8. Functional separator consisted of polyimide nonwoven fabrics and polyethylene coating layer for lithium-ion batteries

    Science.gov (United States)

    Shi, Chuan; Zhang, Peng; Huang, Shaohua; He, Xinyi; Yang, Pingting; Wu, Dezhi; Sun, Daoheng; Zhao, Jinbao

    2015-12-01

    In this paper, a composite membrane with nonwoven polyimide (PI) membrane as structural support and polyethylene (PE) particles coating layer as a thermal shutdown layer, is fabricated as the separator for lithium-ion battery. Different from PI nonwoven membrane, the PE coating PI nonwoven composite membrane (PE-PI-S) not only shows excellent thermal shutdown function, similar to traditional multilayer PP/PE/PP separator, but also exhibits much higher thermal stability, better wettability to the polar electrolyte and lower internal resistance than the PP/PE/PP separator. The electrolyte uptake and ionic conductivity of PE-PI-S increase from 58%, 0.84 mS cm-1 to 400%, 1.34 mS cm-1, respectively. Furthermore, the thermal shutdown function of PE-PI-S can be controlled widely in the temperature range from 120 °C to more than 200 °C while the multilayer PP/PE/PP separator only with a shutdown temperature range from 130 °C to 160 °C. Lithium ion battery with PE-PI-S nonwoven separator also shows excellent stable cycling and good rate performance.

  9. Photosensitive-polyimide based method for fabricating various neural electrode architectures

    Science.gov (United States)

    Kato, Yasuhiro X.; Furukawa, Shigeto; Samejima, Kazuyuki; Hironaka, Naoyuki; Kashino, Makio

    2012-01-01

    An extensive photosensitive-polyimide (PSPI)-based method for designing and fabricating various neural electrode architectures was developed. The method aims to broaden the design flexibility and expand the fabrication capability for neural electrodes to improve the quality of recorded signals and integrate other functions. After characterizing PSPI's properties for micromachining processes, we successfully designed and fabricated various neural electrodes even on a non-flat substrate using only one PSPI as an insulation material and without the time-consuming dry etching processes. The fabricated neural electrodes were an electrocorticogram (ECoG) electrode, a mesh intracortical electrode with a unique lattice-like mesh structure to fixate neural tissue, and a guide cannula electrode with recording microelectrodes placed on the curved surface of a guide cannula as a microdialysis probe. In vivo neural recordings using anesthetized rats demonstrated that these electrodes can be used to record neural activities repeatedly without any breakage and mechanical failures, which potentially promises stable recordings for long periods of time. These successes make us believe that this PSPI-based fabrication is a powerful method, permitting flexible design, and easy optimization of electrode architectures for a variety of electrophysiological experimental research with improved neural recording performance. PMID:22719725

  10. Stable beams

    CERN Multimedia

    2015-01-01

    Stable beams: two simple words that carry so much meaning at CERN. When LHC page one switched from "squeeze" to "stable beams" at 10.40 a.m. on Wednesday, 3 June, it triggered scenes of jubilation in control rooms around the CERN sites, as the LHC experiments started to record physics data for the first time in 27 months. This is what CERN is here for, and it’s great to be back in business after such a long period of preparation for the next stage in the LHC adventure.   I’ve said it before, but I’ll say it again. This was a great achievement, and testimony to the hard and dedicated work of so many people in the global CERN community. I could start to list the teams that have contributed, but that would be a mistake. Instead, I’d simply like to say that an achievement as impressive as running the LHC – a machine of superlatives in every respect – takes the combined effort and enthusiasm of everyone ...

  11. Selectively deposited copper on laser-treated polyimide using electroless plating

    Science.gov (United States)

    Zhao, Gang; Phillips, Harvey M.; Zheng, HongYu; Tam, Siu Chung; Liu, Wen Qing; Wen, Gongling; Gong, Zhiben; Lam, Yee Loy

    2000-06-01

    Many reviews about the interconnection line fabrication by laser processing method were reported recently. UV laser process polyimide has been studied thoroughly during the past decade. In this report, we discussed the utilization of surface potential changing on polyimide film irradiated by excimer KrF laser and metallized the UV laser treated polyimide surface by electroless copper deposition. A new negatively charged polymer stabilized Pd solution was applied as catalyst in this experiment. We also produced pattern-wised fine line on KrF laser induced PI surface using this method.

  12. Functionally Graded Polyimide Nanocomposite Foams for Ablative and Inflatable/Flexible/Deplorable Structures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of the proposed research is to develop functionally graded polyimide foams as light-weight, high performance thermal protection systems (TPS) for...

  13. Integration of temperature sensors in polyimide-based thin-film electrode arrays

    National Research Council Canada - National Science Library

    M. F. Porto Cruz; E. Fiedler; O. F. Cota Monjarás; T. Stieglitz

    2015-01-01

    ... caused by electrical or optogenetical stimulation could be accurately controlled. Within this work, a thin-film platinum RTD embedded in polyimide and a readout system based on the Wheatstone bridge configuration are presented...

  14. Resonant infrared pulsed laser deposition of a polyimide precursor

    Energy Technology Data Exchange (ETDEWEB)

    Dygert, N L; Schriver, K E; Jr, R F Haglund [Department of Physics and Astronomy and W M Keck Foundation Free-Electron Laser Centre, Vanderbilt University, Nashville TN 37235 (United States)

    2007-04-15

    Poly(amic acid) (PAA), a precursor to polyimide, was successfully deposited on substrates without reaching curing temperature, by resonant infrared pulsed laser ablation. The PAA was prepared by dissolving pyromellitic dianhydride and 4, 4' oxidianiline in the polar solvent Nmethyl pyrrolidinone (NMP). The PAA was deposited in droplet-like morphologies when ablation occurred in air, and in string-like moieties in the case of ablation in vacuum. In the as-deposited condition, the PAA was easily removed by washing with NMP; however, once cured thermally for thirty minutes, the PAA hardened, indicating the expected thermosetting property. Plume shadowgraphy showed very clear contrasts in the ablation mechanism between ablation of the solvent alone and the ablation of the PAA, even at low concentrations. A Wavelength dependence in plume velocity was also observed.

  15. Graphite fluoride as a solid lubricant in a polyimide binder

    Science.gov (United States)

    Fusaro, R. L.; Sliney, H. E.

    1972-01-01

    Polyimide resin (PI) was shown to be a suitable binder material for the solid lubricant graphite fluoride, (CF(1.1))n. Comparisons were made to similar tests using PI-bonded MOS2 films, graphite fluoride rubbed films, and MOS2 rubbed films. The results showed that, at any one specific temperature between 25 and 400 C, the wear life of PI-bonded graphite fluoride films exceeded those of the other three films by at least a factor of 2 and by as much as a factor of 60. Minimum friction coefficients for the PI-bonded films were 0.08 for graphite fluoride and 0.04 for MOS2. The rider wear rates for the two PI-bonded films at 25 C were nearly equal.

  16. Polyimide membranes for alcohols dehydration: from basic aspects to separation applications

    OpenAIRE

    Leo, Mariangela

    2011-01-01

    The first part of this work aimed to the determination of the absorption and desorption kinetics of an alcohol (methanol) inside a commercial polyimide (PMDA ODA) and to the identification of the interactions with polymeric network. The understanding of the molecular mechanisms of diffusion can be helpful in designing the chemical structure of future polymers for optimal transport properties. The diffusion of methanol into polyimide films was studied by in situ FTIR spectroscopy, one of th...

  17. RAPID COMMUNICATION: Fine-hole drilling in Upilex polyimide and glass by TEA ? laser ablation

    Science.gov (United States)

    Dyer, P. E.; Waldeck, I.; Roberts, G. C.

    1997-03-01

    Small-scale hole formation in Upilex polyimide and soda-lime glass using TEA 0022-3727/30/6/003/img2 laser ablation is reported. Hole dimensions as small as 0022-3727/30/6/003/img3 produced in the polyimide suggest optical resolution rather than thermal degradation effects limit the feature size attainable in infrared TEA 0022-3727/30/6/003/img2 laser polymer ablation.

  18. Molecular Engineering of Azobenzene-Functionalized Polyimides to Enhance Both Photomechanical Work and Motion (POSTPRINT)

    Science.gov (United States)

    2014-09-01

    concentrations of azobenzene in both linear and cross-linked PIs, 30 mol % azobenzene diamine (4) and 20 mol % of azobenzene triamine (7) were added...AFRL-RX-WP-JA-2014-0204 MOLECULAR ENGINEERING OF AZOBENZENE - FUNCTIONALIZED POLYIMIDES TO ENHANCE BOTH PHOTOMECHANICAL WORK AND MOTION...August 2014 4. TITLE AND SUBTITLE MOLECULAR ENGINEERING OF AZOBENZENE - FUNCTIONALIZED POLYIMIDES TO ENHANCE BOTH PHOTOMECHANICAL WORK AND MOTION

  19. Characterization study of an aqueous developable photosensitive polyimide on 300-mm wafers

    Science.gov (United States)

    Flack, Warren W.; Kulas, Scott; Franklin, Craig L.

    2001-09-01

    The advent of 300 mm wafer processing for semiconductor manufacturing has had a great impact on the development of photolithographic materials, equipment and associated processes. At the same time advanced packaging techniques for these semiconductor devices are making strides for smaller, faster and lower cost parts with improved reliability. Photosensitive polyimides are used for passivation stress buffer relief and soft error protection on almost all memory devices such as DRAM as well as final passivation layers for subsequent interconnect bumping operations on most of today's advanced microprocessors. For processing simplicity and total cost of ownership, it is desirable to use an aqueous developable polyimide to maintain compatibility with standard photoresist processes. This study will investigate the feasibility of processing photosensitive polyimides on 300 mm wafers. The performance of a commercially available, positive acting, aqueous developable polyimide is examined at a thickness appropriate for logic devices. A broadband stepper is utilized since polyimides are highly aromatic polymers that strongly absorb UV light below 350 nm. This stepper exposes photosensitive films using mercury vapor spectrum output from 390 nm to 450 nm (g and h-line) and allows rapid exposure of both broadband as well as narrow spectral sensitive films. The system has been optimized for thick photoresists and polyimides and uses a combination of low numerical aperture with maximum wafer level intensity to achieve well formed images in thick films. Process capability for 300 mm wafers is determined by analyzing polyimide film thickness uniformity and critical dimension (CD) control across the wafer. Basic photoresist characterization techniques such as cross sectional SEM analysis, process linearity and process windows are also used to establish lithographic capabilities. The trade-offs for various process capability windows are reviewed to determine the optimum process

  20. Dense film polyimide membranes for aggressive sour gas feed separations

    KAUST Repository

    Kraftschik, Brian

    2013-02-01

    Dense film membranes of the copolyimide 6FDA-DAM:DABA (3:2) are studied for simultaneous removal of CO2 and H2S from sour natural gas streams. Pure and mixed gas permeation as well as pure gas sorption data are reported at 35°C and pressures up to 62bar. The H2S partial pressures used are representative of highly aggressive field operations. Penetrant-induced plasticization effects are evident at feed pressures below 1bar in pure H2S feeds; sub-Tg thermal annealing is used to effectively mitigate this effect, and these annealed films are used throughout the study. Surprisingly, H2S/CH4 selectivity nearly doubles for mixed gas testing in comparison to the pure component ideal selectivity values and approaches the level of a state-of-the-art glassy polymer, cellulose acetate (CA), at H2S partial pressures above 2bar. Furthermore, permeation experiments using a 9.95% H2S, 19.9% CO2, 70.15% CH4 mixture at low feed pressures give CO2/CH4 selectivity of up to 49-over 30% greater than the pure component selectivity for 6FDA-DAM:DABA (3:2). The overall sour gas separation performance of this polyimide is comparable to high-performance rubbery polymer membranes, which have been reported for only moderate H2S partial pressure feeds, and is superior to that for CA based on a practical combined acid gas separation efficiency metric that we introduce. Finally, methods for continued development of the current polyimide membrane material for aggressive sour gas separations are presented. © 2012 Elsevier B.V.

  1. Effect of Atmospheric Pressure Plasma Modification on Polyimide and Adhesive Joining with Titanium

    Science.gov (United States)

    Akram, M.; Jansen, K. M. B.; Ernst, L. J.; Bhowmik, S.; Ajeesh, G.; Ahmed, S.; Chakraborty, D.

    2015-10-01

    This investigation highlights the effect of surface modification on polyimide by atmospheric pressure plasma treatment with different exposure time. Surface modification of polymer by plasma treatment essentially creates physical and chemical changes such as cross-linking and formation of free radicals. It also forms oxygen functionalization in the form of polar groups on polymer surface, hence improving the wetting and adhesion properties. It is observed that surface energy of the polymer increases with increasing exposure time of atmospheric pressure plasma. However, prolonged exposure time of plasma results in deterioration of the surface layer of polyimide resulting in degradation and embrittlement. Scanning electron microscopy and atomic force microscopy analysis reveal that there is a considerable morphological change on the polymer surface due to atmospheric pressure plasma treatment. X-ray photo electron spectroscopy analysis reveals that the oxygen functionalities of polymer surface increases significantly when polyimide is exposed to atmospheric pressure plasma. Untreated and atmospheric pressure plasma-treated polyimide sheet are adhesive bonded by employing polyimide adhesive as well as with titanium substrate. Due to surface modification of polyimide, it is observed that there is a significant increase in lap shear tensile strength, and therefore, this technology is highly acceptable for aviation and space applications.

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

    Science.gov (United States)

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

    2012-01-01

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

  3. The compressive behaviour and constitutive equation of polyimide foam in wide strain rate and temperature

    Directory of Open Access Journals (Sweden)

    Yoshimoto Akifumi

    2015-01-01

    Full Text Available These days, polymer foams, such as polyurethane foam and polystyrene foam, are used in various situations as a thermal insulator or shock absorber. In general, however, their strength is insufficient in high temperature environments because of their low glass transition temperature. Polyimide is a polymer which has a higher glass transition temperature and high strength. Its mechanical properties do not vary greatly, even in low temperature environments. Therefore, polyimide foam is expected to be used in the aerospace industry. Thus, the constitutive equation of polyimide foam that can be applied across a wide range of strain rates and ambient temperature is very useful. In this study, a series of compression tests at various strain rates, from 10−3 to 103 s−1 were carried out in order to examine the effect of strain rate on the compressive properties of polyimide foam. The flow stress of polyimide foam increased rapidly at dynamic strain rates. The effect of ambient temperature on the properties of polyimide foam was also investigated at temperature from − 190 °C to 270°∘C. The flow stress decreased with increasing temperature.

  4. Novel thermally cross-linked polyimide membranes for ethanol dehydration via pervaporation

    KAUST Repository

    Xu, Sheng

    2015-12-01

    © 2015 Elsevier B.V. In this work, two novel carboxyl-containing polyimides, 2,2\\'-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride-4,4\\'-diaminodiphenylmethane/3,5-diaminobenzoic acid (6FDA-MDA/DABA, FMD) and 3,3\\',4,4\\'-benzophenone tetracarboxylic dianhydride-4,4\\'-diaminodiphenylmethane/3,5-diaminobenzoic acid (BTDA-MDA/DABA, BMD), are synthesized via chemical and thermal imidization methods, respectively, and employed as pervaporation membranes for ethanol dehydration. Chemical structures of the two polyimides are examined by FTIR and TGA to confirm the successful synthesis. A post thermal treatment of the polyimide membranes with the temperature range of 250 to 400. °C is applied, and its effects on the membrane morphology and separation performance are studied and characterized by FTIR, TGA, WXRD, solubility and sorption test. It is believed that the thermal treatment of the carboxyl-containing polyimide membrane at a relative low temperature only leads to the physical annealing, while it may cause the decarboxylation-induced cross-linking at a higher temperature. In addition, the operation temperature in pervaporation is also varied and shown to be an important factor to affect the final membrane performance. Performance benchmarking shows that the developed polyimide membranes both have superior pervaporation performance to most other flat-sheet dense membranes. This work is believed to shed useful insights on polyimide membranes for pervaporation applications.

  5. Synthesis, Processing, and Characterization of Inorganic-Organic Hybrid Cross-Linked Silica, Organic Polyimide, and Inorganic Aluminosilicate Aerogels

    Science.gov (United States)

    Nguyen, Baochau N.; Guo, Haiquan N.; McCorkle, Linda S.

    2014-01-01

    As aerospace applications become ever more demanding, novel insulation materials with lower thermal conductivity, lighter weight and higher use temperature are required to fit the aerospace application needs. Having nanopores and high porosity, aerogels are superior thermal insulators, among other things. The use of silica aerogels in general is quite restricted due to their inherent fragility, hygroscopic nature, and poor mechanical properties, especially in extereme aerospace environments. Our research goal is to develop aerogels with better mechanical and environmental stability for a variety of aeronautic and space applications including space suit insulation for planetary surface missions, insulation for inflatable structures for habitats, inflatable aerodynamic decelerators for entry, descent and landing (EDL) operations, and cryotank insulation for advance space propulsion systems. Different type of aerogels including organic-inorganic polymer reinforced (hybrid) silica-based aerogels, polyimide aerogels and inorganic aluminosilicate aerogels have been developed and examined.

  6. Preparation of polyimide/Al{sub 2}O{sub 3} composite films as improved solid dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Alias, Asliza; Ahmad, Z. [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Pulau Pinang (Malaysia); Ismail, A.B., E-mail: badri@eng.usm.my [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Pulau Pinang (Malaysia)

    2011-06-15

    Highlights: > We prepare and characterize polyimide-alumina composite as solid dielectric. > Prolong the curing time at low temperature reduces the composite s shrinkage problem. > Dielectric constant increases with the increase of alumina content. > Thermal properties is improved with the addition of alumina. - Abstract: Considerable demand for solid thin-film dielectrics with high dielectric constants for use in the fabrication of capacitors has been observed. In this study, polyimide (PI)/Al{sub 2}O{sub 3} composite films were prepared by incorporating different micron-sized {alpha}-Al{sub 2}O{sub 3} contents into PI derived from pyromellitic dianyhydride and 4,4'-oxydianiline via ultrasonication. Chemical structure, morphology, dielectric and thermal properties were investigated by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), LCR meter and Perkin Elmer Pyris 6. FTIR spectra showed complete imidization, and all characteristic peaks of the imide groups are observed in PI and PI/Al{sub 2}O{sub 3} composite films. XRD patterns revealed that the PI/Al{sub 2}O{sub 3} composite exhibits peaks similar to those of {alpha}-Al{sub 2}O{sub 3}, indicating that the crystal structure of {alpha}-Al{sub 2}O{sub 3} remains unchanged and stable after being doped into the PI matrix. SEM micrographs showed uniform distribution of {alpha}-Al{sub 2}O{sub 3} particles in the PI matrix. Meanwhile, the dielectric constant, dielectric loss and thermal stability of PI/Al{sub 2}O{sub 3} increases with the addition of {alpha}-Al{sub 2}O{sub 3} content.

  7. Atomic step-and-terrace surface of polyimide sheet for advanced polymer substrate engineering

    Science.gov (United States)

    Tan, G.; Shimada, K.; Nozawa, Y.; Kaneko, S.; Urakami, T.; Koyama, K.; Komura, M.; Matsuda, A.; Yoshimoto, M.

    2016-07-01

    Typical thermostable and flexible polyimide polymers exhibit many excellent properties such as strong mechanical and chemical resistance. However, in contrast to single-crystal substrates like silicon or sapphire, polymers mostly display disordered and rough surfaces, which may result in instability and degradation of the interfaces between thin films and polymer substrates. As a step toward the development of next-generation polymer substrates, we here report single-atom-layer imprinting onto the polyimide sheets, resulting in an ultrasmooth 0.3 nm high atomic step-and-terrace surface on the polyimides. The ultrasmooth polymer substrates are expected to be applied to the fabrication of nanostructures such as superlattices, nanowires, or quantum dots in nanoscale-controlled electronic devices. We fabricate smooth and atomically stepped indium tin oxide transparent conducting oxide thin films on the imprinted polyimide sheets for future use in organic-based optoelectronic devices processed with nanoscale precision. Furthermore, toward 2D polymer substrate nanoengineering, we demonstrate nanoscale letter writing on the atomic step-and-terrace polyimide surface via atomic force microscopy probe scratching.

  8. Fabrication and evaluation of dispersed-Ag nanoparticles-in-polyimide thin films

    Science.gov (United States)

    Sonehara, Makoto; Watanabe, Yuki; Yamaguchi, Sota; Kato, Takanori; Yoshisaku, Yasuaki; Sato, Toshiro; Itoh, Eiji

    2017-10-01

    A thin-film common-mode filter (TF-CMF) for cell phones in the UHF band was fabricated and evaluated. The TF-CMF consisted of multiple metal-insulator-metal (MIM) capacitors and inductors. The sizes of the 0.70-1.0 GHz band-type and 1.8-2.0 GHz band-type TF-CMFs are 1,140 × 1,260 × 10.5 µm3, and 1,060 × 1,060 × 10.5 µm3, respectively. The footprint in both types of TF-CMFs is over 1 mm2. In order to miniaturize the TF-CMF, we proposed to change a polyimide-only to a polyimide with dispersed Ag nanoparticles with high permittivity in the insulator layer for the MIM capacitor of the TF-CMF. A polyimide (\\text{polyimide precursor}:\\text{toluene with dispersed Ag nanoparticles} = 100:1) thin film with dispersed high-density Ag nanoparticles has a relative permittivity of about 8, which is twice as high as that of the polyimide-only thin film. If the capacitance and distance between electrodes are the same, then the capacitor footprint may be halved.

  9. Effects of nanofiller morphology and aspect ratio on the rheo-mechanical properties of polyimide nanocomposites

    Directory of Open Access Journals (Sweden)

    2008-07-01

    Full Text Available New polyimide nanocomposites containing organically modified montmorillonite (MMT, synthetic silicate (chrysotile nanotubes (SNT, and zirconium dioxide (ZrO2 were prepared to investigate the influence of the nanoparticle morphology on the nanocomposite rheology and mechanical properties under selected conditions that the materials are likely to encounter during use. The efficiency of homogeneous dispersion of the nanoparticles in the polyimide matrix was studied by measuring the rheology of model oligoimides (OI dispersions containing the desired amounts of the nanoparticles. The OI/nanoparticles dispersions showed significant increase in complex viscosity with increasing concentration of the nanoparticles that depended strongly on the nanoparticle morphology and aspect ratio. Polyimide nanocomposite films (PI-PM prepared from the poly(amic acid of poly(pyromellitic dianhydride-co-4,4′-oxydianiline (PM filled with the desired concentration of the nanoparticles showed an increase in tensile modulus with increasing nanoparticle concentration in the order MMT>SNT>ZrO2. In contrast to the PI-PM/MMT films, the PI-PM films filled with 10 vol% of SNT and ZrO2 showed higher sample failure strains, suggesting that the SNT and ZrO2 may be more effective in improving the ductility of the polyimide nanocomposites for applications where the relatively brittle polyimide/MMT nanocomposites films are not useable.

  10. Synthesis, characterization and thermal analysis of polyimide-cobalt ferrite nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Mazuera, David, E-mail: jesus.mazuera@upr.edu [Department of Engineering Science and Materials, University of Puerto Rico, 259 Alfonso Valdez Blvd Stefani Bldg of S-603, Mayaguez, 00680 (Puerto Rico); Perales, Oscar, E-mail: oscarjuan.perales@upr.edu [Department of Engineering Science and Materials, University of Puerto Rico, 259 Alfonso Valdez Blvd Stefani Bldg of S-603, Mayaguez, 00680 (Puerto Rico); Suarez, Marcelo; Singh, Surinder [Department of Engineering Science and Materials, University of Puerto Rico, 259 Alfonso Valdez Blvd Stefani Bldg of S-603, Mayaguez, 00680 (Puerto Rico)

    2010-09-15

    Research highlights: {center_dot} Polyimide-cobalt ferrite nanocomposites were successfully produced. {center_dot} Produced nanocomposites are suitable for use at temperatures below 80 deg. C. {center_dot} Magnetic properties of nanocomposites were no sensitive to particle agglomeration. {center_dot} Good distribution of clustered nanoparticles was achieved in produced composites. - Abstract: Cobalt ferrite nanocrystals were synthesized under size-controlled conditions in aqueous phase and incorporated into a polyimide matrix at various volumetric loads. Synthesized 20 nm cobalt ferrite single crystals, which exhibited a room-temperature coercivity of 2.9 kOe, were dispersed in polyimide precursor using two techniques: homogenizer and ball milling. These suspensions were then cured to develop the polyimide structure in the resulting nanocomposites. Produced films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction and vibrating sample magnetometry, which confirmed the formation of the desired phases. As expected, the saturation magnetization in the nanocomposites varied according to the polyimide/ferrite weight ratio, while coercivity remained at the value corresponding to pure cobalt ferrite nanocrystals. Thermal degradation, thermal stability and dynamic mechanical analyses tests were also carried out to assess the effect of the concentration of the ferrite disperse phase on the thermo-mechanical behavior of the corresponding nanocomposites as well as the used dispersion techniques.

  11. Gas Permeation Properties of Soluble Aromatic Polyimides Based on 4-Fluoro-4,4'-Diaminotriphenylmethane.

    Science.gov (United States)

    Guzmán-Lucero, Diego; Palomeque-Santiago, Jorge Froylán; Camacho-Zúñiga, Claudia; Ruiz-Treviño, Francisco Alberto; Guzmán, Javier; Galicia-Aguilar, Alberto; Aguilar-Lugo, Carla

    2015-04-21

    A series of new organic polyimides were synthesized from 4-fluoro-4'4"-diaminotriphenylmethane and four different aromatic dianhydrides through a one-step, high-temperature, direct polycondensation in m-cresol at 180-200 °C, resulting in the formation of high-molecular-weight polyimides (inherent viscosities ~ 1.0-1.3 dL/g). All the resulting polyimides exhibited good thermal stability with initial decomposition temperatures above 434 °C, glass-transition temperatures between 285 and 316 °C, and good solubility in polar aprotic solvents. Wide-angle X-ray scattering data indicated that the polyimides were amorphous. Dense membranes were prepared by solution casting and solvent evaporation to evaluate their gas transport properties (permeability, diffusivity, and solubility coefficients) toward pure hydrogen, helium, oxygen, nitrogen, methane, and carbon dioxide gases. In general, the gas permeability was increased as both the fractional free volume and d-spacing were also increased. A good combination of permeability and selectivity was promoted efficiently by the bulky hexafluoroisopropylidene and 4-fluoro-phenyl groups introduced into the polyimides. The results indicate that the gas transport properties of these films depend on both the structure of the anhydride moiety, which controls the intrinsic intramolecular rigidity, and the 4-fluoro-phenyl pendant group, which disrupts the intermolecular packing.

  12. Gas Permeation Properties of Soluble Aromatic Polyimides Based on 4-Fluoro-4,4'-Diaminotriphenylmethane

    Directory of Open Access Journals (Sweden)

    Diego Guzmán-Lucero

    2015-04-01

    Full Text Available A series of new organic polyimides were synthesized from 4-fluoro-4'4"-diaminotriphenylmethane and four different aromatic dianhydrides through a one-step, high-temperature, direct polycondensation in m-cresol at 180–200 °C, resulting in the formation of high-molecular-weight polyimides (inherent viscosities ~ 1.0–1.3 dL/g. All the resulting polyimides exhibited good thermal stability with initial decomposition temperatures above 434 °C, glass-transition temperatures between 285 and 316 °C, and good solubility in polar aprotic solvents. Wide-angle X-ray scattering data indicated that the polyimides were amorphous. Dense membranes were prepared by solution casting and solvent evaporation to evaluate their gas transport properties (permeability, diffusivity, and solubility coefficients toward pure hydrogen, helium, oxygen, nitrogen, methane, and carbon dioxide gases. In general, the gas permeability was increased as both the fractional free volume and d-spacing were also increased. A good combination of permeability and selectivity was promoted efficiently by the bulky hexafluoroisopropylidene and 4-fluoro-phenyl groups introduced into the polyimides. The results indicate that the gas transport properties of these films depend on both the structure of the anhydride moiety, which controls the intrinsic intramolecular rigidity, and the 4-fluoro-phenyl pendant group, which disrupts the intermolecular packing.

  13. Gas Permeation Properties of Soluble Aromatic Polyimides Based on 4-Fluoro-4,4'-Diaminotriphenylmethane

    Science.gov (United States)

    Guzmán-Lucero, Diego; Froylán Palomeque-Santiago, Jorge; Camacho-Zúñiga, Claudia; Ruiz-Treviño, Francisco Alberto; Guzmán, Javier; Galicia-Aguilar, Alberto; Aguilar-Lugo, Carla

    2015-01-01

    A series of new organic polyimides were synthesized from 4-fluoro-4'4"-diaminotriphenylmethane and four different aromatic dianhydrides through a one-step, high-temperature, direct polycondensation in m-cresol at 180–200 °C, resulting in the formation of high-molecular-weight polyimides (inherent viscosities ~ 1.0–1.3 dL/g). All the resulting polyimides exhibited good thermal stability with initial decomposition temperatures above 434 °C, glass-transition temperatures between 285 and 316 °C, and good solubility in polar aprotic solvents. Wide-angle X-ray scattering data indicated that the polyimides were amorphous. Dense membranes were prepared by solution casting and solvent evaporation to evaluate their gas transport properties (permeability, diffusivity, and solubility coefficients) toward pure hydrogen, helium, oxygen, nitrogen, methane, and carbon dioxide gases. In general, the gas permeability was increased as both the fractional free volume and d-spacing were also increased. A good combination of permeability and selectivity was promoted efficiently by the bulky hexafluoroisopropylidene and 4-fluoro-phenyl groups introduced into the polyimides. The results indicate that the gas transport properties of these films depend on both the structure of the anhydride moiety, which controls the intrinsic intramolecular rigidity, and the 4-fluoro-phenyl pendant group, which disrupts the intermolecular packing. PMID:28788041

  14. Fabrication of polyimide based microfluidic channels for biosensor devices

    DEFF Research Database (Denmark)

    Zulfiqar, Azeem; Pfreundt, Andrea; Svendsen, Winnie Edith

    2015-01-01

    The ever-increasing complexity of the fabrication process of Point-of-care (POC) devices, due to high demand of functional versatility, compact size and ease-of-use, emphasizes the need of multifunctional materials that can be used to simplify this process. Polymers, currently in use for the fabr......The ever-increasing complexity of the fabrication process of Point-of-care (POC) devices, due to high demand of functional versatility, compact size and ease-of-use, emphasizes the need of multifunctional materials that can be used to simplify this process. Polymers, currently in use...... for the fabrication of the often needed microfluidic channels, have limitations in terms of their physicochemical properties. Therefore, the use of a multipurpose biocompatible material with better resistance to the chemical, thermal and electrical environment, along with capability of forming closed channel...... microfluidics is inevitable. This paper demonstrates a novel technique of fabricating microfluidic devices using polyimide (PI) which fulfills the aforementioned properties criteria. A fabrication process to pattern microfluidic channels, using partially cured PI, has been developed by using a dry etching...

  15. Surface relief gratings in azobenzene supramolecular systems based on polyimides

    Science.gov (United States)

    Schab-Balcerzak, Ewa; Sobolewska, Anna; Stumpe, Joachim; Hamryszak, Lukasz; Bujak, Piotr

    2012-12-01

    The paper describes formation of new supramolecular azopolymers based on hydrogen bonds as perspective materials for laser induced surface relief gratings (SRGs) and for polarization gratings. Supramolecular films were built on the basis of hydrogen bonds between the functional groups of polymer and azobenzene derivatives, that is 4-[4-(3-hydroxypropyloxy)phenylazo]-pyridine and 4-[4-(6-hydroxyhexyloxy)phenylazo]pyridine. Polymers with imide rings, i.e., poly(esterimide)s and poly(etherimide)s, with phenolic hydroxyl or carboxylic groups were applied as matrixes for polymer-dye supramolecular systems. They revealed glass transition temperatures (Tg) in the range of 170-260 °C, whereas supramolecular systems exhibited lower Tg (88-187 °C). The polymers were easily soluble in aprotic polar solvents and exhibited remarkable good film forming properties. Moreover, new chromophore 4-[4-(3-hydroxypropyloxy)phenylazo]pyridine was synthesized and characterized. The light induced SRGs formation and simultaneous formation of the polarization gratings were explored in prepared polymer-chromophore assembles films using a holographic grating recording technique. First time to the best of our knowledge SRGs were formed in hydrogen-bonded supramolecular systems based on polyimides. The highest SRG amplitude and thus the highest diffraction efficiency were obtained in poly(esterimide)s with the hydroxyl functional group. Additionally, the thermal stability of the photoinduced surface gratings and polarization gratings were tested revealing in the case of the SRGs partial stability and almost complete erasure of the polarization gratings.

  16. Preparation of Thermoplastic Polyimide Ultrafine Fiber Nonwovens by Electrospinning

    Directory of Open Access Journals (Sweden)

    CHEN Jun

    2018-02-01

    Full Text Available The superfine fiber of thermoplastic polyimide(LPI, whose average diameter ranges from 0.36μm to 1.47μm, was prepared through electrospinning with DMAc as solvent. It lays a good foundation for the mass preparation of LPI non-woven. The influence of electrospinning process conditions, including LPI concentration, flow rate and voltage, on morphology of LPI fiber was investigated systematically. The results show that the average diameter increases and the fibers diameter distribution turns wider with the LPI concentration increasing from 22%(mass fraction, same as below to 30%. Meanwhile, when the concentration is rather lower, some cambiform fibers can be observed. As the concentration increases, the cambiform fiber disappears. While the concentration increases continually, the fibers are adhered to be flakiness. The change of the spinning voltage makes little difference on the average diameter of fibers; the average diameter of fibers increases with the increase of the flow rate of LPI solution; when the flow rate is more than 1.5mL/h, the fibers start to be adhered, the cambiform fibers appear while the flow rate is over 1.8mL/h. Through optimizing the process, the LPI fibers with average diameter of 1.18μm were prepared under 30℃ with the conditions of 28% concentration, 15kV voltage, 1.2mL/h flow rate and the 25cm receiving distance.

  17. Photomechanically coupled viscoelasticity of azobenzene polyimide polymer networks

    Science.gov (United States)

    Roberts, Dennice; Worden, Matt; Chowdhury, Sadiyah; Oates, William S.

    2017-07-01

    Polyimide-based azobenzene polymer networks have demonstrated superior photomechanical performance over more conventional azobenzene-doped pendent and cross-linked polyacrylate networks. These materials exhibit larger yield stress and glass transition temperatures and thus provide robustness for active control of adaptive structures directly with polarized, visible light. Whereas photochemical reactions clearly lead to deformation, as indicated by a rotation of a linear polarized light source, temperature and viscoelasticity can also influence deformation and complicate interpretation of the photostrictive and shape memory constitutive behavior. To better understand this behavior we develop a rate-dependent constitutive model and experimentally quantify the material behavior in these materials. The rate dependent deformation induced in these materials is quantified experimentally through photomechanical stress measurements and infrared camera measurements. Bayesian uncertainty analysis is used to assess the role of internal polymer network evolution and azobenzene excitation on both thermomechanical and photomechanical deformation in the presence polarized light of different orientations. A modified Arrhenius relation is proposed and validated using Bayesian statistics which provide connections between free volume, shape memory, and polarized light.

  18. Improving the leakage current of polyimide-based resistive memory by tuning the molecular chain stack of the polyimide film

    Science.gov (United States)

    Wu, Chi-Chang; Hsiao, Yu-Ping; You, Hsin-Chiang; Lin, Guan-Wei; Kao, Min-Fang; Manga, Yankuba B.; Yang, Wen-Luh

    2018-02-01

    We have developed an organic-based resistive random access memory (ReRAM) by using spin-coated polyimide (PI) as the resistive layer. In this study, the chain distance and number of chain stacks of PI molecules are investigated. We employed different solid contents of polyamic acid (PAA) to synthesize various PI films, which served as the resistive layer of ReRAM, the electrical performance of which was evaluated. By tuning the PAA solid content, the intermolecular interaction energy of the PI films is changed without altering the molecular structure. Our results show that the leakage current in the high-resistance state and the memory window of the PI-based ReRAM can be substantially improved using this technique. The superior properties of the PI-based ReRAM are ascribed to fewer molecular chain stacks in the PI films when the PAA solid content is decreased, hence suppressing the leakage current. In addition, a device retention time of more than 107 s can be achieved using this technique. Finally, the conduction mechanism in the PI-based ReRAM was analyzed using hopping and conduction models.

  19. Atomic oxygen erosion resistance of polyimide/ZrO{sub 2} hybrid films

    Energy Technology Data Exchange (ETDEWEB)

    Xiao Fei [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, No. 37, Xueyuan Road, Haidian District, Beijing 100191 (China); Wang Kai, E-mail: wangkai@buaa.edu.cn [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, No. 37, Xueyuan Road, Haidian District, Beijing 100191 (China); Zhan Maosheng [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, No. 37, Xueyuan Road, Haidian District, Beijing 100191 (China)

    2010-10-01

    A series of polyimide/zirconia (PI/ZrO{sub 2}) hybrid films were synthesized based on zirconium n-butoxide, pyromellitic acid dianhydride (PMDA) and 4,4'-oxydianiline (ODA) by a sol-gel process. The atomic oxygen (AO) exposure tests were carried out using a ground-based atomic oxygen effects simulation facility. The effects of ZrO{sub 2} content on the morphology and structure evolvement of PI/ZrO{sub 2} hybrid films were investigated using field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectrometer (XPS), respectively. The results indicated that a zirconia-rich layer was formed on the polyimide film sourcing from the zirconium n-butoxide after AO exposure, which decreased the erosion rate and obviously improved the AO resistance of polyimide films.

  20. Evaluation of two polyimides and of an improved liner retention design for self-lubricating bushings

    Science.gov (United States)

    Sliney, H. E.

    1984-01-01

    Two different polyimide polymers were studied and the effectiveness of a design feature to improve retention of the self lubricating composite liners under high load was evaluated. The basic bearing design consisted of a molded layer of chopped graphite-fiber-reinforced-polyimide (GFRP) composite bonded to the bore of a steel bushing. The friction, wear, and load carrying ability of the bushings were determined in oscillating tests at 25, 260 and 315 C at radial unit loads up to 260 MPa. Friction coefficients were typically 0.15 to 0.25. Bushings with liners containing a new partially fluorinated polymer were functional, but had a lower load capacity and higher wear rate than those containing a more conventional, high temperature polyimide. The liner retention design feature reduced the tendency of the liners to crack and work out of the contact zone under high oscillating loads.

  1. Thermal analysis and its application in evaluation of fluorinated polyimide membranes for gas separation

    KAUST Repository

    Qiu, Wulin

    2011-08-01

    Seven polyimides based on (4,4′-hexafluoroisopropylidene) diphthalic anhydride, 6FDA, with different chemical structures were synthesized in a single pot two-step procedure by first producing a high molecular weight polyamic acid (PAA), followed by reaction with acetic anhydride to produce polyimide (PI). The resulting polymers were characterized using thermal analysis techniques including TGA, derivative weight analysis, TGA-MS, and DSC. The decarboxylation-induced thermal cross-linking, ester cross-linking through a diol, and ion-exchange reactions of selected polyimide membranes were investigated. Cross-linking of polymer membranes was confirmed by solubility tests and CO 2 permeability measurements. The thermal analysis provides simple and timesaving opportunities to characterize the polymer properties, the ability to optimize polymer cross-linking conditions, and to monitor polymer functionalization to develop high performance polymeric membranes for gas separations. © 2011 Elsevier Ltd. All rights reserved.

  2. Room Temperature Halogenation of Polyimide Film Surface using Chlorine Trifluoride Gas

    Science.gov (United States)

    Habuka, Hitoshi; Kosuga, Takahiro; Koike, Kunihiko; Aida, Toshihiro; Takeuchi, Takashi; Aihara, Masahiko

    2004-02-01

    In order to develop a new application of chlorine trifluoride gas, the halogenation of a polyimide film surface at room temperature and at atmospheric pressure is studied for the first time. The polyimide film surface after exposure to the chlorine trifluoride gas shows a decreased water contact angle with increasing chlorine trifluoride gas concentration and exposure period. Since both X-ray photoelectron spectroscopy and infrared absorption spectroscopy simultaneously showed the formation of a carbon-chlorine bond and carbon-fluorine bond, it is concluded that the chlorine trifluoride gas can easily and safely perform the halogenation of the polyimide film surface under the stated conditions using a low-cost process and equipment.

  3. Environmental

    Directory of Open Access Journals (Sweden)

    Sawsan M. Aboul Ezz

    2014-01-01

    Full Text Available Rotifers are one of the most common, abundant components of plankton in the coastal waters of the Mediterranean Sea, which means that they can be used as bio-indicators and provide useful information on the long-term dynamics of the El-Mex Bay ecosystem. Rotifera species were quantitatively and qualitatively assessed in the El-Mex Bay, west of Alexandria at eight stations to study spatial, temporal, dominance, and abundance of the rotifer community and their relation with changes in environmental conditions. Samples were collected seasonally from autumn 2011 to autumn 2012. Ecological parameters were determined and correlated with total rotifers abundance to gain information about the forces that structure the rotifer community in this dynamic environment. A total of 38 rotifer species were identified belonging to 16 genera within 12 families and 3 orders under one class and contributed about 12.1% of the total zooplankton in the study area with an average of 1077 specimens/m3. Maximum density was observed in summer 2012 with an average of 1445 specimens/m3. During autumn 2011 rotifers appeared in low density (434 specimens/m3. The predominant species Ascomorpha saltans, Brachionus urceolaris, Synchaeta oblonga, Synchaeta okai, Synchaeta pectinata and Synchaeta tremula were recorded in all study stations of the bay. Salinity, temperature, depth, and chlorophyll-a concentration were the most important environmental factors co-related with the abundance of rotifers in the El-Mex Bay. A significant positive correlation between the total rotifer abundance and chlorophyll-a was observed during winter 2012 and summer 2012 (r = 0.763 and r = 0.694, respectively, at p ⩽ 0.05.

  4. Gas separation performance of 6FDA-based polyimides with different chemical structures

    KAUST Repository

    Qiu, Wulin

    2013-10-01

    This work reports the gas separation performance of several 6FDA-based polyimides with different chemical structures, to correlate chemical structure with gas transport properties with a special focus on CO2 and CH 4 transport and plasticization stability of the polyimides membranes relevant to natural gas purification. The consideration of the other gases (He, O2 and N2) provided additional insights regarding effects of backbone structure on detailed penetrant properties. The polyimides studied include 6FDA-DAM, 6FDA-mPDA, 6FDA-DABA, 6FDA-DAM:DABA (3:2), 6FDA-DAM:mPDA (3:2) and 6FDA-mPDA:DABA (3:2). Both pure and binary gas permeation were investigated. The packing density, which is tunable by adjusting monomer type and composition of the various samples, correlated with transport permeability and selectivity. The separation performance of the polyimides for various gas pairs were also plotted for comparison to the upper bound curves, and it was found that this family of materials shows attractive performance. The CO 2 plasticization responses for the un-cross-linked polyimides showed good plasticization resistance to CO2/CH4 mixed gas with 10% CO2; however, only the cross-linked polyimides showed good plasticization resistance under aggressive gas feed conditions (CO 2/CH4 mixed gas with 50% CO2 or pure CO 2). For future work, asymmetric hollow fibers and carbon molecular sieve membranes based on the most attractive members of the family will be considered. © 2013 Elsevier Ltd. All rights reserved.

  5. Precision polyimide single surface thin film shell apertures and active boundary control

    Science.gov (United States)

    Flint, Eric M.; Lindler, Jason E.; Hall, Jonathan L.; Rankine, Charles; Reggelbrugge, Mark

    2006-06-01

    This paper discusses the current status of self supporting precision membrane optical shell technology (MOST) apertures based on thin (25 to 125 um thick) polyimide and polyester films primary shell. Optically relevant doubly curved reflective apertures are realized by inducing permanent curvature into thin substrates that can then be coated. The initial thin nature provides both very low areal density (20 to 200 grams/m2) and compatibility with compact roll stowage. The induced curvature/depth provides the ability to support the shell around the periphery at discrete locations and considerable structural and dynamic stiffness. The discrete mounts also provide an excellent location with which to improve the surface figure and to reject environmental and host structure induced errors. Material microroughness on the leading substrate/coating combination has been measured to down to 3 nm rms over small (100x100um's) sample sizes with white light interferometry. A variety of reflective coated substrates have also been shown to have sub micron rms surface roughness over up to 100mm diameter test apertures using interferometric measurements. Best materials currently have 20nm rms surface roughness noise floors at these sizes. The ability to fabricate shells over a range of prescriptions (R/0.9 to R/2.2) and a range of sizes (0.1 to 0.75m diameter) has been demonstrated. Global surface figure accuracies of 2 to 4 microns rms have been demonstrated at the 0.2m size, and further improvements are anticipated through ongoing improved fabrication techniques (preliminary results indicate sub-micron rms values). The ability of discrete boundary control to improve the shape and maintain it in the face of disturbances (gravity for example) is demonstrated as is the ability to implement high amplitude (multi-wave) Zernike mode surface figure control. Results extending boundary control to interferometric optical level are also presented.

  6. Stable Isotope Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Tissue samples (skin, bone, blood, muscle) are analyzed for stable carbon, stable nitrogen, and stable sulfur analysis. Many samples are used in their entirety for...

  7. Environmental changes around the Jurassic/Cretaceous transition: New nannofossil, chemostratigraphic and stable isotope data from the Lókút section (Transdanubian Range, Hungary)

    Science.gov (United States)

    Grabowski, J.; Haas, J.; Stoykova, K.; Wierzbowski, H.; Brański, P.

    2017-10-01

    New biostratigraphical, chemical and stable isotope (C, O) data are presented from the Lókút section (Transdanubian Range, Hungary) representing a ca. 13 m thick continuous succession of Lower Tithonian-Lower Berriasian pelagic limestones. The study is conducted to verify timing of nannofossil events and major palaeoenvironmental changes at the Jurassic/Cretaceous transition including lithogenic input, palaeoredox and palaeoproductivity variations. Nannofossil zones from NJT 16b to NKT have been identified in the Lókút section and correlated with magnetostratigraphy, covering an interval from polarity zone M21r to M18r. The nannofossil Zone NJT 16b spans the interval from the upper part of M21r to lowermost part of M19n2n but its lower limit is poorly defined due to large diachronism in first occurrence (FO) of Nannoconus infans in various Tethyan sections. FOs of N. kamptneri minor and N. steinmannii minor are situated in the topmost part of the M19n2n and lowermost part of M19n1r magnetozones, respectively. They are located ca. 2-2.5 m above the J/K boundary defined as Intermedia/Alpina subzonal boundary, which falls within the lower half of magnetozone M19n2n. The position of first occurrences of these taxa is similar to that from the Puerto Escaño section (southern Spain) and slightly lower than in Italian sections (Southern Alps). Concentrations of chemical element proxies of terrigenous transport (Al, K, Rb, Th) decrease towards the top of the Lókút section, which suggests a decrease in input of terrigenous material and increasing carbonate productivity during the Early Tithonian and the Berriasian. Slight oxygen depletion at the sea bottom (decrease of Th/U ratio), and large increase in concentrations of productive elements (P, Ba, Ni, Cu) is observed upsection. Nutrients supply via upwelling seems to be the most likely explanation. Increase in phosphorus accumulation rate and a microfacies change from Saccocoma to calpionellid dominated took place in

  8. Influences on the stable oxygen and carbon isotopes in gerbillid rodent teeth in semi-arid and arid environments: Implications for past climate and environmental reconstruction

    Science.gov (United States)

    Jeffrey, Amy; Denys, Christiane; Stoetzel, Emmanuelle; Lee-Thorp, Julia A.

    2015-10-01

    The stable isotope composition of small mammal tissues has the potential to provide detailed information about terrestrial palaeoclimate and environments, because their remains are abundant in palaeontological and archaeological sites, and they have restricted home ranges. Applications to the Quaternary record, however, have been sparse and limited by an acute lack of understanding of small mammal isotope ecology, particularly in arid and semi-arid environments. Here we document the oxygen and carbon isotope composition of Gerbillinae (gerbil) tooth apatite across a rainfall gradient in northwestern Africa, in order to test the relative influences of the 18O/16O in precipitation or moisture availability on gerbil teeth values, the sensitivity of tooth apatite 13C/12C to plant responses to moisture availability, and the influence of developmental period on the isotopic composition of gerbil molars and incisors. The results show that the isotopic composition of molars and incisors from the same individuals differs consistent with the different temporal periods reflected by the teeth; molar teeth are permanently rooted and form around the time of birth, whereas incisors grow continuously. The results indicate that tooth choice is an important consideration for applications as proxy Quaternary records, but also highlights a new potential means to distinguish seasonal contexts. The oxygen isotope composition of gerbil tooth apatite is strongly correlated with mean annual precipitation (MAP) below 600 mm, but above 600 mm the teeth reflect the oxygen isotope composition of local meteoric water instead. Predictably, the carbon isotope composition of the gerbil teeth reflected C3 and C4 dietary inputs, however arid and mesic sites could not be distinguished because of the high variability displayed in the carbon isotope composition of the teeth due to the microhabitat and short temporal period reflected by the gerbil. We show that the oxygen isotope composition of small

  9. A versatile multi-user polyimide surface micromachinning process for MEMS applications

    KAUST Repository

    Carreno, Armando Arpys Arevalo

    2015-04-01

    This paper reports a versatile multi-user micro-fabrication process for MEMS devices, the \\'Polyimide MEMS Multi-User Process\\' (PiMMPs). The reported process uses polyimide as the structural material and three separate metallization layers that can be interconnected depending on the desired application. This process enables for the first time the development of out-of-plane compliant mechanisms that can be designed using six different physical principles for actuation and sensing on a wafer from a single fabrication run. These principles are electrostatic motion, thermal bimorph actuation, capacitive sensing, magnetic sensing, thermocouple-based sensing and radio frequency transmission and reception. © 2015 IEEE.

  10. Physical deposition of thin polyimide layers by applying an argon plasma assisted process

    Energy Technology Data Exchange (ETDEWEB)

    Dimov, D; Georgiev, A; Spassova, E; Assa, J; Dineff, P; Danev, G, E-mail: dean@clf.bas.b

    2010-11-01

    A novel method for physical deposition of thin polyimide layers by applying an argon plasma assisted process has been developed. The influence of the plasma on the combined molecular flux of the two thermally evaporated precursors - 4,4'- oxydianiline and pyromellitic dianhydride was investigated. The process parameters were changed in the limlts 0,4 - 2 A for the anode current and 80 - 170 V for the anode voltage. Their influence was studied using FTIR spectroscopy and electron microscopy techniques. It was proposed that the plasma flux crossing the molecular flows of the polyimide precursors enhances the imidization process by partly activating the precursor molecules in the gas phase.

  11. Electrospinning of polyimide nanofibres – effects of working parameters on morphology

    Directory of Open Access Journals (Sweden)

    Kohse Stefanie

    2017-09-01

    Full Text Available The use of the electrospinning technique is a promising and versatile method for producing fibrous nonwovens from various polymers. Here we present fibre formation via direct electrospinning of a soluble polyimide, a class of polymers that is typically insoluble. In this study solution parameters as the solvent and the polymer concentration are investigated. Furthermore relevant process parameters are varied for optimization of the performance. The presented data indicate polyimide as a promising material for the fabrication of nanofibrous nonwovens via direct electrospinning.

  12. Environmental status of the NE Adriatic Sea, Istria, Croatia: Insights from mussel Mytilus galloprovincialis condition indices, stable isotopes and metal(loid)s.

    Science.gov (United States)

    Kanduč, Tjaša; Šlejkovec, Zdenka; Falnoga, Ingrid; Mori, Nataša; Budič, Bojan; Kovačić, Ines; Pavičić-Hamer, Dijana; Hamer, Bojan

    2017-09-28

    The environmental status of the marine environment in the NE Adriatic Sea was assessed, using as a bioindicator species the Mediterranean mussel Mytilus galloprovincialis Lamarck, 1819. Samples were collected seasonally from mariculture sites and from major Istrian ports between the years 2010 and 2013. The condition indices of mussels ranged from 13.3 to 20.9% at mariculture sites and from 14.3 to 23.3% at port locations. The seasonally δ13CDIC values of seawater varied between -10.9 to 0.7‰. Pollution by sewage sludge (based on δ15N values) was confirmed only in two ports. Tissue concentrations of Mn, Co, Ni, Cu, Zn, Se, Cd, and Pb were significantly higher in the tissue of the mussels collected from the ports (polluted sites). Arsenobetaine was the major As compound present in the samples and there was no significant difference in the levels of total As in mussel tissues from mariculture and port sites. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. Analysis of thermoplastic polyimide + polymer liquid crystal blends

    Science.gov (United States)

    Gopalanarayanan, Bhaskar

    Thermoplastic polyimides (TPIs) exhibit high glass transition temperatures (Tsbgs), which make them useful in high performance applications. Amorphous and semicrystalline TPIs show sub-Tsbg relaxations, which can aid in improving strength characteristics through energy absorption. The alpha relaxation of both types of TPIs indicates a cooperative nature. The semicrystalline TPI shows thermo-irreversible cold crystallization phenomenon. The polymer liquid crystal (PLC) used in the blends is thermotropic and with longitudinal molecular structure. The small heat capacity change (Delta Csb{p}) associated with the glass transition indicates the PLC to be rigid rod in nature. The PLC shows a small endotherm associated with the melting. The addition of PLC to the semicrystalline TPI does not significantly affect the Tsbg or the melting point (Tsbm). The cold crystallization temperature (Tsbc) increases with the addition of the PLC, indicating channeling phenomenon. The addition of PLC also causes a negative deviation of the Delta Csb{p}, which is another evidence for channeling. The TPI, PLC and their blends show high thermal stability. The semicrystalline TPI absorbs moisture; this effect decreases with the addition of the PLC. The absorbed moisture does not show any effect on the degradation. The addition of PLC beyond 30 wt.% does not result in an improvement of properties. The amorphous TPI + PLC blends also show the negative deviation of Delta Csb{p} from linearity with composition. The addition of PLC causes a decrease in the thermal conductivity in the transverse direction to the PLC orientation. The thermomechanical analysis indicates isotropic expansivity for the amorphous TPI and a small anisotropy for the semicrystalline TPI. The PLC shows large anisotropy in expansivity. Even 5 wt.% concentration of PLC in the blend induces considerable anisotropy in the expansivity. Thus, blends show controllable expansivity through PLC concentration. Amorphous TPI + PLC

  14. Solution Based Deposition of Polyimide Ablators for NIF Capsules

    Energy Technology Data Exchange (ETDEWEB)

    Cook, R

    2002-07-11

    Between June 1997 and March 2002 Luxel Corporation was contracted to explore the possibility of preparing NIF scale capsules with polyimide ablators using solution-based techniques. This work offered a potential alternative to a vapor deposition approach talking place at LLNL. The motivation for pursuing the solution-based approach was primarily two-fold. First, it was expected that much higher strength capsules (relative to vapor deposition) could be prepared since the solution precursors were known to produce high strength films. Second, in applying the ablator as a fluid it was expected that surface tension effects would lead to very smooth surfaces. These potential advantages were offset by expected difficulties, primary among them that the capsules would need to be levitated in some fashion (for example acoustically) during coating and processing, and that application of the coating uniformly to thicknesses of 150 pm on levitated capsules would be difficult. Because of the expected problems with the coupling of levitation and coating, most of the initial effort was to develop coating and processing techniques on stalk-mounted capsules. The program had some success. Using atomizer spray techniques in which application of {approx}5 {micro}m fluid coatings were alternated with heating to remove solvent resulted in up to 70 {micro}m thick coatings that were reasonably smooth at short wavelengths, and showed only about a 1 {micro}m thickness variation over long wavelengths. More controlled deposition with an inkjet devise was also developed. However difficult technical problems remained, and these problems coupled with the relative success of the vapor deposition approach led to the termination of the solution-based work in 2002. What follows is a compilation of the progress reports submitted by Luxel for this work which spanned a number of separate contracts. The reports are arranged chronologically, the last report in the collection has a modest summary of what

  15. Synthesis and characteristics of polyimide/titania nano hybrid films

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, M.-H. [Department of Chemical and Materials Engineering, Chin-Yi Institute of Technology, Taichung 41111, Taiwan (China)]. E-mail: tsaimh@chinyi.ncit.edu.tw; Liu, S.-J. [Department of Chemical and Materials Engineering, Chin-Yi Institute of Technology, Taichung 41111, Taiwan (China); Chiang, P.-C. [Lam Research Corporation, Hsinchu 300, Taiwan (China)

    2006-11-23

    Polyimide/titania (PI/TiO{sub 2}) nano hybrid films are synthesized by sol-gel technology. [4,4'-(4,4'-Isopropylidenediphenoxy) bis (phthalic anhydride)] (IDPA), 4,4'-diaminodiphenyl ether (ODA) and 3-aminopropyltrimethoxysilane (APrTMOS) mixed entirely and reacted at room temperature to form the polyamic acid (PAA). Tetraethyl orthotitanate (Ti(OEt){sub 4}) and actylacetone, the latter one is used as chelating agent, are then added to the polyamic acid. After imidization at high temperature, PI/TiO{sub 2} hybrid films with different block chain length, 5000 of PAA and 15000 g mol{sup -1}, and a cross-linked structure are formed. The resulting hybrid films, containing relatively small amounts of titania, exhibit higher transparency and flexibility. Moreover, as compared with pure PI, the hybrid film formed from APrTMOS has better ability to form a film with a higher titania content. Due to the high and low refractive index (RI) of TiO{sub 2} and APrTMOS, their introduction may lead to the change of the RI of hybrid films. From the transmission electron microscope (TEM) images; the particle size of titania decreases with increasing APrTMOS content. Thermal decomposition temperatures (T {sub d}), with a 5% weight loss, are in the range of 400-540 deg. C. The dynamic mechanical thermal analysis showed a systematic increase of glass transition temperature, along with a broader and weaker tan {delta} peak with increasing titania content.

  16. Kinetics of imidization and crosslinking for AFR700B polyimide

    Energy Technology Data Exchange (ETDEWEB)

    Russell, J.D. [Wright Laboratory, Wright-Patterson AFB, OH (United States); Kardos, J.L. [Washington Univ., St. Louis, MO (United States)

    1996-12-31

    The imidization kinetics for AFR700B polyimide were determined using Fourier transform infrared spectroscopy (FTIR) by following the increase in imide groups as tracked with the 1360 cm{sup -1} band over several isotherms. Imidization occurs at an rapid initial rate, followed by a slow rate. The reaction rates for both the fast and slow regions were found to be first order with respect to the increase in the 1360 cm{sup -1} band. The activation energy and pre-exponential factor were found for each region. The formation of imide rings in AFR700B was found to occur until approximately 300{degrees}C. This was confirmed by the presence of water up to 300{degrees}C in thermogravimetric analysis-mass spectroscopy data. Literature has shown that imidization is mass transfer limited. Thus, the kinetics should be coupled with a mass transfer relation to accurately describe the imidization reaction. While FTIR studies of AFR700B allowed no insight into crosslinking due to the small concentrations of the end groups, dynamic mechanical analysis (DMA) studies showed that the application of pressure greatly affects the crosslinked network structure and the glass transition temperature (T{sub g}). Applying pressure during cure keeps the cyclopentadiene evolved during the reverse Diels-Alder reaction in solution and allows it to participate in crosslinking. Thus for panels cured under pressure and postcured to 400{degrees}C, the storage modulus (G`) and T{sub g} increase with increasing cure temperature. DMA studies also showed an increase in G` at temperatures above 450{degrees}C indicating increased crosslinking. Thermogravimetric analysis-mass spectroscopy (TGA-MS) showed that this could be due to crosslinking between polymer chains.

  17. Pressure-sensitive strain sensor based on a single percolated Ag nanowire layer embedded in colorless polyimide

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Chan-Jae [Display Materials & Components Research Center, Korea Electronics Technology Institute, 68 Yatap-dong, Bundang-gu, Seongnam 463-816 (Korea, Republic of); Jun, Sungwoo [Display Materials & Components Research Center, Korea Electronics Technology Institute, 68 Yatap-dong, Bundang-gu, Seongnam 463-816 (Korea, Republic of); Display and Nanosystem Laboratory, College of Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Ju, Byeong-Kwon [Display and Nanosystem Laboratory, College of Engineering, Korea University, Seoul 136-713 (Korea, Republic of); Kim, Jong-Woong, E-mail: wyjd@keti.re.kr [Display Materials & Components Research Center, Korea Electronics Technology Institute, 68 Yatap-dong, Bundang-gu, Seongnam 463-816 (Korea, Republic of)

    2017-06-01

    This paper presents the fabrication of an elastomer-free, transparent, pressure-sensitive strain sensor consisting of a specially designed silver nanowire (AgNW) pattern and colorless polyimide (cPI). A percolated AgNW network was patterned with a simple tandem compound circuit, which was then embedded in the surface of the cPI via inverted layer processing. The resulting film-type sensor was highly transparent (~93.5% transmittance at 550 nm) and mechanically stable (capable of resisting 10000 cycles of bending to a 500 µm radius of curvature). We demonstrated that a thin, transparent, and mechanically stable electrode can be produced using a combination of AgNWs and cPI, and used to produce a system sensitive to pressure-induced bending. The capacitance of the AgNW tandem compound electrode pattern grew via fringing, which increased with the pressure-induced bending applied to the surface of the sensor. The sensitivity was four times higher than that of an elastomeric pressure sensor made with the same design. Finally, we demonstrated a skin-like pressure sensor attached to the inside wrist of a human arm. - Highlights: • A thin, transparent pressure sensor was fabricated from AgNWs and cPI. • An AgNW network was patterned with a simple circuit, and then embedded into cPI. • The resulting film-type sensor was highly transparent and mechanically stable. • The sensor sensitivity was 4x higher than that of an elastomeric pressure sensor.

  18. Photo-Induced Vertical Alignment of Liquid Crystals via In Situ Polymerization Initiated by Polyimide Containing Benzophenone

    Directory of Open Access Journals (Sweden)

    Fei Wang

    2017-06-01

    Full Text Available Vertical alignment of liquid crystal (LC was achieved in an easy and effective way: in situ photopolymerization of dodecyl acrylate (DA monomers initiated by polyimide based on 3,3′,4,4′-benzophenonetetracarboxylic dianhydride and 3,3′-dimethyl-4,4′-diaminodiphenyl methane (BTDA-DMMDA PI. The alignment behavior and alignment stabilities were characterized by a polarizing optical microscope (POM, which showed a stable vertical alignment after 12 h of thermal treatment. The chemical structures, morphology, and water contact angles of alignment films peeled from LC cells with and without DA monomers were analyzed by means of a Fourier transform infrared spectrometer (FTIR, a scanning electron microscope (SEM, and a contact angle tester, separately. The results confirmed that the DA monomers underwent self-polymerization and grafting polymerization initiated by the BTDA-DMMDA PI under ultraviolet irradiation, which aggregated on the surfaces of PI films. The water contact angles of the alignment films were about 15° higher, indicating a relative lower surface energy. In conclusion, the vertical alignment of LC was introduced by the low surface free energy of PI films grafted with DA polymer and intermolecular interactions between LC and DA polymers.

  19. A rapid, accurate and sensitive method with the new stable isotopic tags based on microwave-assisted dispersive liquid-liquid microextraction and its application to the determination of hydroxyl UV filters in environmental water samples.

    Science.gov (United States)

    Li, Xiu; Chen, Guang; Liu, Jianjun; Liu, Yuxia; Zhao, Xianen; Cao, Ziping; Xia, Lian; Li, Guoliang; Sun, Zhiwei; Zhang, Shijuan; Wang, Hua; You, Jinmao

    2017-05-15

    A rapid, accurate and sensitive method, using the stable isotope labeling (SIL), microwave-assisted dispersive liquid-liquid micro extraction (MADLLME) and the ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), was developed and validated for the determination of hydroxyl UV Filters in environmental water samples. A pair of new isotopic tags D0-/D3-1-methylindole-3-acetic acid (D0-/D3-MIAA) is synthesized, with which a simple yet efficient pretreatment MADLLME-SIL is developed. Under the optimized conditions (80℃, 240W, 180s), the sample pretreatment including analyte extraction, pre-concentration and isotope labeling can be finished conveniently in only 9min. D0-/D3-MIAA labeling improves the chromatographic retention by strengthening the hydrophobicity and enhances the MS response for 3-4 orders of magnitude. Excellent linearity is established by the H/D ratios of 1/10-10/1 with the correlation coefficients >0.9990. The quite low detection limits (0.54-1.79ng/L) are achieved, ensuring the trace detection. This method is successfully applied to a series of environmental water samples. The recoveries (93.2%~103.5%) are significantly improved and the analysis time is largely reduced (filters in water samples. Copyright © 2017 Elsevier B.V. All rights reserved.

  20. Ag-functionalized carbon molecular-sieve membranes based on polyelectrolyte/polyimide blend precursors

    NARCIS (Netherlands)

    Barsema, J.N.; van der Vegt, N.F.A.; Koops, G.H.; Wessling, Matthias

    2005-01-01

    We prepared dense flat-sheet Ag-functionalized carbon molecular-sieve (CMS) membranes from blends of P84 co-polyimide and a sulfonated poly(ether ether ketone) with a Ag+ counterion (AgSPEEK). These blends offer the possibility of producing new functionalized precursor structures, which were

  1. Synthesis and Characterization of Poly(maleic Anhydride)s Cross-linked Polyimide Aerogels

    Science.gov (United States)

    Guo, Haiquan; Meador, Mary Ann B.

    2015-01-01

    With the development of technology for aerospace applications, new thermal insulation materials are required to be flexible and capable of surviving high heat flux. For instance, flexible insulation is needed for inflatable aerodynamic decelerators which are used to slow spacecraft for entry, descent and landing (EDL) operations. Polyimide aerogels have low density, high porosity, high surface area, and better mechanical properties than silica aerogels and can be made into flexible thin films, thus they are potential candidates for aerospace needs. The previously reported cross-linkers such as octa(aminophenyl)silsesquioxane (OAPS) and 1,3,5-triaminophenoxybenzene (TAB) are either expensive or not commercially available. Here, we report the synthesis of a series of polyimide aerogels cross-linked using various commercially available poly(maleic anhydride)s, as seen in Figure 1. The amine end capped polyimide oligomers were made with 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA) and diamine combinations of dimethylbenzidine (DMBZ) and 4, 4-oxydianiline (ODA). The resulting aerogels have low density (0.12 gcm3 to 0.16 gcm3), high porosity (90) and high surface area (380-554 m2g). The effect of the different poly(maleic anhydride) cross-linkers and polyimide backbone structures on density, shrinkage, porosity, surface area, mechanical properties, moisture resistance and thermal properties will be discussed.

  2. CO2 Plasticization of Polyethersulfone/Polyimide Gas-Separation Membranes

    NARCIS (Netherlands)

    Kapantaidakis, G.; Koops, G.H.; Wessling, Matthias; Kaldis, S.P.; Sakellaropoulos, G.P.

    2003-01-01

    This work reports the CO2 plasticization of gas-separation hollow-fiber membranes based on polyimide and polyethersulfone blends. The feed pressure effect on the permeance of pure gases (CO2, N2) and the separation performance of a gaseous mixture (CO2/N2, 55/45%) is examined. Contrary to dense

  3. Thermoplastic-thermosetting merged polyimides via furan-maleimide Diels–Alder polymerization

    Directory of Open Access Journals (Sweden)

    Yogesh S. Patel

    2017-02-01

    Full Text Available Novel thermoplastic-thermosetting merged polyimide system has been developed via Diels–Alder intermolecular polymerization of bisfuran namely, 2,5-bis(furan-2-ylmethylcarbamoyl terephthalic acid A with a series of bismaleimides B1–4. Thus obtained intermediate Diels–Alder adducts C1–4 were aromatized and imidized (i.e. cyclized through carboxylic and amide groups to afford thermoplastic-thermosetting merged polyimides D1–4. Bisfuran A was prepared by the condensation of pyromellitic dianhydride with furan-2-ylmethanamine and characterized by elemental, spectral, thermal and LCMS analyses. Synthesized Diels–Alder adducts C1–4 and polyimides D1–4 were characterized by elemental analysis, spectral features, number average molecular weight (Mn‾, degree of polymerization (DP and thermal analysis. To facilitate the correct structural assessment and to be able to verify the occurrence of the DA adducts and PIs, a model compound 4 was prepared from phthalic anhydride and furan-2-ylmethanamine in a similar way. FTIR spectral features of polyimides D1–4 were compared with model compound 4 and they were found to be quite identical. The ‘in situ' void-free glass fiber reinforced composites GFRC1–4 were prepared from the produced system and characterized by chemical, mechanical and electrical analyses. All the composites showed good mechanical, electrical and thermal properties and good resistance to organic solvents and mineral acids.

  4. Circuits and AMOLED display with self-aligned a-IGZO TFTs on polyimide foil

    NARCIS (Netherlands)

    Nag, M.; Bhoolokam, A.; Smout, S.; Willegems, M.; Muller, R.; Myny, K.; Schols, S.; Ameys, M.; Genoe, J.; Ke, T.H.; Vicca, P.; Ellis, T.; Cobb, B.; Kumar, A.; Steen, J.L.P.J. van der; Gelinck, G.; Fukui, Y.; Obata, K.; Groeseneken, G.; Heremans, P.; Steudel, S.

    2015-01-01

    A process to make self-aligned top-gate amorphous indium-gallium-zinc-oxide (a-IGZO) thin-film transistors (TFTs) on polyimide foil is presented. The source/drain (S/D) region's parasitic resistance reduced during the SiN interlayer deposition step. The sheet resistivity of S/D region after exposure

  5. Residue-free plasma etching of polyimide coatings for small pitch vias with improved step coverage

    NARCIS (Netherlands)

    Mimoun, B.A.Z.; Pham, H.T.M.; Henneken, V.; Dekker, R.

    2013-01-01

    The authors have found that patterning polyimide coatings containing organosilane adhesion promoter using pure oxygen plasma resulted in a thin silicon-rich residue layer. They show in this paper that adding small amounts of fluorine-containing gas to the etching gas mixture is necessary in order to

  6. Photopiezoelectric Composites of Azobenzene-Functionalized Polyimides and Polyvinylidene Fluoride (Postprint)

    Science.gov (United States)

    2014-10-01

    is a diamine containing two azobenzenes per molecule and synthesized according to our previous publica- tion. [ 25 ] The generic chemical structure...AFRL-RX-WP-JA-2015-0026 PHOTOPIEZOELECTRIC COMPOSITES OF AZOBENZENE -FUNCTIONALIZED POLYIMIDES AND POLYVINYLIDENE FLUORIDE (POSTPRINT...3. DATES COVERED (From – To) 24 December 2009 – 15 September 2014 4. TITLE AND SUBTITLE PHOTOPIEZOELECTRIC COMPOSITES OF AZOBENZENE - FUNCTIONALIZED

  7. Impact of Backbone Rigidity on the Photomechanical Response of Glassy, Azobenzene-Functionalized Polyimides (Postprint)

    Science.gov (United States)

    2014-01-13

    azoBPA- diamine ). The azobenzene -functionalized linear polymers exhibit glass transition temperatures (Tg) ranging from 276 to 307 °C and maintain...polymerization of five dianhydride monomers with a newly synthesized diamine (azoBPA- diamine ). The azobenzene -functionalized linear polymers exhibit... diamine monomer and used it to prepare five, amorphous azobenzene -functionalized linear polyimides through polymer- ization with structurally

  8. Time-dependent permeation of carbon dioxide through a polyimide membrane above the plasticization pressure

    NARCIS (Netherlands)

    Wessling, Matthias; Huisman, I.; van den Boomgaard, Anthonie; Smolders, C.A.; Smolders, C.A.

    1995-01-01

    The time-dependent permeation behavior of a glassy polyimide is studied above and below the plasticization pressure with carbon dioxide as the permeating gas. The work particularly focuses on the quantification of the slow increase in permeability at feed pressures above the plasticization pressure.

  9. Effect of Atmospheric Pressure Plasma Modification on Polyimide and Adhesive Joining with Titanium

    NARCIS (Netherlands)

    Akram, M.; Jansen, K.M.B.; Ernst, L.J.; Bhowmik, S.; Ajeesh, G.; Ahmed, S.; Chakraborty, D.

    2015-01-01

    This investigation highlights the effect of surface modification on polyimide by atmospheric pressure plasma treatment with different exposure time. Surface modification of polymer by plasma treatment essentially creates physical and chemical changes such as cross-linking and formation of free

  10. 77 FR 33768 - Certain Polyimide Films, Products Containing Same, and Related Methods; Notice of Request for...

    Science.gov (United States)

    2012-06-07

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Certain Polyimide Films, Products Containing Same, and Related Methods; Notice of Request for... viewed on the Commission's electronic docket (EDIS) at http://edis.usitc.gov . Hearing-impaired persons...

  11. 77 FR 47092 - Certain Polyimide Films, Products Containing Same, and Related Methods; Notice of Commission...

    Science.gov (United States)

    2012-08-07

    ... COMMISSION Certain Polyimide Films, Products Containing Same, and Related Methods; Notice of Commission Determination to Partially Review and Partially Vacate the Final Initial Determination of the Administrative Law... the U.S. International Trade Commission has determined to partially review and partially vacate the...

  12. High-performance intrinsically microporous dihydroxyl-functionalized triptycene-based polyimide for natural gas separation

    KAUST Repository

    Alaslai, Nasser Y.

    2016-03-22

    A novel polyimide of intrinsic microporosity (PIM-PI) was synthesized from a 9,10-diisopropyl-triptycene-based dianhydride (TPDA) and dihydroxyl-functionalized 4,6-diaminoresorcinol (DAR). The unfunctionalized TPDA-m-phenylenediamine (mPDA) polyimide derivative was made as a reference material to evaluate the effect of the OH group in TPDA-DAR on its gas transport properties. Pure-gas permeability coefficients of He, H2, N2, O2, CH4, and CO2 were measured at 35 °C and 2 atm. The BET surface area based on nitrogen adsorption of dihydroxyl-functionalized TPDA-DAR (308 m2g-1) was 45% lower than that of TPDA-mPDA (565 m2g-1). TPDA-mPDA had a pure-gas CO2 permeability of 349 Barrer and CO2/CH4 selectivity of 32. The dihydroxyl-functionalized TPDA-DAR polyimide exhibited enhanced pure-gas CO2/CH4 selectivity of 46 with a moderate decrease in CO2 permeability to 215 Barrer. The CO2 permeability of TPDA-DAR was ∼30-fold higher than that of a commercial cellulose triacetate membrane coupled with 39% higher pure-gas CO2/CH4 selectivity. The TPDA-based dihydroxyl-containing polyimide showed good plasticization resistance and maintained high mixed-gas selectivity of 38 when tested at a typical CO2 natural gas wellhead CO2 partial pressure of 10 atm.

  13. Effect of using polyimide capillaries during thermal experiments on the particle size distribution of supported Pt nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Gámez-Mendoza, Liliana; Resto, Oscar; Martínez-Iñesta, María

    2015-09-20

    Kapton HN-type polyimide capillaries are commonly used as sample holders for transmission X-ray experiments at temperatures below 673 K because of their thermal stability, high X-ray transmittance and low cost. Using high-angle annular dark field scanning high-resolution transmission electron microscopy and thermogravimetric analysis, this work shows that using polyimide capillaries leads to the overgrowth of supported Pt nanoparticles during reduction at temperatures below the glass transition temperature (Tg= 658 K) owing to an outgassing of water from the polyimide. Quartz capillaries were also studied and this overgrowth was not observed.

  14. Polyimide-Clay Composite Materials for Space Application

    Science.gov (United States)

    Orwoll, Robert A.; Connell, John W. (Technical Monitor)

    2005-01-01

    The introduction of nanometer-sized clay particles into a polyimide matrix has been shown to enhance the physical properties of specific polymer systems. The clay comprises large stacked platelets of the oxides of aluminum and silicon. These sheets have long dimensions on the order of tenths of a micrometer and thicknesses of several nanometers. Homogeneous dispersion of the clay platelets in the polymer matrix is necessary to achieve those enhancements in polymer properties. Natural montmorillonite with the empirical formula Na0.33Mg0.33Al1.67(OH)2(Si4O10) contains exchangeable inorganic cations. The clay lamellae stack together with the positive sodium ions situated between the surfaces of the individual sheets to balance negatively charged oxygen atoms that are on the surfaces of the sheets. These surface charges contribute to strong electrostatic forces which hold the sheets together tightly. Exfoliation can be accomplished only with unusual measures. In preparing clay nanocomposites, we have taken two steps to try to reduce these interlamellar forces in order to promote the separation (exfoliation) of the sheets and the dispersion of the individual clay particles throughout the organic polymer matrix. In the first step, some of the surface Na(+) ions are replaced with Li(+) ions. Unlike sodium cations, the lithium cations migrate into the interior of the lamellae when the system is heated. Their departure from the surface reduces the surface charge and therefore the attractive forces between the sheets. The loss of alkali metal cations from the surface can be measured as the cation exchange capacity (CEC) of the clay. For example, we found that the CEC of montmorillonite clay was reduced by almost two thirds by treating it with lithium ions and heating to 250 C for 24 hr. Lesser heating has a smaller effect on the CEC. X-ray diffraction measurements show that the d-spacing decreased from ca. 1.34 to 0.97 nm, apparently a consequence of a collapse of the clay

  15. Etude préliminaire de la stabilité à l'hydrolyse des polyimides 6F Preliminary Study of the Hydrolysis Stability of 6f Polyimides

    Directory of Open Access Journals (Sweden)

    Mileo J. C.

    2006-11-01

    Full Text Available L'évaluation comparative du comportement en solution des polylmides 6F fait ressortir que ces nouveaux polymères, doués d'une stabilité thermique élevée par référence à l'analyse thermogravimétrique, ont, par contraste, une résistance beaucoup plus limitée aux influences ioniques et que l'hydrolyse, qui entraîne une réduction substantielle de leur masse moléculaire, est, dans leur cas, un processus de dégradation d'importance majeure. Despite its importance, particularly during the phase-inversion creation of asymmetrical gaseous-permeation membranes, the behavior in solution of polyImides derived from 4,4'-hexafluoroisopropylidenediphthalic anhydride has not, to our knowledge, been the subject of any published report. The present project was thus undertaken to assess the hydrolysis resistance of such polymers. This article describes and interprets some results highlighting the influence of structural factors. The products, which differ in the nature of both the initial diamine and dianhydride, were prepared by thermal polyheterocyclization in a single stage in different solvents at 200°C, and their stability was determined by the variations in their intrinsic viscosity after aging in a sealed tube at 90°C. Hydrolysis does not affect all 6F polyImides in a uniform way but seems to be governed by differences in the chemical affinity and in the morphology of the chains. Polymers having an increasing number of alkyl groups on the aminated remainder show a less and less marked susceptibility. A more specific fragility, however, affects polyImides having a carboxylic acid group. Other polar substituents have a stabilizing influence. A comparison with other polyImides is undeniably unfavorable to 6F derivatives. Degradation is very marked in dipolar aprotic solvents, whereas it appears quite limited in m-cresol. It apparantly cannot be blamed on the possible presence of uncyclized acid-amide units. The influence of the amount of

  16. Impact of silver metallization and electron irradiation on the mechanical deformation of polyimide films

    Science.gov (United States)

    Muradov, A. D.; Mukashev, K. M.; Yar-Mukhamedova, G. Sh.; Korobova, N. E.

    2017-11-01

    The impact of silver metallization and electron irradiation on the physical and mechanical properties of polyimide films has been studied. The metal that impregnated the structure of the polyimide substrate was 1-5 μm. The surface coatings contained 80-97% of the relative silver mirror in the visible and infrared regions. Irradiation was performed at the ELU-6 linear accelerator with an average beam electron energy of 2 MeV, an integral current of up to 1000 μA, a pulse repetition rate of 200 Hz, and a pulse duration of 5 μs. The absorbed dose in the samples was 10, 20, 30, and 40 MGy. The samples were deformed at room temperature under uniaxial tension on an Instron 5982 universal testing system. The structural changes in the composite materials that result from the impact of the physical factors were studied using an X-ray diffractometer DRON-2M in air at 293 K using Cu K α radiation (λαCu = 1.5418 Å). A substantial growth of mechanical characteristics resulting from the film metallization, as compared to the pure film, was observed. The growth of the ultimate strength by Δσ = 105 MPa and the plasticity by Δɛ = 75% is connected with the characteristics of the change of structure of the metallized films and the chemical etching conditions. The electron irradiation of the metallized polyimide film worsens its elastic and strength characteristics due to the formation of new phases in the form of silver oxide in the coating. The concentration of these phases increased with increasing dose, which was also the result of the violation of the ordered material structure, namely, the rupture of polyimide macromolecule bonds and the formation of new phases of silver in the coating. A mathematical model was obtained that predicts the elastic properties of silver metallized polyimide films. This model agrees with the experimental data.

  17. Pristine and thermally-rearranged gas separation membranes from novel o-hydroxyl-functionalized spirobifluorene-based polyimides

    KAUST Repository

    Ma, Xiaohua

    2014-01-01

    A novel o-hydroxyl-functionalized spirobifluorene-based diamine monomer, 2,2′-dihydroxyl-9,9′-spiro-bifluorene- 3,3′-diamine (HSBF), was successfully prepared by a universal synthetic method. Two o-hydroxyl-containing polyimides, denoted as 6FDA-HSBF and SPDA-HSBF, were synthesized and characterized. The BET surface areas of 6FDA-HSBF and SPDA-HSBF are 70 and 464 m2 g-1, respectively. To date, SPDA-HSBF exhibits the highest CO2 permeability (568 Barrer) among all hydroxyl-containing polyimides. The HSBF-based polyimides exhibited higher CO2/CH4 selectivity than their spirobifluorene (SBF) analogues (42 for 6FDA-HSBF vs. 27 for 6FDA-SBF) due to an increase in their diffusivity selectivity. Polybenzoxazole (PBO) membranes obtained from HSBF-based polyimide precursors by thermal rearrangement showed enhanced permeability but at the cost of significantly decreased selectivity.

  18. stableGP

    Data.gov (United States)

    National Aeronautics and Space Administration — The code in the stableGP package implements Gaussian process calculations using efficient and numerically stable algorithms. Description of the algorithms is in the...

  19. Stable canonical rules

    NARCIS (Netherlands)

    Iemhoff, R.; Bezhanishvili, N.; Bezhanishvili, Guram

    2016-01-01

    We introduce stable canonical rules and prove that each normal modal multi-conclusion consequence relation is axiomatizable by stable canonical rules. We apply these results to construct finite refutation patterns for modal formulas, and prove that each normal modal logic is axiomatizable by stable

  20. Stable canonical rules

    NARCIS (Netherlands)

    Bezhanishvili, G.; Bezhanishvili, N.; Iemhoff, R.

    We introduce stable canonical rules and prove that each normal modal multi-conclusion consequence relation is axiomatizable by stable canonical rules. We apply these results to construct finite refutation patterns for modal formulas, and prove that each normal modal logic is axiomatizable by stable

  1. Growth and decay of surface voltage on silver diffused polyimide exposed to 3-15 keV electrons

    Energy Technology Data Exchange (ETDEWEB)

    Mahapatra, S K; Dhole, S D; Bhoraskar, V N [Department of Physics, University of Pune, Pune-411007 (India)

    2007-02-21

    During electron irradiation, the growth in the surface voltage on virgin and silver diffused polyimide sample was studied by varying electron energy from 3 to 15 keV and beam diameter from 3 to 15 mm. At a constant beam current, the surface voltage increased nonlinearly with electron energy but decreased slowly with beam diameter at fixed electron energy. At a surface voltage around saturation or beyond 3 kV, the electron beam was switched off and the decay in the surface voltage was studied for a period of 9 x 10{sup 4} s. The surface analysis revealed that the relative concentrations of carbon increased and that of the oxygen and the nitrogen decreased in the electron irradiated virgin and silver diffused polyimide sample, however in different proportions. Under the identical conditions of electron irradiation, the growth rate of the surface voltage, the post irradiated surface resistivity and the voltage decay constant of the silver diffused polyimide were lower than that of the virgin polyimide. The results of the present study reveal that the resistance of the silver diffused polyimide to keV electrons is higher than that of the virgin polyimide.

  2. Stable isotopes as a useful tool for revealing the environmental fate and trophic effect of open-sea-cage fish farm wastes on marine benthic organisms with different feeding guilds.

    Science.gov (United States)

    Wai, Tak-Cheung; Leung, Kenneth M Y; Wu, Rudolf S S; Shin, Paul K S; Cheung, S G; Li, X Y; Lee, Joseph H W

    2011-01-01

    Environmental fate of fish farm wastes (FFW) released from an open-sea-cage farm at Kat O, Hong Kong was examined by measuring carbon and nitrogen stable isotope (SI) ratios in selected benthic organisms collected along a 2000 m transect from the farm. Our results showed that FFW significantly influenced the energy utilization profile of consumers near the fish farm. Although nitrogen enrichment effect on δ15N was anticipated in biota near the farm, the predicted patterns did not consistently occur in all feeding guilds. Two species of suspension-feeders, which relied on naturally δ15N-depleted sources, were δ15N-enriched near the fish farm. In contrast, both species of benthic grazer and deposit-feeder, which relied on naturally δ15N-enriched algal sources, were δ15N-depleted under the influence of FFW. The SI signatures of biota can, therefore, serve as feasible biomarkers for FFW discharges only when the trophic structure of the receiving environment is fully elucidated. Copyright © 2011 Elsevier Ltd. All rights reserved.

  3. Formation of separating layers under conditions of the thermal aging of sorbents modified by fluorinated polyimide

    Science.gov (United States)

    Yakovleva, E. Yu.; Shundrina, I. K.; Gerasimov, E. Yu.; Vaganova, T. A.

    2014-03-01

    Thermogravimetry, elemental analysis, low-temperature nitrogen adsorption, high-resolution electron microscopy, and gas chromatography are used to study the effect of the content of perfluorinated polyimide when used as a stationary phase for modifying Chromosorb P NAW diatomite supports and aluminum oxide, and the effect of thermal aging conditions on changes in their texture and chromatographic characteristics. It is shown that Chromosorb P NAW + 5 wt % of polyimide (PI) adsorbent thermally aged at 700°C in a flow of inert gas exhibits properties of carbon molecular sieves, while aluminum oxide impregnated with 10 wt % of PI and thermally aged at 250°C allows us to selectively separate permanent and organic gases, as well separate saturated and unsaturated hydrocarbons.

  4. Optical properties of polyimides films treated by nanosecond pulsed electrical discharges in water

    Science.gov (United States)

    Sava, Ion; Kruth, Angela; Kolb, Juergen F.; Miron, Camelia

    2018-01-01

    Fluorinated polyimide films containing cobalt chloride based on hexafluoroisopropylidenediphthalic dianhydride and 4,4‧-diamino-3,3‧-dimethyl diphenylmethane were treated by nanosecond pulsed electrical discharges generated in distilled water. The polyimide films have been characterized by Fourier transform infrared (FTIR) spectra and contact angle measurements, optical transmission spectroscopy, and fluorescence spectroscopy. Significant changes in some intrinsic fluorescence features, such as the intensity and position of the emission peak, have been observed during exposure to water plasma. These effects have been considered to correlate with the development of specific chemical interactions between the liquid and the macromolecules, including the formation of hydrogen bridges. A slight increase in surface hydrophobicity was observed after plasma treatment. FTIR spectra showed a decrease in the intensity of the absorption band and an opening of the imide ring, depending on the treatment time.

  5. Branched Rod-Coil Polyimide-Poly(Alkylene Oxide) Copolymers and Electrolyte Compositions

    Science.gov (United States)

    Meador, Maryann B. (Inventor); Tigelaar, Dean M. (Inventor)

    2014-01-01

    Crosslinked polyimide-poly(alkylene oxide) copolymers capable of holding large volumes of liquid while maintaining good dimensional stability. Copolymers are derived at ambient temperatures from amine endcapped amic-acid oligomers subsequently imidized in solution at increased temperatures, followed by reaction with trifunctional compounds in the presence of various additives. Films of these copolymers hold over four times their weight at room temperature of liquids such as ionic liquids (RTIL) and/or carbonate solvents. These rod-coil polyimide copolymers are used to prepare polymeric electrolytes by adding to the copolymers various amounts of compounds such as ionic liquids (RTIL), lithium trifluoromethane-sulfonimide (LiTFSi) or other lithium salts, and alumina.

  6. Synthesis and characterization of nanostructured sulfonated polyimides for proton exchange membrane fuel cells

    Science.gov (United States)

    Zou, Lijun

    Sulfonated polyimides (SPI) are considered to be good candidates for proton exchange membranes (PEMs) since they exhibit high strength, good film-forming ability, chemical resistance, thermal stability, and, in their hydrated state, relatively high proton conductivity. Despite intense research in the area of SPIs, fundamental investigations of hydrophilic/hydrophobic phase segregation and studies of humidity dependent morphologies are scarce. In an effort to influence the order and distribution of ionic groups in rigid-rod SPIs and to understand the interrelationships between morphology, hydration and proton conductivity, two novel model systems of SPI polymers containing hydrophobic polysiloxane (SPI-PSX) and hydrophilic silica nanoparticles (SPI-Si) were developed. The first model system of sulfonated polyimide containing hydrophobic polysiloxane segmented copolymers was prepared by a one-pot synthesis. SPI-PSX materials were evaluated using 1H NMR, size-exclusion chromatography. The presence of ion-containing diamines in the reaction mixture was found to inhibit stoichiometric incorporation of hydrophobic siloxane segments. Siloxane segments were found to lower the thermal stability of the polyimide host. Equilibrium water sorption studies of free standing films of copolymers with and without siloxane segments show that the presence of siloxane segments does not interfere with water swelling, which suggests a microphase-segregated morphology may exist. TEM and SAXS analyses show evidence of phase-segregation in sulfonated polyimides and reveal that siloxane segments strongly affect ionic clustering. However, proton conductivity only changes slightly when polysiloxane segments are incorporated. Sulfonated polyimides containing hydrophilic silica nanoparticles is our second model system developed for stabilizing the dispersed morphologies to promote proton conductivity. SPI-Si nanocomposites were prepared by a pre-polymer of anhydride-terminated sulfonated

  7. Out of the Autoclave Fabrication of LaRC[TradeMark] PETI-9 Polyimide Laminates

    Science.gov (United States)

    Cano, Robert J.; Jensen, Brian J.

    2013-01-01

    The NASA Langley Research Center developed polyimide system, LaRC PETI-9, has successfully been processed into composites by high temperature vacuum assisted resin transfer molding (HT-VARTM). To extend the application of this high use temperature material to other out-of-autoclave (OOA) processing techniques, the fabrication of PETI- 9 laminates was evaluated using only a vacuum bag and oven cure. A LaRC PETI-9 polyimide solution in NMP was prepared and successfully utilized to fabricate unidirectional IM7 carbon fiber prepreg that was subsequently processed into composites with a vacuum bag and oven cure OOA process. Composite panels of good quality were successfully fabricated and mechanically tested. Processing characteristics, composite panel quality and mechanical properties are presented in this work. The resultant properties are compared to previously developed LaRC material systems processed by both autoclave and OOA techniques including the well characterized, autoclave processed LaRC PETI-5.

  8. Fabrication of carbon nanotube-polyimide composite hollow microneedles for transdermal drug delivery.

    Science.gov (United States)

    Lyon, Bradley J; Aria, Adrianus I; Gharib, Morteza

    2014-12-01

    We introduce a novel method for fabricating hollow microneedles for transdermal drug delivery using a composite of vertically-aligned carbon nanotubes and polyimide. Patterned bundles of carbon nanotubes are used as a porous scaffold for defining the microneedle geometry. Polyimide resin is wicked through the carbon nanotube scaffold to reinforce the structure and provide the prerequisite strength for achieving skin penetration. The high aspect ratio and bottom-up assembly of carbon nanotubes allow the structure of the microneedles to be created in a single step of nanotube fabrication, providing a simple, scalable method for producing hollow microneedles. To demonstrate the utility of these microneedles, liquid delivery experiments are performed. Successful delivery of aqueous methylene blue dye into both hydrogel and swine skin in vitro is demonstrated. Electron microscopy images of the microneedles taken after delivery confirm that the microneedles do not sustain any structural damage during the delivery process.

  9. Development of High Temperature Type Vacuum Insulation Panel using Soluble Polyimide and Characteristic Evaluation

    Science.gov (United States)

    Araki, Kuninari; Kamoto, Daigorou; Matsuoka, Shin-Ichi

    The utilization is expected from the high-insulated characteristic as a tool for energy saving also in the high temperature insulation fields as in vacuum insulation panels (VIP) in the future. For high temperature, the material composition and process of VIP were reviewed, the SUS foil was adopted as packaging material, and soluble polyimide was developed as the thermo compression bonding material for high temperature VIP at 150°C. To lower the glass-transition temperature (Tg) under 200°C, we elaborated the new soluble polyimide using aliphatic diamine copolymer, and controlled Tg to about 176°C. By making from trial VIP and evaluations, it was possible to be maintain high performance concerning the coefficient of thermal conductivity [λ<0.008 W/(m·K) at 150°C].

  10. Graphite/Polyimide Composites Subjected to Biaxial Loads at Elevated Temperatures

    Science.gov (United States)

    Kumosa, Maciej S.; Sutter, J. K.

    2007-01-01

    First, we will review our most important research accomplishments from a five year study concerned with the prediction of mechanical properties of unidirectional and woven graphite/polyimide composites based on T650-35, M40J and M60J fibers embedded in either PMR-15 or PMR-II-50 polyimide resins. Then, an aging model recently developed for the composites aged in nitrogen will be proposed and experimentally verified on an eight harness satin (8HS) woven T650-35/PMR-15 composite aged in nitrogen at 315 C for up to 1500 hours. The study was supported jointly between 1999 and 2005 by the AFOSR, the NASA Glenn Research Center, and the National Science Foundation.

  11. Degradation of Mechanical Properties of Spacecraft Polyimide Film Exposed to Radiation Environments

    Science.gov (United States)

    Zicai, Shen; Yuming, Liu; Weiquan, Feng; Chunqing, Zhao; Yigang, Ding

    Polyimide films are widely used in spacecraft, but their mechanical properties would degrade in radiation environments that include electrons, protons, atomic oxygen, near ultraviolet or far ultraviolet, etc. Implications of using polyimide films in spacecraft are reviewed in this paper. The degradation of mechanical properties of Kapton film exposed to electrons and far ultraviolet radiation environments were studied. It is known that the tensile strength and the rupture elongation of Kapton film decrease with the increase of the tensile deformation rate and the electron and far ultraviolet radiation. The far ultraviolet radiation will cause the rupture and cross linkage of molecular bonds in the film, deoxidation of C-CO, denitrification of C-N. The increase of C-H percentage is attributed mainly to the mechanical property degradation of Kapton film under far ultraviolet irradiation.

  12. Development of a novel ozone- and photo-stable HyPer5 red fluorescent dye for array CGH and microarray gene expression analysis with consistent performance irrespective of environmental conditions

    Directory of Open Access Journals (Sweden)

    Kille Peter

    2008-11-01

    Full Text Available Abstract Background Array-based comparative genomic hybridization (CGH and gene expression profiling have become vital techniques for identifying molecular defects underlying genetic diseases. Regardless of the microarray platform, cyanine dyes (Cy3 and Cy5 are one of the most widely used fluorescent dye pairs for microarray analysis owing to their brightness and ease of incorporation, enabling high level of assay sensitivity. However, combining both dyes on arrays can become problematic during summer months when ozone levels rise to near 25 parts per billion (ppb. Under such conditions, Cy5 is known to rapidly degrade leading to loss of signal from either "homebrew" or commercial arrays. Cy5 can also suffer disproportionately from dye photobleaching resulting in distortion of (Cy5/Cy3 ratios used in copy number analysis. Our laboratory has been active in fluorescent dye research to find a suitable alternative to Cy5 that is stable to ozone and resistant to photo-bleaching. Here, we report on the development of such a dye, called HyPer5, and describe its' exceptional ozone and photostable properties on microarrays. Results Our results show HyPer5 signal to be stable to high ozone levels. Repeated exposure of mouse arrays hybridized with HyPer5-labeled cDNA to 300 ppb ozone at 5, 10 and 15 minute intervals resulted in no signal loss from the dye. In comparison, Cy5 arrays showed a dramatic 80% decrease in total signal during the same interval. Photobleaching experiments show HyPer5 to be resistant to light induced damage with 3- fold improvement in dye stability over Cy5. In high resolution array CGH experiments, HyPer5 is demonstrated to detect chromosomal aberrations at loci 2p21-16.3 and 15q26.3-26.2 from three patient sample using bacterial artificial chromosome (BAC arrays. The photostability of HyPer5 is further documented by repeat array scanning without loss of detection. Additionally, HyPer5 arrays are shown to preserve sensitivity and

  13. An investigation into the improvement of adhesive strength of polyimides by incorporation of elastomeric nanoparticles.

    Science.gov (United States)

    Khoee, Sepideh; Mahdavian, Ali Reza; Bairamy, Warahram; Ashjari, Mohsen

    2009-08-15

    Copoly(styrene-butyl acrylate-ethyleneglycoldimethacrylate) (St-BA-EGDMA) nanoparticles were prepared using miniemulsion polymerization technique. Then the dispersed nanoparticles in DMAc were added to in situ condensation polymerization media of pyromellitic dianhydride (PMDA) and oxydianiline (ODA) and consequently, homogenous polyamic acid solution containing the nanoparticles was obtained. Novel polymer-polymer nanocomposites were prepared by casting of PMDA-ODA polyamic acid solution with various content of the above elastomeric nanoparticle (ENP) on a glass plate followed by thermal imidization. All samples were characterized after preparation by FT-IR spectroscopy, transition electron microscopy (TEM), thermal gravimetry analysis (TGA) and differential scanning calorimetery (DSC). To investigate the adhesion strength of polyimides filled with (St-BA-EGDMA) nanoparticles, lap shear strength (LSS) test was examined on different metallic surfaces. Effect of nanoparticles content on the adhesion properties of this polymer was considerable for aluminum surface. Lap-shear strength and adhesive energy of the bonded samples were found to initially increase with the increase in ENP wt%, but decrease after a critical value. It was shown that by increasing the nanoparticles amount up to 25 wt%, the adhesion strength of polyimides increased due to the good wetability of surfaces. After that and by increasing the nanoparticles amount, the adhesion strength decreased according to the diminished strength between polyimide chains. Scanning Electron Microscopy (SEM) micrographs of the fractured surfaces were taken to determine the failure mode. They showed that by increasing the nanoparticle content in the polyimide matrix, failure mode was converted from adhesion failure to cohesion one.

  14. Ultra-microporous triptycene-based polyimide membranes for high-performance gas separation

    KAUST Repository

    Ghanem, Bader

    2014-03-11

    A highly permeable and highly selective polyimide of intrinsic microporosity is prepared using a 9,10-diisopropyl-triptycene contortion center. The three-dimensionality and shape-persistence of triptycene afford exceptional sieving-based gas separation performance transcending the latest permeability/selectivity trade-offs for industrial gas separations involving oxygen and hydrogen. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Fabrication of SERS Active Surface on Polyimide Sample by Excimer Laser Irradiation

    Directory of Open Access Journals (Sweden)

    T. Csizmadia

    2014-01-01

    Full Text Available A possible application of excimer laser irradiation for the preparation of surface enhanced Raman spectroscopy (SERS substrate is demonstrated. A polyimide foil of 125 μm thickness was irradiated by 240 pulses of focused ArF excimer laser beam (λ = 193 nm, FWHM = 20 ns. The applied fluence was varied between 40 and 80 mJ/cm2. After laser processing, the sample was coated with 40 nm silver by PLD in order to create a conducting layer required for the SERS application. The SERS activity of the samples was tested by Raman microscopy. The Raman spectra of Rhodamine 6G aqueous solution (c=10−3 mol/dm3 were collected from the patterned and metalized areas. For areas prepared at 40–60 mJ/cm2 laser fluences, the measured Raman intensities have shown a linear dependence on the applied laser fluence, while above 60 mJ/cm2 saturation was observed. The morphology of the SERS active surface areas was investigated by scanning electron microscopy. Finite element modeling was performed in order to simulate the laser-absorption induced heating of the polyimide foil. The simulation resulted in the temporal and spatial distribution of the estimated temperature in the irradiated polyimide sample, which are important for understanding the structure formation process.

  16. Harnessing Three Dimensional Anatomy of Graphene Foam to Induce Superior Damping in Hierarchical Polyimide Nanostructures.

    Science.gov (United States)

    Nautiyal, Pranjal; Boesl, Benjamin; Agarwal, Arvind

    2017-03-01

    Graphene foam-based hierarchical polyimide composites with nanoengineered interface are fabricated in this study. Damping behavior of graphene foam is probed for the first time. Multiscale mechanisms contribute to highly impressive damping in graphene foam. Rippling, spring-like interlayer van der Waals interactions and flexing of graphene foam branches are believed to be responsible for damping at the intrinsic, interlayer and anatomical scales, respectively. Merely 1.5 wt% graphene foam addition to the polyimide matrix leads to as high as ≈300% improvement in loss tangent. Graphene nanoplatelets are employed to improve polymer-foam interfacial adhesion by arresting polymer shrinkage during imidization and π-π interactions between nanoplatelets and foam walls. As a result, damping behavior is further improved due to effective stress transfer from the polymer matrix to the foam. Thermo-oxidative stability of these nanocomposites is investigated by exposing the specimens to glass transition temperature of the polyimide (≈400 °C). The composites are found to retain their damping characteristics even after being subjected to such extreme temperature, attesting their suitability in high temperature structural applications. Their unique hierarchical nanostructure provides colossal opportunity to engineer and program material properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Tuning the adhesion between polyimide substrate and MWCNTs/epoxy nanocomposite by surface treatment

    Science.gov (United States)

    Bouhamed, Ayda; Kia, Alireza Mohammadian; Naifar, Slim; Dzhagan, Volodymyr; Müller, Christian; Zahn, Dietrich R. T.; Choura, Slim; Kanoun, Olfa

    2017-11-01

    MWCNTs/epoxy nanocomposite thin films are coated on the polyimide (PI) flexible substrate, to be used as a strain sensor. Previous studies showed that the adhesion between polyimide and other materials are very poor. In this work, two approaches, oxygen plasma cleaning and simple solvent cleaning are performed for activation of the polyimide surface. In order to understand the impact of both cleaning techniques, the physicochemical properties of PI are measured and characterized using contact angle measurements (CAMs), X-ray photoelectron spectroscopy(XPS), and atomic force microscopy (AFM). In addition, the adhesion properties of PI/[MWCNTs/epoxy] systems by varying surface treatment time are investigated and evaluated using force-distance measurements by AFM. The results illustrate that the activated surface exhibits higher surface energy for oxygen plasma cleaning in comparison with the solvent cleaning method. The improvement can be related to the increase of oxygen concentration, which is accompanied by the enhancement of the polar component to 53.79 mN/m due to the formation of functional groups on the surface and the change of the substrate surface roughness from 1.72 nm to 15.5 nm. As a result, improved adhesion was observed from force-distance measurement between PI/[MWCNTs/epoxy] systems due to oxygen plasma effects.

  18. Mechanical response of two polyimides through coarse-grained molecular dynamics simulations

    Science.gov (United States)

    Sudarkodi, V.; Sooraj, K.; Nair, Nisanth N.; Basu, Sumit; Parandekar, Priya V.; Sinha, Nishant K.; Prakash, Om; Tsotsis, Tom

    2018-03-01

    Coarse-grained molecular dynamics (MD) simulations allow us to predict the mechanical responses of polymers, starting merely with a description of their molecular architectures. It is interesting to ask whether, given two competing molecular architectures, coarse-grained MD simulations can predict the differences that can be expected in their mechanical responses. We have studied two crosslinked polyimides PMR15 and HFPE52—both used in high- temperature applications—to assess whether the subtle differences in their uniaxial stress–strain responses, revealed by experiments, can be reproduced by carefully coarse-grained MD models. The coarse graining procedure for PMR15 is outlined in this work, while the coarse grain forcefields for HFPE52 are borrowed from an earlier one (Pandiyan et al 2015 Macromol. Theory Simul. 24 513–20). We show that the stress–strain responses of both these polyimides are qualitatively reproduced, and important insights into their deformation and failure mechanisms are obtained. More importantly, the differences in the molecular architecture between the polyimides carry over to the differences in the stress–strain responses in a manner that parallels the experimental results. A critical assessment of the successes and shortcomings of predicting mechanical responses through coarse-grained MD simulations has been made.

  19. Electroless plating preparation and electromagnetic properties of Co-coated carbonyl iron particles/polyimide composite

    Science.gov (United States)

    Zhou, Yingying; Zhou, Wancheng; Li, Rong; Qing, Yuchang; Luo, Fa; Zhu, Dongmei

    2016-03-01

    To solve the serious electromagnetic interference problems at elevated temperature, one thin microwave-absorbing sheet employing Co-coated carbonyl iron particles and polyimide was prepared. The Co-coated carbonyl iron particles were successfully prepared using an electroless plating method. The microstructure, composition, phase and static magnetic properties of Co-coated carbonyl iron particles were characterized by combination of scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The electromagnetic parameters of Co-coated carbonyl iron particles/polyimide composite were measured in the frequency range of 2-18 GHz, and the electromagnetic loss mechanism of the material-obtained was discussed. The microwave absorption properties of composites before and after heat treatment at 300 °C for 100 h were characterized in 2-18 GHz frequency range. It was established that composites based on Co-coated carbonyl iron demonstrate thermomagnetic stability, indicating that Co coating reduces the oxidation of carbonyl iron. Thus, Co-coated carbonyl iron particles/polyimide composites are useful in the design of microwave absorbers operating at temperatures up to 300 °C.

  20. Synthesis and characterization of polyimide thin films obtained by thermal evaporation and solid state reaction

    Directory of Open Access Journals (Sweden)

    Al-Ajaj Ikram Atta

    2016-03-01

    Full Text Available In this research polyimide films were prepared by physical vapor deposition (PVD, using solid state reaction of pyromellitic dianhydride (PMDA and p-phenylene diamine (PDA to form poly(amic acid (PAA films. The resultant films were converted to polyimide by thermal treatment, usually below 300 °C. For this study, a FT-IR spectrometer has been used to measure the effect of imidization temperature on the chemical structure of the vapor-deposited thin films of aromatic PI. When temperature increased, an increase in all absorption peaks was observed. This suggests that residual PAA monomers continued to be converted into PI. The surface topology of the PI films obtained at imidization temperatures of 150, 200, 250 °C for 1 hour was further examined by using AFM atomic force microscopy. It can be clearly seen that the surface became rougher with increasing imidization temperature. The thermal stability of polyimide was also studied by using thermogravimetric analysis (TGA.

  1. Measurement and analysis of thickness change in the curing and drying processes of polyimide films

    Energy Technology Data Exchange (ETDEWEB)

    Kook, H.J.; Kim, D.J. [Sung Kyun Kwan University, Suwon (Korea, Republic of)

    1998-05-01

    The thickness change of semirigid polyimide, pyromellitic dianhydride-4,4`-oxydianiline (PMDA-ODA), films during the curing and drying processes was monitored using laser interferometer system and the effects of scanning rate and pre-baking time on it were analyzed. The variation of imidization extent in the curing process for different temperature scanning rates was investigated using Fourier transform-infrared spectroscopy. As the pre-baking time increased, the initial film thickness in the curing process decreased significantly. As the temperature scanning rate increased, the temperatures at which the variation of film thickness and imidization extent started and completed increased. The values of film thickness were higher for higher scanning rates at the same temperatures in the curing process. The thermal expansion coefficient of cured polyimide film was determined from measurement of the temperature dependence of film thickness. In the drying process of swelled polyimide films, the temperature dependence of solvent diffusion coefficient was determined from the curve fitting of the theoretical time dependent fractional solvent mass residue in the film to the experimental results obtained at varying temperatures,with the extraction of the activation energy from it.

  2. Superparamagnetic polyimide/{gamma}-Fe{sub 2}O{sub 3} nanocomposite films: Preparation and characterization

    Energy Technology Data Exchange (ETDEWEB)

    Zhan Jiayu; Tian Guofeng; Jiang Lizhong; Wu Zhanpeng [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China); Wu Dezhen [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)], E-mail: wdz@mail.buct.edu.cn; Yang Xiaoping; Jin Riguang [State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029 (China)

    2008-07-31

    Polyimide/{gamma}-Fe{sub 2}O{sub 3} nanocomposite films with superparamagnetic behavior have been prepared by thermal curing of the magnetite (Fe{sub 3}O{sub 4}) nanoparticles-containing poly(amic acid) (PAA) derived from pyromellitic dianhydride (PMDA) and 4,4'-oxydianiline (4,4'-ODA) in N,N-dimethylacetamide (DMAc). To improve the dispersion of the doped nanoparticles, the amine-functionalized Fe{sub 3}O{sub 4} nanoparticles reacted with the PMDA dianhydride in DMAc firstly, and then polymerization was carried out by adding 4,4'-ODA and then PMDA to form the PAA-grafted magnetic particles. Thermal treatment of the Fe{sub 3}O{sub 4}-doped precursor film converted the PAA into its final polyimide form with concomitant transformation of Fe{sub 3}O{sub 4} into {gamma}-Fe{sub 2}O{sub 3}, yielding a polyimide film with superparamagnetic behavior. The distribution of nanoparticles in the polymer matrix was investigated by transmission electron microscopy and field emission scanning electron microscopy. The nanoparticles and composite films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, magnetic and mechanical measurement.

  3. Formation of hierarchical porous graphene films with defects using a nanosecond laser on polyimide sheet

    Science.gov (United States)

    Wang, Fangcheng; Wang, Kedian; Dong, Xia; Mei, Xuesong; Zhai, Zhaoyang; Zheng, Buxiang; Lv, Jing; Duan, Wenqiang; Wang, Wenjun

    2017-10-01

    The cost of effective preparation of graphene-based nanomaterials is a challenge in high-performance flexible electrodes. We demonstrated the formation of hierarchical porous graphene (HPG) films with defects from polyimide (PI) sheets using a high repetition rate nanosecond fiber laser. The honeycomb structure with mesopores and macropores can be rapidly induced on the polyimide by the localized focused laser beam in air atmosphere. Employing laser direct writing method, the one-step synthesis and patterning of conductive HPG films were achieved directly on the surface of polyimide sheets. The results show that the unique honeycomb porous structure on HPG film is composed of few-layer graphene or graphene stacks. The lattice structure of graphene nanoplatelets contains the Stone-Wales defects. Furthermore, there are a lot of small-size graphene nanoplatelets on the surface of HPG films with high content of edge defects. These two defects can not only enhance the adsorption without compromising on high diffusivity of ions, but also contribute to the infiltration and flow of electrolyte on the surface of electrode. The proposed one-step laser direct writing technique with highly valuable suitable for developing large-scale fabrication of conductive HPG based flexible electrodes at low-cost.

  4. Feasibility of microelectrode array (MEA) based on silicone-polyimide hybrid for retina prosthesis.

    Science.gov (United States)

    Kim, Eui Tae; Kim, Cinoo; Lee, Seung Woo; Seo, Jong-Mo; Chung, Hum; Kim, Sung June

    2009-09-01

    To adopt micropatterning technology in manufacturing silicone elastomer-based microelectrode arrays for retinal stimulation, a silicone-polyimide hybrid microelectrode array was proposed and tested in vivo. Gold microelectrodes were created by semiconductor manufacturing technology based on polyimide and were hybridized with silicone elastomer by spin coating. The stability of the hybrid between the two materials was flex and blister tested. The feasibility of the hybrid electrode was evaluated in the rabbit eye by reviewing optical coherence tomography (OCT) findings after suprachoroidal implantation. The flex test showed no dehiscence between the two materials for 24 hours of alternative flexion and extension from -45.0 degrees to +45.0 degrees . During the blister test, delamination was observed at 8.33 +/- 1.36 psi of pressure stress; however, this property was improved to 11.50 +/- 1.04 psi by oxygen plasma treatment before hybridization. OCT examination revealed that the implanted electrodes were safely located in the suprachoroidal space during the 4-week follow-up period. The silicone-polyimide hybrid microelectrode array showed moderate physical properties, which are suitable for in vivo application. Appropriate pretreatment before hybridization improved electrode stability. In vivo testing indicated that this electrode is suitable as a stimulation electrode in artificial retina.

  5. Improved antifouling performance of ultrafiltration membrane via preparing novel zwitterionic polyimide

    Science.gov (United States)

    Huang, Haitao; Yu, Jiayu; Guo, Hanxiang; Shen, Yibo; Yang, Fan; Wang, Han; Liu, Rong; Liu, Yang

    2018-01-01

    On the basis of the outstanding fouling resistance of zwitterionic polymers, an antifouling ultrafiltration membrane was fabricated through phase inversion induced by immersion precipitation method, directly using the novel zwitterionic polyimide (Z-PI), which was synthesized via a two-step procedure including polycondensation and quaternary amination reaction, as membrane material. The chemical structure and composition of the obtained polymer were confirmed by using FTIR, 1H NMR and XPS analysis, and its thermal stability was thoroughly characterized by TGA measurement, respectively. The introduction of zwitterionic groups into polyimide could effectively increase membrane pore size, porosity and wettability, and convert the membrane surface from hydrophobic to highly hydrophilic. As a result, Z-PI membrane displayed significantly improved water permeability compared with that of the reference polyimide (R-PI) membrane without having an obvious compromise in protein rejection. According to the static adsorption and dynamic cycle ultrafiltration experiments of bovine serum albumin (BSA) solution, Z-PI membrane exhibited better fouling resistant ability, especially irreversible fouling resistant ability, suggesting superior antifouling property and long-term performance stability. Moreover, Z-PI membrane had a water flux recovery ratio of 93.7% after three cycle of BSA solution filtration, whereas only about 68.5% was obtained for the control R-PI membrane. These findings demonstrated the advantages of Z-PI membrane material and aimed to provide a facile and scalable method for the large-scale preparation of low fouling ultrafiltration membranes for potential applications.

  6. Flexible Polyimide Aerogel Cross-linked by Poly(maleic Anhydride-alt-alkylene)

    Science.gov (United States)

    Guo, Haiquan; Meador, Mary Ann B.; Wilkewitz, Brittany Marie

    2014-01-01

    Aerogels are potential materials for aerospace applications due to their lower thermal conductivity, lighter weight, and low dielectric constant. However, silica aerogels are restricted due to their inherent fragility, hygroscopic nature, and poor mechanical properties, especially in extreme aerospace environments. In order to fit the needs of aerospace applications, developing new thermal insulation materials that are flexible, and moisture resistant is needed. To this end, we fabricated a series of polyimide aerogels crosslinked with different poly(maleic anhydride-alt-alkylene)s as seen in Scheme 1. The polyimide oligomers were made with 3,3,4,4-biphenyltetracarboxylic dianhydride (BPDA), and different diamines or diamine combinations. The resulting aerogels have low density (0.06 gcm3 to 0.16 gcm3) and high surface area (240-440 m2g). The effect of the different backbone structures on density, shrinkage, porosity, surface area, mechanical properties, moisture resistance and thermal properties will be discussed. These novel polyalkylene-imide aerogels may be potential candidates for applications such as space suit insulation for planetary surface missions, insulation for inflatable structures for habitats, inflatable aerodynamic decelerators for entry, descent and landing (EDL) operations, and cryotank insulation for advance space propulsion systems. Scheme 1. Network of polyimide aerogels crosslinked with deifferent poly(maleic anhydride).

  7. STATISTIC METHODS OF POLYIMIDE ENAMEL ISOLATION DEFECTIVE NON-DESTRUCTIVE CONTROL AT THE CONDITIONS OF PRODUCTION

    Directory of Open Access Journals (Sweden)

    O. V. Golik

    2017-03-01

    Full Text Available In this paper can be used to not-destructive technological testing of defects isolation enameled wire with polyimide polymer. The thesis is devoted to the statistical method for processing, comparison and analysis of results of measurements of parameters isolation it enameled wire because of mathematical model of trend for application in active technological monitoring is developed; to development used of the recommendations for parameters of such testing. Is theoretically justified and the possibility of a diminution of dependence of an error from a velocity of movement of a wire for want of quantifying of defects enameled isolation not destroying tests by high voltage. This work is devoted to the statistical method for processing, comparison and analysis of results of measurements of parameters of polyimide isolation. The method is operating not destroying technological monitoring an amount of enameled isolation defect. The dependence of average value of amount of defects for enameled wire ПЭЭИДХ2 – 200 with two–sheeted polyimide by isolation in a range of nominal diameter 0.56 mm is experimentally determined. The technological monitoring purpose is reducing of quantifying of enameled isolation defect.

  8. Novel spirobifluorene- and dibromospirobifluorene-based polyimides of intrinsic microporosity for gas separation applications

    KAUST Repository

    Ma, Xiaohua

    2013-12-23

    Two series of novel intrinsically microporous polyimides were synthesized from 9,9′-spirobifluorene-2,2′-diamine (SBF) and its bromine-substituted analogue 3,3′-dibromo-9,9′-spirobifluorene-2, 2′-diamine (BSBF) with three different dianhydrides (6FDA, PMDA, and SPDA). All polymers exhibited high molecular weight, good solubility in common organic solvents, and high thermal stability. Bromine-substituted polyimides showed significantly increased gas permeabilities but slightly lower selectivities than the SBF-based polyimides. The CO2 permeability of PMDA-BSBF (693 Barrer) was 3.5 times as high as that of PMDA-SBF (197 Barrer), while its CO2/CH4 selectivity was similar (19 vs 22). Molecular simulations of PMDA-SBF and PMDA-BSBF repeat units indicate that the twist angle between the PMDA and fluorene plane changes from 0 in PMDA-SBF to 77.8 in PMDA-BSBF, which decreases the ability of the polymer to pack efficiently due to severe steric hindrance induced by the bromine side groups. © 2013 American Chemical Society.

  9. INVERSE STABLE SUBORDINATORS.

    Science.gov (United States)

    Meerschaert, Mark M; Straka, Peter

    2013-01-01

    The inverse stable subordinator provides a probability model for time-fractional differential equations, and leads to explicit solution formulae. This paper reviews properties of the inverse stable subordinator, and applications to a variety of problems in mathematics and physics. Several different governing equations for the inverse stable subordinator have been proposed in the literature. This paper also shows how these equations can be reconciled.

  10. Stable Boundary Layer Issues

    OpenAIRE

    Steeneveld, G.J.

    2012-01-01

    Understanding and prediction of the stable atmospheric boundary layer is a challenging task. Many physical processes are relevant in the stable boundary layer, i.e. turbulence, radiation, land surface coupling, orographic turbulent and gravity wave drag, and land surface heterogeneity. The development of robust stable boundary layer parameterizations for use in NWP and climate models is hampered by the multiplicity of processes and their unknown interactions. As a result, these models suffer ...

  11. INVERSE STABLE SUBORDINATORS

    Science.gov (United States)

    MEERSCHAERT, MARK M.; STRAKA, PETER

    2013-01-01

    The inverse stable subordinator provides a probability model for time-fractional differential equations, and leads to explicit solution formulae. This paper reviews properties of the inverse stable subordinator, and applications to a variety of problems in mathematics and physics. Several different governing equations for the inverse stable subordinator have been proposed in the literature. This paper also shows how these equations can be reconciled. PMID:25045216

  12. Preparation, characterization, and application of TiO2-patterned polyimide film as a photocatalyst for oxidation of organic contaminants.

    Science.gov (United States)

    Ramasundaram, Subramaniyan; Seid, Mingizem Gashaw; Lee, Wonseop; Kim, Chan Ul; Kim, Eun-Ju; Hong, Seok Won; Choi, Kyoung Jin

    2017-10-15

    Photocatalytically active TiO2-patterned polyimide (PI) films (PI-TiO2) were fabricated using thermal transfer patterning (TTP). When subjected to hot pressing, the TiO2 nanoparticles electrosprayed on steel mesh templates were successfully transferred and formed checker plate patterns on PI film. FE-SEM studies confirmed that pressing at 350°C and 100MPa was optimum for obtaining patterns with uniform TiO2 coverage. When the quantity of TiO2 on the template increased, the amount of it immobilized on PI film also increased from 0.3245 to 1.2378mg per 25cm(2). XPS studies confirmed the presence TiO2 on the patterns, and indicated the formation of carboxylic acid and amide groups on the PI surface during TTP. When tested under UVA irradiation, PI-TiO2 with 1.2378mg/25cm(2) TiO2 loading exhibited the highest photocatalytic performance for methylene blue (10μM) degradation, with a rate constant of 0.0225min(-1) and stable photocatalytic efficacy for 25 cycles of reuse. The PI-TiO2 was also successfully used to degrade amoxicillin, atrazine, and 4-chlorophenol. During photocatalysis, the toxicity of 4-chlorophenol against Vibrio fischeri and the antibiotic activity of amoxicillin against Escherichia coli were decreased. Overall, TTP was found to be a potentially scalable method for fabricating robust immobilized TiO2 photocatalyst. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Evolutionary Stable Strategy

    Indian Academy of Sciences (India)

    IAS Admin

    After Maynard-Smith and Price [1] mathematically derived why a given behaviour or strategy was adopted by a certain proportion of the population at a given time, it was shown that a strategy which is currently stable in a population need not be stable in evolutionary time (across generations). Additionally it was sug-.

  14. Stable Boundary Layer Issues

    NARCIS (Netherlands)

    Steeneveld, G.J.

    2012-01-01

    Understanding and prediction of the stable atmospheric boundary layer is a challenging task. Many physical processes are relevant in the stable boundary layer, i.e. turbulence, radiation, land surface coupling, orographic turbulent and gravity wave drag, and land surface heterogeneity. The

  15. Photolithography-free laser-patterned HF acid-resistant chromium-polyimide mask for rapid fabrication of microfluidic systems in glass

    Science.gov (United States)

    Zamuruyev, Konstantin O.; Zrodnikov, Yuriy; Davis, Cristina E.

    2017-01-01

    Excellent chemical and physical properties of glass, over a range of operating conditions, make it a preferred material for chemical detection systems in analytical chemistry, biology, and the environmental sciences. However, it is often compromised with SU8, PDMS, or Parylene materials due to the sophisticated mask preparation requirements for wet etching of glass. Here, we report our efforts toward developing a photolithography-free laser-patterned hydrofluoric acid-resistant chromium-polyimide tape mask for rapid prototyping of microfluidic systems in glass. The patterns are defined in masking layer with a diode-pumped solid-state laser. Minimum feature size is limited to the diameter of the laser beam, 30 µm minimum spacing between features is limited by the thermal shrinkage and adhesive contact of the polyimide tape to 40 µm. The patterned glass substrates are etched in 49% hydrofluoric acid at ambient temperature with soft agitation (in time increments, up to 60 min duration). In spite of the simplicity, our method demonstrates comparable results to the other current more sophisticated masking methods in terms of the etched depth (up to 300 µm in borosilicate glass), feature under etch ratio in isotropic etch (~1.36), and low mask hole density. The method demonstrates high yield and reliability. To our knowledge, this method is the first proposed technique for rapid prototyping of microfluidic systems in glass with such high performance parameters. The proposed method of fabrication can potentially be implemented in research institutions without access to a standard clean-room facility.

  16. Synthesis and characterization of novel triptycene dianhydrides and polyimides of intrinsic microporosity based on 3,3ʹ-dimethylnaphthidine

    KAUST Repository

    Ghanem, Bader

    2016-08-29

    Two intrinsically microporous polyimides were obtained by high-temperature, one-pot poly-condensation reaction of novel triptycene-based dianhydrides containing dimethyl- or diisopropyl-bridgehead groups with a commercially available highly sterically hindered 3,3 \\'-dimethylnaphthidine (DMN) diamine monomer. The dimethyl bridgehead groups in the triptycene building block provided the DMN-based polyimide (TDA1-DMN) with larger surface area (760 m(2) g(-1)) than the diisopropyl-based polyimide (TDA1-DMN) (680 m(2) g(-1)), greater fraction of ultramicroporosity, as observed from N-2 and CO2 NLDFT adsorption analysis, and higher gas permeability and selectivity. Wide-angle X-ray diffraction (WAXD) measurements demonstrated that TDA1-DMN and TDAi3-DMN exhibited a bimodal pore size distribution, where TDA1-DMN showed smaller d-spacing values and broader intensity peaks. Both TDADMN-based polyimides showed very high gas permeabilities with moderate selectivities. For example, fresh TDA1-DMN exhibited an O-2 permeability of 783 Barrer coupled with an O-2/N-2 selectivity of 4.3 and H-2 permeability of 3050 Barrer with H-2/N-2 selectivity of 16.7, values that surpassed the 2008 Robeson permeability/selectivity upper bounds. Physical aging of the TDA-DMN polyimide films over a period of 250 days showed relatively small changes in permeability (similar to 20%) and selectivity (similar to 5%). (C) 2016 Elsevier Ltd. All rights reserved.

  17. Synthesis and Characterization of Novel Processable and Flexible Polyimides Containing 3,6-Di(4-carboxyphenylpyromellitic Dianhydride

    Directory of Open Access Journals (Sweden)

    Muhammad Kaleem Khosa

    2014-01-01

    Full Text Available A series of six novel polyimides containing 3,6-di(4-carboxyphenylpyromellitic dianhydride were synthesized via two steps condensation method. Aromatic diamines monomers, 4-(4-aminophenoxy-N-(4-(4-aminophenoxybenzylidene-3-chloroaniline (DA1, 4-(4-amino-3-methylphenoxy-N-(4-(4-amino-3-methylphenoxybenzylidene-3-chloroaniline (DA2, 4-(4-amino-2-methylphenoxy-N-(4-(4-amino-2-methylphenoxybenzylidene-3-chloroaniline (DA3 4-(4-aminophenoxy-N-(4-(4-aminophenoxybenzylidene-2-methylaniline (DA4, 4-(4-amino-3-methylphenoxy-N-(4-(4-amino-3-methylphenoxybenzylidene-2-methylaniline (DA5, and 4-(4-amino-2-methylphenoxy-N-(4-(4-amino-2-methylphenoxybenzylidene-2-methylaniline (DA6 were prepared and used to synthesize new polyimides by reaction with resynthesized 3,6-di(4-carboxyphenylpyromellitic dianhydride by using two-step condensation method. The inherent viscosities of polyimides range from 0.68–1.04 dL gm−1 and were soluble in polar solvents. Polyimides have excellent thermal stability by showing 10% weight loss temperature was above 450°C. Their glass transition temperatures lie in the range of 250–335°C. Wide-angle X-ray diffractometer investigations revealed the amorphous nature of polyimides. Therefore, these polymers can be a potential candidate as processable high performance polymeric materials.

  18. The effect of masterbatch technique on the properties of the unsaturated polyester filled with P84 polyimide and MWCNT hybrid composites

    Science.gov (United States)

    Ibrahim, Nik Noor Idayu Nik; Romli, Ahmad Zafir; Mamauod, Siti Nur Liyana

    2017-09-01

    The masterbatch technique was developed in this study for the purpose of reducing the production time where the powder P84 Polyimide was "coated" with liquid MEKP prior to the addition into the unsaturated polyester resin. In our previous research, the interaction of masterbatch P84 Polyimide in unsaturated polyester as a single filler resulted in better tensile strength and strain at break compared to the samples prepared through standard technique. As in hybrid filler composites, between P84 Polyimide with MWCNT, the tensile strength and strain at break reduced while the tensile modulus increased. The density result showed that the masterbatch technique samples exhibited lower void content than the standard technique samples. The presence of a layer of peroxide on the surface of P84 Polyimide particles resulted in the stronger filler-filler interaction. This stronger filler-filler interaction between the particles of P84 Polyimide and MWCNT chains had produced more compact structure which leads to the lower void content. The observation using the optical microscope identified that in the hybrid composites, the particles of P84 Polyimide became black instead of yellow. This might be due to the chains of MWCNT that wrapped around the P84 Polyimide particles since the presence of a peroxide layer on the surface of P84 Polyimide attracted the MWCNT chains closer toward it.

  19. Normal modified stable processes

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler; Shephard, N.

    2002-01-01

    This paper discusses two classes of distributions, and stochastic processes derived from them: modified stable (MS) laws and normal modified stable (NMS) laws. This extends corresponding results for the generalised inverse Gaussian (GIG) and generalised hyperbolic (GH) or normal generalised inverse...... Gaussian (NGIG) laws. The wider framework thus established provides, in particular, for added flexibility in the modelling of the dynamics of financial time series, of importance especially as regards OU based stochastic volatility models for equities. In the special case of the tempered stable OU process...

  20. Stable Allocation Mechanism

    OpenAIRE

    Baïou, Mourad; Balinski, Michel

    2002-01-01

    The stable allocation problem is the generalization of the well-known and much studied stable (0,1)-matching problems to the allocation of real numbers (hours or quantities). There are two distinct sets of agents, a set I of "employees" or "buyers" and a set J of "employers" or "sellers", each agent with preferences over the opposite set and each with a given available time or quantity. In common with its specializations, and allocation problem may have exponentially many stable solutions (th...

  1. Preparation of nanoporous polyimide thin films via layer-by-layer self-assembly of cowpea mosaic virus and poly(amic acid)

    Energy Technology Data Exchange (ETDEWEB)

    Peng Bo; Wu Guojun; Lin Yuan [State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China); Wang Qian [Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC, 29208 (United States); Su Zhaohui, E-mail: zhsu@ciac.jl.cn [State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun, Jilin 130022 (China)

    2011-09-01

    Low dielectric (low-{kappa}) materials are of key importance for the performance of microchips. In this study, we show that nanosized cowpea mosaic virus (CPMV) particles can be assembled with poly(amic acid) (PAA) in aqueous solutions via the layer-by-layer technique. Then, upon thermal treatment CPMV particles are removed and PAA is converted into polyimide in one step, resulting in a porous low-{kappa} polyimide film. The multilayer self-assembly process was monitored by quartz crystal microbalance and UV-Vis spectroscopy. Imidization and the removal of the CPMV template was confirmed by Fourier transform infrared spectroscopy and atomic force microscopy respectively. The dielectric constant of the nanoporous polyimide film thus prepared was 2.32 compared to 3.40 for the corresponding neat polyimide. This work affords a facile approach to fabrication of low-{kappa} polyimide ultrathin films with tunable thickness and dielectric constant.

  2. An investigation of plasma pretreatments and plasma polymerized thin films for titanium/polyimide adhesion

    Science.gov (United States)

    Difelice, Ronald Attilio

    Plasma pretreatments are environmentally benign and energy efficient processes for modifying the surface chemistry of materials. In an effort to improve the strength of the titanium alloy/FM-5 polyimide adhesive joint for aerospace applications, oxygen plasma pretreatments and novel thin plasma polymerized (PP) films were investigated as adhesion promoters. Plasma treatments were carried out using custom-built, low pressure, radio frequency, inductively coupled plasma reactors. Ti-6Al-4V coupons were plasma treated and used to prepare miniature single lap shear (SLS) joints. The effects of plasma pretreatments on surface chemistry were studied using x-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Fourier transform infrared analysis (FTIR), and contact angle measurements. Relationships between composition, mechanical properties, and adhesion of PP films on Ti-6Al-4V and silicon wafers were investigated. The nanomechanical properties (modulus, hardness and adhesion) were studied using atomic force microscopy (AFM) nanoindentation and nanoscratch testing. A design of experiments (DOE) three factorial model was used to optimize the parameters for oxygen plasma treatments. Oxygen plasma pretreatments enhanced joint strength by cleaning the titanium surface and creating an extended oxide layer. Nanoindentation of oxygen plasma treated substrates showed no change in the surface mechanical properties due to the oxygen plasma treatment. This suggested that the improved SLS strength of the oxygen plasma pretreated substrates was due to the cleaning of the substrate and the removal of carbonaceous contaminants, rather than any changes in the morphology of the oxide layer. PP acetylene films were predominantly carbon, with oxygen as the other main constituent (incorporated mostly as C-O and C=O). For all SLS specimens tested, the adhesion between PP acetylene and FM-5 adhesive was adequate. However, the strength of SLS joints was limited by the

  3. Molecular Simulation of Ionic Polyimides and Composites with Ionic Liquids as Gas-Separation Membranes.

    Science.gov (United States)

    Abedini, Asghar; Crabtree, Ellis; Bara, Jason E; Turner, C Heath

    2017-10-24

    Polyimides are at the forefront of advanced membrane materials for CO2 capture and gas-purification processes. Recently, ionic polyimides (i-PIs) have been reported as a new class of condensation polymers that combine structural components of both ionic liquids (ILs) and polyimides through covalent linkages. In this study, we report CO2 and CH4 adsorption and structural analyses of an i-PI and an i-PI + IL composite containing [C4mim][Tf2N]. The combination of molecular dynamics (MD) and grand canonical Monte Carlo (GCMC) simulations is used to compute the gas solubility and the adsorption performance with respect to the density, fractional free volume (FFV), and surface area of the materials. Our results highlight the polymer relaxation process and its correlation to the gas solubility. In particular, the surface area can provide meaningful guidance with respect to the gas solubility, and it tends to be a more sensitive indicator of the adsorption behavior versus only considering the system density and FFV. For instance, as the polymer continues to relax, the density, FFV, and pore-size distribution remain constant while the surface area can continue to increase, enabling more adsorption. Structural analyses are also conducted to identify the nature of the gas adsorption once the ionic liquid is added to the polymer. The presence of the IL significantly displaces the CO2 molecules from the ligand nitrogen sites in the neat i-PI to the imidazolium rings in the i-PI + IL composite. However, the CH4 molecules move from the imidazolium ring sites in the neat i-PI to the ligand nitrogen atoms in the i-PI + IL composite. These molecular details can provide critical information for the experimental design of highly selective i-PI materials as well as provide additional guidance for the interpretation of the simulated adsorption systems.

  4. Thin film growth into the ion track structures in polyimide by atomic layer deposition

    Science.gov (United States)

    Mättö, L.; Malm, J.; Arstila, K.; Sajavaara, T.

    2017-09-01

    High-aspect ratio porous structures with controllable pore diameters and without a stiff substrate can be fabricated using the ion track technique. Atomic layer deposition is an ideal technique for depositing thin films and functional surfaces on complicated 3D structures due to the high conformality of the films. In this work, we studied Al2O3 and TiO2 films grown by ALD on pristine polyimide (Kapton HN) membranes as well as polyimide membranes etched in sodium hypochlorite (NaOCl) and boric acid (BO3) solution by means of RBS, PIXE, SEM-EDX and helium ion microcopy (HIM). The focus was on the first ALD growth cycles. The areal density of Al2O3 film in the 400 cycle sample was determined to be 51 ± 3 × 1016 at./cm2, corresponding to the thickness of 55 ± 3 nm. Furthermore, the growth per cycle was 1.4 Å/cycle. The growth is highly linear from the first cycles. In the case of TiO2, the growth per cycle is clearly slower during the first 200 cycles but then it increases significantly. The growth rate based on RBS measurements is 0.24 Å/cycle from 3 to 200 cycles and then 0.6 Å/cycle between 200 and 400 cycles. The final areal density of TiO2 film after 400 cycles is 148 ± 3 × 1015 at./cm2 which corresponds to the thickness of 17.4 ± 0.4 nm. The modification of the polyimide surface by etching prior to the deposition did not have an effect on the Al2O3 and TiO2 growth.

  5. 6 MeV pulsed electron beam induced surface and structural changes in polyimide

    Energy Technology Data Exchange (ETDEWEB)

    Mathakari, Narendra L.; Bhoraskar, Vasant N. [Microtron Accelerator Laboratory, Department of Physics, University of Pune, Ganeshkhind, Pune 411007, Maharashtra (India); Dhole, Sanjay D., E-mail: sanjay@physics.unipune.ernet.i [Microtron Accelerator Laboratory, Department of Physics, University of Pune, Ganeshkhind, Pune 411007, Maharashtra (India)

    2010-04-15

    Thin films of polyimide (PMDA-ODA, Kapton) having 50 mum thickness were irradiated with 6 MeV pulsed electron beam. The bulk and surface properties of pristine and irradiated samples were characterized by several techniques such as stress-strain measurements, Fourier Transform Infrared (FTIR), UV-vis spectroscopy, contact angle, atomic force microscopy (AFM) and profilometry. The tensile strength, percentage elongation and strain energy show an enhancement from pristine value of 73-89 MPa, 10-22% and 4.75-14.2 MJ/m{sup 3} respectively at the maximum fluence of 4 x 10{sup 15} electrons/cm{sup 2}. This signifies that polyimide being an excessively aromatic polymer is crosslinked due to high-energy electron irradiation. In surface properties, the contact angle shows a significant decrease from 59 deg. to 32 deg. indicating enhancement in hydrophilicity. This mainly attributes to surface roughening, which is due to the electron beam induced sputtering. The surface roughening is confirmed in AFM and profilometry measurements. The AFM images clearly show that surface roughness increases after electron irradiation. Moreover, the roughness average (R{sub a}) as measured from surface profilograms is found to increase from 0.06 to 0.1. The FTIR and UV-vis spectra do not show noticeable changes as regards to scissioning of bonds and the oxidation. This work leads to a definite conclusion that 6 MeV pulsed electron beam can be used to bring about desired changes in surface as well as bulk properties of polyimide, which is considered to be a high performance space quality polymer.

  6. Effect of Two Synthetic Methods of Polyimide/Poly(Vinylidene Fluoride) Composites on Their Dielectric Properties

    Science.gov (United States)

    Mao, Xin; Yang, Jie; Du, Lirong; Guo, Wenfeng; Li, Chengzhang; Tang, Xianzhong

    2017-08-01

    All-organic polyimide (PI)/poly(vinylidene fluoride) (PVDF) dielectric composites were fabricated via two synthesis methods. The dielectric and thermal properties of the PI/PVDF composites were investigated. The results indicated that the dielectric properties of the composites synthesized by these two methods were enhanced through the introduction of PVDF, and the composites exhibited excellent thermal stability. In addition, the composites prepared by solution blending exhibited superior dielectric properties and thermal properties compared with the composites prepared by in situ polymerization.

  7. Synthesis of γ-Fe2O3 nanoparticles embedded in polyimide

    Science.gov (United States)

    Chung, Yoon; Lim, Sung K.; Kim, C. K.; Kim, Young-Ho; Yoon, C. S.

    2004-05-01

    A mono-layer of γ-Fe2O3 nanoparticles embedded in a polyimide (PI) matrix was fabricated by oxidizing Fe metal film between two PI precursor layers. There was a critical Fe thickness (~7nm) above which a continuous layer of γ-Fe2O3 film was formed in the PI film. Below the critical Fe thickness, the oxide film broke up into fine particles whose size was ~10nm with narrow size distribution. This method offers a unique way of covering a large surface area with fine magnetic oxide nanoparticles for a potential application in high-density data storage media.

  8. Bias stress instability of double-gate a-IGZO TFTs on polyimide substrate

    Science.gov (United States)

    Cho, Won-Ju; Ahn, Min-Ju

    2017-09-01

    In this study, flexible double-gate thin-film transistor (TFT)-based amorphous indium-galliumzinc- oxide (a-IGZO) was fabricated on a polyimide substrate. Double-gate operation with connected front and back gates was compared with a single-gate operation. As a result, the double-gate a- IGZO TFT exhibited enhanced electrical characteristics as well as improved long-term reliability. Under positive- and negative-bias temperature stress, the threshold voltage shift of the double-gate operation was much smaller than that of the single-gate operation.

  9. Low void content autoclave molded titanium alloy and polyimide graphite composite structures.

    Science.gov (United States)

    Vaughan, R. W.; Jones, R. J.; Creedon, J. F.

    1972-01-01

    This paper discusses a resin developed for use in autoclave molding of polyimide graphite composite stiffened, titanium alloy structures. Both primary and secondary bonded structures were evaluated that were produced by autoclave processing. Details of composite processing, adhesive formulary, and bonding processes are provided in this paper, together with mechanical property data for structures. These data include -65 F, room temperature, and 600 F shear strengths; strength retention after aging; and stress rupture properties at 600 F under various stress levels for up to 1000 hours duration. Typically, shear strengths in excess of 16 ksi at room temperature with over 60% strength retention at 600 F were obtained with titanium alloy substrates.

  10. Laser printed graphene on polyimide electrodes for magnetohydrodynamic pumping of saline fluids

    KAUST Repository

    Khan, Mohammed Asadullah

    2017-08-09

    An efficient, scalable pumping device is reported that avoids moving parts and is fabricated with a cost-effective method. The magnetohydrodynamic pump has electrodes facilely made by laser printing of polyimide. The electrodes exhibit a low sheet resistance of 22.75 Ω/square. The pump is implemented in a channel of 240 mm2 cross-section and has an electrode length of 5 mm. When powered by 7.3 V and 12.43 mA/cm2, it produces 13.02 mm/s flow velocity.

  11. Organic/inorganic-polyimide nanohybrid materials for advanced opto-electronic applications

    Science.gov (United States)

    Ando, Shinji

    2009-02-01

    Nano-hybridization techniques based on the pyrolytic reactions of organo-soluble metallic precursors dissolved in poly(amic acid)s followed by spontaneous precipitation of metal/inorganic nano-particles in solid polyimide (PI) films is facile and effective for functionalization of PI optical and electronic materials. The organic/inorganinc PI nanohybrid materials, which were recently developed by the authors, having a variety of functionalities such as a) high refractive indices, b) low refractive indices, c) controlled thermo-optical property and its anisotropy, d) high polarizing property, and e) high thermal conductivity are reviewed with future prospects on their advanced opto-electronic applications.

  12. Calcium stable isotope geochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Gausonne, Nikolaus [Muenster Univ. (Germany). Inst. fuer Mineralogie; Schmitt, Anne-Desiree [Strasbourg Univ. (France). LHyGeS/EOST; Heuser, Alexander [Bonn Univ. (Germany). Steinmann-Inst. fuer Geologie, Mineralogie und Palaeontologie; Wombacher, Frank [Koeln Univ. (Germany). Inst. fuer Geologie und Mineralogie; Dietzel, Martin [Technische Univ. Graz (Austria). Inst. fuer Angewandte Geowissenschaften; Tipper, Edward [Cambridge Univ. (United Kingdom). Dept. of Earth Sciences; Schiller, Martin [Copenhagen Univ. (Denmark). Natural History Museum of Denmark

    2016-08-01

    This book provides an overview of the fundamentals and reference values for Ca stable isotope research, as well as current analytical methodologies including detailed instructions for sample preparation and isotope analysis. As such, it introduces readers to the different fields of application, including low-temperature mineral precipitation and biomineralisation, Earth surface processes and global cycling, high-temperature processes and cosmochemistry, and lastly human studies and biomedical applications. The current state of the art in these major areas is discussed, and open questions and possible future directions are identified. In terms of its depth and coverage, the current work extends and complements the previous reviews of Ca stable isotope geochemistry, addressing the needs of graduate students and advanced researchers who want to familiarize themselves with Ca stable isotope research.

  13. On stable Baire classes

    OpenAIRE

    Karlova, Olena; Mykhaylyuk, Volodymyr

    2015-01-01

    We introduce and study adhesive spaces. Using this concept we obtain a characterization of stable Baire maps $f:X\\to Y$ of the class $\\alpha$ for wide classes of topological spaces. In particular, we prove that for a topological space $X$ and a contractible space $Y$ a map $f:X\\to Y$ belongs to the $n$'th stable Baire class if and only if there exist a sequence $(f_k)_{k=1}^\\infty$ of continuous maps $f_k:X\\to Y$ and a sequence $(F_k)_{k=1}^\\infty$ of functionally ambiguous sets of the $n$'th...

  14. Performance of 6FDA–6FpDA polyimide for propylene/propane separations

    KAUST Repository

    Das, Mita

    2010-12-01

    This work addresses the challenges faced by previous researchers with 6FDA-6FpDA polyimide for propylene/propane separations due to plasticization. A study of film annealing temperature is reported to optimize plasticization suppression in elevated temperature permeation on properly annealed dense films made with high molecular weight polymer. A detailed analysis of pure and mixed gas results using different permeability models is shown in this work. The annealing effects in terms of plasticization suppression and permeability and selectivity changes are discussed in detail. According to our best knowledge, this is for the first time plasticization suppression for propylene/propane has been reported with any polyimide dense film membrane. Results of pure gas sorption experiments using a pressure decay method with un-annealed and annealed films are discussed and used to analyze the permeation data using the dual-mode model. Mixed gas permeation results also are explained with dual mode and bulk flow transport models. © 2010 Elsevier B.V.

  15. Laser bonded microjoints between titanium and polyimide for applications in medical implants.

    Science.gov (United States)

    Mian, A; Newaz, G; Vendra, L; Rahman, N; Georgiev, D G; Auner, G; Witte, R; Herfurth, H

    2005-03-01

    Bioencapsulation of medical implant devices, and neural implant devices in particular, requires development of reliable hermetic joints between packaging materials that are often dissimilar. Titanium-polyimide is one of the biocompatible material systems, which are of interest to our research groups at Wayne State University and Fraunhofer USA. We have found processing conditions for successful joining of titanium with polyimide using near-infrared diode lasers or fiber lasers along transmission bonding lines with widths ranging from 200 to 300 microm. Laser powers of 2.2 and 3.8 W were used to create these joints. Laser-joined samples were tested in a microtester under tensile loading to determine joint strengths. In addition, finite element analysis (FEA) was conducted to understand the stress distribution within the bond area under tensile loading. The FEA model provides a full-field stress distribution in and around the joint that cause eventual failure. Results from the investigation provide an initial approach to characterize laser-fabricated microjoints between dissimilar materials that can be potentially used in optimization of bio-encapsulation design.

  16. High-Tg, Low-Dielectric Epoxy Thermosets Derived from Methacrylate-Containing Polyimides

    Directory of Open Access Journals (Sweden)

    Chien-Han Chen

    2017-12-01

    Full Text Available Three methacrylate-containing polyimides (Px–MMA; x = 1–3 were prepared from the esterification of hydroxyl-containing polyimides (Px–OH; x = 1–3 with methacrylic anhydride. Px–MMA exhibits active ester linkages (Ph–O–C(=O– that can react with epoxy in the presence of 4-dimethylaminopyridine (DMAP, so Px–MMA acted as a curing agent for a dicyclopentadiene-phenol epoxy (HP7200 to prepare epoxy thermosets (Px–MMA/HP7200; x = 1–3 thermosets. For property comparisons, P1–OH/HP7200 thermosets were also prepared. The reaction between active ester and epoxy results in an ester linkage, which is less polar than secondary alcohol resulting from the reaction between phenolic OH and epoxy, so P1–MMA/HP7200 are more hydrophobic and exhibit better dielectric properties than P1–OH/HP7200. The double bond of methacrylate can cure at higher temperatures, leading to epoxy thermosets with a high-Tg and moderate-to-low dielectric properties.

  17. Synthesis and gas transport properties of hydroxyl-functionalized polyimides with intrinsic microporosity

    KAUST Repository

    Ma, Xiaohua

    2012-05-08

    A newly designed diamine monomer, 3,3,3′,3′-tetramethyl-1, 1′-spirobisindane-5,5′-diamino-6,6′-diol, was successfully used to synthesize two types of polyimides for membrane-based gas separation applications. The novel polymers integrate significant microporosity and polar hydroxyl groups, showing the combined features of polymers of intrinsic microporosity (PIMs) and functional polyimides (PIs). They possess high thermal stability, good solubility, and easy processability for membrane fabrication; the resulting membranes exhibit good permeability owing to the intrinsic microporosity introduced by the highly contorted PIM segments as well as high CO 2/CH 4 selectivity that arises from the hydroxyl groups. The membranes show CO 2/CH 4 selectivities of >20 when tested with a 1:1 CO 2/CH 4 mixture for feed pressures up to 50 bar. In addition, the incorporation of hydroxyl groups and microporosity in the polymers enhances their affinity to water, leading to remarkable water sorption capacities of up to 22 wt % at 35 °C and 95% relative humidity. © 2012 American Chemical Society.

  18. Synthesis of Polyimides in Molecular-Scale Confinement for Low-Density Hybrid Nanocomposites.

    Science.gov (United States)

    Isaacson, Scott G; Fostvedt, Jade I; Koerner, Hilmar; Baur, Jeffery W; Lionti, Krystelle; Volksen, Willi; Dubois, Geraud; Dauskardt, Reinhold H

    2017-11-08

    In this work, we exploit a confinement-induced molecular synthesis and a resulting bridging mechanism to create confined polyimide thermoset nanocomposites that couple molecular confinement-enhanced toughening with an unprecedented combination of high-temperature properties at low density. We describe a synthesis strategy that involves the infiltration of individual polymer chains through a nanoscale porous network while simultaneous imidization reactions increase the molecular backbone stiffness. In the extreme limit where the confinement length scale is much smaller than the polymer's molecular size, confinement-induced molecular mechanisms give rise to exceptional mechanical properties. We find that polyimide oligomers can undergo cross-linking reactions even in such molecular-scale confinement, increasing the molecular weight of the organic phase and toughening the nanocomposite through a confinement-induced energy dissipation mechanism. This work demonstrates that the confinement-induced molecular bridging mechanism can be extended to thermoset polymers with multifunctional properties, such as excellent thermo-oxidative stability and high service temperatures (>350 °C).

  19. Temperature dependence and the dispersion of nonlinear optical properties of chromophore-containing polyimide thin films

    Science.gov (United States)

    Gorkovenko, A. I.; Plekhanov, A. I.; Simanchuk, A. E.; Yakimanskiy, A. V.; Nosova, G. I.; Solovskaya, N. A.; Smirnov, N. N.

    2014-12-01

    Detailed investigations of the quadratic nonlinear response of a series of new polyimides with covalently attached chromophore DR13 are performed by the Maker fringes method in the range of fundamental wavelength from 850 to 1450 nm. Polymer films with thickness of 100-400 nm were spin-coated on glass substrates and corona poled. For these materials, the maximum values of the second harmonic generation coefficients d33 are 80-120 pm/V. A red shift of the nonlinear response dispersion with respect to the linear absorption spectrum was observed for the DR13 chromophore. The temperature dependences of linear absorption and nonlinear coefficients d33 for studied structures are observed. It was found that the temperature changes of the absorption spectra lead to appreciable contribution to the value of the nonlinear coefficient d33. The demonstrated high temperature stability (up to 120 °C) of chromophore-containing polyimide thin films makes it possible to eliminate the degradation of their nonlinear optical properties in the future applications of such structures.

  20. Time-Resolved WAXD and FTIR Studies on Imidization-Induced Molecular Ordering in Polyimide Precursors

    Science.gov (United States)

    Ree, Moonhor; Shin, Tae Joo; Lee, Byeongdu; Wang, Xiaodong; Youn, Hwa Shik; Lee, Ki-Bong

    2000-03-01

    In general, aromatic polyimides are not melt-processable and not soluble in common solvents so that they are always processed in their soluble precursor forms and followed by imidization. Most poyimide precursors are poorly ordered in the solid state but molecular ordering develops during imidization. In this study, the imidization-induced molecular ordering in precursors of PMDA-ODA polyimide was examined in detail by time-resolved wide-angle X-ray diffraction using synchrotron radiation source at Pohang Accelerator Laboratory while the degree of imidization was monitored by time-resolved FT-IR spectroscopy. The imidization was conducted isothermally and non-isothermally over 20-400 C under nitrogen atmosphere. The imidization behavior was dependent on the precursor types: polyamic acid started to imidize at 120 C while polyamic diethyl ester began to imidize at 190 C. The molecular ordering was strongly dependent on the degree of imidization: the molecular ordering was found to be developed as the imidization began. The molecular ordering behavior will be discussed in detail with considering precursor types and their imidization kinetics. [This study was supported in part by the Ministry of Industry and the Ministry of Science & Technology (G7 Project Program) and by POSCO].

  1. Gas Permeation and Physical Aging Properties of Iptycene Diamine-Based Microporous Polyimides

    KAUST Repository

    Alghunaimi, Fahd

    2015-05-12

    The synthesis and gas permeation properties of two 6FDA-dianhydride-based polyimides prepared from 2,6-diaminotriptycene (6FDA-DAT1) and its extended iptycene analog (6FDA-DAT2) are reported. The additional benzene ring on the extended triptycene moiety in 6FDA–DAT2 increases the free volume over 6FDA-DAT1 and reduces the chain packing efficiency. The BET surface area based on nitrogen adsorption in 6FDA-DAT2 (450 m2g−1) is ~40% greater than that of 6FDA-DAT1 (320 m2g−1). 6FDA-DAT1 shows a CO2 permeability of 120 Barrer and CO2/CH4 selectivity of 38, whereas 6FDA-DAT2 exhibits a 75% increase in CO2 permeability to 210 Barrer coupled with a moderate decrease in selectivity (CO2/CH4=30). Interestingly, minimal physical aging was observed over 150 days for both polymers and attributed to the high internal free volume of the shape-persistent iptycene geometries. The aged polyimides maintained CO2/CH4 selectivities of 25-35 along with high CO2 permeabilities of 90-120 Barrer up to partial CO2 pressures of 10 bar of an aggressive 50:50 CO2:CH4 mixed-gas feed, suggesting potential application in membranes for natural gas sweetening.

  2. Stable Unhappy Marriages.

    Science.gov (United States)

    Heaton, Tim B.; Albrecht, Stan L.

    1991-01-01

    Examined prevalence and determinants of stable unhappy marriage using data from national survey. Results indicated age, lack of prior marital experience, commitment to marriage as an institution, low social activity, lack of control over one's life, and belief that divorce would detract from happiness were all predictive of stability in unhappy…

  3. The stable subgroup graph

    Directory of Open Access Journals (Sweden)

    Behnaz Tolue

    2018-07-01

    Full Text Available In this paper we introduce stable subgroup graph associated to the group $G$. It is a graph with vertex set all subgroups of $G$ and two distinct subgroups $H_1$ and $H_2$ are adjacent if $St_{G}(H_1\\cap H_2\

  4. Cofinal stable logics

    NARCIS (Netherlands)

    Bezhanishvili, G.; Bezhanishvili, N.; Ilin, J.

    2016-01-01

    We generalize the (∧,∨)-canonical formulas to (∧,∨)-canonical rules, and prove that each intuitionistic multi-conclusion consequence relation is axiomatizable by (∧,∨)-canonical rules. This yields a convenient characterization of stable superintuitionistic logics. The (∧,∨)-canonical formulas are

  5. Effects of strain rate and elevated temperature on compressive flow stress and absorbed energy of polyimide foam

    Directory of Open Access Journals (Sweden)

    Horikawa K.

    2012-08-01

    Full Text Available In this study, at first, the effect of strain rate on the strength and the absorbed energy of polyimide foam was experimentally examined by carrying out a series of compression tests at various strain rates, from 10−3 to 103 s−1. This polyimide foam has open cell structure with small cell size of 0.3 ∼ 0.6 mm. In the measurement of impact load, a special load cell with a small part for sensing load was adopted. For the measurement of the displacement, a high-speed camera was used. It was found that the flow stress of polyimide foam and the absorbed energy up to a strain of 0.4 increased with the increase of the strain rates. Secondly, the effect of ambient temperature on the strength and absorbed energy of polyimide foam was also investigated by using a sprit Hopkinson pressure bar apparatus and testing at elevated temperatures of 100 and 200 ∘C. With the increase of temperature, the strength and absorbed energy decreased and the effect is smaller in dynamic tests than static tests.

  6. Spectroscopic investigation of different concentrations of the vapour deposited copper phthalocyanine as a "guest" in polyimide matrix.

    Science.gov (United States)

    Georgiev, Anton; Yordanov, Dancho; Dimov, Dean; Assa, Jacob; Spassova, Erinche; Danev, Gencho

    2015-04-05

    Nanocomposite layers 250 nm copper phthalocyanine/polyimide prepared by simultaneous vapour deposition of three different sources were studied. Different concentrations of copper phthalocyanine as a "guest" in polyimide matrix as a function of conditions of the preparation have been determined by FTIR (Fourier Transform Infrared) and UV-VIS (Ultraviolet-Visible) spectroscopies. The aim was to estimate the possibility of the spectroscopic methods for quantitative determination of the "guest" and compare with the quality of the polyimide thin films in relation to the "guest" concentration. The band at 1334 cm(-1) has been used for quantitative estimation of "guest" in polyimide matrix. The concentrations of the copper phthalocyanine less than 20% require curve fitting techniques with Fourier self deconvolution. The relationship between "guest" concentrations and degree of imidization, as well as the electronic UV-VIS spectra are discussed in relation to the composition, imidization degree and the two crystallographic modification of the embedded chromophore. Copyright © 2015 Elsevier B.V. All rights reserved.

  7. In-situ imidization analysis in microscale thin films of an ester-type photosensitive polyimide for microelectronic packaging applications

    NARCIS (Netherlands)

    Windrich, Frank; Kappert, Emiel; Malanin, Mikhail; Eichhorn, Klaus-Jochen; Haussler, Liane; Benes, Nieck Edwin; Voit, Brigitte

    2016-01-01

    The imidization reaction in thin films of an ester-type photosensitive polyimide is investigated in the temperature range of 50–450 °C by temperature dependent rapid-scan in-situ FT-IR spectroscopy, thermo-ellipsometric analysis and thermogravimetric analysis coupled with evolved gas analysis. The

  8. Flexible polyimides through one-pot synthesis as water-soluble binders for silicon anodes in lithium ion batteries

    Science.gov (United States)

    Yao, Dahua; Yang, Yu; Deng, Yonghong; Wang, Chaoyang

    2018-03-01

    A series of polyimides, which contain polyethylene glycol (PEG) segments with different molecular weight in the polymer chains, are synthesized through a facile one-pot method and characterized by Fourier transform infrared spectroscopy and hydrogen nuclear magnetic resonance spectroscopy. The main part of polyimides is originated from trimellitic anhydride chloride (TMAC) and 4,4‧-methylenedianiline, onto which PEG segments are introduced through an esterification reaction with TMAC. These obtained polyimides, which acquire excellent water solubility after being neutralized by triethylamine, are applied as water-soluble binders to silicon negative electrodes for lithium ion batteries, and significantly improve the electrochemical performance of silicon anodes. Specially, the PI-200 (polyimide copolymerized with PEG-200) based silicon electrode exhibits a high initial discharge capacity of 2989.7 mAh g-1 and remains about 2235.5 mAh g-1 after 200 cycles at the current density of 0.1 C (420 mA g-1).

  9. Rational design of intrinsically ultramicroporous polyimides containing bridgehead-substituted triptycene for highly selective and permeable gas separation membranes

    KAUST Repository

    Swaidan, Raja

    2014-08-12

    Highly ultramicroporous, solution-processable polyimides bearing 9,10-bridgehead-substituted triptycene demonstrated the highest BET surface area reported for polyimides (840 m2 g-1) and several new highs in gas selectivity and permeability for hydrogen (1630-3980 barrers, H2/CH4 ∼ 38) and air (230-630 barrers, O 2/N2 = 5.5-5.9) separations. Two new dianhydrides bearing 9,10-diethyl- and 9,10-dipropyltriptycenes indicate that the ultramicroporosity is optimized for fast polymeric sieving with the use of short, bulky isopropyl bridgeheads and methyl-substituted diamines (TrMPD, TMPD, and TMBZ) that increase intrachain rigidity. Mechanically, the triptycene-based analogue of a spirobisindane-based polyimide exhibited 50% increases in both tensile strength at break (94 MPa) and elastic modulus (2460 MPa) with corresponding 90% lower elongations at break (6%) likely due to the ability of highly entangled spiro-based chains to unwind. To guide future polyimide design, structure/property relationships are suggested between the geometry of the contortion center, the diamine and bridgehead substituent, and the mechanical, microstructural, and gas transport properties. © 2014 American Chemical Society.

  10. Experiments Related to the Fabrication of Carbon Fiber/AMB-21 Polyimide Composite Tubes Using the RTM Process

    Science.gov (United States)

    Exum, Daniel

    1996-01-01

    AMB-21 is a new polymer developed by Mr. Ray Vannucci, NASA, LeRC as a noncarcinogenic polyimide matrix which may be suitable for fabricating composite parts by the Resin Transfer Modeling (RTM) process. The polyimide for this project was prepared at the Center of Composite Materials Research at N.C. A&T State University because it is not currently an item of commerce. The RTM process is especially suitable for producing geometrically complex composite parts at a low cost. Because of the high melting point and very high viscosity at the time of processing, polyimides have not been extensively used in the RTM process. The process for preparing AMB-21 as well as the process for fabricating composite plates will be described. The basic fabrication process consists of injecting a solvent solution of AMP-21 into a carbon fiber preform, evaporating the solvent, imidizing the polyimide, and vacuum/compression modeling the impregnated preform. All the above molding steps are preformed in a specially designed RTM mold which will be described. The results of this process have been inconsistent. Where as some experiments have resulted in a reasonably sound panels, others have not. Further refinements of the process are required to establish a reliable process.

  11. Surface modification of polyimide by atmospheric pressure plasma for adhesive bonding with titanium and its application to aviation and space

    NARCIS (Netherlands)

    Akram, M.; Bhowmik, S.; Jansen, K.M.B.; Ernst, L.J.

    2011-01-01

    It is noted that in search of long term and efficient service performance in the context of future generation of aerospace materials, there is increasing need of metal-high performance polymer composite. Based on these considerations, high temperature resistant polymeric sheet such as Polyimide

  12. Stable carbon isotope ratios from archaeological charcoal as palaeoenvironmental indicators

    CSIR Research Space (South Africa)

    Hall, G

    2008-01-01

    Full Text Available The potential to provide environmental proxies using stable carbon isotopes from modern and archaeological charcoal is explored. Experiments on modern Podocarpus (Yellowwoods) show that δ13C values of stems, branches and charcoal preserve proxy...

  13. Stable Hybrid Adaptive Control,

    Science.gov (United States)

    1982-07-01

    STABLE HYBRID ADAPTIVE CONTROL(U) YALE UNIV NEW HAVEN i/i CT CENTER FOR SYSTEMS SCIENCE K S NARENDRA ET AL. JUL 82 8286 Ne@04-76-C-8e7 UNCLASSIFIED...teasrallepsaaw1tflbe~ll b ydd Il"t 5 As is the comtanuous Case cistral to the stability analysis of the hybrid ~IVt* COnRol PO* IMare the sur Models

  14. Anisotropic properties of high-temperature polyimide thin films: Dielectric and thermal-expansion behaviors

    Science.gov (United States)

    Ree, M.; Chen, K.-J.; Kirby, D. P.; Katzenellenbogen, N.; Grischkowsky, D.

    1992-09-01

    Multilayer poly(p-phenylene biphenyltetracarboximide) (BPDA-PDA) polyimide films of 172 μm total thickness (11.4 μm per layer) were prepared from the poly(amic acid) precursor solution through repetition of a spin-coat/softbake/cure process. Wide-angle x-ray diffraction results indicate that the polyimide molecules in the multilayer films are highly ordered along the chain axes as well as in the lateral direction and furthermore are highly oriented in the film plane as observed in a single-layer film of 11.4 μm thickness. The multilayer films showed the same dynamic mechanical properties and glass transition behavior (Tg = 330 °C) as a single-layer film. For the multilayer films both the in-plane dielectric constant (ɛ'XY) and out-of-plane thermal-expansion coefficient (αZ) were measured using time-domain spectroscopy and conventional thermal mechanical analysis, respectively. The ɛ'XY at room temperature was 3.69 (±0.08) over a frequency range of 0.35-2.50 THz. A similar ɛ'XY is predicted at frequencies of ≤0.35 THz. In contrast to the ɛ'XY, a relatively lower out-of-plane dielectric constant (ɛ'Z) was observed: ɛ'Z = 2.96-3.03 (±0.02) at 1 MHz, depending on moisture content in the film. The dielectric loss ɛ`Z at 1 MHz was 0.011-0.014 (±0.001), depending on moisture content. The measured αZ was 74 ppm/°C over the temperature range of 25-150 °C, which was much higher than αXY = 2.6-5 ppm/°C. Consequently, large anisotropic ɛ' and α have been observed in the in plane and out of plane of the thermally imidized BPDA-PDA films. The anisotropic ɛ' and α were caused by high in-plane orientation of the polyimide molecules highly ordered along the chain axes in the films.

  15. Hydroxyl-Containing Aromatic Polyimides for Carbon Dioxide Removal from Natural Gas

    KAUST Repository

    Alaslai, Nasser Y.

    2017-10-01

    Natural gas is among the most dominant resources to provide energy supplies and Saudi Arabia ranks among the top 5 producers worldwide. However, prior to use of methane, natural gas has to be treated to remove other feed gas components, such as H2O, CO2, H2S, N2 and C2+ hydrocarbons. Most NG fields in KSA contain about 10 mol% carbon dioxide that has to be reduced to less than 2 mol% for pipeline delivery. The conventional unit operations for natural gas separations, that is, molecular sieves, amine absorption, cryogenic distillation, and turbo expansion exhibit some disadvantages in terms of economics, operational flexibility or system footprint. One of the most attractive alternative is membrane technology in either standalone- or hybrid system configuration. Currently, the only two membrane materials used in industrial natural gas applications are cellulose acetate and polyimide, which have moderate permeability and fairly low selectivity when tested under realistic industrial conditions. The goal for future research is to develop unique polymeric membranes, which can at least partially replace conventional gas processing in future natural gas projects. This will support global economics and specifically the economy of Saudi Arabia. Newly developed polymeric materials must meet certain criteria to be used on a commercial scale. These criteria include: (i) high permeability and selectivity, (ii) processability into thin films, (iii) mechanical and thermal stability, and (iv) chemical stability against feed gas components. This project focused on the removal of carbon dioxide from natural gas by developing and characterizing functionalized aromatic polyimide membrane materials that exhibit very high selectivity under aggressive mixed-gas conditions. 6FDA-DAR demonstrated a mixed-gas CO2/CH4 selectivity of 78 at a CO2 partial pressure of 10 bar with no pronounced indication of plasticization. Combining hydroxyl- and carboxyl groups in a miscible polyimide blend led

  16. Flexible superconducting Nb transmission lines on thin film polyimide for quantum computing applications

    Science.gov (United States)

    Tuckerman, David B.; Hamilton, Michael C.; Reilly, David J.; Bai, Rujun; Hernandez, George A.; Hornibrook, John M.; Sellers, John A.; Ellis, Charles D.

    2016-08-01

    We describe progress and initial results achieved towards the goal of developing integrated multi-conductor arrays of shielded controlled-impedance flexible superconducting transmission lines with ultra-miniature cross sections and wide bandwidths (dc to >10 GHz) over meter-scale lengths. Intended primarily for use in future scaled-up quantum computing systems, such flexible thin-film niobium/polyimide ribbon cables could provide a physically compact and ultra-low thermal conductance alternative to the rapidly increasing number of discrete coaxial cables that are currently used by quantum computing experimentalists to transmit signals between the several low-temperature stages (from ˜4 K down to ˜20 mK) of a dilution refrigerator. We have concluded that these structures are technically feasible to fabricate, and so far they have exhibited acceptable thermo-mechanical reliability. S-parameter results are presented for individual 2-metal layer Nb microstrip structures having 50 Ω characteristic impedance; lengths ranging from 50 to 550 mm were successfully fabricated. Solderable pads at the end terminations allowed testing using conventional rf connectors. Weakly coupled open-circuit microstrip resonators provided a sensitive measure of the overall transmission line loss as a function of frequency, temperature, and power. Two common microelectronic-grade polyimide dielectrics, one conventional and the other photo-definable (PI-2611 and HD-4100, respectively) were compared. Our most striking result, not previously reported to our knowledge, was that the dielectric loss tangents of both polyimides, over frequencies from 1 to 20 GHz, are remarkably low at deep cryogenic temperatures, typically 100× smaller than corresponding room temperature values. This enables fairly long-distance (meter-scale) transmission of microwave signals without excessive attenuation, and also permits usefully high rf power levels to be transmitted without creating excessive dielectric

  17. Preparation and applications of carbon film obtained by pulse-laser irradiation to polyimide; Polyimide eno pulse laser shosha ni yotte erareru tanso film to sono oyo

    Energy Technology Data Exchange (ETDEWEB)

    Endo, M.; Naito, K.; Ishibe, S.; Ueda, M.; Kasai, T. [Shinshu University, Nagano (Japan); Oshida, K. [Nagano National College of Technology, Nagano (Japan)

    1997-05-20

    Described in this report is a novel effort for forming conductive paths by directly carbonizing a high-polymer film by laser beam irradiation. In the experiment, a polymer film is attached onto a movable X-Y stage, accommodated in a chamber, and then exposed to 10Hz pulsed YAG laser irradiation. A polyimide film is chosen for the experiment because it is easily cabonized in an ordinary pyrolytic process for the realization of high crystallinity. The carbon is then subjected to microscopic scrutiny for its structural details under the FE-SEM and TEM. It is found as the result that possibilities are high that the thus-obtained carbon may be used for the construction of practical circuits. It is found also that carbonization advances with the passage of irradiation time in a nitrogen atmosphere and that the carbon layer does not grow in thickness in the ordinary atmosphere where oxidation occurs simultaneously with carbonization. It is expected that this technique will be applied to the formation of highly conductive paths because it allows the easy and proper deposition of nickel onto the carbonized paths. 10 refs., 9 figs.

  18. Modification of Bisphenol-A Based Bismaleimide Resin (BPA-BMI) with an Allyl-Terminated Hyperbranched Polyimide (AT-PAEKI)

    National Research Council Canada - National Science Library

    Qin, Haihu; Mather, Patrick T; Baek, Jong-Beom; Tan, Loon-Seng

    2006-01-01

    As a continuation of previous work involving synthesis of an allyl-functionalized hyperbranched polyimide, AT-PAEKI, we have studied the use of this reactive polymer as a modifier of bisphenol-A based...

  19. Steam Pyrolysis of Polyimides: Effects of Steam on Raw Material Recovery.

    Science.gov (United States)

    Kumagai, Shogo; Hosaka, Tomoyuki; Kameda, Tomohito; Yoshioka, Toshiaki

    2015-11-17

    Aromatic polyimides (PIs) have excellent thermal stability, which makes them difficult to recycle, and an effective way to recycle PIs has not yet been established. In this work, steam pyrolysis of the aromatic PI Kapton was performed to investigate the recovery of useful raw materials. Steam pyrolysis significantly enhanced the gasification of Kapton at 900 °C, resulting in 1963.1 mL g(-1) of a H2 and CO rich gas. Simultaneously, highly porous activated carbon with a high BET surface area was recovered. Steam pyrolysis increased the presence of polar functional groups on the carbon surface. Thus, it was concluded that steam pyrolysis shows great promise as a recycling technique for the recovery of useful synthetic gases and activated carbon from PIs without the need for catalysts and organic solvents.

  20. Self-Lubricating Polytetrafluoroethylene/Polyimide Blends Reinforced with Zinc Oxide Nanoparticles

    Directory of Open Access Journals (Sweden)

    Liwen Mu

    2015-01-01

    Full Text Available ZnO nanoparticle reinforced polytetrafluoroethylene/polyimide (PTFE/PI nanocomposites were prepared and their corresponding tribological and mechanical properties were studied in this work. The influences of ZnO loading, sliding load, and velocity on the tribological properties of ZnO/PTFE/PI nanocomposites were systematically investigated. Results reveal that nanocomposites reinforced with 3 wt% ZnO exhibit the optimal tribological and mechanical properties. Specifically, the wear loss decreased by 20% after incorporating 3 wt% ZnO compared to unfilled PTFE/PI. Meanwhile, the impact strength, tensile strength, and elongation-at-break of 3 wt% ZnO/PTFE/PI nanocomposite are enhanced by 85, 5, and 10% compared to pure PTFE/PI blend. Microstructure investigation reveals that ZnO nanoparticles facilitate the formation of continuous, uniform, and smooth transfer film and thus reduce the adhesive wear of PTFE/PI.

  1. The influence of moisture on charge relaxation in modified polyimide films

    Directory of Open Access Journals (Sweden)

    Almaz M. Kamalov

    2016-10-01

    Full Text Available The charge relaxation processes in the films based on polyimide and polytetrafluoroethylene (the latter serves as a coating have been studied. The coating effect on the charge relaxation processes in the films under high humidity conditions was revealed. The obtained experimental data was analyzed in the context of the present-day knowledge of the charge relaxation mechanism. The complex spectra of the thermally stimulated depolarization currents (TSDC were resolved into individual components described by the first-order kinetics equations using computer simulation. The TSDC activation energies were calculated and interpreted in terms of the mechanism of release of charge carriers. It was shown that the polytetrafluoroethylene coats on film surfaces lead to an essential increase in the electret state stability at elevated temperature and high humidity.

  2. FABRICATION AND CHARACTERIZATION OF POLYIMIDE/POLYETHERSULFONE-FUMED SILICA MIXED MATRIX MEMBRANE FOR GAS SEPARATION

    Directory of Open Access Journals (Sweden)

    A. F. Ismail

    2012-01-01

    Full Text Available This study is performed primarily to investigate the feasibility of fumed silica as inorganic material towards gas separation performance of mixed matrix membrane. In this study, polyimide/polyethersulfone (PES-fumed silica mixed matrix membranes were casted using dry/wet technique. The results from the FESEM, DSC and FTIR analysis confirmed that the structure and physical properties of membrane is influenced by inorganic filler. FESEM’s cross-section view indicated good compatibility between polymer and fumed silica for all of range fumed silica used in this study. The gas separation performance of the mixed matrix membranes with fumed silica were relatively higher compared to that of the neat PI/PES membrane. PI/PES-fumed silica 5 wt% yielded significant selectivity enhancement of 7.21 and 40.47 for O2/N2, and CO2/CH4, respectively.

  3. Optical fiber humidity sensor based on the direct response of the polyimide film.

    Science.gov (United States)

    Bian, Ce; Hu, Manli; Wang, Ruohui; Gang, Tingting; Tong, Rongxin; Zhang, Lisong; Guo, Teng; Liu, Xiaobo; Qiao, Xueguang

    2018-01-10

    An optical fiber humidity sensor based on an optical Fabry-Perot interferometer is proposed and experimentally demonstrated. The sensor is constructed by a short section of hollow-core fiber coated with a polyimide (PI) film. Taking advantage of the direct response of the PI film, a sensitivity of up to 1.309 nm/%RH can be achieved in the humidity change range from 40% RH to 80% RH. The temperature sensitivity is measured to be 43.57 pm/°C when the temperature changes from 25°C to 55°C. Because of its simple structure, fast response time, convenient production, and good reproducibility, the proposed sensor will be competitive in the field of cultural relic humidity monitoring and pharmaceutical storage.

  4. Rapid plasma treatment of polyimide for improved adhesive and durable copper film deposition

    Energy Technology Data Exchange (ETDEWEB)

    Usami, Kenji [Department of Electrical Engineering and Computer Science, Nagoya University (Japan); Ishijima, Tatsuo, E-mail: ishijima@nagoya-u.jp [Plasma Nanotechnology Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Toyoda, Hirotaka [Department of Electrical Engineering and Computer Science, Nagoya University (Japan); Plasma Nanotechnology Research Center, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan)

    2012-10-30

    To improve adhesion at the interface between Cupper (Cu) and polyimide (PI) layers, a PI film surface was treated with a microwave-excited plasma. The Ar/N{sub 2} plasma treatment improved the Cu adhesion force to 10 N/cm even for PI substrates with absorbed water. A dramatic improvement of the adhesion durability was achieved by depositing a thin carbon film (C) on the PI substrate as an interlayer between PI and Cu using a microwave plasma followed by treatment with the Ar/N{sub 2} plasma prior to the Cu deposition. After a 20-h accelerated aging test, the reduction of the adhesion force for the resulting Cu/C/PI sample was only 10%, whereas that for the Cu/PI sample was 55%. To gain insight into the film properties, the interface between the Cu and PI film was investigated by X-ray photoelectron spectroscopy.

  5. A unique 3D ultramicroporous triptycene-based polyimide framework for efficient gas sorption applications

    KAUST Repository

    Ghanem, Bader

    2016-10-03

    A novel 3D ultramicroporous triptycene-based polyimide framework with high surface area (1050 m2 g−1) and thermal stability was synthesized. It exhibits relatively high CO2 (3.4 mmol g−1 at 273 K and 1 bar), H2 (7 mmol g−1 at 77 K and 1 bar), and olefin sorption capacity, good CO2/N2 (45) and CO2/CH4 (9.6) selectivity at 273 K and 1 bar, as well as promising C2H4/CH4 and C3H6/CH4 selectivities at 298 K, making it a potential candidate for CO2 capture, H2 storage, and hydrocarbon gas separation applications.

  6. Monopole quasi-Yagi antenna on polyimide substrate for flexible electronics

    Science.gov (United States)

    Liu, Jianying; Dai, Fang; Zhang, Yichen; Yu, Xin; Cai, Lulu; Zuo, Panpan; Wang, Mengjun

    2017-01-01

    In this paper, a flexible monopole quasi-Yagi antenna printed on 50um thick polyimide substrate is designed for integration within modern flexible electronic devices. The antenna has a wide working band (5.22-6.6 GHz) that covers WLAN 5.8GHz (5.725-5.825GHz). Parameters changes of proposed modeling are analyzed to achieve desired impedance matching and resonant frequency. The reflection coefficient, gain and radiation efficiency are indicated to be still robust when the proposed antenna is under various bending directions. It is worth noting that radiation patterns have an effect when antenna is bent in the y-axis direction. The antenna prototype is fabricated and tested where the simulated results agree with measured ones.

  7. Hybrid copper complex-derived conductive patterns printed on polyimide substrates

    Science.gov (United States)

    Lee, Byoungyoon; Jeong, Sooncheol; Kim, Yoonhyun; Jeong, Inbum; Woo, Kyoohee; Moon, Jooho

    2012-06-01

    We synthesized new copper complexes that can be readily converted into highly conductive Cu film. Mechanochemical milling of copper (I) oxide suspended in formic acid resulted in the submicron-sized Cu formate together Cu nanoparticles. The submicrometer-sized Cu formates are reactive toward inter-particle sintering and metallic Cu seeds present in the Cu complexes assist their decomposition and the nucleation of Cu. The hybrid copper complex film printed on polyimide substrate is decomposed into dense and uniform Cu layer after annealing at 250 °C for 30 min under nitrogen atmosphere. The resulting Cu film exhibited a low resistivity of 8.2 μΩ·cm and good adhesion characteristics.

  8. Integration of temperature sensors in polyimide-based thin-film electrode arrays

    Directory of Open Access Journals (Sweden)

    Cruz M. F. Porto

    2015-09-01

    Full Text Available Continuous monitoring of the tissue temperature surrounding implantable devices could be of great advantage. The degree and duration of the immune activation in response to the implant, which is responsible for signal deterioration, could be inferred from the associated temperature raise and the heating caused by electrical or optogenetical stimulation could be accurately controlled. Within this work, a thin-film platinum RTD embedded in polyimide and a readout system based on the Wheatstone bridge configuration are presented. The RTD offers a sensitivity of 8.5 Ω· °C−1 and a precision of 4.1 Ω. The accuracy of the complete system calibrated for temperatures ranging from 34 to 41 °C lies between the classes A and B defined by the standard IEC 751, which correspond to tolerances of ±0.22 and ±0.48 °C at 37 °C, respectively.

  9. Effect of Atmosphere on Recovery Dynamics of Polyimide Film Damaged by Electron Radiation

    Science.gov (United States)

    Plis, E.; Engelhart, D. P.; Cooper, R.; Humagain, S.; Brunetti, M.; Koch, A.; Greenbaum, S.; Ferguson, D.; Hoffmann, R.

    2017-09-01

    Since electrons are the primary charged particles at the geosynchronous Earth orbit (GEO), understanding of their interactions with spacecraft materials, such as polyimide (PI, Kapton-H®), is important. Understanding of the chemical nature of electron damage and its effect on PI’s electrical and optical properties is still limited. Thus, predictive spacecraft models (electrical charging, thermal, etc) are restricted to only pristine material properties. This is a major source of error in spacecraft construction and anomaly resolution, since material properties change after exposure to the space environment. Ground based measurements are critical to understanding the dynamics of spacecraft materials however it will be shown in this work that standard material handling practice and exposure to air are unacceptable for these studies.

  10. Property modification of nafion via polymer blending with polyimide (Conference Presentation)

    Science.gov (United States)

    Hwang, Taeseon; Nam, Jungsoo; Lee, Dong-Chan; Kim, Kwang Jin

    2017-04-01

    The blended ion exchange membrane between Nafion and Polyimide (PI) was used for fabrication of the ionic polymer-metal composite (IPMC) not only to redeem inherent drawbacks of Nafion such as high cost or environment-unfriendliness but also to enhance mechanical properties of Nafion. PI solution was blended in Nafion solution by a volume ratio and membranes were prepared through solution casting method. The prepared blended Nafion membranes can be fabricated IPMCs with electroless plating of platinum electrode onto its surface. The surface resistance of all prepared IPMCs is measured through 2-point probe. This study investigated the chemical structure and mechanical properties of prepared blended membranes. Moreover, we characterized the cross-section morphology and studied the electromechanical performances (displacement and blocking force) of prepared IPMC actuators. The prepared IPMC actuators with blended Nafion membranes were demonstrated comparable electromechanical performance by significantly reducing the content of Nafion.

  11. Polyimide Aerogels and Porous Membranes for Ultrasonic Impedance Matching to Air

    Science.gov (United States)

    Swank, Aaron J.; Sands, Obed S.; Meador, Mary Ann B.

    2014-01-01

    This work investigates acoustic impedance matching materials for coupling 200 kHz ultrasonic signals from air to materials with similar acoustic properties to that of water, flesh, rubber and plastics. Porous filter membranes as well as a new class of cross-linked polyimide aerogels are evaluated. The results indicate that a single impedance matching layer consisting of these new aerogel materials will recover nearly half of the loss in the incident-to-transmitted ultrasound intensity associated with an air/water, air/flesh or air/gelatin boundary. Furthermore, the experimental results are obtained where other uncertainties of the "real world" are present such that the observed impedance matching gains are representative of real-world applications. Performance of the matching layer devices is assessed using the idealized 3-layer model of infinite half spaces, yet the experiments conducted use a finite gelatin block as the destination medium.

  12. Etched FBG coated with polyimide for simultaneous detection the salinity and temperature

    Science.gov (United States)

    Luo, Dong; Ma, Jianxun; Ibrahim, Zainah; Ismail, Zubaidah

    2017-06-01

    In marine environment, concrete structures can corrode because of the PH alkalinity of concrete paste; and the salinity PH is heavily related with the concentration of salt in aqueous solutions. In this study, an optical fiber salinity sensor is proposed on the basis of an etched FBG (EFBG) coated with a layer of polyimide. Chemical etching is employed to reduce the diameter of FBG and to excite Cladding Mode Resonance Wavelengths (CMRWs). CMRW and Fundamental Mode Resonance Wavelength (FMRW) can be used to measure the Refractive index (RI) and temperature of salinity. The proposed sensor is then characterized with a matrix equation. Experimental results show that FMRW and 5th CMRW have the detection sensitivities of 15.407 and 125.92 nm/RIU for RI and 0.0312 and 0.0435 nm/°C for temperature, respectively. The proposed sensor can measure salinity and temperature simultaneously.

  13. Sodium hypochlorite as a developer for heavy ion tracks in polyimide

    Energy Technology Data Exchange (ETDEWEB)

    Klintberg, Lena E-mail: lena.klintberg@angstrom.uu.se; Lindeberg, Mikael; Thornell, Greger

    2001-12-01

    The developing and etching of heavy ion tracks in polyimide with sodium hypochlorite have been studied to gain control over the parameters that affect the etch result. The shape of the resulting pores is a function of both alkalinity and hypochlorite content of the solution. Sodium hypochlorite decomposes during etching, and the rate constant has been determined as a function of the alkalinity at 62 deg. C. Polished cross-sections have been examined to determine the pore shape, and this method has shown to be a straightforward way to characterise the pores. Decreasing the alkalinity gives more cylindrical pores, but increases the decomposition rate of the hypochlorite solution and decreases the etch rate.

  14. FABRICATION AND ATTACHMENT OF POLYIMIDE FILL TUBES TO PLASTIC NIF CAPSULES

    Energy Technology Data Exchange (ETDEWEB)

    Takagi, M; Saito, K; Frederick, C; Nikroo, A; Cook, R

    2006-12-08

    We have developed a technique for drawing commercially available polyimide tubing to the required fill tube dimensions. The tubes are then precisely cut with an Excimer laser to produce a clean, flat tip. We have also demonstrated that one can use the Excimer laser to drill less than a 5 {micro}m diameter through hole in the {approx}150 wall of a NIF dimension GDP shell, and can then create a 10-15 {micro}m diameter, 20-40 {micro}m deep counterbore centered on the through hole with the same laser. Using a home built assembly station the tube is carefully inserted into the counterbore and glued in place with UV-cure epoxy, using a LED UV source to avoid heating the joint. We expect that the same joining technique can be used for Be shells.

  15. Characterization of the Structure-Processing-Performance Relations of Phenylethynyl Phthalic Anhydride Crosslinked Fluorinated Polyimides (AFR-PEPA-N) and Their Carbon Fiber Composites

    Science.gov (United States)

    2007-04-12

    FA9550-04-1-0137 Relations of Phenylethynyl Phthalic Anhydride Crosslinked Fluorinated Polyimides (AFR-PEPA-N) and Their Carbon Fiber Composites 5b. GRANT...structure-processing-performance relations of phenylethynyl phthatic anhydride crosslinked fluorinated polyimides (AFR-PEPA-N) and their carbon fiber...Prescribed by ANSI Std. Z39.18 FINAL REPORT CHARACTERIZATION OF THE STRUCTURE - PROCESSING - PERFORMANCE RELATIONS OF PHENYLETHYNYL PHTHALIC

  16. High purity polyimide analysis by solid sampling graphite furnace atomic absorption spectrometry

    Science.gov (United States)

    Santos, Rafael F.; Carvalho, Gabriel S.; Duarte, Fabio A.; Bolzan, Rodrigo C.; Flores, Erico M. M.

    2017-03-01

    In this work, Cr, Cu, Mn, Na and Ni were determined in high purity polyimides (99.5%) by solid sampling graphite furnace atomic absorption spectrometry (SS-GFAAS) using Zeeman effect background correction system with variable magnetic field, making possible the simultaneous measurement at high or low sensitivity. The following analytical parameters were evaluated: pyrolysis and atomization temperatures, feasibility of calibration with aqueous solution, linear calibration range, sample mass range and the use of chemical modifier. Calibration with aqueous standard solutions was feasible for all analytes. No under or overestimated results were observed and up to 10 mg sample could be introduced on the platform for the determination of Cr, Cu, Mn, Na and Ni. The relative standard deviation ranged from 3 to 20%. The limits of detection (LODs) achieved using the high sensitivity mode were as low as 7.0, 2.5, 1.7, 17 and 0.12 ng g- 1 for Cr, Cu, Mn, Na and Ni, respectively. No addition of chemical modifier was necessary, except for Mn determination where Pd was required. The accuracy was evaluated by analyte spike and by comparison of the results with those obtained by inductively coupled plasma optical emission spectrometry and inductively coupled plasma mass spectrometry after microwave-assisted digestion in a single reaction chamber system and also by neutron activation analysis. No difference among the results obtained by SS-GFAAS and those obtained by alternative analytical methods using independent techniques. SS-GFAAS method showed some advantages, such as the determination of metallic contaminants in high purity polyimides with practically no sample preparation, very low LODs, calibration with aqueous standards and determination in a wide range of concentration.

  17. Synthesis, characterization, and study of photoinduced optical anisotropy in polyimides containing side azobenzene units.

    Science.gov (United States)

    Schab-Balcerzak, Ewa; Siwy, Mariola; Kawalec, Michal; Sobolewska, Anna; Chamera, Agata; Miniewicz, Andrzej

    2009-07-30

    In this paper, novel processable aromatic polymers with imide rings and attached as side-chain azobenzene units are presented. Polymers differ in the chemical structures of chromophores and polymer backbones. Azopolymers were obtained by a two-step synthetic approach. This includes the preparation of a precursor poly(esterimide) and poly(etherimide) with pendant phenolic hydroxyl groups, followed by the covalent bonding of NLO chromophores onto the polyimide backbone by the Mitsunobu reaction. The degree of functionalization of polymers was estimated by UV-vis spectroscopy. Polymers were characterized and evaluated by FT-IR, (1)H NMR, X-ray, UV-vis, DSC, and TGA methods. The synthesized polymers exhibited glass transition temperatures in the range of 167-228 degrees C, thermal stability with decomposition temperatures in the range of 275-446 degrees C, and excellent solubilities in common organic solvents. The light-induced optical anisotropy was studied in obtained azopolymers with the help of a holographic grating recording technique. Two polarization geometries were applied for the grating inscription s-s and p-p. The influence of the polarization geometry on the diffraction efficiency dynamics and on the depth of the surface modulation was not observed, which is different from results reported in the literature. Surface relief gratings, which appeared after the light exposure, were observed by atomic force microscopy. Additionally, the optical anisotropy in poly(esterimide)s was investigated by photoinduced birefringence measurements. For the first time, in polyimide with covalently bonded azobenzene derivatives, the high photoinduced birefringence (Delta n = 0.01) was measured.

  18. Stable and Enforceable

    DEFF Research Database (Denmark)

    Hallett, Andrew Hughes; Hougaard Jensen, Svend E.

    2011-01-01

    -term stabilisation. We argue for public sector debt targets as a practical way to achieve such a set up, and an excess debt protocol is constructed to give enforceable form to those targets. The ideas of “fiscal space” and optimal debt levels are used to provide a mechanism for identifying a stable region within...... which the debt targeting regime should operate. Making these factors explicit would both improve the credibility of planned fiscal policies and reduce risk premia on borrowing costs. We finally show how Europe’s competitiveness pact, and debt restructuring operations, can be used to maximise...

  19. Effect of Addition of Colloidal Silica to Films of Polyimide, Polyvinylpyridine, Polystyrene, and Polymethylmethacrylate Nano-Composites

    Directory of Open Access Journals (Sweden)

    Soliman Abdalla

    2016-02-01

    Full Text Available Nano-composite films have been the subject of extensive work for developing the energy-storage efficiency of electrostatic capacitors. Factors such as polymer purity, nanoparticle size, and film morphology drastically affect the electrostatic efficiency of the dielectric material that forms the insulating film between the conductive electrodes of a capacitor. This in turn affects the energy storage performance of the capacitor. In the present work, we have studied the dielectric properties of four highly pure amorphous polymer films: polymethyl methacrylate (PMMA, polystyrene, polyimide and poly-4-vinylpyridine. Comparison between the dielectric properties of these polymers has revealed that the higher breakdown performance is a character of polyimide (PI and PMMA. Also, our experimental data shows that adding colloidal silica to PMMA and PI leads to a net decrease in the dielectric properties compared to the pure polymer.

  20. Constraining the role of iron in environmental nitrogen transformations. Dual stable isotope systematics of abiotic NO2- reduction by Fe(II) and its production of N2O

    Energy Technology Data Exchange (ETDEWEB)

    Johnston, David [Harvard Univ., Cambridge, MA (United States); Wankel, Scott David [Woods Hole Oceanographic Inst., MA (United States); Buchwald, Carolyn [Woods Hole Oceanographic Inst., MA (United States); Hansel, Colleen [Woods Hole Oceanographic Inst., MA (United States)

    2015-09-16

    Redox reactions involving nitrogen and iron have been shown to have important implications for mobilization of priority contaminants. Thus, an understanding of the linkages between their biogeochemical cycling is critical for predicting subsurface mobilization of radionuclides such as uranium. Despite mounting evidence for biogeochemical interactions between iron and nitrogen, our understanding of their environmental importance remains limited. Here we present an investigation of abiotic nitrite (NO2-) reduction by Fe(II) or ‘chemodenitrification,’ and its relevance to the production of nitrous oxide (N2O), specifically focusing on dual (N and O) isotope systematics under a variety of environmentally relevant conditions. We observe a range of kinetic isotope effects that are regulated by reaction rates, with faster rates at higher pH (~8), higher concentrations of Fe(II) and in the presence of mineral surfaces. A clear non-linear relationship between rate constant and kinetic isotope effects of NO2- reduction was evident (with larger isotope effects at slower rates) and is interpreted as reflecting the dynamics of Fe(II)-N reaction intermediates. N and O isotopic composition of product N2O also suggests a complex network of parallel and/or competing pathways. Our findings suggest that NO2- reduction by Fe(II) may represent an important abiotic source of environmental N2O, especially in iron-rich environments experiencing dynamic redox variations. This study provides a multi-compound, multi-isotope framework for evaluating the environmental occurrence of abiotic NO2- reduction and N2O formation, helping future studies constrain the relative roles of abiotic and biological N2O production pathways.

  1. High performance carbon molecular sieving membranes derived from pyrolysis of metal-organic framework ZIF-108 doped polyimide matrices.

    Science.gov (United States)

    Jiao, Wenmei; Ban, Yujie; Shi, Zixing; Jiang, Xuesong; Li, Yanshuo; Yang, Weishen

    2016-12-11

    Carbon molecular sieve membranes (CMSMs) were fabricated by pyrolysis of MOF-doped polyimide mixed matrix membranes. ZIF-108 (Zn(2-nitroimidazolate)2) was used as a dopant to tailor the micropores of the as-prepared CMSMs into narrow ultramicropores, providing a remarkable combination of permeability and selectivity of membranes in CO2/CH4, O2/N2 and N2/CH4 separation.

  2. Development and demonstration of manufacturing processes for fabricating graphite/Larc-160 polyimide structural elements, part 4, paragraph B

    Science.gov (United States)

    1981-01-01

    Progress in the development of processes for production of Celion/LARC-160 graphite-polyimide materials, quality control, and the fabrication of Space Shuttle composite structure components is reported. Liquid chromatographic analyses of three repeatibility batches were performed and are compared to previous Hexcel standard production and to variables study LARC-160 intermediate resins. Development of processes for chopped fiber molding are described and flexural strength, elastic modulus, and other physical and mechanical properties of the molding are presented.

  3. Polyimide Dielectric Layer on Filaments for Organic Field Effect Transistors: Choice of Solvent, Solution Composition and Dip-Coating Speed

    Directory of Open Access Journals (Sweden)

    Rambausek Lina

    2014-09-01

    Full Text Available In today’s research, smart textiles is an established topic in both electronics and the textile fields. The concept of producing microelectronics directly on a textile substrate is not a mere idea anymore and several research institutes are working on its realisation. Microelectronics like organic field effect transistor (OFET can be manufactured with a layered architecture. The production techniques used for this purpose can also be applied on textile substrates. Besides gate, active and contact layers, the isolating or dielectric layer is of high importance in the OFET architecture. Therefore, generating a high quality dielectric layer that is of low roughness and insulating at the same time is one of the fundamental requirements in building microelectronics on textile surfaces. To evaluate its potential, we have studied polyimide as a dielectric layer, dip-coated onto copper-coated polyester filaments. Accordingly, the copper-coated polyester filament was dip-coated from a polyimide solution with two different solvents, 1-methyl-2-pyrrolidone (NMP and dimethylformaldehyde. A variety of dip-coating speeds, solution concentrations and solvent-solute combinations have been tested. Their effect on the quality of the layer was analysed through microscopy, leak current measurements and atomic force microscopy (AFM. Polyimide dip-coating with polyimide resin dissolved in NMP at a concentration of 15w% in combination with a dip-coating speed of 50 mm/min led to the best results in electrical insulation and roughness. By optimising the dielectric layer’s properties, the way is paved for applying the subsequent semi-conductive layer. In further research, we will be working with the organic semiconductor material TIPS-Pentacene

  4. Compositional optimization of polyimide-based SEPPI membranes using a genetic algorithm and high-throughput techniques.

    OpenAIRE

    Vandezande, P.; Gevers, LEM; Weyens, Nele; Vankelecom, IFJ

    2009-01-01

    Asymmetric, nanosized zeolite-filled solvent resistant nanofiltration (SRNF) membranes, prepared from emulsified polyimide (PI) solutions via the earlier reported solidification of emulsified polymer solutions via phase inversion (SEPPI) method, were optimized for their performance in the separation of rose bengal (RB) from 2-propanol (IPA). All membranes were prepared and tested in a parallellized, miniaturized, and automated manner using laboratory-developed high-throughput experimentation ...

  5. Development of a Multi-User Polyimide-MEMS Fabrication Process and its Application to MicroHotplates

    KAUST Repository

    Lizardo, Ernesto B.

    2013-05-08

    Micro-electro-mechanical systems (MEMS) became possible thanks to the silicon based technology used to fabricate integrated circuits. Originally, MEMS fabrication was limited to silicon based techniques and materials, but the expansion of MEMS applications brought the need of a wider catalog of materials, including polymers, now being used to fabricate MEMS. Polyimide is a very attractive polymer for MEMS fabrication due to its high temperature stability compared to other polymers, low coefficient of thermal expansion, low film stress and low cost. The goal of this thesis is to expand the Polyimide usage as structural material for MEMS by the development of a multi-user fabrication process for the integration of this polymer along with multiple metal layers on a silicon substrate. The process also integrates amorphous silicon as sacrificial layer to create free-standing structures. Dry etching is used to release the devices and avoid stiction phenomena. The developed process is used to fabricate platforms for micro-hotplate gas sensors. The fabrication steps for the platforms are described in detail, explaining the process specifics and capabilities. An initial testing of the micro-hotplate is presented. As the process was also used as educational tool, some designs made by students and fabricated with the Polyimide-MEMS process are also presented.

  6. Structure and Transport Properties of Mixed-Matrix Membranes Based on Polyimides with ZrO2 Nanostars

    Directory of Open Access Journals (Sweden)

    Maria P. Sokolova

    2016-11-01

    Full Text Available Mixed-matrix membranes based on amorphous and semi-crystalline polyimides with zirconium dioxide (ZrO2 nanostars were synthesized. Amorphous poly(4,4′-oxydiphenylenepyromellitimide and semi-crystalline polyimide prepared from 1,4-bis(4-aminophenoxybenzene and 4,4’-oxydiphthalic anhydride were used. The effect of ZrO2 nanostars on the structure and morphology of nanocomposite membranes was studied by wide-angle X-ray scattering, scanning electron microscopy, atomic force microscopy, and contact angle measurements. Thermal properties and stability were investigated by thermogravimetric analysis and differential scanning calorimetry. Transport properties of hybrid membranes containing 5 wt % ZrO2 were tested for pervaporation of a mixture of butanol–water with 10 wt % H2O content. It was found that a significant amount of the ZrO2 added to the semi-crystalline polyimide is encapsulated inside spherulites. Therefore, the beneficial influence of inorganic filler on the selectivity of mixed-matrix membrane with respect to water was hampered. Mixed-matrix membranes based on amorphous polymer demonstrated the best performance, because water molecules had higher access to inorganic particles.

  7. New developments in thermally stable polymers

    Science.gov (United States)

    Hergenrother, Paul M.

    1991-01-01

    Advances in high-temperature polymers since 1985 are discussed with the emphasis on the chemistry. High-temperature polymers refer to materials that exhibit glass-transition temperatures greater than 200 C and have the chemical structure expected to provide high thermooxidative stability. Specific polymers or series of polymers were selected to show how the chemical structure influences certain properties. Poly(arylene ethers) and polyimides are the two principal families of polymers discussed. Recent work on poly(arylene ethers) has concentrated on incorporating heterocyclic units within the polymer backbone. Recent polyimide work has centered on the synthesis of new polymers from novel monomers, several containing the trifluoromethyl group strategically located on the molecule. Various members in each of these polymer families display a unique combination of properties, heretofore unattainable. Other families of polymers are also briefly discussed with a polymer from an AB maleimidobenzocyclobutene exhibiting an especially attractive combination of properties.

  8. Influence of horse stable environment on human airways

    Directory of Open Access Journals (Sweden)

    Pringle John

    2009-05-01

    environmental exposure levels in equine stables. Respirable dust and 1,3-β-glucan levels were increased at winter stabling conditions. Some employees (3/13 had signs of bronchial obstruction, which may be aggravated by working in the stable environment. This study contributes to the identification of suitable biomarkers to monitor the indoor horse stable environment and the personnel. An improved management of the stable climate will be beneficial for the health of both stable workers and horses.

  9. Large stable magnetic domains

    Science.gov (United States)

    Pulliam, G. R.; Ross, W. E.; MacNeal, B.; Bailey, R. F.

    1982-03-01

    Large, thin-film single domain areas have been observed, in the absence of a bias field, in garnets with magnetization perpendicular to the film plane.1,2 The domain stability in the work by Krumme1 was attributed to a combination of low saturation magnetization and a low Curie temperature. Uchishiba2 relates the stability in his double layer system to appropriate anisotropy fields in one layer compared to the magnetization in the other layer. A more complete model for large domain stability in a bias field free environment is given in this work. Three distinct stability regimes are predicted by the model and all have been observed experimentally. Areas 3.5-cm in diameter have been made into stable single domains. This was achieved in a material showing a zero bias strip width of 4.5 μm. The single domain diameter was, therefore, 7500 times the equilibrium energy domain width. The technique developed and the model have led to a new means for observing magnetic defects. More importantly, it also offers a means for measuring the strength of the defects. Possible applications of the model are also discussed.

  10. A simulated RTM process for fabricating polyimide (AMB-21) carbon fiber composites

    Science.gov (United States)

    Avva, V. Sarma; Sadler, Robert L.; Thomas, Shanon

    1995-01-01

    An experimental polyimide matrix, AMB-21 - supplied by NASA/LeRC, was especially formulated to be non-carcinogenic. It was also expected to be amenable to a Resin Transfer Molding Process (RTM). AMB-21 is a solid at room temperature and must be heated to a very high temperature to obtain a fluid state. However, even after heating it to a realistic high temperature, it was found to be too viscous for use in a RTM process. As a result, a promising approach was experimented leading to the introduction of the resin into a solvent solution in order to obtain a viscosity suitable for RTM. A mixture of methanol and tetrahydroferone was found to be a suitable solvent mixture. The matrix solution was introduced into carbon-fiber preform using two techniques: (1) injection of matrix into a Resin Transfer Mold after positioning the preform into the 'mold cavity', and (2) infiltration of matrix into the preform using the 'autoclave through-the-thickness transfer process'. After completing the resin transfer (infiltration) process, the 'filled' preform was heated to 300 F for one hour to reduce the solvent content. The temperature was then increased to 400 F under a vacuum to complete the solvent evaporation and to remove volatile products of the polyimide imidization. The impregnated preform was removed from the mold and press-cured at 200 psi and 600 FF for two hours. The resulting panel was found to be of reasonably good quality. This observation was based on the results obtained from short beam shear strength (700-8000 psi) tests and microscopic examination of the cross-section indicating a very low level of porosity. Further, the flash around the molded panels from the compression molding was free of porosity indicating the removal of volatiles, solvents, and other imidization products. Based on these studies, a new RTM mold containing a diaphragm capable of applying 200 psi at 600 F has been designed and constructed with the expectation that it will allow the

  11. Novel organo soluble poly imides and polyimide nano composites based on 1,4-bis(4-aminophenyl)-1,3,4-oxadiaz olyl)benzene, BAOB, via BAOB-modified organo clay

    Energy Technology Data Exchange (ETDEWEB)

    Mansoori, Y.; Darvishi, K., E-mail: ya_mansoori@yahoo.com [University of Mohaghegh Ardabili, Faculty of Science, Department of Applied Chemistry, Daneshgah, Ardabil (Iran, Islamic Republic of)

    2014-10-01

    New, thermally stable poly imides (PI) containing a 1,3,4-oxadiazole ring in the polymer backbone based on 1,4-bis((4-aminophenyl)-1,3,4-oxadiaz olyl)benzene, BAOB, were synthesized. The prepared polymers were soluble in polar and aprotic solvents. The obtained results reveal that within the prepared polymers, polyimide which has been obtained from BAOB and 4,4-oxy diphthalic dianhydride, ODPA, has the most improved thermal properties. In the next part, thermally stable organophilic clay was obtained via cation exchange reaction between sodium montmorillonite (Na-MMT) and the hydrochloride salt of BAOB. Then, a series of PI/clay nano composite materials (PCNs) were synthesized from the in situ polymerization reaction of BAOB and ODPA via thermal imidization, BAOB-MMT was used as the filler at different concentrations. Intercalation of polymer chains within the organo clay galleries was confirmed by W XRD. The glass transition temperature is increased with respect to pristine PI for PCNs 1-3 wt %. At high clay loadings, the aggregation of organo clay particles results in a decrease in T{sub g}. In the Sem images of the pure polymer too many micro-cracks were observed in the background, while surface homogeneity of PCN 1 wt % is increased and micro-cracks are reduced. (Author)

  12. Stable electroosmotically driven actuators

    Science.gov (United States)

    Sritharan, Deepa; Motsebo, Mylene; Tumbic, Julia; Smela, Elisabeth

    2013-04-01

    We have previously presented "nastic" actuators based on electroosmotic (EO) pumping of fluid in microchannels using high electric fields for potential application in soft robotics. In this work we address two challenges facing this technology: applying EO to meso-scale devices and the stability of the pumping fluid. The hydraulic pressure achieved by EO increases with as 1/d2, where d is the depth of the microchannel, but the flow rate (which determines the stroke and the speed) is proportional to nd, where n is the number of channels. Therefore to get high force and high stroke the device requires a large number of narrow channels, which is not readily achievable using standard microfabrication techniques. Furthermore, for soft robotics the structure must be soft. In this work we present a method of fabricating a three-dimensional porous elastomer to serve as the array of channels based on a sacrificial sugar scaffold. We demonstrate the concept by fabricating small pumps. The flexible devices were made from polydimethylsiloxane (PDMS) and comprise the 3D porous elastomer flanked on either side by reservoirs containing electrodes. The second issue addressed here involves the pumping fluid. Typically, water is used for EO, but water undergoes electrolysis even at low voltages. Since EO takes place at kV, these systems must be open to release the gases. We have recently reported that propylene carbonate (PC) is pumped at a comparable rate as water and is also stable for over 30 min at 8 kV. Here we show that PC is, however, degraded by moisture, so future EO systems must prevent water from reaching the PC.

  13. Pretilt angle control of liquid crystal molecules by photoaligned films of azobenzene-containing polyimide with a different content of side-chain

    Science.gov (United States)

    Usami, Kiyoaki; Sakamoto, Kenji; Yokota, Junichiro; Uehara, Yoichi; Ushioda, Sukekatsu

    2008-12-01

    We have investigated the pretilt angle of liquid crystal (LC) molecules induced by photoaligned films of a series of polyimides. The polyimides were random copolymers synthesized from pyromellitic dianhydride and a mixture of 4,4'-diaminoazobenzene and 4-[4'-propylbi(cyclohexan)-4-yl]phenyl 3,5-diaminobenzoate (PBCP-DABA). PBCP-DABA is a diamine to introduce a side-chain structure into polyimide. We found that the pretilt angle of LC molecules can be controlled from 0° to 90° by varying the molar fraction (x) of PBCP-DABA from 0 to 0.5. Defect-free uniform LC alignment was observed for x ≤0.125 and x ≥0.3, but threadlike textures appeared for 0.15≤x≤0.25. Since the interaction between the polyimide backbone structure and the LC molecule may be blocked by relatively dense side-chains, the appearance of threadlike texture is tentatively attributed to weak azimuthal anchoring strength of the photoaligned polyimide films with x ≥0.15.

  14. Effect of heterocyclic based organoclays on the properties of polyimide-clay nanocomposites.

    Science.gov (United States)

    Krishnan, P Santhana Gopala; Joshi, Mangala; Bhargava, Prachur; Valiyaveettil, Suresh; He, Chaobin

    2005-07-01

    Polyimide-clay nanocomposites were prepared from their precursor, namely, polyamic acid, by the solution-casting method. Organomodified montmorillonite (MMT) clay was prepared by treating Na+MMT (Kunipia F) with three different intercalating agents, namely, piperazine dihydrochloride, 1,3-bis(4-piperidinylpropane) dihydrochloride and 4,4'-bipiperidine dihydrochloride at 80 degrees C. Polyamic acid solutions containing various weight percentages of organomodified MMT were prepared by reacting 4,4'-(1,1'-biphenyl-4,4'-diyldioxy)dianiline with bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride in N-methyl-2-pyrrolidinone containing dispersed particles of organomodified MMT at 20 degrees C. Nanocomposite films were prepared from these solutions by solution casting and heated subsequently at a programmed heating rate. These films were transparent and brown in color. The extent of layer separation in nanocomposite films depends upon the chemical structure of the organoclay. These films were characterized by inherent viscosity, FT-IR, DSC, TMA, WAXD, TEM, UV, and TGA. The tensile behavior and surface energy studies were also investigated. The nanocomposite films had superior tensile properties, thermal behavior, and solvent resistance. Among the three organoclays, piperazine dihydrochloride was the best modifier.

  15. The effects of high electronic energy loss on the chemical modification of polyimide

    CERN Document Server

    SunYouMei; Jin Yun Fan; Liu Chang Long; LiuJie; Wang Zhi Guang; Zhang Qi; Zhu Zhi Yong

    2002-01-01

    In order to observe the role of electronic energy loss (dE/dX) sub e on chemical modification of polyimide (PI), the multi-layer stacks (corresponding to different dE/dX) were irradiated by different swift heavy ions (1.37 GeV Ar sup 4 sup 0 , 1.98 GeV Kr sup 8 sup 4 , 1.755 GeV Xe sup 1 sup 3 sup 6 and 2.636 GeV U sup 2 sup 3 sup 8) under vacuum and room temperature. The chemical changes of modified PI films were studied by Fourier transform infrared (FTIR) and ultraviolet/visible (UV/Vis) absorption spectroscopy. The degradation of PI was investigated in the fluence range from 1x10 sup 1 sup 0 to 5.5x10 sup 1 sup 2 ions/cm sup 2 and different electronic energy loss from 0.77 to 11.5 keV/nm. The FTIR results show the absorbance of the typical function group decrease exponentially as a function of fluence. The alkyne end group was found after irradiation and its formation radii were 5.6 and 5.9 nm corresponding to 8.8 and 11.5 keV/nm Xe irradiation respectively. UV/Vis analysis indicates the radiation induced...

  16. Highly Sulfonated Diamine Synthesized Polyimides and Protic Ionic Liquid Composite Membranes Improve PEM Conductivity

    Directory of Open Access Journals (Sweden)

    Bor-Kuan Chen

    2015-06-01

    Full Text Available A novel sulfonated diamine was synthesized from 1,4-bis(4-aminophenoxy benzene [pBAB]. Sulfonated polyimides (SPIs were synthesized from sulfonated pBAB, 1,4-bis(4-aminophenoxy-2-sulfonic acid benzenesulfonic acid [pBABTS], various diamines and aromatic dianhydrides. Composite proton exchange membranes (PEMs made of novel SPIs and a protic ionic liquid (PIL 1-vinyl-3-H-imidazolium trifluoromethanesulfonate [VIm][OTf] showed substantially increased conductivity. We prepared an SPI/PIL composite PEM using pBABTS, 4,4′-(9-fluorenylidene dianiline (9FDA as diamine, 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride (DSDA as dianhydride and 40 wt % [VIm][OTf] with a high conductivity of 16 mS/cm at 120 °C and anhydrous condition. pBABTS offered better conductivity, since the chemical structure had more sulfonated groups that provide increased conductivity. The new composite membrane could be a promising anhydrous or low-humidity PEM for intermediate or high-temperature fuel cells.

  17. High-Glass-Transition-Temperature Polyimides Developed for Reusable Launch Vehicle Applications

    Science.gov (United States)

    Chuang, Kathy; Ardent, Cory P.

    2002-01-01

    Polyimide composites have been traditionally used for high-temperature applications in aircraft engines at temperatures up to 550 F (288 C) for thousands of hours. However, as NASA shifts its focus toward the development of advanced reusable launch vehicles, there is an urgent need for lightweight polymer composites that can sustain 600 to 800 F (315 to 427 C) for short excursions (hundreds of hours). To meet critical vehicle weight targets, it is essential that one use lightweight, high-temperature polymer matrix composites in propulsion components such as turbopump housings, ducts, engine supports, and struts. Composite materials in reusable launch vehicle components will heat quickly during launch and reentry. Conventional composites, consisting of layers of fabric or fiber-reinforced lamina, would either blister or encounter catastrophic delamination under high heating rates above 300 C. This blistering and delamination are the result of a sudden volume expansion within the composite due to the release of absorbed moisture and gases generated by the degradation of the polymer matrix. Researchers at the NASA Glenn Research Center and the Boeing Company (Long Beach, CA) recently demonstrated a successful approach for preventing this delamination--the use of three-dimensional stitched composites fabricated by resin infusion.

  18. Microwave sintering of Ag-nanoparticle thin films on a polyimide substrate

    Directory of Open Access Journals (Sweden)

    S. Fujii

    2015-12-01

    Full Text Available Ag-nanoparticle thin films on a polyimide substrate were subjected to microwave sintering by use of a single-mode waveguide applicator. A two-step sintering process was employed. First, at low conductivities of the film, the film sample was placed at the site of the maximum electric field and subjected to microwave irradiation. Second, when the conductivity of the film increased, the film sample was placed at the site of the maximum magnetic field and again subjected to microwave irradiation. The microwave sintering process was completed within 1.5 min, which is significantly lower than the time required for the oven heating process. The resulting conductivity of the film, albeit only 30% of that of the bulk material, was seven times that of a film annealed at the same temperature in a furnace. Scanning electron microscopy images revealed that the nanoparticles underwent both grain necking and grain growth during microwave sintering. In addition, this sintering process was equivalent to the oven heating process performed at a 50 °C higher annealing temperature. An electromagnetic wave simulation and a heat transfer simulation of the microwave sintering process were performed to gain a thorough understanding of the process.

  19. Design, fabrication and test of graphite/polyimide composite joints and attachments for advanced aerospace vehicles

    Science.gov (United States)

    Barclay, D. L.

    1980-01-01

    Results of an experimental program to develop several types of graphite/polyimide (GR/PI) bonded and bolted joints for lightly loaded flight components for advanced space transportation systems and high speed aircraft are presented. Tasks accomplished include: a literature survey; design of static discriminator specimens; design allowables testing; fabrication of test panels and specimens; small specimen testing; and standard joint testing. Detail designs of static discriminator specimens for each of the four major attachment types are presented. Test results are given for the following: (1) transverse tension of Celion 3000/PMR-15 laminate; (2) net tension of a laminate for both a loaded and unloaded bolt hole; (3) comparative testing of bonded and co-cured doublers along with pull-off tests of single and double bonded angles; (4) single lap shear tests, transverse tension and coefficient of thermal expansion tests of A7F (LARC-13 amide-imide modified) adhesive; and (5) tension tests of standard single lap, double lap, and symmetric step lap bonded joints. Also, included are results of a finite element analysis of a single lap bonded composite joint.

  20. Carbon molecular sieve gas separation membranes based on an intrinsically microporous polyimide precursor

    KAUST Repository

    Ma, Xiaohua

    2013-10-01

    We report the physical characteristics and gas transport properties for a series of pyrolyzed membranes derived from an intrinsically microporous polyimide containing spiro-centers (PIM-6FDA-OH) by step-wise heat treatment to 440, 530, 600, 630 and 800 C, respectively. At 440 C, the PIM-6FDA-OH was converted to a polybenzoxazole and exhibited a 3-fold increase in CO2 permeability (from 251 to 683 Barrer) with a 50% reduction in selectivity over CH4 (from 28 to 14). At 530 C, a distinct intermediate amorphous carbon structure with superior gas separation properties was formed. A 56% increase in CO2-probed surface area accompanied a 16-fold increase in CO2 permeability (4110 Barrer) over the pristine polymer. The graphitic carbon membrane, obtained by heat treatment at 600 C, exhibited excellent gas separation properties, including a remarkable CO2 permeability of 5040 Barrer with a high selectivity over CH4 of 38. Above 600 C, the strong emergence of ultramicroporosity (<7 Å) as evidenced by WAXD and CO2 adsorption studies elicits a prominent molecular sieving effect, yielding gas separation performance well above the permeability-selectivity trade-off curves of polymeric membranes. © 2013 Elsevier Ltd. All rights reserved.

  1. Preparation of Solution Blown Polyamic Acid Nanofibers and Their Imidization into Polyimide Nanofiber Mats

    Directory of Open Access Journals (Sweden)

    Jing Li

    2017-11-01

    Full Text Available Solution blow spinning (SBS is an innovative process for spinning micro/nanofibers. In this paper, polyamic acid (PAA nanofibers were fabricated via a SBS apparatus and then imidized into polyimide (PI nanofibers via thermal process. The morphology and diameter distributions of PAA nanofibers were determined by scanning electron microscope (SEM and Image Tool software, the processing parameters, including PAA concentration, solution feeding rate, gas pressure, nozzle size, and receiving distance were investigated in details. The fourier transform infrared spectroscopy (FTIR was used to characterize the chemical changes in the nanofibers after thermal imidization. The results showed that the solution concentration exhibited a notable correlation with spinnability, and the formation of bead defects in PAA nanofibers. Solution feeding rate, gas pressure, nozzle size, and receiving distance affected nanofiber production efficiency and diameter distribution. The average diameters of fibers produced ranged from 129.6 to 197.7 nm by varying SBS parameters. Precisely, PAA nanofibers with good morphology were obtained and the average diameter of nanofibers was 178.2 nm with optimum process parameter. After thermal imidization, the PI nanofibers exhibited obvious adhesion morphology among interconnected fibers, with an increased average diameter of 209.1 nm. The tensile strength of resultant PI nanofiber mat was 12.95 MPa.

  2. Carbon molecular sieve membranes derived from Matrimid® polyimide for nitrogen/methane separation

    KAUST Repository

    Ning, Xue

    2014-01-01

    A commercial polyimide, Matrimid® 5218, was pyrolyzed under an inert argon atmosphere to produce carbon molecular sieve (CMS) dense film membranes for nitrogen/methane separation. The resulting CMS dense film separation performance was evaluated using both pure and mixed N2/CH4 permeation tests. The effects of final pyrolysis temperature on N 2/CH4 separation are reported. The separation performance of all CMS dense films significantly exceeds the polymer precursor dense film. The CMS dense film pyrolyzed at 800 C shows very attractive separation performance that surpasses the polymer membrane upper bound line, with N 2 permeability of 6.8 Barrers and N2/CH4 permselectivity of 7.7 from pure gas permeation, and N2 permeability of 5.2 Barrers and N2/CH4 permselectivity of 6.0 from mixed gas permeation. The temperature dependences of permeabilities, sorption coefficients, and diffusion coefficients of the membrane were studied, and the activation energy for permeation and diffusion, as well as the apparent heats of sorption are reported. The high permselectivity of this dense film is shown to arise from a significant entropic contribution in the diffusion selectivity. The study shows that the rigid \\'slit-shaped\\' CMS pore structure can enable a strong molecular sieving effect to effectively distinguish the size and shape difference between N2 and CH4. © 2013 Elsevier Ltd. All rights reserved.

  3. A novel TFC forward osmosis (FO) membrane supported by polyimide (PI) microporous nanofiber membrane

    Science.gov (United States)

    Chi, Xiang-Yu; Zhang, Ping-Yun; Guo, Xue-Jiao; Xu, Zhen-Liang

    2018-01-01

    A novel interfacial polymerization (IP) procedure on polyimide (PI) microporous nanofiber membrane support with mean pore size 1.27 μm was reported. Using m-phenylenediamine (MPD) as aqueous phase monomer, trimesoyl chloride (TMC) as organic phase monomer, ethanol as aqueous phase co-solvent, thin-film composite (TFC) forward osmosis (FO) membrane was fabricated by two IP procedures. The first IP procedure with the unconventional order (ie, the membrane was immersed in the TMC organic phase first, then in the co-solvent ethanol-water MPD aqueous phase) was used to diminish the pore size of PI microporous nanofiber membrane support for the formation of the polyamide layer. The secondary IP procedure was employed to form the relatively dense polyamide layer with conventional order (ie, the membrane was immersed in the co-solvent ethanol-water MPD aqueous phase first, then in the TMC organic phase). The experimental results showed that higher ethanol concentration led to the relatively higher pure water permeability in RO process and osmotic water flux in FO process, whereas NaCl rejection in RO process decreased and reverse salt flux increased. The specific salt flux (Js/Jv) of TFC FO PI nanofiber membrane (PIN-2-4) could be as low as 0.095 g/L in FO mode. These results could be attributed to influence of the addition of ethanol into aqueous phase on the surface morphology, hydrophilicity and polyamide layer structure.

  4. Superhydrophobic Polyimide via Ultraviolet Photooxidation: The Evolution of Surface Morphology and Hydrophobicity under Different Ultraviolet Intensities

    Directory of Open Access Journals (Sweden)

    Hongyu Gu

    2015-01-01

    Full Text Available Ultraviolet (UV photooxidation has recently been developed to fabricate superhydrophobic polyimide (PI films in combination with fluoroalkylsilane modification. However, it remains unclear whether the surface morphology and hydrophobicity are sensitive to technical parameters such as UV intensity and radiation environment. Herein, we focus on the effects of UV intensity on PI surface structure and wettability to gain comprehensive understanding and more effective control of this technology. Scanning electron microscopy (SEM and atomic force microscopy (AFM results showed that UV intensity governed the evolutionary pattern of surface morphology: lower UV intensity (5 mW/cm2 facilitated in-plane expansion of dendritic protrusions while stronger UV (10 and 15 mW/cm2 encouraged localized growth of protrusions in a piling-up manner. Surface roughness and hydrophobicity maximized at the intensity of 10 mW/cm2, as a consequence of the slowed horizontal expansion and preferred vertical growth of the protrusions when UV intensity increased. Based on these results, the mechanism that surface micro/nanostructures developed in distinct ways when exposed to different UV intensities was proposed. Though superhydrophobicity (water contact angle larger than 150° can be achieved at UV intensity not less than 10 mW/cm2, higher intensity decreased the effectiveness. Therefore, the UV photooxidation under 10 mW/cm2 for 72 h is recommended to fabricate superhydrophobic PI films.

  5. Langmuir-Blodgett films of physical and chemical polyimide mixtures from linear and network precursors

    Energy Technology Data Exchange (ETDEWEB)

    Wang Jinwei [Department of Materials Physics and Chemistry, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083 (China)]. E-mail: wangjw@mater.ustb.edu.cn

    2007-05-16

    Physical and chemical mixture Langmuir-Blodgett polyimide films were obtained by reacting mellitic acid hexamethyl ester with pyromellitic anhydride and 4,4'-diaminodiphenyl ether followed by formation of polyamic acid salts with octadecyl amine. The additions of mellitic acid hexamethyl ester provided more reinforcement to the copolymers than the blends because of the more evenly distributed linear and network segments as observed from the {pi}-A isotherms. The alkyl chains randomly tilted to the normal of the substrate at an angle about 20{sup o} while the tilt angels increased with the increase of the amount of mellitic acid hexamethyl ester. The ordered chain packing pattern along the dipping direction was disrupted and even disappeared if more mellitic acid hexamethyl ester was added as shown from the atomic force microscopy images. Accordingly, the X-ray diffraction results showed that the crystallinity decreased with the increase of the amount of mellitic acid hexamethyl ester. The branched component, the mellitic acid hexamethyl ester, had much more effects both in structure and morphology on the copolymers than on the blends.

  6. Surface modification of POSS–polyimide hybrid films by atomic oxygen using ECR plasma

    Energy Technology Data Exchange (ETDEWEB)

    Duo, Shuwang, E-mail: swduo@126.com [Jiangxi Key Laboratory of Surface Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); Ke, Huan; Liu, Tingzhi; Song, Mimi [Jiangxi Key Laboratory of Surface Engineering, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); Li, Meishuan [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China)

    2013-07-15

    A novel polyimide (PI) hybrid nanocomposite containing polyhedral oligomeric silsesquioxane (POSS) had been prepared by copolymerization of trisilanolphenyl-POSS, 4,4′-oxydianiline (ODA), and pyromellitic dianhydride (PMDA). The atomic oxygen (AO) resistance of these PI/POSS hybrid films was tested in the ground-based AO simulation facility. Exposed and unexposed surfaces were characterized by SEM and XPS. The SEM images showed that the surface of the 20 wt.% PI/POSS became much less rough than that of the pristine PI. Mass measurements of the samples showed that the erosion yield of the PI/POSS (20 wt.%) hybrid film was 1.2 × 10{sup −25} cm{sup 3}/atom, and reduced to 4.3% of that of the PI film. The XPS data indicated that the carbon content of the near-surface region was decreased from 66.0 to 7.0 at.% after AO exposure. The ratio of oxygen and silicon concentrations in the near-surface region increased to 2.08 after AO exposure. The nanometer-sized structure of POSS, with its large surface area, had led AO-irradiated samples to form a SiO{sub 2} passivation layer, which protected the underlying polymer from further AO attack. The incorporation of POSS into the PI could dramatically improve the AO resistance of PI films in low earth orbit environment.

  7. Porous Polyimide Membranes Prepared by Wet Phase Inversion for Use in Low Dielectric Applications

    Directory of Open Access Journals (Sweden)

    Jung Ah Lim

    2013-04-01

    Full Text Available A wet phase inversion process of polyamic acid (PAA allowed fabrication of a porous membrane of polyimide (PI with the combination of a low dielectric constant (1.7 and reasonable mechanical properties (Tensile strain: 8.04%, toughness: 3.4 MJ/m3, tensile stress: 39.17 MPa, and young modulus: 1.13 GPa, with further thermal imidization process of PAA. PAA was simply synthesized from purified pyromellitic dianhydride (PMDA and 4,4-oxydianiline (ODA in two different reaction solvents such as γ-butyrolactone (GBL and N-methyl-2-pyrrolidinone (NMP, which produce Mw/PDI of 630,000/1.45 and 280,000/2.0, respectively. The porous PAA membrane was fabricated by the wet phase inversion process based on a solvent/non-solvent system via tailored composition between GBL and NMP. The porosity of PI, indicative of a low electric constant, decreased with increasing concentration of GBL, which was caused by sponge-like formation. However, due to interplay between the low electric constant (structural formation and the mechanical properties, GBL was employed for further exploration, using toluene and acetone vs. DI-water as a coagulation media. Non-solvents influenced determination of the PAA membrane size and porosity. With this approach, insight into the interplay between dielectric properties and mechanical properties will inform a wide range of potential low-k material applications.

  8. Low-stress photosensitive polyimide suspended membrane for improved thermal isolation performance

    Science.gov (United States)

    Fan, J.; Xing, R. Y.; Wu, W. J.; Liu, H. F.; Liu, J. Q.; Tu, L. C.

    2017-11-01

    In this paper, we introduce a method of isolating thermal conduction from silicon substrate for accommodating thermal-sensitive micro-devices. This method lies in fabrication of a low-stress photosensitive polyimide (PSPI) suspension structure which has lower thermal conductivity than silicon. First, a PSPI layer was patterned on a silicon wafer and hard baked. Then, a cavity was etched from the backside of the silicon substrate to form a membrane or a bridge-shape PSPI structure. After releasing, a slight deformation of about 20 nm was observed in the suspended structures, suggesting ultralow residual stress which is essential for accommodating micro-devices. In order to investigate the thermal isolation performance of the suspended PSPI structures, micro Pirani vacuum gauges, which are thermal-sensitive, had been fabricated on the PSPI structures. The measurement results illustrated that the Pirani gauges worked as expected in the range from 1– 470 Pa. Moreover, the results of the Pirani gauges based on the membrane and bridge structures were comparable, indicating that the commonly used bridge-shape structure for further reducing thermal conduction was unnecessary. Due to the excellent thermal isolation performance of PSPI, the suspended PSPI membrane is promising to be an outstanding candidate for thermal isolation applications.

  9. Microfabrication of plastic-PDMS microfluidic devices using polyimide release layer and selective adhesive bonding

    Science.gov (United States)

    Wang, Shuyu; Yu, Shifeng; Lu, Ming; Zuo, Lei

    2017-05-01

    In this paper, we present an improved method to bond poly(dimethylsiloxane) (PDMS) with polyimide (PI) to develop flexible substrate microfluidic devices. The PI film was separately fabricated on a silicon wafer by spin coating followed by thermal treatment to avoid surface unevenness of the flexible substrate. In this way, we could also integrate flexible substrate into standard micro-electromechanical systems (MEMS) fabrication. Meanwhile, the adhesive epoxy was selectively transferred to the PDMS microfluidic device by a stamp-and-stick method to avoid epoxy clogging the microfluidic channels. To spread out the epoxy evenly on the transferring substrate, we used superhydrophilic vanadium oxide film coated glass as the transferring substrate. After the bonding process, the flexible substrate could easily be peeled off from the rigid substrate. Contact angle measurement was used to characterize the hydrophicity of the vanadium oxide film. X-ray photoelectron spectroscopy analysis was conducted to study the surface of the epoxy. We further evaluated the bonding quality by peeling tests, which showed a maximum bonding strength of 100 kPa. By injecting with black ink, the plastic microfluidic device was confirmed to be well bonded with no leakage for a day under 1 atm. This proposed versatile method could bond the microfluidic device and plastic substrate together and be applied in the fabrication of some biosensors and lab-on-a-chip systems.

  10. Self lubricating composites for medium temperatures in space based on polyimide SINTIMID

    Science.gov (United States)

    Merstallinger, A.; Bieringer, H.; Kubinger, E.; Gaillard, L.; Brenner, J.; Mozdzen, G.

    2005-07-01

    The paper is surveying the results of an ESA-project on a polyimide composite named "SINTIMID". The main target was to find a self lubricating composite (SLC) which is suitable for missions to the inner solar system, where operating temperatures up to 300°C in vacuum are expected. The paper comprises a short introduction into the requirements derived from ECSS for SLC material intended for use in journal bearings working in space. It covers a brief description of new equipments for medium temperatures "vacuum tribometer" and "Journal Bearing Test rig". The presented results will cover mainly the friction and wear behaviour and component test performance. The influences of parameters like load, speed, atmosphere and temperature are discussed and compared to other already known materials, e.g. Vespel SP3. The verification procedure included three phases: a screening on several compositions with different fillers and combinations, a detailed friction test campaign on two best compositions (15M and 30M) and a final bush testing on only the best (15M=15w% MoS2). All material properties in relation to ECSS E30 were verified. No objections to the requirements were identified. Finally, a recommendation for design of bushes was set up on the results.

  11. Polyimide encapsulated lithium-rich cathode material for high voltage lithium-ion battery.

    Science.gov (United States)

    Zhang, Jie; Lu, Qingwen; Fang, Jianhua; Wang, Jiulin; Yang, Jun; NuLi, Yanna

    2014-10-22

    Lithium-rich materials represented by xLi2MnO3·(1 - x)LiMO2 (M = Mn, Co, Ni) are attractive cathode materials for lithium-ion battery due to their high specific energy and low cost. However, some drawbacks of these materials such as poor cycle and rate capability remain to be addressed before applications. In this study, a thin polyimide (PI) layer is coated on the surface of Li1.2Ni0.13Mn0.54Co0.13O2 (LNMCO) by a polyamic acid (PAA) precursor with subsequently thermal imidization process. X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM) results confirm the successful formation of a PI layer (∼3 nm) on the surface of LNMCO without destruction of its main structure. X-ray photoelectron spectroscopy (XPS) spectra show a slight shift of the Mn valence state from Mn(IV) to Mn(III) in the PI-LNMCO treated at 450 °C, elucidating that charge transfer takes place between the PI layer and LNMCO surface. Electrochemical performances of LNMCO including cyclic stability and rate capability are evidently improved by coating a PI nanolayer, which effectively separates the cathode material from the electrolyte and stabilizes their interface at high voltage.

  12. An Ensemble Learning for Predicting Breakdown Field Strength of Polyimide Nanocomposite Films

    Directory of Open Access Journals (Sweden)

    Hai Guo

    2015-01-01

    Full Text Available Using the method of Stochastic Gradient Boosting, ten SMO-SVR are constructed into a strong prediction model (SGBS model that is efficient in predicting the breakdown field strength. Adopting the method of in situ polymerization, thirty-two samples of nanocomposite films with different percentage compositions, components, and thicknesses are prepared. Then, the breakdown field strength is tested by using voltage test equipment. From the test results, the correlation coefficient (CC, the mean absolute error (MAE, the root mean squared error (RMSE, the relative absolute error (RAE, and the root relative squared error (RRSE are 0.9664, 14.2598, 19.684, 22.26%, and 25.01% with SGBS model. The result indicates that the predicted values fit well with the measured ones. Comparisons between models such as linear regression, BP, GRNN, SVR, and SMO-SVR have also been made under the same conditions. They show that CC of the SGBS model is higher than those of other models. Nevertheless, the MAE, RMSE, RAE, and RRSE of the SGBS model are lower than those of other models. This demonstrates that the SGBS model is better than other models in predicting the breakdown field strength of polyimide nanocomposite films.

  13. Free volume analysis and gas transport mechanisms of aromatic polyimide membranes: a molecular simulation study.

    Science.gov (United States)

    Chang, Kai-Shiun; Tung, Chieng-Chi; Wang, Ko-Shung; Tung, Kuo-Lun

    2009-07-23

    Molecular simulation techniques were adopted to investigate membrane free volume morphologies and gas-transport mechanisms in the aromatic polyimide (PI) membranes composed of various diamines and dianhydrides. A molecular dynamics (MD) technique was adopted to analyze the fractional free volume (FFV), fractional accessible volume (FAV), free volume size and shape, and diffusion mechanisms. A Monte Carlo (MC) method was used to analyze the gas sorption behaviors in the membranes. The FFV, FAV, and free volume morphology analyses reveal that bulky groups in the PI membranes contributed to the formation of a larger and more continuous free volume. The thermal motion analysis shows that a greater effective free volume in the membranes promoted effective motion, such as jumping and diffusive motions. The sorption analysis indicates that the larger free volume provides more sites for gas molecule absorption. The MD and MC results provide good agreement with the experimental data from past reports, which validates the feasibility of molecular simulation techniques in gas separation membranes at a molecular scale.

  14. Conducting-tip AFM Studies of Multi-Walled Carbon Nanotube/Polyimide Nanocomposites

    Science.gov (United States)

    Trionfi, A.; Scrymgeour, D.; Hsu, J. W. P.; Arlen, M. J.; Wang, D.; Tan, L.-S.; Vaia, R. A.

    2008-03-01

    Electrical transport studies of multi-walled carbon nanotube (c-MWNT)/polymer nanocomposites have shown metallic behavior with conductivity σ=σ0( φ-φc )^t above the percolation threshold. The conductivity depends on three aspects of the conducting network (CN): the conductivity of the constituent c-MWNT, the number of c-MWNT making up the CN, and the detailed interconnectivity of the CN. Using conducting-tip atomic force microscopy (C-AFM), we have studied the density and conductivity of the c-MWNT CN as a function of c-MWNT loading between 0.5 - 5.0 wt % in a polyimide matrix. Using the Principle of Delesse, the volume fraction of the c-MWNT CN can be calculated from the conducting areal density measured in the C-AFM scans. The results of the C-AFM tests have shown localized areas of electrical transport associated with c-MWNT as well a clear dependence of conducting areal density and conductivity on the c-MWNT loading. This work was performed in part at the US Department of Energy, Center for Integrated Nanotechnologies, at Los Alamos and Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a Lockheed-Martin Company, for the U. S. Department of Energy under Contract No. DE-AC04-94AL85000.

  15. High-performance polyimide nanocomposites with core-shell AgNWs@BN for electronic packagings

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yongcun; Liu, Feng, E-mail: liufeng@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an Shaanxi 710072 (China)

    2016-08-22

    The increasing density of electronic devices underscores the need for efficient thermal management. Silver nanowires (AgNWs), as one-dimensional nanostructures, possess a high aspect ratio and intrinsic thermal conductivity. However, high electrical conductivity of AgNWs limits their application for electronic packaging. We synthesized boron nitride-coated silver nanowires (AgNWs@BN) using a flexible and fast method followed by incorporation into synthetic polyimide (PI) for enhanced thermal conductivity and dielectric properties of nanocomposites. The thinner boron nitride intermediate nanolayer on AgNWs not only alleviated the mismatch between AgNWs and PI but also enhanced their interfacial interaction. Hence, the maximum thermal conductivity of an AgNWs@BN/PI composite with a filler loading up to 20% volume was increased to 4.33 W/m K, which is an enhancement by nearly 23.3 times compared with that of the PI matrix. The relative permittivity and dielectric loss were about 9.89 and 0.015 at 1 MHz, respectively. Compared with AgNWs@SiO{sub 2}/PI and Ag@BN/PI composites, boron nitride-coated core-shell structures effectively increased the thermal conductivity and reduced the permittivity of nanocomposites. The relative mechanism was studied and discussed. This study enables the identification of appropriate modifier fillers for polymer matrix nanocomposites.

  16. Effects of polyimide pyrolysis conditions on carbon molecular sieve membrane properties

    Energy Technology Data Exchange (ETDEWEB)

    Geiszler, V.C.; Koros, W.J. [Univ. of Texas, Austin, TX (United States)

    1996-09-01

    In previous research, carbon molecular sieve (CMS) membranes for gas separations have been produced using either a vacuum pyrolysis or an inert purge pyrolysis technique on a precursor which is often polymeric. This study compares both techniques using the same polyimide precursor material. Additional pyrolysis variables included the type of inert purge gas (argon, helium, and carbon dioxide), purge flow rate, and temperature. Vacuum pyrolysis produced more selective but less productive CMS membranes than the inert purge pyrolyzed membranes. High purge gas flow rates (i.e., 200 standard cubic centimeters per minute or cm{sup 3}(STP)/min) produced a much higher permeability, but lower selectivity membrane compared to those produced in a low purge flow rate (20 cm{sup 3}(STP)/min). By raising the pyrolysis temperature from 550 to 800 C, the effective pore size was reduced, thereby making the CMS membranes more selective but less productive. Mixed gas tests using oxygen/nitrogen and hydrogen/nitrogen mixtures were used to evaluate membrane performance.

  17. Cross-Linkable Polyimide Membranes for Improved Plasticization Resistance and Permselectivity in Sour Gas Separations

    KAUST Repository

    Kraftschik, Brian

    2013-09-10

    A series of cross-linkable membrane materials based on the 6FDA-DAM:DABA (3:2) polyimide backbone were synthesized for improved sour gas separation performance, in terms of both membrane stability and permselectivity. Short-chain poly(ethylene glycol) (PEG) molecules were used as cross-linking agents in an esterification-based cross-linking reaction. Pure and mixed gas permeation and pure gas sorption experiments were performed on dense films of these materials. Compared to unmodified 6FDA-DAM:DABA (3:2), higher sour gas permselectivity and membrane stability were achieved under aggressive feed conditions. H2S-induced plasticization was not evident until pure H2S feed pressures greater than approximately 6-8 bar. Pure CO 2-induced plasticization only occurred at feed pressures greater than about 25 bar. Under mixed gas feed conditions with 20% H2S, 20% CO2, and 60% CH4 at 35 C, attractive selectivities above 22 and 27 for H2S/CH4 and CO2/CH4, respectively, were observed for a feed pressure of 62 bar with both triethylene glycol and tetraethylene glycol cross-linking agents. © 2013 American Chemical Society.

  18. Sulfur removal from fuel using zeolites/polyimide mixed matrix membrane adsorbents.

    Science.gov (United States)

    Lin, Ligang; Wang, Andong; Dong, Meimei; Zhang, Yuzhong; He, Benqiao; Li, Hong

    2012-02-15

    A novel membrane adsorption process was proposed for the sulfur removal from fuels. The mixed matrix membranes (MMMs) adsorbents composed of polyimide (PI) and various Y zeolites were prepared. By the detailed characterization of FT-IR, morphology, thermal and mechanical properties of MMMs adsorbents, combining the adsorption and desorption behavior research, the process-structure-function relationship was discussed. Field-emission scanning electron microscope (FESEM) images show that the functional particles are incorporated into the three-dimensional network structure. MMMs adsorbents with 40% of zeolites content possess better physical properties, which was confirmed by mechanical strength and thermo stability analysis. Influence factors including post-treatment, content of incorporated zeolites, adsorption time, temperature, initial sulfur concentration as well as sulfur species on the adsorption performance of MMMs adsorbents have been evaluated. At 4 wt.% zeolites content, adsorption capacity for NaY/PI, AgY/PI and CeY/PI MMMs adsorbents come to 2.0, 7.5 and 7.9 mg S/g, respectively. And the regeneration results suggest that the corresponding spent membranes can recover about 98%, 90% and 70% of the desulfurization capacity, respectively. The distinct adsorption and desorption behavior of MMMs adsorbents with various functional zeolites was markedly related with their various binding force and binding mode with sulfur compounds. Copyright © 2011 Elsevier B.V. All rights reserved.

  19. A new high-performance ionic polymer-metal composite based on Nafion/polyimide blends

    Science.gov (United States)

    Nam, Jungsoo; Hwang, Taeseon; Kim, Kwang Jin; Lee, Dong-Chan

    2017-03-01

    For the first time, we report ion-exchange membranes based on Nafion and polyimide (PI, Kapton) blends to fabricate ionic polymer-metal composites (IPMCs). Polyamic acid [PAA, poly(pyromellitic dianhydride-co-4,4‧-oxydianiline), as a precursor of PI] solution was blended with Nafion solution using physical blending method to provide PAA-Nafion blend membrane. This work demonstrates that, by simple physical blending method, the thermal and mechanical properties of Nafion can be improved while maintaining the excellent actuating performance. After thermal imidization, PAA converted into PI, resulting in PI-Nafion blend membrane. Optimum conditions to cast PAA-Nafion blends and thermal imidization have been established, and blend membranes with PI wt% of 6, 12, 18, and 30 were prepared. Fourier transform infrared spectroscopy confirmed the incorporation of PI in the Nafion matrix. Thermal decomposition unique to the PI became more noticeable as the content of PI increased, which was measured by thermogravimetric analysis. Dynamic mechanical analysis showed that the storage modulus (E‧) increased as a function of PI content while loss modulus (E″) exhibited only a minor change, which resulted in the decrease in the damping properties (tan δ). The blend membranes were fabricated into IPMCs by deposition of platinum electrode onto the membrane surface through electroless plating process. Among tested, NPI-18 IPMC actuator, which has 18 wt% of PI in Nafion, showed comparable electromechanical performance to the commercially available Nafion 117 IPMC actuator.

  20. Essentially asymptotically stable homoclinic networks

    NARCIS (Netherlands)

    Driesse, R.; Homburg, A.J.

    2009-01-01

    Melbourne [An example of a nonasymptotically stable attractor, Nonlinearity 4(3) (1991), pp. 835-844] discusses an example of a robust heteroclinic network that is not asymptotically stable but which has the strong attracting property called essential asymptotic stability. We establish that this

  1. Triptycene dimethyl-bridgehead dianhydride-based intrinsically microporous hydroxyl-functionalized polyimide for natural gas upgrading

    KAUST Repository

    Alghunaimi, Fahd

    2016-07-28

    The synthesis and gas permeation properties of a high-performance hydroxyl-functionalized PIM-polyimide (TDA1-APAF) prepared from a novel 9,10-dimethyl-2,3,6,7-triptycene tetracarboxylic dianhydride (TDA1) and a commercially available 2,2-bis(3-amino-4-hydroxyphenyl)-hexafluoropropane (APAF) diamine monomer are reported. The microporous polymer had a BET surface area based on nitrogen adsorption of 260 m2 g−1. A freshly prepared sample exhibited excellent gas permeation properties: (i) CO2 permeability of 40 Barrer coupled with a CO2/CH4 selectivity of 55 and (ii) H2 permeability of 94 Barrer with a H2/CH4 selectivity of 129. Physical aging over 250 days resulted in significantly enhanced CO2/CH4 and H2/CH4 selectivities of 75 and 183, respectively with only ~ 25% loss in CO2 and H2 permeability. Aged TDA1-APAF exhibited 5-fold higher pure-gas CO2 permeability (30 Barrer) and two-fold higher CO2/CH4 permselectivity over conventional dense cellulose triacetate membranes at 2 bar. In addition, TDA1-APAF polyimide had a N2/CH4 selectivity of 2.3, thereby making it potentially possible to bring natural gas with low, but unacceptable nitrogen content to pipeline specification. Gas mixture permeation experiments with a 1:1 CO2/CH4 feed mixture demonstrated higher mixed- than pure-gas selectivity and plasticization resistance up to 30 bar. These results suggest that intrinsically microporous hydroxyl-functionalized triptycene-based polyimides are promising candidate membrane materials for removal of CO2 from natural gas and hydrogen purification in petrochemical refinery applications.

  2. Comparative study of all-printed polyimide humidity sensors with single- and multiwalled carbon nanotube gas-permeable top electrodes

    Science.gov (United States)

    Itoh, Eiji; Yuan, Zihan

    2017-05-01

    We have developed printed capacitive humidity sensors with highly gas permeable carbon nanotube top electrodes using solution techniques. The hydrophobic, porous multiwalled carbon nanotube (MWCNT) network was suitable for gas permeation, and the response of the capacitive humidity sensors was faster than that of a device with a single-walled carbon nanotube (SWCNT) top electrode. The newly developed measurement system consisting of a small measurement chamber, a computer-controlled high-speed solenoid valve, and a mass-flow controller enabled us to vary the ambient relative humidity within 0.1 s. A comparative study of the devices consisting of a 1.1-µm-thick partially fluorinated polyimide dielectric layer and an MWCNT or SWCNT top electrode revealed that the rise time (humidification process) of the device with MWCNTs (0.49 s) in the transient measurement was almost 3 times shorter than that with SWCNTs (1.48 s) owing to the hydrophobic surface of the MWCNTs. A much larger difference was observed during the drying process (recovery time) probably owing to the hydrophilic parts of the SWCNT surface. It was revealed that the response time was almost proportional to the square of the thickness of the polyimide dielectric layer, d, and the sensitivity was inversely proportional to d. The rise time decreased to 0.15 s and a sensitivity per unit area of 12.1 pF %RH-1 cm-2 was obtained in a device with 0.6-µm-thick polyimide and MWCNT top electrodes. This value is suitable for use in high-speed humidity sensors to realize a real-time humidity and breath-sensing measurement system.

  3. Optical anisotropy of polyimide and polymethacrylate containing photocrosslinkable chalcone group in the side chain under irradiation of a linearly polarized UV light

    Energy Technology Data Exchange (ETDEWEB)

    Choi, Dong Hoon; Cha, Young Kwan [Kyunghee Univ., Yongin (Korea, Republic of)

    2002-03-01

    Photocrosslinkable soluble polyimide and polymethacrylate compound were synthesized for studying the optically induced anisotropy of the thin films. Chalcone group was introduced into the side chain unit of two polymers. We observed a photodimerization behavior between the double bonds in the chalcone group and an optical anisotropy of these materials by irradiation of a linearly polarized UV light (LPL). Optical anisotropy of the thin film was also investigated by using polarized UV absorption spectroscopy.The dynamic property of optical anisotropy in photoreactive polyimide was compared to that in polymethacrylate containing chalcone group in the side chain.

  4. Optical anisotropy of polyimide and polymethacrylate containing photocrosslinkable chalcone group in the side chain under irradiation of a linearly polarized UV light

    CERN Document Server

    Choi, D H

    2002-01-01

    Photocrosslinkable soluble polyimide and polymethacrylate compound were synthesized for studying the optically induced anisotropy of the thin films. Chalcone group was introduced into the side chain unit of two polymers. We observed a photodimerization behavior between the double bonds in the chalcone group and an optical anisotropy of these materials by irradiation of a linearly polarized UV light (LPL). Optical anisotropy of the thin film was also investigated by using polarized UV absorption spectroscopy.The dynamic property of optical anisotropy in photoreactive polyimide was compared to that in polymethacrylate containing chalcone group in the side chain.

  5. Equation-of-state measurements of polyimide at pressures up to 5.8 TPa using low-density foam with laser-driven shock waves.

    Science.gov (United States)

    Takamatsu, K; Ozaki, N; Tanaka, K A; Ono, T; Nagai, K; Nakai, M; Watari, T; Sunahara, A; Nakano, M; Kataoka, T; Takenaka, H; Yoshida, M; Kondo, K; Yamanaka, T

    2003-05-01

    The laser-driven equation-of-state (EOS) experiments for polyimide are presented. The experiments were performed with emission measurements from the rear sides of shocked targets at up to a laser intensity of 10(14) W/cm(2) or higher with 351 nm wavelength and 2.5 ns duration. Polyimide Hugoniot data were obtained up to 0.6 TPa with good accuracy. Applying low-density foam ablator to the EOS unknown material, we also obtained the data at a highest pressure of 5.8 TPa in the nonmetal materials. Those data were in agreement with the theoretical curves.

  6. Characterization of a prototype batch of long polyimide cables designed for fast data transmission on ATLAS ITk strip staves

    CERN Document Server

    Dopke, Jens; The ATLAS collaboration; Sawyer, Craig; Sullivan, Stephanie W

    2018-01-01

    The silicon-strip system in the ATLAS ITk detector has individual sensor modules mounted on staves to provide integrated solution for mechanical support, power, cooling, and data transmission. The data and power are transmitted to individual modules on polyimide tapes placed on thermo-mechanical stave cores. The 1.4 m long tapes transmit module data at the rate of 640 Mbps, along with providing several multi-drop clock and command links, and power lines. The first batch of 25 tapes has been produced. We characterized the line impedance and its variation across the batch, examined the tape cross-section, and assessed the variation between design and fabrication.

  7. Electro-active Polymer Actuator Based on Sulfonated Polyimide with Highly Conductive Silver Electrodes Via Self-metallization.

    Science.gov (United States)

    Song, Jiangxuan; Jeon, Jin-Han; Oh, Il-Kwon; Park, K C

    2011-10-04

    We report here a facile synthesis of high performance electro-active polymer actuator based on a sulfonated polyimide with well-defined silver electrodes via self-metallization. The proposed method greatly reduces fabrication time and cost, and obviates a cation exchange process required in the fabrication of ionic polymer-metal composite actuators. Also, the self-metallized silver electrodes exhibit outstanding metal-polymer adhesion with high conductivity, resulting in substantially larger tip displacements compared with Nafion-based actuators. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Polyimide/silica hybrids via the sol-gel route: High performance materials for the new technological challenges

    Directory of Open Access Journals (Sweden)

    2009-07-01

    Full Text Available The present review article describes in detail the state-of-the-art of organic-inorganic hybrid materials based on polyimide/silica components. The article is divided in three parts. In the first the basic processing route for the preparation of these systems is described, i.e. the sol-gel technique, along with the strategies developed to control the final morphology. In the second part the curing characteristics, the dynamic-mechanical and the mechanical and fracture properties of hybrids with different morphologies are reviewed. Finally, the more technologically relevant applications devised for these high performance materials are discussed.

  9. Fabrication of Polyimide-Matrix/Carbon and Boron-Fiber Tape

    Science.gov (United States)

    Belvin, Harry L.; Cano, Roberto J.; Treasure, Monte; Shahood, Thomas W.

    2007-01-01

    The term HYCARB denotes a hybrid composite of polyimide matrices reinforced with carbon and boron fibers. HYCARB and an improved process for fabricating dry HYCARB tapes have been invented in a continuing effort to develop lightweight, strong composite materials for aerospace vehicles. Like other composite tapes in this line of development, HYCARB tapes are intended to be used to build up laminated structures having possibly complex shapes by means of automated tow placement (ATP) - a process in which a computer-controlled multiaxis machine lays down prepreg tape or tows. The special significance of the present process for making dry HYCARB for ATP is that it contributes to the reduction of the overall cost of manufacturing boron-reinforced composite-material structures while making it possible to realize increased compression strengths. The present process for making HYCARB tapes incorporates a "wet to dry" process developed previously at Langley Research Center. In the "wet to dry" process, a flattened bundle of carbon fiber tows, pulled along a continuous production line between pairs of rollers, is impregnated with a solution of a poly(amide acid) in N-methyl-2-pyrrolidinone (NMP), then most of the NMP is removed by evaporation in hot air. In the present case, the polyamide acid is, more specifically, that of LaRC. IAX (or equivalent) thermoplastic polyimide, and the fibers are, more specifically, Manganite IM7 (or equivalent) polyacrylonitrile- based carbon filaments that have a diameter of 5.2 m and are supplied in 12,000-filament tows. The present process stands in contrast to a prior process in which HYCARB tape was made by pressing boron fibers into the face of a wet carbon-fiber/ poly(amide acid) prepreg tape . that is, a prepreg tape from which the NMP solvent had not been removed. In the present process, one or more layer(s) of side-by-side boron fibers are pressed between dry prepreg tapes that have been prepared by the aforementioned gwet to dry h

  10. Microscopic degradation mechanism of polyimide film caused by surface discharge under bipolar continuous square impulse voltage

    Science.gov (United States)

    Luo, Yang; Wu, Guang-Ning; Liu, Ji-Wu; Peng, Jia; Gao, Guo-Qiang; Zhu, Guang-Ya; Wang, Peng; Cao, Kai-Jiang

    2014-02-01

    Polyimide (PI) film is an important type of insulating material used in inverter-fed motors. Partial discharge (PD) under a sequence of high-frequency square impulses is one of the key factors that lead to premature failures in insulation systems of inverter-fed motors. In order to explore the damage mechanism of PI film caused by discharge, an aging system of surface discharge under bipolar continuous square impulse voltage (BCSIV) is designed based on the ASTM 2275 01 standard and the electrical aging tests of PI film samples are performed above the partial discharge inception voltage (PDIV). The chemical bonds of PI polymer chains are analyzed through Fourier transform infrared spectroscopy (FTIR) and the dielectric properties of unaged and aged PI samples are investigated by LCR testers HIOKI 3532-50. Finally, the micro-morphology and micro-structure changes of PI film samples are observed through scanning electron microscopy (SEM). The results show that the physical and chemical effects of discharge cut off the chemical bonds of PI polymer chains. The fractures of ether bond (C—O—C) and imide ring (C—N—C) on the backbone of a PI polymer chain leads to the decrease of molecular weight, which results in the degradation of PI polymers and the generation of new chemical groups and materials, like carboxylic acid, ketone, aldehydes, etc. The variation of microscopic structure of PI polymers can change the orientation ability of polarizable units when the samples are under an AC electric field, which would cause the dielectric constant ɛ to increase and dielectric loss tan δ to decrease. The SEM images show that the degradation path of PI film is initiated from the surface and then gradually extends to the interior with continuous aging. The injection charge could result in the PI macromolecular chain degradation and increase the trap density in the PI polymer bulk.

  11. Biomimetic electroactive polyimide with rose petal-like surface structure for anticorrosive coating application

    Directory of Open Access Journals (Sweden)

    W. F. Ji

    2017-08-01

    Full Text Available In this work, an electroactive polyimide (EPI coating with biomimetic surface structure of rose petal used in anticorrosion application was first presented. First of all, amino-capped aniline trimer (ACAT was synthesized by oxidative coupling reaction, followed by characterized through Fourier transform infrared spectroscooy (FTIR, liquid chromatography – mass spcerometry (LC-MS and proton nuclear magnetic resonance (1H-NMR spectroscopy. Subsequently, as-prepared ACAT was reacted with isopropylidenediphenoxy-bis(phthalic anhydride (BPADA to give electroactive poly(amic acid (EPAA. Moreover, poly(dimethylsiloxane (PDMS was used to be the soft negative template for pattern transfer from the surface of rose petal to the surface of polymer coating. The EPI coating with biomimetic structure was obtained by programmed heating the EPAA slurry casting onto the negative PDMS template. The anticorrosive performance of as-prepared biomimetic EPI coating was demonstrated by performing a series of electrochemical measurements (Tafel, Nyquist, and Bode plots upon cold-rolled steel (CRS electrode in a NaCl aqueous solution. It should be noted that the biomimetic EPI coating with rose petal-like structure was found to exhibit better anticorrosion than that of EPI without biomimetic structure. Moreover, the surface contact angle of water droplets for biomimetic EPI coating was found to be ~150°, which is significantly higher than that of EPI coating with smooth structure (~87°, indicating that the EPI coating with biomimetic structure reveals better hydrophobicity. The apparent mechanism for improved anticorrosive properties is twofold: (1 the biomimetic structure of EPI coating can repel water droplets. (2 electroactivity of EPI coating promotes the formation of densely passive layer of metal oxide on metallic surface.

  12. Carbonization of polyimide by swift heavy ion irradiations: Effects of stopping power and velocity

    Energy Technology Data Exchange (ETDEWEB)

    Costantini, J.-M. [DMN/SRMA, CEA/SACLAY, F-91191 Gif-sur-Yvette Cedex (France)]. E-mail: jean-marc.costantini@cea.fr; Salvetat, J.-P. [CRMD, CNRS, 1B rue de la Ferollerie, F-45071, Orleans Cedex 2 (France); Couvreur, F. [DMN/SEMI, CEA/SACLAY, F-91191 Gif-sur-Yvette Cedex (France); Bouffard, S. [CIRIL, CEA-CNRS-ISMRA, rue Claude Bloch, BP 5133, F-14070 Caen Cedex 5 (France)

    2005-07-01

    We have studied the carbonization of polyimide Kapton-H (pyromellitic dianhydride-oxydialinine, PMDA-ODA) thin films under heavy ion irradiations in the electronic slowing down regime. Irradiations were performed with 650-MeV Ni, 843-MeV Xe, 2.6-GeV Xe, 1.1-GeV Ta, and 707-MeV Pb ions that were transmitted through the polymer films with the electronic stopping power ranging between 3.5 and 17 keV nm{sup -1}. Room-temperature ac/dc electrical conductivity measurements, together with ESR, UV-visible optical absorption, and micro-Raman spectroscopy were used to characterize the irradiated films. These new data are compared to our previous results obtained with heavy ion irradiations in the 1-MeV uma{sup -1} energy range. At the largest fluences near 10{sup 13} cm{sup -2} the resulting carbonaceous material is found to be 8-9 orders of magnitude less conducting than with the slower ions. Such large dc-conductivity deviations are confirmed by the spin-lattice relaxation times deduced from the ESR line saturation measurements that are two orders of magnitude longer with the swift ions than with the slower ions. The evolution of the Raman spectra also shows that the appearance of a conjugated sp{sup 2}-bonded structure is delayed with respect to the slow ion case, and is probably incomplete in the observed fluence range. The yield of paramagnetic centers is found to decrease when the ion energy increases. This is interpreted by an ion-velocity effect on damage due to a dilution of the deposited energy in the ion tracks. We think that this also induces a smaller sp{sup 2} cluster density impeding charge transport in the carbonaceous material.

  13. Peculiarities of the initial stages of carbonization processes in polyimide-based nanocomposite films containing carbon nanoparticles

    Directory of Open Access Journals (Sweden)

    I.V. Gofman

    2015-12-01

    Full Text Available Carbonization of the polyimide-based composite films containing carbon nanoparticles, namely nanofibers and nanocones/disks, in the temperature range 500–550°C was studied and the kinetics of the initial stage of carbonization and the effect of the filler on the mechanical properties of the carbonized films were evaluated. Two polyimides (PIs characterized by different macrochains’ rigidity and different degrees of ordering of the intermolecular structure were used. The character of the nanofiller’s action on the kinetics of the carbonization process depends on the heating rate. In this work, the intensity of the destruction of the PI matrix of the composite films was shown to be slightly higher than that of films of the same polymers with no filler. The introduction of the carbon nanoparticles into both PIs provokes the increase in the ultimate deformation values of the partially carbonized films, while the carbonization of the unfilled PI films yields the brittle materials. The Young’s modulus values of the materials based on the rigid-rod PI do not increase after carbonization, while those for compositions based on the PI with semi-rigid chains increase substantially. Carbon nanocones/disks are characterized by the best compatibility with matrix PIs in comparison with carbon nanofibers.

  14. A Filmy Black-Phosphorus Polyimide Saturable Absorber for Q-Switched Operation in an Erbium-Doped Fiber Laser

    Directory of Open Access Journals (Sweden)

    Tianxian Feng

    2016-11-01

    Full Text Available We demonstrate an erbium-doped fiber laser passively Q-switched by a black-phosphorus polyimide film. The multi-layer black-phosphorus (BP nanosheets were prepared via a liquid exfoliation approach exploiting N-methylpyrrolidone as the dispersion liquid. By mixing the BP nanosheets with polyimide (PI, a piece of BP–PI film was obtained after evaporating the mixture in a petri dish. The BP–PI saturable absorber had a modulation depth of 0.47% and was inserted into an erbium-doped fiber laser to realize passive Q-switched operations. The repetition rate of the Q-switched laser increased from 5.73 kHz to 31.07 kHz when the laser pump was enhanced from 31.78 mW to 231.46 mW. Our results show that PI is an excellent host material to protect BP from oxidation, and the BP–PI film can act as a promising nonlinear optical device for laser applications.

  15. Comparison of in situ polymerization and solution-dispersion techniques in the preparation of Polyimide/Montmorillonite (MMT) Nanocomposites.

    Science.gov (United States)

    Ahmad, Mansor Bin; Gharayebi, Yadollah; Salit, Mohd Sapuan; Hussein, Mohd Zobir; Shameli, Kamyar

    2011-01-01

    In this paper, Polyimide/Montmorillonite Nanocomposites (PI/MMT NCs), based on aromatic diamine (4-Aminophenyl sulfone) (APS) and aromatic dianhydride (3,3',4,4'-benzophenonetetracarboxylic dianhydride) (BTDA) were prepared using in situ polymerization and solution-dispersion techniques. The prepared PI/MMT NCs films were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). The XRD results showed that at the content of 1.0 wt % Organo Montmorillonite (OMMT) for two techniques and 3.0 wt % OMMT for the in situ polymerization technique, the OMMT was well-intercalated, exfoliated and dispersed into polyimide matrix. The OMMT agglomerated when its amount exceeded 10 wt % and 3.0 wt % for solution-dispersion and in situ polymerization techniques respectively. These results were confirmed by the TEM images of the prepared PI/MMT NCs. The TGA thermograms indicated that thermal stability of prepared PI/MMT NCs were increased with the increase of loading that, the effect is higher for the samples prepared by in situ polymerization technique.

  16. Research Update: Polyimide/CaCu3Ti4O12 nanofiber functional hybrid films with improved dielectric properties

    Directory of Open Access Journals (Sweden)

    Yang Yang

    2013-11-01

    Full Text Available This work reports the excellent dielectric properties of polyimide (PI embedded with CaCu3Ti4O12 (CCTO nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz–1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67 is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

  17. Improving the Conductivity of Sulfonated Polyimides as Proton Exchange Membranes by Doping of a Protic Ionic Liquid

    Directory of Open Access Journals (Sweden)

    Bor-Kuan Chen

    2014-10-01

    Full Text Available Proton exchange membranes (PEMs are a key component of a proton exchange membrane fuel cell. Sulfonated polyimides (SPIs were doped by protic ionic liquid (PIL to prepare composite PEMs with substantially improved conductivity. SPIs were synthesized from diamine, 2,2-bis[4-(4-amino-phenoxyphenyl]propane (BAPP, sulfonated diamine, 4,4'-diamino diphenyl ether-2,2'-disulfonic acid (ODADS and aromatic anhydride. BAPP improved the mechanical and thermal properties of SPIs, while ODADS enhanced conductivity. A PIL, 1-vinylimidazolium trifluoromethane-sulfonate ([VIm][OTf], was utilized. [VIm][OTf] offered better conductivity, which can be attributed to its vinyl chemical structure attached to an imidazolium ring that contributed to ionomer-PIL interactions. We prepared sulfonated polyimide/ionic liquid (SPI/IL composite PEMs using 50 wt% [VIm][OTf] with a conductivity of 7.17 mS/cm at 100 °C, and in an anhydrous condition, 3,3',4,4'-diphenyl sulfone tetracarboxylic dianhydride (DSDA was used in the synthesis of SPIs, leading to several hundred-times improvement in conductivity compared to pristine SPIs.

  18. Dielectric properties of polyimide/SiO{sub 2} hollow spheres composite films with ultralow dielectric constant

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Zhou, E-mail: hongzhou@hrbust.edu.cn [School of Materials Science and Engineering, Harbin University of Science and Technology, Harbin 150040 (China); Key Laboratory of Engineering Dielectrics and its Application Ministry of Education, Harbin University of Science and Technology, Harbin 150040 (China); Dongyang, Wei; Yong, Fan; Hao, Chen; Yusen, Yang; Jiaojiao, Yu; Liguo, Jin [School of Materials Science and Engineering, Harbin University of Science and Technology, Harbin 150040 (China)

    2016-01-15

    Highlights: • Polyimide/silica hollow spheres films with ultralow dielectric constant were obtained. • Smaller nanoscale silica hollow spheres were uniformly distributed in the polymer matrix. • Air volume content in the hybrid composite films was calculated. - Abstract: In this study, polyimide (PI)/SiO{sub 2} hollow spheres (SHS) composite films were prepared by incorporating different contents of 20–50 nm sized SHS into PI derived from pyromellitic dianhydride (PMDA) and 4,4′-oxydianiline (ODA). The dielectric constant of the PI films was reduced from 3.41 to 2.09 for a hybrid film containing 10 wt.% SHS. When the content of SHS was >10 wt.%, the dielectric constant increased due to the aggregation of the SHS. The ultralow dielectric constant could be attributed to the presence of air voids within the structure of SHS itself as well as the air between the PI matrix and the SHS. Furthermore, the air content in the PI/SHS composite films was calculated by Bruggeman's Effective Medium Theory. The PI/SHS composite films with ultralow dielectric constant and low dielectric loss can be considered as good candidate for advanced dielectric materials.

  19. Dynamic load capacities of graphite fiber: Polyimide composites in oscillating plain bearings to 340 C (650 F)

    Science.gov (United States)

    Sliney, H. E.; Jacobson, T. P.; Munson, H. E.

    1975-01-01

    Load capacities were determined for plain spherical bearings with self-lubricating spherical elements of graphite-fiber-reinforced-polyimide, and for plain cylindrical bearings with thin-wall liners of the composite in the bearing bores. Composites consisted of a 1-to-1 weight ratio of graphite fibers and polyimide. Oscillation was at an amplitude of + or - 15 deg at a frequency of 1 hertz. Bearings with composite ball material had a load capacity of approximately 69 MN/sq m (10 000 psi) at room temperature 25 MN/sq m (3600 psi) at 340 C (650 F). Bearings with thin-wall composite liners had much higher load capacities of 280 MN/sq m (40 000 psi) at room temperature amd 240 MN/sq m (35 000 psi) at 320 C (600 F). Friction coefficients were in the range of 0.12 to 0.19. The addition of 10 wt.% graphite fluoride solid lubricant to the composition of the thin-wall liners reduced friction coefficients into the range of 0.10 to 0.12.

  20. Synthesis and properties of reprocessable sulfonated polyimides cross-linked via acid stimulation for use as proton exchange membranes

    Science.gov (United States)

    Zhang, Boping; Ni, Jiangpeng; Xiang, Xiongzhi; Wang, Lei; Chen, Yongming

    2017-01-01

    Cross-linked sulfonated polyimides are one of the most promising materials for proton exchange membrane (PEM) applications. However, these cross-linked membranes are difficult to reprocess because they are insoluble. In this study, a series of cross-linkable sulfonated polyimides with flexible pendant alkyl side chains containing trimethoxysilyl groups is successfully synthesized. The cross-linkable polymers are highly soluble in common solvents and can be used to prepare tough and smooth films. Before the cross-linking reaction is complete, the membranes can be reprocessed, and the recovery rate of the prepared films falls within an acceptable range. The cross-linked membranes are obtained rapidly when the cross-linkable membranes are immersed in an acid solution, yielding a cross-linking density of the gel fraction of greater than 90%. The cross-linked membranes exhibit high proton conductivities and tensile strengths under hydrous conditions. Compared with those of pristine membranes, the oxidative and hydrolytic stabilities of the cross-linked membranes are significantly higher. The CSPI-70 membrane shows considerable power density in a direct methanol fuel cell (DMFC) test. All of these results suggest that the prepared cross-linked membranes have great potential for applications in proton exchange membrane fuel cells.

  1. Pt-free carbon-based fuel cell catalyst prepared from spherical polyimide for enhanced oxygen diffusion

    Science.gov (United States)

    Nabae, Yuta; Nagata, Shinsuke; Hayakawa, Teruaki; Niwa, Hideharu; Harada, Yoshihisa; Oshima, Masaharu; Isoda, Ayano; Matsunaga, Atsushi; Tanaka, Kazuhisa; Aoki, Tsutomu

    2016-01-01

    The development of a non-precious metal (NPM) fuel cell catalyst is extremely important to achieve globalization of polymer electrolyte fuel cells due to the cost and scarcity of platinum. Here, we report on a NPM cathode catalyst prepared by the pyrolysis of spherical polyimide nanoparticles that contain small amounts of Fe additive. 60 nm diameter Fe-containing polyimide nanoparticles were successfully synthesized by the precipitation polymerization of pyromellitic acid dianhydride and 1,3,5-tris(4-aminophenyl)benzene with Fe(acac)3 (acac = acetylacetonate) as an additive. The particles were subsequently carbonized by multistep pyrolysis to obtain the NPM catalyst while retaining the small particle size. The catalyst has good performance and promising durability for fuel cell applications. The fuel cell performance under a 0.2 MPa air atmosphere at 80 °C of 1.0 A cm−2 at 0.46 V is especially remarkable and better than that previously reported. PMID:26987682

  2. Liquid density analysis of sucrose and alcoholic beverages using polyimide guided Love-mode acoustic wave sensors

    Science.gov (United States)

    Turton, Andrew; Bhattacharyya, Debabrata; Wood, David

    2006-02-01

    A liquid density sensor using Love-mode acoustic waves has been developed which is suitable for use in the food and drinks industries. The sensor has an open flat surface allowing immersion into a sample and simple cleaning. A polyimide waveguide layer allows cheap and simple fabrication combined with a robust chemically resistant surface. The low shear modulus of polyimide allows thin guiding layers giving a high sensitivity. A dual structure with a smooth reference device exhibiting viscous coupling with the wave, and a patterned sense area to trap the liquid causing mass loading, allows discrimination of the liquid density from the square root of the density-viscosity product (ρη)0.5. Frequency shift and insertion loss change were proportional to (ρη)0.5 with a non-linear response due to the non-Newtonian nature of viscous liquids at high frequencies. Measurements were made with sucrose solutions up to 50% and different alcoholic drinks. A maximum sensitivity of 0.13 µg cm-3 Hz-1 was achieved, with a linear frequency response to density. This is the highest liquid density sensitivity obtained for acoustic mode sensors to the best of our knowledge.

  3. Development of a Mechatronic Syringe Pump to Control Fluid Flow in a Microfluidic Device Based on Polyimide Film

    Science.gov (United States)

    Sek Tee, Kian; Sharil Saripan, Muhammad; Yap, Hiung Yin; Fhong Soon, Chin

    2017-08-01

    With the advancement in microfluidic technology, fluid flow control for syringe pump is always essential. In this paper, a mechatronic syringe pump will be developed and customized to control the fluid flow in a poly-dimethylsiloxane (PDMS) microfluidic device based on a polyimide laminating film. The syringe pump is designed to drive fluid with flow rates of 100 and 1000 μl/min which intended to drive continuous fluid in a polyimide based microfluidic device. The electronic system consists of an Arduino microcontroller board and a uni-polar stepper motor. In the system, the uni-polar stepper motor was coupled to a linear slider attached to the plunger of a syringe pump. As the motor rotates, the plunger pumps the liquid out of the syringe. The accuracy of the fluid flow rate was determined by adjusting the number of micro-step/revolution to drive the stepper motor to infuse fluid into the microfluidic device. With the precise control of the electronic system, the syringe pump could accurately inject fluid volume at 100 and 1000 μl/min into a microfluidic device.

  4. Proton flux effects and prediction on the free radicals behavior of polyimide in vacuum using EPR measurements in ambient

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Chengyue [Physics Department, Harbin Institute of Technology, Harbin 150001 (China); National Key Lab of Materials Behaviors and Evaluation Technology in Space Environments, Harbin Institute of Technology, Harbin 150001 (China); Wu, Yiyong, E-mail: wuyiyong@hit.edu.cn [National Key Lab of Materials Behaviors and Evaluation Technology in Space Environments, Harbin Institute of Technology, Harbin 150001 (China); Xiao, Jingdong [National Key Lab of Materials Behaviors and Evaluation Technology in Space Environments, Harbin Institute of Technology, Harbin 150001 (China); Yu, Sui [Physics Department, Harbin Institute of Technology, Harbin 150001 (China); Yi, Zhong; Shen, Zicai [Chinese Academy of Sciences, Beijing 100029 (China); Wang, Li [Qian Xuesen Laboratory of Space Technology, Beijing 100029 (China); Wang, Yi [Lanzhou Institute of Physics, CAST, Lanzhou 730000 (China)

    2017-04-15

    Irradiation flux is an important parameter to the material irradiation damage investigation, for space material irradiation damage evaluation and the accelerated ground-based test, the irradiation flux effects cannot be ignored. In this paper, the polyimide was set as the research object, the irradiation flux effect and mechanism are investigated by the means of electron paramagnetic resonance test, and based on the free radical dynamic analysis, the dynamics mode of free radical population in vacumm can be established as a function of irradiation time (or proton irradiation flux). The results show that the free radical anneal process in vacuum follows the exponential mode, and the characteristic time constant τ{sub radical-vacuum} is about 1.9 h. Furthermore, a simplified method is proposed with the investigation of the free radical behavior of the irradiated surface modification polyimide (TiO{sub 2}/PI), and the characteristic time constant τ{sub bulk} is 1.9 h, which is almost the same to the value of τ{sub radical-vacuum}.

  5. Using wind turbines in sky scrapers to develop the stable ...

    African Journals Online (AJOL)

    ... therefore to protect the natural sources, reduction of environmental pollution and reduction of energy consumption, supplying the wind turbine has play the important role to produce wind energy and changing it to mechanical energy and also electricity to fulfill the stable development in the building section, so because in ...

  6. Epoxy/Glass and Polyimide (LaRC(TradeMark) PETI-8)/Carbon Fiber Metal Laminates Made by the VARTM Process

    Science.gov (United States)

    Cano, Roberto J.; Loos, Alfred C.; Jensen, Brian J.; Britton, Sean M.; Tuncol, Goker; Long, Kai

    2010-01-01

    Recent work at NASA Langley Research Center (LaRC) has concentrated on developing new polyimide resin systems for advanced aerospace applications that can be processed without the use of an autoclave. Polyimide composites are very attractive for applications that require a high strength to weight ratio and thermal stability. Vacuum assisted resin transfer molding (VARTM) has shown the potential to reduce the manufacturing cost of composite structures. Fiber metal laminates (FML) made via this process with aluminum, glass fabric, and epoxy resins have been previously fabricated at LaRC. In this work, the VARTM process has been refined for epoxy/glass FMLs and extended to the fabrication of FM Ls with titanium/carbon fabric layers and a polyimide system developed at NASA, LARC(TradeMark) PETI-8. Resin flow pathways were introduced into the titanium foils to aid the infiltration of the polyimide resin. Injection temperatures in the range of 250-280 C were required to achieve the necessary VARTM viscosities (<10 Poise). Laminate quality and initial mechanical properties will be presented.

  7. Synthesis and characterization of soluble, blue-fluorescent polyamides and polyimides containing substituted p-terphenyl as well as long aliphatic segments in the main chain

    NARCIS (Netherlands)

    Mikroyannidis, JA; Tsivgoulis, GM

    1999-01-01

    A novel class of semiflexible polyamides and polyimides bearing substituted p-terphenyl as well as long aliphatic segments in the main chain were synthesized through pyrylium salts. Characterization of polymers was accomplished by inherent viscosity, elemental analysis, FT-IR, NMR, UV-vis

  8. Effect of spinning conditions on the structure and the gas permeation properties of high flux polyethersulfone-polyimide blend hollow fibers

    NARCIS (Netherlands)

    Kapantaidakis, G.; Koops, G.H.; Wessling, Matthias

    2002-01-01

    In this work, the effects of major spinning parameters, such as: polymer concentration, air gap distance, bore fluid composition, and take-up velocity on the structure and the permeation properties of polyethersulfone-polyimide gas separation hollow fibers are discussed in detail. It is shown that a

  9. Changes of the Electrical and Optical Character of Polyimide Films (and the Chemistry that Drives Them) Due to Exposure to High Energy GEO-like Electrons

    Science.gov (United States)

    2015-10-18

    electrical conduction of aluminized polyimide film after simulated aging in a GEO-like electron environment. We correlate these data with the chemical...and D. Yang, "Damage effect of keV proton irradiation on aluminized Kapton film," Radiation Physics and Chemistry, vol. 77, pp. 482-489, 2008. [21] T

  10. Stable Boundary Layer Education (STABLE) Final Campaign Summary

    Energy Technology Data Exchange (ETDEWEB)

    Turner, David D. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

    2016-03-01

    The properties of, and the processes that occur in, the nocturnal stable boundary layer are not well understood, making it difficult to represent adequately in numerical models. The nocturnal boundary layer often is characterized by a temperature inversion and, in the Southern Great Plains region, a low-level jet. To advance our understanding of the nocturnal stable boundary layer, high temporal and vertical resolution data on the temperature and wind properties are needed, along with both large-eddy simulation and cloud-resolving modeling.

  11. Multi-step surface functionalization of polyimide based evanescent wave photonic biosensors and application for DNA hybridization by Mach-Zehnder interferometer

    Energy Technology Data Exchange (ETDEWEB)

    Melnik, Eva [Health and Environment Department, Nano Systems, AIT Austrian Institute of Technology GmbH, Donau-City-Strasse 1, 1220 Vienna (Austria); Department of Analytical Chemistry, University of Vienna, Waehringer Strasse 38, 1090 Vienna (Austria); Bruck, Roman [Health and Environment Department, Nano Systems, AIT Austrian Institute of Technology GmbH, Donau-City-Strasse 1, 1220 Vienna (Austria); Hainberger, Rainer, E-mail: rainer.hainberger@ait.ac.at [Health and Environment Department, Nano Systems, AIT Austrian Institute of Technology GmbH, Donau-City-Strasse 1, 1220 Vienna (Austria); Laemmerhofer, Michael, E-mail: michael.laemmerhofer@univie.ac.at [Department of Analytical Chemistry, University of Vienna, Waehringer Strasse 38, 1090 Vienna (Austria)

    2011-08-12

    Highlights: {yields} We realize a biosensing platform for polyimide evanescent photonic wave sensors. {yields} We show that the surface functionalization via silanisation and biotinylation followed by streptavidin immobilization do not destroy or damage the thin polyimide film. {yields} A highly dense streptavidin layer enables the immobilisation of biotinylated ligands such as biotinylated ssDNA for the selective measurement of DNA hybridization. - Abstract: The process of surface functionalization involving silanization, biotinylation and streptavidin bonding as platform for biospecific ligand immobilization was optimized for thin film polyimide spin-coated silicon wafers, of which the polyimide film serves as a wave guiding layer in evanescent wave photonic biosensors. This type of optical sensors make great demands on the materials involved as well as on the layer properties, such as the optical quality, the layer thickness and the surface roughness. In this work we realized the binding of a 3-mercaptopropyl trimethoxysilane on an oxygen plasma activated polyimide surface followed by subsequent derivatization of the reactive thiol groups with maleimide-PEG{sub 2}-biotin and immobilization of streptavidin. The progress of the functionalization was monitored by using different fluorescence labels for optimization of the chemical derivatization steps. Further, X-ray photoelectron spectroscopy and atomic force microscopy were utilized for the characterization of the modified surface. These established analytical methods allowed to derive information like chemical composition of the surface, surface coverage with immobilized streptavidin, as well as parameters of the surface roughness. The proposed functionalization protocol furnished a surface density of 144 fmol mm{sup -2} streptavidin with good reproducibility (13.9% RSD, n = 10) and without inflicted damage to the surface. This surface modification was applied to polyimide based Mach-Zehnder interferometer

  12. Environmentally stable picosecond fibre laser with broad tuning range

    OpenAIRE

    Traynor, N.J.; Chen, Z. J.; de Porta, J.; Minelly, J. D.; Grudinin, A. B.

    1997-01-01

    We demonstrate a robust, mode-locked, tunable Yb doped fibre laser. The use of dual mode-locked and Q-switched operation in a passively mode-locked configuration allows us to generate 5 ps pulses with a peak power of 750 W at a repetition rate of 100 MHz

  13. Environmentally stable/self-powered ultraviolet photodetectors with high sensitivity

    Science.gov (United States)

    Yang, Shengxue; Tongay, Sefaattin; Li, Shu-Shen; Xia, Jian-Bai; Wu, Junqiao; Li, Jingbo

    2013-09-01

    Here, we demonstrate self-powered ultraviolet photodetectors that are capable of generating opposite current flow when illuminated at different wavelengths. The photodetectors are composed of n-ZnO/Polyaniline (PANI) p-n and PANI/ZnGa2O4 type-II heterojunctions and operate without any need for external power source. Devices display superior stability in ambient conditions within months. Results provide opportunities for developing devices for optical recognition.

  14. Environmental effects on the stable carbon and oxygen isotopic ...

    African Journals Online (AJOL)

    USER

    2010-08-16

    Aug 16, 2010 ... In addition, the report from Thailand Meteoro- logical Department asserts that there was a very heavy rainfall with severe floods in Thailand after July 5 to. August 2000 when the maximum rainfall was recorded at. 343.8 mm for 24 h in Trat Province of eastern Thailand on August 31, 2000. We suspect that ...

  15. Environmental effects on the stable carbon and oxygen isotopic ...

    African Journals Online (AJOL)

    The X-radiograph of the vertical section of the Porites coral skeleton was examined and three pairs of density bandings including intermediate bandings were observed in one year, suggesting that additional factors other than sea surface temperature (SST) were associated during the process of band formation.

  16. Environmental effects on the stable carbon and oxygen isotopic ...

    African Journals Online (AJOL)

    USER

    2010-08-16

    Table 1). Sample preparation and analytical methods. A slab (~5 mm ..... deutérium, oxygène-18, hélium-3 et tritium, á l′étude de la circulation de la Mer Rouge. Oceanol. Acta. 12: 165-174. Brown BE, Le Tissier MDA, Howard ...

  17. Quantitative scanning thermal microscopy of graphene devices on flexible polyimide substrates

    Science.gov (United States)

    Sadeghi, Mir Mohammad; Park, Saungeun; Huang, Yu; Akinwande, Deji; Yao, Zhen; Murthy, Jayathi; Shi, Li

    2016-06-01

    A triple-scan scanning thermal microscopy (SThM) method and a zero-heat flux laser-heated SThM technique are investigated for quantitative thermal imaging of flexible graphene devices. A similar local tip-sample thermal resistance is observed on both the graphene and metal areas of the sample, and is attributed to the presence of a polymer residue layer on the sample surface and a liquid meniscus at the tip-sample junction. In addition, it is found that the tip-sample thermal resistance is insensitive to the temperature until it begins to increase as the temperature increases to 80 °C and exhibits an abrupt increase at 110 °C because of evaporation of the liquid meniscus at the tip-sample junction. Moreover, the variation in the tip-sample thermal resistance due to surface roughness is within the experimental tolerance except at areas with roughness height exceeding tens of nanometers. Because of the low thermal conductivity of the flexible polyimide substrate, the SThM measurements have found that the temperature rise in flexible graphene devices is more than one order of magnitude higher than those reported for graphene devices fabricated on a silicon substrate with comparable dimensions and power density. Unlike a graphene device on a silicon substrate where the majority of the electrical heating in the graphene device is conducted vertically through the thin silicon dioxide dielectric layer to the high-thermal conductivity silicon substrate, lateral heat spreading is important in the flexible graphene devices, as shown by the observed decrease in the average temperature rise normalized by the power density with decreasing graphene channel length from about 30 μm to 10 μm. However, it is shown by numerical heat transfer analysis that this trend is mainly caused by the size scaling of the thermal spreading resistance of the polymer substrate instead of lateral heat spreading by the graphene. In addition, thermoelectric effects are found to be negligible

  18. Preparation and properties of in situ amino-functionalized graphene oxide/polyimide composite films

    Science.gov (United States)

    Lu, Yunhua; Hao, Jican; Xiao, Guoyong; Chen, Lin; Wang, Tonghua; Hu, Zhizhi

    2017-11-01

    The pure light-colored and transparent polyimide (PI) film was prepared from aromatic dianhydride 4,4‧-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and diamine 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene (6FAPB) in the solvent of DMAc via two-step method. Graphene oxide (GO) was in situ grafted with 6FAPB and directly used as a functional inorganic nanofiller to further synthesize poly(amic acid) (PAA)/GO solution. Then, PI/GO composite films with different loadings of GO were prepared by the thermal imidization. The mechanical, thermal, optical, electrical, surface properties, and electrochemical behavior were characterized. The FTIR and XPS results indicate that amino groups can be successfully grafted on the surface of GO. The tensile strength and Young's modulus of the PI-1.0%GO composite film were increased to 118.4 MPa and 2.91 GPa, respectively, which was an approximate improvement of 30.8% and 39.9% compared with pure PI film. These PI/GO composites showed around 256 °C for the glass transition temperature, and around 535 °C for the 5% thermal decomposition temperature, respectively. However, the optical transmittance was significantly decreased from 81.5% (pure PI) to 0.8% (PI-1.0%GO). Besides, the electrical conductivity increased from 1.6 × 10-13 S/m (pure PI) to 2.5 × 10-9 S/m (PI-1.0%GO). Furthermore, when the incorporation of GO was 1.0 wt%, an obvious reduction from 1.08% (pure PI) to 0.65% in the water uptake was observed for the PI/GO composite films, and the water surface contact angle raised from 72.5° (pure PI) to 83.5°. The electrochemical behavior showed that the ability of oxygen atom on the imide ring to gain and loss electron was increased due to incorporation of GO. These results indicated that the strong interfacial interaction between GO and PAA as well as uniform dispersion of GO in PI matrix were benefit to improve the mechanical, thermal, electrical properties and so on. The in situ amino-functionalized approach

  19. Residual stress analysis of graphite/polyimide composites using the concept of metallic inclusions

    Science.gov (United States)

    Dragoi, Danut

    The purpose of this thesis is to investigate the use of metal particles (Al, Ag, Nb) embedded between the first and second plies of 6-ply unidirectional and 4-ply 8-harness satin weave cloth carbon/polyimide laminates, as strain sensors for the determination of residual and applied stresses by x-ray diffraction. XRD measurements were made using a Siemens D500 diffractometer with parallel-beam optics a solid state detector and Cu K a radiation. Specimens were subjected to bending loads while irradiated, using a 4-point bending device mounted on the D500 goniometer. Finite Element calculations were performed on a specimen with an isolated spherical particle located at half the distance between neutral axis and the surface of the specimen for the 4-ply laminate and two thirds the distance for the 6-ply laminate. ANSYS v.5.2 was used with tetrahedral Solid92 elements. Eshelby calculations were done using the Eshelby tensor for a spherical inclusion embedded in an infinite homogeneous anisotropic matrix, the known strain matrix for bending and the matrices for thermal expansion of the composite and the metal inclusion. FEM and Eshelby method results were found to be equivalent for an isolated particle in a large volume of matrix, i.e. a volume fraction of filler approaching zero. For XRD measurements, a certain minimum concentration of filler was required in order to have enough diffracted x-ray intensity to obtain measurable peak positions within acceptable limits of errors. For multiple inclusions, the slopes of strains and stresses versus outer pin displacement inside the inclusions do not differ significantly from those in single inclusions, however a remarkable change is in the intercept. This is due to a constant stress-strain field that is added to each particle single solution, because of the multiple inclusion interaction. Strains and stresses obtained by XRD in the embedded particles were sensitive to the residual stresses in the as-cured laminates and

  20. Highly stable six-axis alignment mechanism

    Science.gov (United States)

    Green, Evan; Zheng, Bing; Farinas, Alejandro; Arnone, Dave

    2005-08-01

    One of the major challenges for typical opto-mechanical assemblies is that they require multiple degrees of freedom with large travel (several millimeters) but very small (sub-micron) resolution. After adjustment, assemblies must be stable to a few nanometers to survive environmental and mechanical shock over a lifetime of use. Using parts with engineered mating surfaces, we have developed a low-cost and robust set of components with demonstrated sub-50-nm adjustment resolution and comparable stability after multiple environmental stress events. For this work, we have adopted -30 to +70 C temperature cycling and 10 G (15 ms) half-sine shock as our environmental qualification standards. We apply the methodologies of reliability testing learned for Telcordia qualification of passive fiber optic components to opto-mechanical components and assemblies for capital equipment instruments. Demonstration of sub-50-nm resolution and stability for our developed opto-mechanical components requires a suitable test stand, which we have developed using scanning knife-edge beam profilers and a highly-repeatable kinematic loading base with a built-in reference. We use these test results to develop system error budgets in design and manufacture based on component, assembly, and measurement tolerances. The developed opto-mechanical assemblies have been demonstrated to have sub-50 nm stability in laboratory and field tests.

  1. Pure- and Mixed-Gas Permeation Properties of Highly Selective and Plasticization Resistant Hydroxyl-Diamine-Based 6FDA Polyimides for CO2/CH4 Separation

    KAUST Repository

    Alaslai, Nasser Y.

    2016-01-05

    The effect of hydroxyl functionalization on the m-phenylene diamine moiety of 6FDA dianhydride-based polyimides was investigated for gas separation applications. Pure-gas permeability coefficients of He, H2, N2, O2, CH4, and CO2 were measured at 35 °C and 2 atm. The introduction of hydroxyl groups in the diamine moiety of 6FDA-diaminophenol (DAP) and 6FDA-diamino resorcinol (DAR) polyimides tightened the overall polymer structure due to increased charge transfer complex formation compared to unfunctionalized 6FDA-m-phenylene diamine (mPDA). The BET surface areas based on nitrogen adsorption of 6FDA-DAP (54 m2g−1) and of 6FDA-DAR (45 m2g−1) were ~18% and 32% lower than that of 6FDA-mPDA (66 m2g−1). 6FDA-mPDA had a pure-gas CO2 permeability of 14 Barrer and CO2/CH4 selectivity of 70. The hydroxyl-functionalized polyimides 6FDA-DAP and 6FDA-DAR exhibited very high pure-gas CO2/CH4 selectivities of 92 and 94 with moderate CO2 permeability of 11 and 8 Barrer, respectively. It was demonstrated that hydroxyl-containing polyimide membranes maintained very high CO2/CH4 selectivity (~ 75 at CO2 partial pressure of 10 atm) due to CO2 plasticization resistance when tested under high-pressure mixed-gas conditions. Functionalization with hydroxyl groups may thus be a promising strategy towards attaining highly selective polyimides for economical membrane-based natural gas sweetening.

  2. Modeling of the viscoelastic behavior of a polyimide matrix at elevated temperature

    Science.gov (United States)

    Crochon, Thibaut

    Use of Polymer Matrix Composite Materials (PMCMs) in aircraft engines requires materials able to withstand extreme service conditions, such as elevated temperatures, high mechanical loadings and an oxidative environment. In such an environment, the polymer matrix is likely to exhibit a viscoelastic behavior dependent on the mechanical loading and temperature. In addition, the combined effects of elevated temperature and the environment near the engines are likely to increase physical as well as chemical aging. These various parameters need to be taken into consideration for the designer to be able to predict the material behavior over the service life of the components. The main objective of this thesis was to study the viscoelastic behavior of a high temperature polyimide matrix and develop a constitutive theory able to predict the material behavior for every of service condition. Then, the model had to have to be implemented into commercially available finite-element software such as ABAQUS or ANSYS. Firstly, chemical aging of the material at service temperature was studied. To that end, a thermogravimetric analysis of the matrix was conducted on powder samples in air atmosphere. Two kinds of tests were performed: i) kinetic tests in which powder samples were heated at a constant rate until complete sublimation; ii) isothermal tests in which the samples were maintained at a constant temperature for 24 hours. The first tests were used to develop a degradation model, leading to an excellent fit of the experimental data. Then, the model was used to predict the isothermal data but which much less success, particularly for the lowest temperatures. At those temperatures, the chemical degradation was preceded by an oxidation phase which the model was not designed to predict. Other isothermal degradation tests were also performed on tensile tests samples instead of powders. Those tests were conducted at service temperature for a much longer period of time. The samples

  3. Multivariate Max-Stable Spatial Processes

    KAUST Repository

    Genton, Marc G.

    2014-01-06

    Analysis of spatial extremes is currently based on univariate processes. Max-stable processes allow the spatial dependence of extremes to be modelled and explicitly quantified, they are therefore widely adopted in applications. For a better understanding of extreme events of real processes, such as environmental phenomena, it may be useful to study several spatial variables simultaneously. To this end, we extend some theoretical results and applications of max-stable processes to the multivariate setting to analyze extreme events of several variables observed across space. In particular, we study the maxima of independent replicates of multivariate processes, both in the Gaussian and Student-t cases. Then, we define a Poisson process construction in the multivariate setting and introduce multivariate versions of the Smith Gaussian extremevalue, the Schlather extremal-Gaussian and extremal-t, and the BrownResnick models. Inferential aspects of those models based on composite likelihoods are developed. We present results of various Monte Carlo simulations and of an application to a dataset of summer daily temperature maxima and minima in Oklahoma, U.S.A., highlighting the utility of working with multivariate models in contrast to the univariate case. Based on joint work with Simone Padoan and Huiyan Sang.

  4. Approximation by Penultimate Stable Laws

    NARCIS (Netherlands)

    L.F.M. de Haan (Laurens); L. Peng (Liang); H. Iglesias Pereira

    1997-01-01

    textabstractIn certain cases partial sums of i.i.d. random variables with finite variance are better approximated by a sequence of stable distributions with indices \\\\alpha_n \\\\to 2 than by a normal distribution. We discuss when this happens and how much the convergence rate can be improved by using

  5. Fiber Optic Cable Thermal Preparation to Ensure Stable Operation

    Science.gov (United States)

    Thoames Jr, William J.; Chuska, Rick F.; LaRocca, Frank V.; Switzer, Robert C.; Macmurphy, Shawn L.; Ott, Melanie N.

    2008-01-01

    Fiber optic cables are widely used in modern systems that must provide stable operation during exposure to changing environmental conditions. For example, a fiber optic cable on a satellite may have to reliably function over a temperature range of -50 C up to 125 C. While the system requirements for a particular application will dictate the exact method by which the fibers should be prepared, this work will examine multiple ruggedized fibers prepared in different fashions and subjected to thermal qualification testing. The data show that if properly conditioned the fiber cables can provide stable operation, but if done incorrectly, they will have large fluctuations in transmission.

  6. Remarkable improvement of the wear resistance of poly(vinylidene difluoride) by incorporating polyimide powder and carbon nanofibers

    Science.gov (United States)

    Min, Chunying; Liu, Dengdeng; Shen, Chen; Zhang, Qiaqia; Shen, Xiaojuan; Zhang, Kan

    2017-10-01

    Poly(vinylidene difluoride) (PVDF) composites reinforced via adding different fillers have attracted wide attention in the field of dielectric materials, but few have been reported in the tribological area. In this paper, the effect of polyimide (PI) powder and carbon nanofibers (CF) as reinforcement phases on the friction and wear performance of PVDF composites has been investigated. It was found that PI powder enhances the mechanical and tribological properties of PVDF and especially as the content of the PI powder reaches 5 wt%. In addition, CF and PI exhibited synergistic effect on the tribological properties of PVDF. With PVDF containing 5 wt% PI powder and 20 wt% CF, the friction and wear behavior of the PVDF composite showed the best performance. PVDF, PI powder and CF can form a consistent network structure, which prevents the polymer molecular chains from moving or deformation, decreasing the wear loss of PVDF composites.

  7. Plasticization-resistant hollow fiber membranes for CO2/CH4 separation based on a thermally crosslinkable polyimide

    KAUST Repository

    Chen, Chien-Chiang

    2011-10-01

    Decarboxylation-induced thermal crosslinking has been demonstrated to be effective for stabilizing membranes against plasticization in dense films. This study extends this promising crosslinking approach from dense films to industrially relevant asymmetric hollow fiber membranes. Crosslinkable asymmetric hollow fiber membranes were spun from a carboxylic acid containing polyimide, 6FDA-DAM:DABA. Dope and spinning conditions were optimized to obtain fibers with a defect-free selective skin layer. It is found that slightly defective fibers suffered severe selectivity loss after thermal crosslinking, suggesting that defect-free property is essential to the performance of the resulting crosslinked hollow fiber membranes. The crosslinked fibers were tested for CO 2/CH 4 separation. The excellent plasticization resistance under high pressure feeds (with highest CO 2 partial pressure of 400psia) suggests that these robust membranes are promising for aggressive natural gas purification. © 2011 Elsevier B.V.

  8. Modifications in physico-chemical properties of 100 MeV oxygen ions irradiated polyimide Kapton-H polymer

    Science.gov (United States)

    Gupta, Sanjeev Kumar; Gupta, Rashi; Singh, Paramjit; Kumar, Vikas; Jaiswal, Manoj Kumar; Chakarvarti, S. K.; Kumar, Rajesh

    2017-09-01

    The optical, structural and chemical properties of polyimide Kapton-H polymer thin film samples were modified by irradiation with 100 MeV O7+ ions (in the fluence range of 1 × 1011 to 5 × 1012 ions/cm2) and the modifications of these properties were observed by UV-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy respectively. The band gap energy of the polymer decreased considerably with discrete increment of the ion fluence (different fluence for each sample) and effective change for the sample irradiated at a fluence of 5 × 1012 ions/cm2 was observed from that of pristine sample. The amorphous nature of the polymer was observed to be decreased with increase of ion fluence. The vibrations of Ctbnd C appeared at mid fluences but the stretching vibrations of Osbnd H bond disappeared at these fluences due to the high LET of the oxygen ions.

  9. Electroless deposition of Au nanoparticles on reduced graphene oxide/polyimide film for electrochemical detection of hydroquinone and catechol

    Science.gov (United States)

    Shen, Xuan; Xia, Xiaohong; Du, Yongling; Wang, Chunming

    2017-09-01

    An electrochemical sensor for determination of hydroquinone (HQ) and catechol (CC) was developed using Au nanoparticles (AuNPs) fabricated on reduced graphene oxide/polyimide (PI/RGO) film by electroless deposition. The electrochemical behaviors of HQ and CC at PI/RGO-AuNPs electrode were investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimized condition, the current responses at PI/RGO-AuNPs electrode were linear over ranges from 1 to 654 mol/L for HQ and from 2 to 1289 mol/L for CC, with the detection limits of 0.09 and 0.2 mol/L, respectively. The proposed electrode exhibited good reproducibility, stability and selectivity. In addition, the proposed electrode was successfully applied in the determination of HQ and CC in tap water and the Yellow River samples.

  10. Development and demonstration of manufacturing processes for fabricating graphite/Larc-160 polyimide structural elements, part 4, paragraph C

    Science.gov (United States)

    1981-01-01

    Progress in the development of processes for production of Celion/LARC-160 graphite-polyimide materials, quality control methods, and the fabrication of Space Shuttle composite structure components is reported. The formulation and processing limits for three batches of resin are presented. Process improvements for simplification of the imidizing and autoclave cure cycles are described. Imidized and autoclave cured test panels were prepared. Celion/LARC-160 cure process verification and the fabrication of honeycomb sandwich panel elements and skin/stringer panels are described. C-scans of laminates imidized at 163 C to 218 C for periods from 30 to 180 minutes, and of process verification laminates made from different batches of prepreg are presented. Failure modes and load/strain characteristics of sandwich elements and C-scans of stringer to skin bond joints are also given.

  11. Application of Cu-polyimide flex circuit and Al-on-glass pitch adapter for the ATLAS SCT barrel hybrid

    CERN Document Server

    Unno, Y; Ikegami, Y; Iwata, Y; Kohriki, T; Kondo, T; Nakano, I; Ohsugi, T; Takashima, R; Tanaka, R; Terada, S; Ujiie, N

    2005-01-01

    We applied the surface build-up Cu-polyimide flex-circuit technology with laser vias to the ATLAS SCT barrel hybrid to be made in one piece from the connector to the electronics sections including cables. The hybrids, reinforced with carbon-carbon substrates, provide mechanical strength, thermal conductivity, low-radiation length, and stability in application-specific integrated circuit (ASIC) operation. By following the design rules, we experienced little trouble in breaking the traces. The pitch adapter between the sensor and the ASICs was made of aluminum traces on glass substrate. We identified that the generation of whiskers around the wire-bonding feet was correlated with the hardness of metallized aluminum. The appropriate hardness has been achieved by keeping the temperature of the glasses as low as room temperature during the metallization. The argon plasma cleaning procedure cleaned the contamination on the gold pads of the hybrids for successful wire bonding, although it was unsuccessful in the alu...

  12. Gas Separation Performance of Carbon Molecular Sieve Membranes Based on 6FDA-mPDA/DABA (3:2) Polyimide

    KAUST Repository

    Qiu, Wulin

    2014-02-23

    6FDA-mPDA/DABA (3:2) polyimide was synthesized and characterized for uncross-linked, thermally crosslinked, and carbon molecular sieve (CMS) membranes. The membranes were characterized with thermogravimetric analysis, FTIR spectroscopy, wide-angle X-ray diffraction, and gas permeation tests. Variations in the d spacing, the formation of pore structures, and changes in the pore sizes of the CMS membranes were discussed in relation to pyrolysis protocols. The uncross-linked polymer membranes showed high CO 2/CH4 selectivity, whereas thermally crosslinked membranes exhibited significantly improved CO2 permeability and excellent CO2 plasticization resistance. The CMS membranes showed even higher CO2 permeability and CO2/CH4 selectivity. An increase in the pyrolysis temperature resulted in CMS membranes with lower gas permeability but higher selectivity. The 550 °C pyrolyzed CMS membranes showed CO2 permeability as high as 14 750 Barrer with CO 2/CH4 selectivity of approximately 52. Even 800 °C pyrolyzed CMS membranes still showed high CO2 permeability of 2610 Barrer with high CO2/CH4 selectivity of approximately 118. Both polymer membranes and the CMS membranes are very attractive in aggressive natural gas purification applications. Permeating through: Polyimide-based uncross-linked, thermally crosslinked, and carbon molecular sieve (CMS) membranes are prepared. Variations in the d spacing, the formation of pore structures, and changes in the pore sizes of the CMS membranes are discussed in relation to pyrolysis protocols. Both the polymer and CMS membranes are very attractive in aggressive natural gas purification applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Thermosetting polyimide resin matrix composites with interpenetrating polymer networks for precision foil resistor chips based on special mechanical performance requirements

    Energy Technology Data Exchange (ETDEWEB)

    Wang, X.Y., E-mail: wxy@tju.edu.cn [School of Electronic Information Engineering, Tianjin University, Tianjin 300072 (China); Ma, J.X.; Li, C.G. [School of Electronic Information Engineering, Tianjin University, Tianjin 300072 (China); Wang, H.X. [ZHENGHE electronics Co., Ltd, Jining 272023 (China)

    2014-04-01

    Highlights: • Macromolecular materials were chosen to modify thermosetting polyimide (TSPI). • The formation of IPN structure in TSPI composite polymers was discussed. • The special mechanical properties required were the main study object. • The desired candidate materials should have proper hardness and toughness. • The specific mechanical data are quantitatively determined by experiments. - Abstract: Based on interpenetrating networks (IPNs) different macromolecular materials such as epoxy, phenolic, and silicone resin were chosen to modify thermosetting polyimide (TSPI) resin to solve the lack of performance when used for protecting precision foil resistor chips. Copolymerization modification, controlled at curing stage, was used to prepare TSPI composites considering both performance and process requirements. The mechanical properties related to trimming process were mainly studied due to the special requirements of the regularity of scratch edges caused by a tungsten needle. The analysis on scratch edges reveals that the generation and propagation of microcracks caused by scratching together with crack closure effect may lead to regular scratch traces. Experiments show that the elongation at break of TSPI composites is the main reason that determines the special mechanical properties. The desired candidate materials should have proper hardness and toughness, and the specific mechanical data are that the mean elongation at break and tensile strength of polymer materials are in the range of 9.2–10.4% and 100–107 MPa, respectively. Possible reasons for the effect of the modifiers chosen on TSPI polymers, the reaction mechanisms on modified TSPI resin and the IPN structure in TSPI composite polymers were discussed based on IR and TG analysis.

  14. Sub- T g Cross-Linking of a Polyimide Membrane for Enhanced CO 2 Plasticization Resistance for Natural Gas Separation

    KAUST Repository

    Qiu, Wulin

    2011-08-09

    Decarboxylation-induced thermal cross-linking occurs at elevated temperatures (∼15 °C above glass transition temperature) for 6FDA-DAM:DABA polyimides, which can stabilize membranes against swelling and plasticization in aggressive feed streams. Despite this advantage, such a high temperature might result in collapse of substructure and transition layers in the asymmetric structure of a hollow fibers based on such a material. In this work, the thermal cross-linking of the 6FDA-DAM:DABA at temperatures much below the glass transition temperature (∼387 °C by DSC) was demonstrated. This sub-Tg cross-linking capability enables extension to asymmetric structures useful for large scale membranes. The resulting polymer membranes were characterized by swelling in known solvents for the un-cross-linked materials, TGA analysis, and permeation tests of aggressive gas feed stream at higher pressure. The annealing temperature and time clearly influence the degree of cross-linking of the membranes, and results in a slight difference in selectivity for membranes under various cross-linking conditions. Results indicate that the sub-Tg thermal cross-linking of 6FDA-DAM:DABA dense film membrane can be carried out completely even at a temperature as low as 330 °C. Permeabilities were tested for the polyimide membranes using both pure gases (He, O2, N2, CH4, CO2) and mixed gases (CO2/CH4). The selectivity of the cross-linked membrane can be maintained even under very aggressive CO2 operating conditions that are not possible without cross-linking. Moreover, the plasticization resistance was demonstrated up to 700 psia for pure CO 2 gas or 1000 psia for 50% CO2 mixed gas feeds. © 2011 American Chemical Society.

  15. Precipitation and stream water stable isotope data from the Marys River, Oregon in water year 2015.

    Data.gov (United States)

    U.S. Environmental Protection Agency — Water stable isotope data collected from a range of streams throughout the Marys River basin in water year 2015, and precipitation data collected within the basin at...

  16. Toward Practical Secure Stable Matching

    Directory of Open Access Journals (Sweden)

    Riazi M. Sadegh

    2017-01-01

    Full Text Available The Stable Matching (SM algorithm has been deployed in many real-world scenarios including the National Residency Matching Program (NRMP and financial applications such as matching of suppliers and consumers in capital markets. Since these applications typically involve highly sensitive information such as the underlying preference lists, their current implementations rely on trusted third parties. This paper introduces the first provably secure and scalable implementation of SM based on Yao’s garbled circuit protocol and Oblivious RAM (ORAM. Our scheme can securely compute a stable match for 8k pairs four orders of magnitude faster than the previously best known method. We achieve this by introducing a compact and efficient sub-linear size circuit. We even further decrease the computation cost by three orders of magnitude by proposing a novel technique to avoid unnecessary iterations in the SM algorithm. We evaluate our implementation for several problem sizes and plan to publish it as open-source.

  17. Stable prenucleation calcium carbonate clusters.

    Science.gov (United States)

    Gebauer, Denis; Völkel, Antje; Cölfen, Helmut

    2008-12-19

    Calcium carbonate forms scales, geological deposits, biominerals, and ocean sediments. Huge amounts of carbon dioxide are retained as carbonate ions, and calcium ions represent a major contribution to water hardness. Despite its relevance, little is known about the precipitation mechanism of calcium carbonate, and specified complex crystal structures challenge the classical view on nucleation considering the formation of metastable ion clusters. We demonstrate that dissolved calcium carbonate in fact contains stable prenucleation ion clusters forming even in undersaturated solution. The cluster formation can be characterized by means of equilibrium thermodynamics, applying a multiple-binding model, which allows for structural preformation. Stable clusters are the relevant species in calcium carbonate nucleation. Such mechanisms may also be important for the crystallization of other minerals.

  18. High precision and stable structures for particle detectors

    CERN Document Server

    Da Mota Silva, S; Hauviller, Claude

    1999-01-01

    The central detectors used in High Energy Physics Experiments require the use of light and stable structures capable of supporting delicate and precise radiation detection elements. These structures need to be highly stable under environmental conditions where external vibrations, high radiation levels, temperature and humidity gradients should be taken into account. Their main design drivers are high dimension and dynamic stability, high stiffness to mass ratio and large radiation length. For most applications, these constraints lead us to choose Carbon Fiber Reinforced Plastics ( CFRP) as structural element. The construction of light and stable structures with CFRP for these applications can be achieved by careful design engineering and further confirmation at the prototyping phase. However, the experimental environment can influence their characteristics and behavior. In this case, theuse of adaptive structures could become a solution for this problem. We are studying structures in CFRP with bonded piezoel...

  19. Synthesis and Characterization of Sulfonated Polyimides as Proton Exchange Membranes for Fuel Cells

    OpenAIRE

    Gunduz, Nazan

    2001-01-01

    Series of homo- and copolyimides containing controlled degrees of sulfonic acid ion conducting pendant groups have been synthesized from both phthalic (five-) and naphthalic (six-membered) dianhydrides and appropriate wholly aromatic diamines and heterocyclic analogues. The goal is to identify thermally and hydrolytically stable ion conducting polymers (ICP) suitable as proton exchange membranes, PEM, for fuel cells. The candidate ICP's have been synthesized and characterized for molecular we...

  20. Fabrication of fluorinated polyimide microgrids using magnetically controlled reactive ion etching (MC-RIE) and their applications to an ion drag integrated micropump

    Science.gov (United States)

    Furuya, Akinori; Shimokawa, Fusao; Matsuura, Tohru; Sawada, Renshi

    1996-09-01

    Magnetically controlled reactive ion etching (MC-RIE) of a fluorinated polyimide substrate achieved etching selectivity of up to 2600, resulting in a smoothly etched surface and structures hundreds of micrometers high having good perpendicularity. This technique is useful for three-dimensional microfabrication. As an example of a typical application, we fabricated an ion drag integrated micropump with microgrid sets consisting of 0960-1317/6/3/003/img1 high pole-shaped counter-electrode elements arranged like a pair of interleaved combs by using a fluorinated polyimide as the structural material, metallization, and lift-off using a ZnO sacrificial layer. This micropump moved ethanol with a flow rate of about 0960-1317/6/3/003/img2 when 200 V was applied to the counter electrodes.

  1. AZ-2000-IECW and StaMet Black Kapton Options for Solar Probe Plus MAG Sensor MLI Kevlar/Polyimide Shells

    Science.gov (United States)

    Choi, Michael K.

    2017-01-01

    AZ-2000-IECW white paint and StaMet black Kapton have been evaluated for the Kevlar/polyimide shells that enclose the Solar Probe Plus Magnetometer (MAG) sensors and multilayer insulation. Flight qualification testing on AZ-2000-IECW painted Kevlar/polyimide laminate was completed at Goddard Space Flight Center. This paint potentially meets all the requirements. However, it has no flight heritage. StaMet is hotter in the sun, and is specular. The results of the MAG thermal balance test show StaMet meets the thermal requirement and heater power budget. The mission prefers to fly StaMet after evaluating the risks of AZ-2000-IECW flaking and glint from StaMet to the Star Trackers.

  2. Experimental modeling of laminar composites for multifrequency eddy current measurements. [Thickness and resistivity measurement on Al/Kapton or Al/polyimide

    Energy Technology Data Exchange (ETDEWEB)

    Heckman, R.V.

    1980-08-01

    This report describes a computer modeling program, originally developed by Dodd and Deeds of Oak Ridge National Laboratory, capable of calculating the experimental voltage amplitudes and phases which can be obtained with rectangular cross-section coils being operated at multiple frequencies. This program was applied to two multilayered composites in order to determine the feasibility of making thickness and resistivity measurements of the individual layers. The results of these calculations indicate that the thickness of the aluminum/Kapton composite layers could be measured to a precision of better than 1% and the resistivity of the conductive layers could be measured to a precision of better than 10%. The second composite, a structure consisting of alternating layers of aluminum and polyimide, a varnish, was found to be measureable also. A minimum of two frequency components were found to be necessary for the aluminum/Kapton composite while three frequencies were found to be necessary for the aluminum polyimide case.

  3. Optically Immersed Bolometer IR Detectors Based on V2O5 Thin Films with Polyimide Thermal Impedance Control Layer for Space Applications

    Science.gov (United States)

    Sumesh, M. A.; Thomas, Beno; Vijesh, T. V.; Mohan Rao, G.; Viswanathan, M.; Karanth, S. P.

    2017-10-01

    Optically immersed bolometer IR detectors were fabricated using electron beam evaporated vanadium oxide as the sensing material. Spin-coated polyimide was used as medium to optically immerse the sensing element to the flat surface of a hemispherical germanium lens. This optical immersion layer also serves as the thermal impedance control layer and decides the performance of the devices in terms of responsivity and noise parameters. The devices were packaged in suitable electro-optical packages and the detector parameters were studied in detail. Thermal time constant varies from 0.57 to 6.0 ms and responsivity from 75 to 757 V W-1 corresponding to polyimide thickness in the range 2 to 70 μm for a detector bias of 9 V in the wavelength region of 14-16 μm. Highest D* obtained was 1.2×108 cmHz1/2 W-1. Noise equivalent temperature difference (NETD) of 20 mK was achieved for devices with polyimide thickness more than 32 μm. The figure of merit, NETD × τ product which describes trade-off between thermal time constant and sensitivity is also extensively studied for devices having different thickness of thermal impedance layers.

  4. Heavy Stable Isotopes: From Exceptional to Expected

    Science.gov (United States)

    Anbar, A.

    2006-12-01

    Less than a decade ago, the stable isotope geochemistry of transition metals and other "heavy" elements was a highly specialized niche confined to a few seemingly exceptional elements. This situation was transformed by the development and refinement of MC-ICP-MS techniques, particularly in the last five years. Measurable stable isotope variations turn out to be ubiquitous across the periodic table, from Li to Hg. It is now safe to assume that the isotopic composition of any element with two or more stable isotopes is measurably variable. What was once exceptional is now expected. Among the first of these new systems to be explored were Fe and Mo isotopes. A number of lessons emerging from this work can be applied to the development of other isotope systems. Most important is that initial expectations are often wrong. For example, based on their environmental chemistries it was expected that redox reactions should produce some of the largest isotope effects for both elements. In the case of Fe, theoretical and experimental studies converge to convincingly indicate that a fractionation of ~ 1.5 ‰/amu occurs between Fe(III) and Fe(II) aquo complexes at equilibrium (e.g., Welch et al., 2003; Anbar et al., 2005). Consistent with these findings, most natural variations of are < 1.5 ‰/amu (e.g., Johnson et al., 2004). This redox-related fractionation is at the heart of emerging interpretations of variations in the isotopic composition of Fe and their application to understanding ancient ocean redox (e.g., Dauphas et al., 2004; Rouxel et al., 2005). In contrast, Mo isotope variations turn out to be controlled only indirectly by redox conditions. Instead, one of the most important Mo isotope effects in the environment appears to be a fractionation of ~ 1 ‰/amu during adsorption of Mo to Mn-oxides (Barling et al., 2001; Siebert et al., 2003). This fractionation has been reproduced in the laboratory (Barling and Anbar, 2004) and appears to be an equilibrium isotope

  5. Thermally stable imaging channeled spectropolarimetry

    Science.gov (United States)

    Craven-Jones, Julia; Way, Brandyn M.; Hunt, Jeff; Kudenov, Michael W.; Mercier, Jeffrey A.

    2013-09-01

    Channeled spectropolarimetry can measure the complete polarization state of light as a function of wavelength. Typically, a channeled spectropolarimeter uses high order retarders made of uniaxial crystal to amplitude modulate the measured spectrum with the spectrally-dependent Stokes polarization information. A primary limitation of conventional channeled spectropolarimeters is related to the thermal variability of the retarders. Thermal variation often forces frequent system recalibration, particularly for field deployed systems. However, implementing thermally stable retarders results in an athermal channeled spectropolarimeter that relieves the need for frequent recalibration. Past work has addressed this issue by developing athermalized retarders using two or more uniaxial crystals. Recently, a retarder made of biaxial KTP and cut at a thermally insensitive angle was used to produce an athermal channeled spectropolarimeter. This paper presents the results of the biaxial crystal system and compares the two thermal stabilization techniques in the context of producing an imaging thermally stable channeled spectropolarimeter. A preliminary design for a snapshot imaging channeled spectropolarimeter is also presented.

  6. Synthesis and gas permeation properties of a novel thermally-rearranged polybenzoxazole made from an intrinsically microporous hydroxyl-functionalized triptycene-based polyimide precursor

    KAUST Repository

    Alghunaimi, Fahd

    2017-06-06

    A hydroxyl-functionalized triptycene-based polyimide of intrinsic microporosity (TDA1-APAF) was converted to a polybenzoxazole (PBO) by heat treatment at 460 °C under nitrogen atmosphere. TDA1-APAF treated for 15 min (TR 460) resulted in a PBO conversion of 95% based on a theoretical weight loss of 11.7 wt% of the polyimide precursor. The BET surface area of the TR 460 (680 m2 g−1) was significantly higher than that of the TDA1-APAF polyimide (260 m2 g−1) as determined by nitrogen adsorption at −196 °C. Heating TDA1-APAF for 30 min (TRC 460) resulted in a weight loss of 13.5 wt%, indicating full conversion to PBO and partial main-chain degradation. The TR 460 membrane displayed excellent O2 permeability of 311 Barrer coupled with an O2/N2 selectivity of 5.4 and CO2 permeability of 1328 Barrer with a CO2/CH4 selectivity of 27. Interestingly, physical aging over 150 days resulted in enhanced O2/N2 selectivity of 6.3 with an O2 permeability of 185 Barrer. The novel triptycene-based TR 460 PBO outperformed all previously reported APAF-polyimide-based PBOs with gas permeation performance close to recently reported polymers located on the 2015 O2/N2 upper bound. Based on this study, thermally-rearranged membranes from hydroxyl-functionalized triptycene-based polyimides are promising candidate membrane materials for air separation, specifically in applications where space and weight of membrane systems are of utmost importance such as nitrogen production for inert atmospheres in fuel lines and tanks on aircrafts and off-shore oil- or natural gas platforms. Mixed-gas permeation experiments also demonstrated good performance of the TR 460 membrane for natural gas sweetening with a CO2 permeability of ∼1000 Barrer and CO2/CH4 selectivity of 22 at a typical CO2 wellhead partial pressure of 10 bar.

  7. Stable rotating dipole solitons in nonlocal media

    DEFF Research Database (Denmark)

    Lopez-Aguayo, Servando; Skupin, Stefan; Desyatnikov, Anton S.

    2006-01-01

    We present the first example of stable rotating two-soliton bound states in nonlinear optical media with nonlocal response. We show that, in contrast to media with local response, nonlocality opens possibilities to generate stable azimuthons.......We present the first example of stable rotating two-soliton bound states in nonlinear optical media with nonlocal response. We show that, in contrast to media with local response, nonlocality opens possibilities to generate stable azimuthons....

  8. Transscleral implantation and neurophysiological testing of subretinal polyimide film electrodes in the domestic pig in visual prosthesis development

    Science.gov (United States)

    Sachs, Helmut G.; Schanze, Thomas; Brunner, Ursula; Sailer, Heiko; Wiesenack, Christoph

    2005-03-01

    Loss of photoreceptor function is responsible for a variety of blinding diseases, including retinitis pigmentosa. Advances in microtechnology have led to the development of electronic visual prostheses which are currently under investigation for the treatment of human blindness. The design of a subretinal prosthesis requires that the stimulation device should be implantable in the subretinal space of the eye. Current limitations in eye surgery have to be overcome to demonstrate the feasibility of this approach and to determine basic stimulation parameters. Therefore, polyimide film-bound electrodes were implanted in the subretinal space in anaesthetized domestic pigs as a prelude to electrical stimulation in acute experiments. Eight eyes underwent surgery to demonstrate the transscleral implantability of the device. Four of the eight eyes were stimulated electrically. In these four animals the cranium was prepared for epidural recording of evoked visual cortex responses, and stimulation was performed with sequences of current impulses. All eight subretinal implantation procedures were carried out successfully with polyimide film electrodes and each electrode was implanted beneath the outer retina of the posterior pole of the operated eyes. Four eyes were used for neurophysiological testing, involving recordings of epidural cortical responses to light and electrical stimulation. A light stimulus response, which occurred 40 ms after stimulation, proved the integrity of the operated eye. The electrical stimuli occurred about 20 ms after the onset of stimulation. The stimulation threshold was approximately 100 µA. Both the threshold and the cortical responses depended on the correspondence between retinal stimulation and cortical recording sites and on the number of stimulation electrodes used simultaneously. The subretinal implantation of complex stimulation devices using the transscleral procedure with consecutive subretinal stimulation is feasible in acute

  9. Are Ionic Liquids Chemically Stable?

    Science.gov (United States)

    Wang, Binshen; Qin, Li; Mu, Tiancheng; Xue, Zhimin; Gao, Guohua

    2017-05-24

    Ionic liquids have attracted a great deal of interest in recent years, illustrated by their applications in a variety of areas involved with chemistry, physics, biology, and engineering. Usually, the stabilities of ionic liquids are highlighted as one of their outstanding advantages. However, are ionic liquids really stable in all cases? This review covers the chemical stabilities of ionic liquids. It focuses on the reactivity of the most popular imidazolium ionic liquids at structural positions, including C2 position, N1 and N3 positions, and C4 and C5 positions, and decomposition on the imidazolium ring. Additionally, we discuss decomposition of quaternary ammonium and phosphonium ionic liquids and hydrolysis and nucleophilic reactions of anions of ionic liquids. The review aims to arouse caution on potential decomposition of ionic liquids and provides a guide for better utilization of ionic liquids.

  10. Stable massive particles at colliders

    Energy Technology Data Exchange (ETDEWEB)

    Fairbairn, M.; /Stockholm U.; Kraan, A.C.; /Pennsylvania U.; Milstead, D.A.; /Stockholm U.; Sjostrand, T.; /Lund U.; Skands, P.; /Fermilab; Sloan, T.; /Lancaster U.

    2006-11-01

    We review the theoretical motivations and experimental status of searches for stable massive particles (SMPs) which could be sufficiently long-lived as to be directly detected at collider experiments. The discovery of such particles would address a number of important questions in modern physics including the origin and composition of dark matter in the universe and the unification of the fundamental forces. This review describes the techniques used in SMP-searches at collider experiments and the limits so far obtained on the production of SMPs which possess various colour, electric and magnetic charge quantum numbers. We also describe theoretical scenarios which predict SMPs, the phenomenology needed to model their production at colliders and interactions with matter. In addition, the interplay between collider searches and open questions in cosmology such as dark matter composition are addressed.

  11. Fubini theorem for multiparameter stable process

    OpenAIRE

    Erraoui, Mohamed; Ouknine, Youssef

    2011-01-01

    We prove stochastic Fubini theorem for general stable measure which will be used to develop some identities in law for functionals of one and two-parameter stable processes. This result is subsequently used to establish the integration by parts formula for stable sheet.

  12. Fubini theorem for multiparameter stable process

    Directory of Open Access Journals (Sweden)

    Mohamed Erraoui

    2011-04-01

    Full Text Available We prove stochastic Fubini theorem for general stable measure which will be used to develop some identities in law for functionals of one and two-parameter stable processes. This result is subsequently used to establish the integration by parts formula for stable sheet.

  13. Gas separation performance of carbon molecular sieve membranes based on 6FDA-mPDA/DABA (3:2) polyimide.

    Science.gov (United States)

    Qiu, Wulin; Zhang, Kuang; Li, Fuyue Stephanie; Zhang, Ke; Koros, William J

    2014-04-01

    6FDA-mPDA/DABA (3:2) polyimide was synthesized and characterized for uncross-linked, thermally crosslinked, and carbon molecular sieve (CMS) membranes. The membranes were characterized with thermogravimetric analysis, FTIR spectroscopy, wide-angle X-ray diffraction, and gas permeation tests. Variations in the d spacing, the formation of pore structures, and changes in the pore sizes of the CMS membranes were discussed in relation to pyrolysis protocols. The uncross-linked polymer membranes showed high CO2 /CH4 selectivity, whereas thermally crosslinked membranes exhibited significantly improved CO2 permeability and excellent CO2 plasticization resistance. The CMS membranes showed even higher CO2 permeability and CO2 /CH4 selectivity. An increase in the pyrolysis temperature resulted in CMS membranes with lower gas permeability but higher selectivity. The 550 °C pyrolyzed CMS membranes showed CO2 permeability as high as 14 750 Barrer with CO2 /CH4 selectivity of approximately 52. Even 800 °C pyrolyzed CMS membranes still showed high CO2 permeability of 2610 Barrer with high CO2 /CH4 selectivity of approximately 118. Both polymer membranes and the CMS membranes are very attractive in aggressive natural gas purification applications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Comparison of photoinduced reorientation of ortho-, meta-, and para-methyl red-doped nematic liquid crystals on rubbed polyimide.

    Science.gov (United States)

    Statman, David; Statman, Ariel T; Wozniak, Kaitlin; Brennan, Christopher

    2015-08-01

    We compare the photoinduced reorientation of the easy axis on rubbed polyimide surfaces for the nematic E7 doped with three isomers of methyl red; ortho, meta, and para. Using optical techniques, the angle and the pitch of the director at the polymer surface were measured before, during, and after photoexcitation of the dye. Optical absorbances were also measured before and after photoexcitation. Extrapolation lengths, hence anchoring energies, were determined with the on/off application of a magnetic field for meta- and para-methyl red-doped nematics. Because of an elastic reorientation of the easy axis in the presence of the magnetic field, we could not determine the extrapolation length of the ortho-methyl red-doped nematic. Our results confirm that photoinduced reorientation is facilitated by desorption of all dyes from the polymer surface. While there is little evidence of weak photoinduced adsorption of meta- and para-methyl red to the surface during photoexcitation, there is strong evidence of photoinduced adsorption of ortho-methyl red, which is long lasting.

  15. "Thermal Stabilization Effect" of Al2O3 nano-dopants improves the high-temperature dielectric performance of polyimide.

    Science.gov (United States)

    Yang, Yang; He, Jinliang; Wu, Guangning; Hu, Jun

    2015-11-24

    Insulation performance of the dielectrics under extreme conditions always attracts widespread attention in electrical and electronic field. How to improve the high-temperature dielectric properties of insulation materials is one of the key issues in insulation system design of electrical devices. This paper studies the temperature-dependent corona resistance of polyimide (PI)/Al2O3 nanocomposite films under high-frequency square-wave pulse conditions. Extended corona resistant lifetime under high-temperature conditions is experimentally observed in the 2 wt% nanocomposite samples. The "thermal stabilization effect" is proposed to explain this phenomenon which attributes to a new kind of trap band caused by nanoparticles. This effect brings about superior space charge characteristics and corona resistance under high temperature with certain nano-doping concentration. The proposed theory is experimentally demonstrated by space charge analysis and thermally stimulated current (TSC) tests. This discovered effect is of profound significance on improving high-temperature dielectric properties of nanocomposites towards various applications.

  16. Synthesis and Compatibility of Ionic Liquid Containing Rod-Coil Polyimide Gel Electrolytes with Lithium Metal Electrodes

    Science.gov (United States)

    Tigelaar, Dean M.; Palker, Allyson E.; Meador, Mary Ann B.; Bennett, William R.

    2008-01-01

    A highly cross-linked polyimide-polyethylene oxide copolymer has been synthesized that is capable of holding large volumes of liquid component, simultaneously maintaining good dimensional stability. An amine end capped oligomer was made that was imidized in solution, followed by reaction with a triisocyanate in the presence of desired additives at ambient temperature. Polymer films are able to hold over 4 times their weight in room temperature ionic liquid RTIL or carbonate solvent. Electrolytes were studied that contained varying amounts of RTIL, lithium trifluoromethanesulfonimide LiTFSi, and alumina nanoparticles. Electrochemical stability of these electrolytes with lithium metal electrodes was studied by galvanic cycling and impedance spectroscopy. Improved cycling stability and decreased interfacial resistance were observed when increasing amounts of RTIL and LiTFSi were added. The addition of small amounts of alumina further decreased interfacial resistance by nearly an order of magnitude. During the course of the study, cycling stability increased from less than 3 to greater than 1000 h at 60 C and 0.25 mA/cm2 current density.

  17. High-performance carbon molecular sieve membranes for ethylene/ethane separation derived from an intrinsically microporous polyimide

    KAUST Repository

    Salinas, Octavio

    2015-11-18

    An intrinsically microporous polymer with hydroxyl functionalities, PIM-6FDA-OH, was used as a precursor for various types of carbon molecular sieve (CMS) membranes for ethylene/ethane separation. The pristine polyimide films were heated under controlled N2 atmosphere at different stages from 500 to 800 °C. All CMS samples carbonized above 600 °C surpassed the polymeric ethylene/ethane upper bound. Pure-gas selectivity reached 17.5 for the CMS carbonized at 800 °C with an ethylene permeability of about 10 Barrer at 2 bar and 35 °C, becoming the most selective CMS for ethylene/ethane separation reported to date. As expected, gravimetric sorption experiments showed that all CMS membranes had ethylene/ethane solubility selectivities close to one. The permselectivity increased with increasing pyrolysis temperature due to densification of the micropores in the CMS membranes, leading to enhanced diffusivity selectivity. Mixed-gas tests with a binary 50:50 v/v ethylene/ethane feed showed a decrease in selectivity from 14 to 8.3 as the total feed pressure was increased from 4 to 20 bar. The selectivity drop under mixed-gas conditions was attributed to non-ideal effects: (i) Competitive sorption that reduced the permeability of ethylene and (ii) dilation of the CMS that resulted in an increase in the ethane permeability.

  18. Enhanced propylene/propane separation by thermal annealing of an intrinsically microporous Hydroxyl-functionalized polyimide membrane

    KAUST Repository

    Swaidan, Ramy Jawdat

    2015-08-06

    Effective separation of propylene/propane is vital to the chemical industry where C3H6 is used as feedstock for a variety of important chemicals. The purity requirements are currently met with cryogenic distillation, which is an extremely energy-intensive process. Hybrid arrangements incorporating highly selective membranes (α>20) have been proposed to “debottleneck” the process and potentially improve the economics. Selective and permeable membranes can be obtained by the design of polymers of intrinsic microporosity (PIMs). In this work, a 250 °C annealed polyimide (PIM-6FDA-OH) membrane produced among the highest reported pure-gas C3H6/C3H8 selectivity of 30 for a solution-processable polymer to date. The high selectivity resulted from enhanced diffusivity selectivity due to the formation of inter-chain charge-transfer-complexes. Although there were some inevitable losses in selectivity under 50:50 mixed-gas feed conditions due to competitive sorption, relatively high selectivities were preserved due to enhanced plasticization resistance.

  19. Silica–silica Polyimide Buffered Optical Fibre Irradiation and Strength Experiment at Cryogenic Temperatures for 355 nm Pulsed Lasers

    CERN Document Server

    Takala, E; Bordini, B; Bottura, L; Bremer, J; Rossi, L

    2012-01-01

    A controlled UV-light delivery system is envisioned to be built in order to study the stability properties of superconducting strands. The application requires a wave guide from room temperature to cryogenic temperatures. Hydrogen loaded and unloaded polyimide buffered silica–silica 100 microm core fibres were tested at cryogenic temperatures. A thermal stress test was done at 1.9 K and at 4.2 K which shows that the minimal mechanical bending radius for the fibre can be 10 mm for testing (transmission was not measured). The cryogenic transmission loss was measured for one fibre to assess the magnitude of the transmission decrease due to microbending that takes place during cooldown. UV-irradiation degradation measurements were done for bent fibres at 4.2 K with a deuterium lamp and 355 nm pulsed lasers. The irradiation tests show that the fibres have transmission degradation only for wavelengths smaller than 330 nm due to the two photon absorption. The test demonstrates that the fibres are suitable for the ...

  20. Effect of chemical modification of graphene on mechanical, electrical, and thermal properties of polyimide/graphene nanocomposites.

    Science.gov (United States)

    Ha, Hun Wook; Choudhury, Arup; Kamal, Tahseen; Kim, Dong-Hun; Park, Soo-Young

    2012-09-26

    Chemically modified graphene sheets were dispersed in a high-performance polyimide (PI) matrix using polyamic acid (PAA)/graphene nanocomposite as a precursor. PI nanocomposite films with different loadings of graphene sheets were prepared by thermal imidization of the as-prepared PAA/graphene nanocomposites. Graphene oxide (GO) synthesized by Hummer's method was chemically reduced with various reducing agents to produce reduced GOs (rGOs). The incorporation of only 5 wt% GO resulted in an ~12-fold and ~18-fold increase in the tensile strength and tensile modulus of PI, respectively, while the PI/rGO nanocomposites were found to have relatively inferior tensile properties. The superior mechanical properties of the PI/GO nanocomposites were attributed to the good dispersion and effective stress transfer between the polymer and GO sheets, as evidenced by the results from X-ray diffraction (XRD) and morphological studies. Furthermore, the PI/GO nanocomposites exhibited higher loading capacity than PI/rGO. The thermo-oxidative stability of PI was also remarkably improved with the addition of both GO and rGOs, but rGOs had a more pronounced effect. The electrical conductivity of PI/rGO nanocomposites was higher than that of PI/GO, suggesting restoration of the graphene basal plane upon the reduction of GO. The highest electrical conductivity was achieved for the l-ascorbic acid reduced GO-reinforced PI nanocomposites.

  1. A highly compliant serpentine shaped polyimide interconnect for front-end strain relief in chronic neural implants

    Directory of Open Access Journals (Sweden)

    Viswanath eSankar

    2013-09-01

    Full Text Available While the signal quality of recording neural electrodes is observed to degrade over time, the degradation mechanisms are complex and less easily observable. Recording microelectrodes failures are attributed to different biological factors such as tissue encapsulation, immune response, and disruption of blood-brain barrier (BBB and non-biological factors such as strain due to micromotion, insulation delamination, corrosion, and surface roughness on the recording site (Polikov et. al., 2005; Prasad et. al., 2011; Streit et. al., 2012; Prasad et. al., 2012. Strain due to brain micromotion is considered to be one of the important abiotic factors contributing to the failure of the neural implants. To reduce the forces exerted by the electrode on the brain, a high compliance 2D serpentine shaped electrode cable was designed, simulated, and measured using polyimide as the substrate material. Serpentine electrode cables were fabricated using MEMS microfabrication techniques, and the prototypes were subjected to load tests to experimentally measure the compliance. The compliance of the serpentine cable was numerically modeled and quantitatively measured to be up to 10 times higher than the compliance of a straight cable of same dimensions and material.

  2. CORRELATION BETWEEN POLYMER PACKING AND GAS TRANSPORT PROPERTIES FOR CO2/N2 SEPARATION IN GLASSY FLUORINATED POLYIMIDE MEMBRANE

    Directory of Open Access Journals (Sweden)

    P. C. TAN

    2016-07-01

    Full Text Available Gas separation performance of a membrane highly hinges on its physical properties. In this study, the interplay between polymer packing of a membrane and its gas transport behaviours (permeability and selectivity was investigated through a series of 6FDA-DAM:DABA (3:2 polyimide membranes with different polymer compactness. The chemical structure and the polymer packing of the resulting membrane were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR and packing density measurement, respectively. CO2/N2 separation efficiency of the membrane was evaluated at 25oC with feed pressure up to 6 bar. N2 permeability was found to rely on the membrane’s packing density, which signified its greater dependence on molecular sieving. In contrast, sorption showed a more vital role in determining the CO2 permeability. In this work, the membrane with a final thickness of 97±2 µm had successfully surpassed the Robeson’s 2008 upper bound plot with a CO2 permeability of 83 Barrer and CO2/N2 selectivity of 97 at 3 bar permeation.

  3. Role of Lewis basicity and van der Waals forces in adhesion of silica MFI zeolites (010) with polyimides.

    Science.gov (United States)

    Lee, Jung-Hyun; Thio, Beng Joo Reginald; Bae, Tae-Hyun; Meredith, J Carson

    2009-08-18

    Adhesion between zeolites and polymers is a central factor in achieving defect-free mixed-matrix membranes for energy-efficient gas separations. In this work, atomic force microscopy (AFM) was used to measure adhesion forces between a pure silica MFI (ZSM-5: Zeolite Socony Mobil-Five) (010) zeolite probe and a series of polyimide (Matrimid 5218, 6FDA-DAM, 6FDA-6FpDA, and 6FDA-DAM:DABA (3:2)) and polyetherimide (Ultem 1000) polymers in air. Combined with measurements of surface energy of the polymer surfaces, the dependence of adhesion on polymer structure was determined. Adhesion force was strongly dependent on the Lewis basicity component of polymer surface energy and was less dependent on van der Waals (VDW) components, by a factor of about 6. Hydrogen bonding likely occurs between the acidic (electron acceptor) component of the zeolite surface (silanols or adsorbed water) and the basic (electron donor) component of the polymer surface. Adhesion force was strongly correlated with the mole fraction of carbonyls per monomer. We conclude that differences in adhesion as a function of polymer structure were primarily controlled by the polymer's Lewis basicity, contributed primarily by carbonyl groups.

  4. In situ polymerization synthesis of Z-scheme tungsten trioxide/polyimide photocatalyst with enhanced visible-light photocatalytic activity

    Science.gov (United States)

    Meng, Pengcheng; Heng, Huimin; Sun, Yanhong; Liu, Xia

    2018-01-01

    A novel direct Z-scheme P-containing tungsten trioxide/polyimide (PWO/PI) photocatalyst was synthesized by an in-situ solid-state polymerization strategy to enhance the visible-light photocatalytic oxidation capacity of PI. The effects of polymerization temperature and PWO content on the physicochemical properties of PWO/PI composites and photocatalytic degradation efficiency of imidacloprid were investigated. The photocatalysts were characterized by X-ray powder diffraction, Fourier transformed infrared spectra, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, UV-vis diffused reflection spectra and N2 adsorption-desorption isothermals. The results showed that the photocatalysts with visible-light photocatalytic activity can already be prepared at 300 °C. The PWO/PI composites exhibited a lamellar structure and PWO was wrapped by PI. After PWO was introduced, there was a significant interaction between PWO and PI, and the visible light response of photocatalysts was also improved. The visible-light photocatalytic degradation efficiency of imidacloprid on 3% PWO/PI-300 composite was about 3.2 times of commercial P25, and the corresponding pseudo-first-order rate constant was about 2.9 times of pristine PI. The Z-scheme photocatalytic system of PWO/PI composites was confirmed by the electron spin resonance technology, terephthalic acid photoluminescence probing technique, reactive species trapping experiments, X-ray photoelectron spectroscopy and photoluminescence of PWO/PI composites and pristine photocatalysts.

  5. Novel Poly(imide dioxime) Sorbents: Development and testing for enhanced extraction of uranium from natural seawater

    Energy Technology Data Exchange (ETDEWEB)

    Das, Sadananda; Brown, Suree S.; Mayes, Richard T.; Janke, Christopher J.; Tsouris, Costas; Kuo, Li-Jung; Gill, Gary A.; Dai, Sheng

    2016-04-09

    A new series of amidoxime-based polymer adsorbents were synthesized at the Oak Ridge National Laboratory (ORNL) by electron beam induced grafting of acrylonitrile and itaconic acid onto polyethylene fiber. Hydroxylamine derivatives of poly(acrylonitrile) (PAN) moiety are demonstrated to possess two kinds of functional groups: open-chain amidoxime and cyclic imide dioxime. The open-chain amidoxime is shown to convert to imide dioxime on heat treatment in the presence of an aprotic solvent, like dimethylsulfoxide (DMSO). The formation of amidoxime and imide dioxime was confirmed by 13-C CPMAS spectra. The adsorbents were evaluated for uranium adsorption efficiency at ORNL with simulated seawater spiked with 8 ppm uranium and 5 gallon seawater in a batch reactor, and in flow-through columns with natural seawater at the Marine Science Laboratory (MSL) of Pacific Northwest National Laboratory (PNNL) at Sequim Bay, WA. The DMSO-heat-treated sorbents adsorbed uranium as high as 4.48 g-U/kg-ads. from seawater. Experimental evidence is presented that the poly(imide dioxime) is primarily responsible for enhanced uranium adsorption capacity from natural seawater. The conjugated system in the imide dioxime ligand possesses increased electron donation ability, which is believed to significantly enhance the uranyl coordination in seawater

  6. The use of a black pigment polyimide, DARC300, as a light absorber on an optical sensor

    Science.gov (United States)

    Gehoski, K. A.; Holm, P. M.; Boggess, K. A.; Scott, C. J.

    2007-03-01

    In the design and fabrication of arrayed opto-electronic detection devices, it is critical to provide optical isolation between the individual array cells to prevent optical crosstalk between channels and contribution from stray light that would otherwise result in degraded signal-to-noise performance. To accomplish this, the light incident between the cells' optical apertures and around the periphery of the array must be blocked from entering the active semiconductor layers. One approach has been to use an opaque layer of metal, but this can lead to reflections and light trapping and ultimate absorption of this stray light in device active regions. Another approach is to use an absorbing material to block stray light. DARC300, a registered trademark of Brewer Science, is an optically absorbing, photo-definable polyimide designed for exactly this purpose. Presented here are the results of the DARC300 blocking layers, including a review of the process development and issues addressed along the way. The most prevalent issues with the DARC300 were the remnants of black pigments after develop, and the insufficiently developed features. A normalized spectral response of a 4-channel, fixed cavity, Fabry-Perot micro spectrometers, with and without the optical blocking layer between cells and around the periphery of the array are shown to greatly enhance device performance with the use of the DARC300 layer.

  7. Synthesis and characterization of flexible and high-temperature resistant polyimide aerogel with ultra-low dielectric constant

    Directory of Open Access Journals (Sweden)

    X. M. Zhang

    2016-10-01

    Full Text Available A polyimide (PI aerogel with excellent combined thermal and dielectric properties was successfully prepared by the polycondensation of 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA, 5-amino-2-(4-aminophenylbenzoxazole (APBO and octa(amino-phenylsilsesquioxane (OAPS crosslinker, followed by a supercritical carbon dioxide (scCO2 drying treatment. The developed PI aerogel exhibited an ultra-low dielectric constant (k of 1.15 at a frequency of 2.75 GHz, a volume resistivity of 5.45·1014 Ω·cm, and a dielectric strength of 132 kV/cm. The flexible PI aerogel exhibited an openpore microstructure consisting of three-dimensional network with tangled nanofibers morphology with a porosity of 85.6% (volume ratio, an average pore diameter of 19.2 nm, and a Brunauer-Emmet-Teller (BET surface area of 428.6 m2/g. In addition, the PI aerogel showed excellent thermal stability with a glass transition temperature (Tg of 358.3 °C, a 5% weight loss temperature over 500 °C, and a residual weight ratio of 66.7% at 750 °C in nitrogen.

  8. Polyimides Based on Asymmetric Dianhydrides (II) (a-BPDA vs a-BTDA) for Resin Transfer Molding (RTM)

    Science.gov (United States)

    Chuang, Kathy C.; Criss, Jim M.; Mintz, Eric A.

    2010-01-01

    A new series of low-melt viscosity imide resins (10-20 poise at 280 C) were formulated from asymmetric 2,3,3',4' -benzophenone dianhydride (a-BTDA) and 4-phenylethynylphthalic endcaps, along with 3,4' -oxydianiline, 3,3' -methylenedianiline and 3,3'- diaminobenzophenone, using a solvent-free melt process. a-BTDA RTM resins exhibited higher glass transition temperatures (Tg's = 330-400 C) compared to those prepared by asymmetric 2,3,3',4' -biphenyl dianhydride, (a-BPDA, Tg's = 320-370 C). These low-melt viscosity imide resins were fabricated into polyimide/T650-35 carbon fiber composites by a RTM process. Composites properties of a-BTDA resins, such as open-hole compression and short-beam shear strength, are compared to those of composites made from a-BPDA based resin at room temperature, 288 C and 315 C. These novel, high temperature RTM imide resins exhibit outstanding properties beyond the performance of conventional RTM resins, such as epoxy and BMI resins which have use-temperatures around 177 C and 232 C for aerospace applications.

  9. But some neutrally stable strategies are more neutrally stable than others

    NARCIS (Netherlands)

    van Veelen, M.

    2010-01-01

    For games in which there is no evolutionarily stable strategy, it can be useful to look for neutrally stable ones. In extensive form games for instance there is typically no evolutionary stable strategy, while there may very well be a neutrally stable one. Such strategies can however still be

  10. Stable piecewise polynomial vector fields

    Directory of Open Access Journals (Sweden)

    Claudio Pessoa

    2012-09-01

    Full Text Available Let $N={y>0}$ and $S={y<0}$ be the semi-planes of $mathbb{R}^2$ having as common boundary the line $D={y=0}$. Let $X$ and $Y$ be polynomial vector fields defined in $N$ and $S$, respectively, leading to a discontinuous piecewise polynomial vector field $Z=(X,Y$. This work pursues the stability and the transition analysis of solutions of $Z$ between $N$ and $S$, started by Filippov (1988 and Kozlova (1984 and reformulated by Sotomayor-Teixeira (1995 in terms of the regularization method. This method consists in analyzing a one parameter family of continuous vector fields $Z_{epsilon}$, defined by averaging $X$ and $Y$. This family approaches $Z$ when the parameter goes to zero. The results of Sotomayor-Teixeira and Sotomayor-Machado (2002 providing conditions on $(X,Y$ for the regularized vector fields to be structurally stable on planar compact connected regions are extended to discontinuous piecewise polynomial vector fields on $mathbb{R}^2$. Pertinent genericity results for vector fields satisfying the above stability conditions are also extended to the present case. A procedure for the study of discontinuous piecewise vector fields at infinity through a compactification is proposed here.

  11. Stable Structures for Distributed Applications

    Directory of Open Access Journals (Sweden)

    Eugen DUMITRASCU

    2008-01-01

    Full Text Available For distributed applications, we define the linear, tree and graph structure types with different variants and modalities to aggregate them. The distributed applications have assigned structures that through their characteristics influence the costs of stages for developing cycle and the costs for exploitation, transferred to each user. We also present the quality characteristics of a structure for a stable application, which is focused on stability characteristic. For that characteristic we define the estimated measure indicators for a level. The influence of the factors of stability and the ways for increasing it are thus identified, and at the same time the costs of development stages, the costs of usage and the costs of maintenance to be keep on between limits that assure the global efficiency of application. It is presented the base aspects for distributed applications: definition, peculiarities and importance. The aspects for the development cycle of distributed application are detailed. In this article, we alongside give the mechanisms for building the defined structures and analyze the complexity of the defined structures for a distributed application of a virtual store.

  12. Advanced thermally stable jet fuels

    Energy Technology Data Exchange (ETDEWEB)

    Schobert, H.H.

    1999-01-31

    The Pennsylvania State University program in advanced thermally stable coal-based jet fuels has five broad objectives: (1) Development of mechanisms of degradation and solids formation; (2) Quantitative measurement of growth of sub-micrometer and micrometer-sized particles suspended in fuels during thermal stressing; (3) Characterization of carbonaceous deposits by various instrumental and microscopic methods; (4) Elucidation of the role of additives in retarding the formation of carbonaceous solids; (5) Assessment of the potential of production of high yields of cycloalkanes by direct liquefaction of coal. Future high-Mach aircraft will place severe thermal demands on jet fuels, requiring the development of novel, hybrid fuel mixtures capable of withstanding temperatures in the range of 400--500 C. In the new aircraft, jet fuel will serve as both an energy source and a heat sink for cooling the airframe, engine, and system components. The ultimate development of such advanced fuels requires a thorough understanding of the thermal decomposition behavior of jet fuels under supercritical conditions. Considering that jet fuels consist of hundreds of compounds, this task must begin with a study of the thermal degradation behavior of select model compounds under supercritical conditions. The research performed by The Pennsylvania State University was focused on five major tasks that reflect the objectives stated above: Task 1: Investigation of the Quantitative Degradation of Fuels; Task 2: Investigation of Incipient Deposition; Task 3: Characterization of Solid Gums, Sediments, and Carbonaceous Deposits; Task 4: Coal-Based Fuel Stabilization Studies; and Task 5: Exploratory Studies on the Direct Conversion of Coal to High Quality Jet Fuels. The major findings of each of these tasks are presented in this executive summary. A description of the sub-tasks performed under each of these tasks and the findings of those studies are provided in the remainder of this volume

  13. Population Games, Stable Games, and Passivity

    Directory of Open Access Journals (Sweden)

    Michael J. Fox

    2013-10-01

    Full Text Available The class of “stable games”, introduced by Hofbauer and Sandholm in 2009, has the attractive property of admitting global convergence to equilibria under many evolutionary dynamics. We show that stable games can be identified as a special case of the feedback-system-theoretic notion of a “passive” dynamical system. Motivated by this observation, we develop a notion of passivity for evolutionary dynamics that complements the definition of the class of stable games. Since interconnections of passive dynamical systems exhibit stable behavior, we can make conclusions about passive evolutionary dynamics coupled with stable games. We show how established evolutionary dynamics qualify as passive dynamical systems. Moreover, we exploit the flexibility of the definition of passive dynamical systems to analyze generalizations of stable games and evolutionary dynamics that include forecasting heuristics as well as certain games with memory.

  14. Environmental Aesthetics

    DEFF Research Database (Denmark)

    Svabo, Connie; Ekelund, Kathrine

    2015-01-01

    The philosophical subfield environmental aesthetics can contribute to the design of sustainable futures. Environmental aesthetics provides a conceptual framework for understanding the relationship between nature and culture. Current positions in environmental aesthetics are lined out and used...

  15. Environmental Performance

    DEFF Research Database (Denmark)

    Svabo, Connie; Lindelof, Anja Mølle

    from the perspective of time and liveness as experienced in art on environmental performance discussing how environmental performances frame the temporality of the world. The paper engages with contemporary examples of environmental performances from various disciplines (sound, video, television...

  16. Stable isotope compounds - production, detection, and application.

    Science.gov (United States)

    Zachleder, Vilém; Vítová, Milada; Hlavová, Monika; Moudříková, Šárka; Mojzeš, Peter; Heumann, Hermann; Becher, Johannes R; Bišová, Kateřina

    2018-01-19

    Stable isotopes are used in wide fields of application from natural tracers in biology, geology and archeology through studies of metabolic fluxes to their application as tracers in quantitative proteomics and structural biology. We review the use of stable isotopes of biogenic elements (H, C, N, O, S, Mg, Se) with the emphasis on hydrogen and its heavy isotope deuterium. We will discuss the limitations of enriching various compounds in stable isotopes when produced in living organisms. Finally, we overview methods for measuring stable isotopes, focusing on methods for detection in single cells in situ and their exploitation in modern biotechnologies. Copyright © 2018. Published by Elsevier Inc.

  17. Surface Morphology of Polyimide Thin Film Dip-Coated on Polyester Filament for Dielectric Layer in Fibrous Organic Field Effect Transistor

    Directory of Open Access Journals (Sweden)

    Rambausek Lina

    2014-09-01

    Full Text Available The idea of wearable electronics automatically leads to the concept of integrating electronic functions on textile substrates. Since this substrate type implies certain challenges in comparison with their rigid electronic companions, it is of utmost importance to investigate the application of materials for generating the electronic functions on the textile substrate. Only when interaction of materials and textile substrate is fully understood, the electronic function can be generated on the textile without changing the textile’s properties, being flexible or stretchable. This research deals with the optimization of the dielectric layer in a fibrous organic field effect transistor (OFET. A transistor can act as an electrical switch in a circuit. In this work, the polyimide layer was dip-coated on a copper-coated polyester filament. After thoroughly investigating the process conditions, best results with minimal thickness and roughness at full insulation could be achieved at a dip-coating speed of 50 mm/min. The polyimide solution was optimal at 15w% and the choice for the solvent NMP was made. In this paper, details on the pre-treatment methods, choice of solvent and dip-coating speed and their effect on layer morphology and thickness, electrical properties and roughness are reported. Results show that the use of polyimide as a dielectric layer in the architecture of a fibrous OFET is promising. Further research deals with the application of the semiconductor layer within the mentioned architecture, to finally build an OFET on a filament for application in smart textiles.

  18. Nanocomposites Derived From a Low-Color Aromatic Polyimide (CP2) and Amine-Functionalized Vapor-Grown Carbon Nanofibers: In Situ Polymerization and Characterization (Preprint)

    Science.gov (United States)

    2007-01-01

    VGCNF are produced by a vapor-phase catalytic process in which a carbon-containing feedstock (e.g., CH4, C2H4, etc.) is pyrolyzed in the presence of...small metal catalyst (e.g., ferrocene, Fe(CO)5, etc.). They have an outer diameter of 60-200 nm, a hollow core of 30-90 nm, and length on the order...and methanesulfonic acid (infra vida ). The molecular weights of the polyimide grafts on VGCNF were calculated based on the assumption that there were

  19. In situ polymerization and performance of alicyclic polyimide/graphene oxide nanocomposites derived from 6FAPB and CBDA

    Science.gov (United States)

    Lu, Yunhua; Hao, Jican; Xiao, Guoyong; Zhao, Hongbin; Hu, Zhizhi; Wang, Tonghua

    2017-02-01

    A series of alicyclic polyimide/graphene oxide(PI/GO) nanocomposites were successfully prepared by in situ polymerization of 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene(6FAPB) and 1,2,3,4-cyclobutanetetracarboxylic dianhydride(CBDA) as well as GO, followed by thermal imidization. The effect of GO on the thermal stability, optical properties, mechanical properties, water absorption and water surface contact angle of the PI-based nanocomposites was investigated. The optical properties of the pure alicyclic PI and corresponding PI-based nanocomposite films showed that the addition of GO reduced the transparency of PI films in the range of 200-800 nm obviously. With the increase of GO loading, the mechanical and thermal properties of alicyclic PI-based nanocomposites were enhanced. For the PI-1.0%GO nanocomposite films, the tensile strength was increased from 96 MPa (pure PI) to 109 MPa, and the Young's modulus was improved from 2.41 GPa (pure PI) to 3.83 GPa. The 10 wt% decomposition temperature for PI-1.0%GO nanocomposite films was increased from 464 (pure PI) to 481 °C, while the glass transition temperature (Tg) of PI/GO was slightly increased. In addition, the water surface contact angle of PI/GO enhanced from 71° to 82.5°, and the water uptake of PI/GO decreased from 2.58% to 1.48% with increasing the GO loadings. The uniform dispersion of GO in PI matrix was proved, and the pure PI and PI/GO nanocomposite films were amorphous.

  20. Effects of Fiber Reinforcement Architecture on the Hygrothermal-Mechanical Performance of Polyimide Matrix Composites for Aeropropulsion Applications

    Science.gov (United States)

    Shin, E. Eugene; Thesken, John C.; Sutter, James K.; Chuang, Kathy; Juhas, John; Veverka, Adrienne; Inghram, Linda; Papadopoulos, Demetrios; Burke, Chris; Scheiman, Dan

    2003-01-01

    A lightweight sandwich support structure, for the combustor chamber of a new generation liquid propellant rocket engine, was designed and fabricated using a polymer matrix composite (PMC) facesheet on a Ti honeycomb core. The PMC facesheet consisted of high stiffness carbon fiber, M40JB, and high temperature Polyimides, such as PMR-II-50 and HFPE-II-52. Six different fiber architectures; four harness satin (4HS) woven fabric, uni-tape, woven-uni hybrid, stitched woven fabric, stitched uni-tape and triaxial braided structures have been investigated for optimum stiffness-thickness-weight-hygrothermal performance design criteria for the hygrothermal-mechanical propulsion service exposure conditions including rapid heating up to 200 F/sec, maximum operating temperature of 600 F, internal pressure up to 100 psi. One of the specific objectives in this study is to improve composite blistering resistance in z-direction at minimum expense of in-plane mechanical properties. An extensive property-performance database including dry-wet mechanical properties at various temperatures, thermal-physical properties, such as blistering onset condition was generated for fiber architecture down-selection and design guidelines. Various optimized process methods such as vacuum bag compression molding, solvent assistant resin transfer molding (SaRTM), resin film infusion (RFI) and autoclaving were utilized for PMC panel fabrication depending on the architecture type. In the case of stitched woven fabric architecture, the stitch pattern in terms of stitch density and yarn size was optimized based on both in-plane mechanical properties and blistering performance. Potential reduction of the in-plane properties transverse to the line of stitching was also evaluated. Efforts have been made to correlate the experimental results with theoretical micro-mechanics predictions. Changes in deformation mechanism and failure sequences in terms of fiber architecture will be discussed.

  1. Electromagnetic interference shielding effectiveness of microcellular polyimide/in situ thermally reduced graphene oxide/carbon nanotubes nanocomposites

    Science.gov (United States)

    Yang, Hongli; Yu, Zhi; Wu, Peng; Zou, Huawei; Liu, Pengbo

    2018-03-01

    A simple and effective method was adopted to fabricate microcellular polyimide (PI)/reduced graphene oxide (GO)/multi-walled carbon nanotubes (MWCNTs) nanocomposites. Firstly, microcellular poly (amic acid) (PAA)/GO/MWCNTs nanocomposites were prepared through solvent evaporation induced phase separation. In this process, PAA and dibutyl phthalate (DBP) co-dissolved in N,N-dimethylacetamide (DMAc) underwent phase separation with DMAc evaporating, and DBP microdomains were formed in continuous PAA phase. Subsequently, PAA was thermally imidized and simultaneously GO was in situ reduced. After DBP was removed, the microcellular PI/reduced GO (RGO)/MWCNTs nanocomposites were finally obtained. When the initial filler loading was 8 wt%, the electrical conductivity of microcellular PI/RGO, PI/MWCNTs and PI/RGO/MWCNTs nanocomposites were 0.05, 0.02 and 1.87 S·m-1, respectively, and the electromagnetic interference (EMI) shielding efficiency (SE) of microcellular PI/RGO, PI/MWCNTs and PI/RGO/MWCNTs nanocomposites were 13.7-15.1, 13.0-14.3 and 16.6-18.2 dB, respectively. The synergistic effect between RGO and MWCNTs enhanced both the electrical conductivity and EMI shielding performance of the microcellular PI/RGO/MWCNTs nanocomposites. The dominating EMI shielding mechanism for these materials was microwave absorption. While the initial loading of GO and MWCNT was 8 wt%, the microcellular PI/RGO/MWCNTs nanocomposite (500 μm thickness) had extremely high specific EMI SE value of 755-823 dB·cm2·g-1. Its thermal stability was also obviously improved, the 5% weight loss temperature in nitrogen was 548 °C. In addition, it also possessed a high Young's modulus of 789 MPa.

  2. Surface decoration of polyimide fiber with carbon nanotubes and its application for mechanical enhancement of phosphoric acid-based geopolymers

    Science.gov (United States)

    Yang, Tao; Han, Enlin; Wang, Xiaodong; Wu, Dezhen

    2017-09-01

    A new methodology to decorate the surface of polyimide (PI) fiber with carbon nanotubes (CNTs) has been developed in this study. This surface decoration was carried out through a surface alkali treatment, a carboxylation modification, surface functionalization with acyl chloride groups and then with amino groups, and a surface graft of CNTs onto PI fiber. Fourier-transform infrared and X-ray photoelectron spectroscopic characterizations confirmed that CNTs were chemically grafted onto the surface of PI fiber, and scanning electron microscopic observation demonstrated the fiber surface was uniformly and densely covered with CNTs. The surface energy and wettability of PI fiber were improved in the presence of CNTs on the fiber surface, which made a contribution to enhance the interfacial adhesion of PI fiber with other inorganic matrices when used as a reinforcing fiber. The application of CNTs-decorated PI fiber for the reinforcement of phosphoric acid-based geopolymers was investigated, and the results indicated that the geopolymeric composites gained a noticeable reinforcement. Compared to unreinforced geopolymer, the geopolymeric composites achieved a remarkable increase in compressive strength by 120% and in flexural strength by 283%. Fractography investigation demonstrated that the interaction adhesion between the fibers and matrix was enhanced due to the surface decoration of PI fiber with CNTs, which contributed to an improvement in fracture-energy dissipation by fiber pullout and fiber debonding from the matrix. As a result, a significant reinforcement effect on geopolymeric composites was achieved through a fiber-bridging mechanism. This study provided an effective methodology to improve the interracial bonding force for PI fiber and also proves a highly efficient application of CNTs-decorated PI fiber for the mechanical enhancement of geopolymeric composites.

  3. Compositional optimization of polyimide-based SEPPI membranes using a genetic algorithm and high-throughput techniques.

    Science.gov (United States)

    Vandezande, Pieter; Gevers, Lieven E M; Weyens, Nele; Vankelecom, Ivo F J

    2009-03-09

    Asymmetric, nanosized zeolite-filled solvent resistant nanofiltration (SRNF) membranes, prepared from emulsified polyimide (PI) solutions via the earlier reported solidification of emulsified polymer solutions via phase inversion (SEPPI) method, were optimized for their performance in the separation of rose bengal (RB) from 2-propanol (IPA). All membranes were prepared and tested in a parallellized, miniaturized, and automated manner using laboratory-developed high-throughput experimentation techniques. Nine different synthesis parameters related to the composition of the casting solutions were thus optimized. In a first, "conventional" approach, a preliminary systematic screening was carried out, in which only four constituents were used, that is, Matrimid PI, NMP as solvent, THF as volatile cosolvent, and an NMP-based zeolite precursor sol as emulsifying agent. A combinatorial strategy, based on a genetic algorithm and a self-adaptive evolutionary strategy, was then applied to optimize the SRNF performance of PI-based SEPPI membranes. This directed approach allowed the screening of an extended, 9-dimensional parameter space, comprising two extra solvents, the two corresponding nanosized zeolite suspensions, as well as another cosolvent. Coupling with high-throughput techniques allowed the preparation of three generations of casting solutions, 176 compositions in total, resulting in 125 testable membranes. With IPA permeances up to 3.3 L.m(-2) h(-1) bar(-1) and RB rejections around 98%, the combinatorially optimized membranes scored significantly better with respect to fluxes and selectivities than the best membranes obtained in the systematic screening. The best SEPPI membranes also showed much higher IPA permeances than two commercial SRNF membranes at similar or slightly lower RB rejections.

  4. Pure- and mixed-gas propylene/propane permeation properties of spiro- and triptycene-based microporous polyimides

    KAUST Repository

    Swaidan, Ramy Jawdat

    2015-06-03

    Solution-processable polyimides of intrinsic microporosity (PIM-PIs) comprising relatively inflexible and contorted backbones have demonstrated outstanding molecular-sieving behavior in membrane-based separation of gas/gas pairs. In this work, the effects of systematically increasing intra-chain rigidity on the propylene/propane separation properties were compared for PIM-PIs made from 2,3,5,6-tetramethyl-1,4-phenylene diamine (TMPD) and (i) spiro-centered dianhyride (SPDA-TMPD or PIM-PI-1) and (ii) 9,10-diisopropyltriptycene-based dianhydride (TPDA-TMPD or KAUST PI-1). Pure-gas experiments at 2 bar and 35 oC showed significant increases in C3H6 permeability and C3H6/C3H8 selectivity by transitioning from PIM-PI-1 (P(C3H6)=393 Barrer, α(C3H6/C3H8)=6) to KAUST-PI-1 (P(C3H6)=817 Barrer, α(C3H6/C3H8)=16), positioning KAUST-PI-1 considerably above the experimentally observed pure-gas C3H6/C3H8 polymer upper bound. However, 50:50 C3H6/C3H8 mixed-gas feeds induced significant losses in C3H6 permeability and C3H6/C3H8 selectivity relative to the 2 bar pure-gas data for PIM-PI-1 and KAUST-PI-1 as the C3H6/C3H8 selectivity dropped from 6 to 3 and 16 to 5, respectively, at 2 bar C3H6 partial pressure due to plasticization and competitive sorption.

  5. Compositional, structural, and optical changes of polyimide implanted by 1.0 MeV Ni+ ions

    Science.gov (United States)

    Mikšová, R.; Macková, A.; Pupikova, H.; Malinský, P.; Slepička, P.; Švorčík, V.

    2017-09-01

    The ion irradiation leads to deep structural and compositional changes in the irradiated polymers. Ni+ ions implanted polymers were investigated from the structural and compositional changes point of view and their optical properties were investigated. Polyimide (PI) foils were implanted with 1.0 MeV Ni+ ions at room temperature with fluencies of 1.0 × 1013-1.0 × 1015 cm-2 and two different ion implantation currents densities (3.5 and 7.2 nA/cm2). Rutherford Back-Scattering (RBS) and Elastic Recoil Detection Analysis (ERDA) were used for determination of oxygen and hydrogen escape in implanted PI. Atomic Force Microscopy (AFM) was used to follow surface roughness modification after the ion implantation and UV-Vis spectroscopy was employed to check the optical properties of the implanted PI. The implanted PI structural changes were analysed using Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR). High energy Ni-ion implantation causes only a minor release of hydrogen and oxygen close to the polymer sub-surface region in about 60 nm thick layer penetrated by the ion beam; especially at ion fluencies below 1.0 × 1014 cm-2. The mostly pronounced structural changes of the Ni implanted PI were found for the samples implanted above ion fluence 1.0 × 1015 cm-2 and at the ion current density 7.2 nA/cm2, where the optical band gap significantly decreases and the reduction of more complex structural unit of PI monomer was observed.

  6. physico-chemical and stable isotopes

    African Journals Online (AJOL)

    This paper details the mineralogical, chemical and stable isotope abundances of calcrete in the Letlhakeng fossil valley. The stable isotope abundances (O and C) of calcretes yielded some values which were tested against the nature of the calcretes – pedogenic or groundwater type. The Kgalagadi (Kalahari) is a vast ...

  7. Stable isotopes and biomarkers in microbial ecology

    NARCIS (Netherlands)

    Boschker, H.T.S.; Middelburg, J.J.

    2002-01-01

    The use of biomarkers in combination with stable isotope analysis is a new approach in microbial ecology and a number of papers on a variety of subjects have appeared. We will first discuss the techniques for analysing stable isotopes in biomarkers, primarily gas chromatography-combustion-isotope

  8. Modelling stable atmospheric boundary layers over snow

    NARCIS (Netherlands)

    Sterk, H.A.M.

    2015-01-01

    Thesis entitled: Modelling Stable Atmospheric Boundary Layers over Snow H.A.M. Sterk Wageningen, 29th of April, 2015 Summary The emphasis of this thesis is on the understanding and forecasting of the Stable Boundary Layer (SBL) over snow-covered surfaces. SBLs typically form at night and in polar

  9. The integrated periodogram for stable processes

    NARCIS (Netherlands)

    Kluppelberg, C; Mikosch, T

    1996-01-01

    We study the asymptotic behavior of the integrated periodogram for alpha-stable linear processes. For alpha is an element of (1, 2) we prove a functional limit theorem for the integrated periodogram. The limit is an alpha-stable analogue to the Brownian bridge. We apply our results to investigate

  10. High order stiffly stable linear multistep methods

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, C.N.

    1979-01-01

    Stiffly stable linear k-step methods of order k for the initial-value problem are studied. Examples for k = 1, 2, and 3 were discovered by use of Adams-type methods. A large family of stiffly stable linear 7-step methods of order 7 was also found.

  11. Recent progress in developing highly efficient and thermally stable nonlinear optical polymers for electro-optics

    Science.gov (United States)

    Luo, Jingdong; Liu, Sen; Haller, Marnie A.; Kang, Jae-Wook; Kim, Tae-Dong; Jang, Sei-Hum; Chen, Baoquan; Tucker, Neil; Li, Hongxiang; Tang, Hong-Zhi; Dalton, Larry R.; Liao, Yi; Robinson, Bruce H.; Jen, Alex K.

    2004-06-01

    Recent development of high-performance nonlinear optical polymers for electro-optics (E-O) is reviewed in this paper. A highly efficient and thermally stable nonlinear optical (NLO) chromophore, namely 2-[4-(2-{5-[2-(4-{Bis-(tert-butyl-dimethyl-silanyloxy)-ethyl]-amino}-phenyl)-vinyl]-thiophen-2-yl}-vinyl)-3-cyano-5-trifluoromethyl-5H-furan-2-ylidene]-malononitrile, has been prepared and incorporated in amorphous polycarbonate (APC) composites. The result from high electric field poling shows a very large E-O coefficient (r33 = 94 pm/V at 1.3 μm), 80% of which can be maintained at 85 °C for more than 500 hours. In addition to this guest/host sysytem, a high Tg side-chain polymer, derived from a 3-D cardo-type polimide with dendron-encapsulated chromophores as pendent groups has also been synthesized and characterized. A high degree of chromophore dipole orientation and a large r33 of 71 pm/V at 1.3 μm can be achieved in this poled polyimide. More than 90% of its E-O activity can be maintained at 85 °C for more than 600 hours. To access the full potential of poled polymers for device applications, we have developed a new lattice-hardening approach to overcome the "nonlinearity-stability-tradeoff" of conventional thermoset methods. By using the Diels-Alder lattice-hardening process, we can achieve the same high poling efficiency and large r33value as in a guest-host system while maintaining good thermal stability seen in densely-crosslinked polymers. By modifying the electronic properties of the crosslinking reagents, we can fine-tune the processing temperature window of the Diels-Alder reactions to achieve hardened materials with optimal properties.

  12. Competition for nutrient and light: stable coexistence, alternative stable states, or competitive exclusion?

    NARCIS (Netherlands)

    Passarge, J.; Hol, S.; Escher, M.; Huisman, J.

    2006-01-01

    Competition theory has put forward three contrasting hypotheses: Competition for nutrients and light may lead to (i) stable coexistence of species, (ii) alternative stable states, or (iii) competitive exclusion. This paper presents a detailed investigation of competition among phytoplankton species

  13. Competition for nutrients and light: Stable coexistence, alternative stable states or competitive exclusion?

    NARCIS (Netherlands)

    Passarge, J.; Hol, S.; Escher, M.; Huisman, J.

    2006-01-01

    Abstract. Competition theory has put forward three contrasting hypotheses: Competition for nutrients and light may lead to (i) stable coexistence of species, (ii) alternative stable states, or (iii) competitive exclusion. This paper presents a detailed investigation of competition among

  14. Design and Synthesis of Polyimides Based on Carbocyclic Pseudo-Tröger’s Base-Derived Dianhydrides for Membrane Gas Separation Applications

    KAUST Repository

    Ma, Xiaohua

    2017-07-24

    Two novel carbocyclic pseudo-Tröger’s base-derived dianhydrides, 5,6,11,12-tetrahydro-5,11-methanodibenzo[a,e][8]annulene-2,3,8,9-tetracarboxylic anhydride (CTB1) and its dione-substituted analogue 6,12-dioxo-5,6,11,12-tetrahydro-5,11-methanodibenzo[a,e][8]annulene-2,3,8,9-tetracarboxylic dianhydride (CTB2), were made and used for the synthesis of soluble polyimides of intrinsic microporosity with 3,3′-dimethylnaphthidine (DMN). The polyimides CTB1-DMN and CTB2-DMN exhibited excellent thermal stability of ∼500 °C and high BET surface areas of 580 and 469 m2 g–1, respectively. A freshly made dione-substituted CTB2-DMN membrane demonstrated promising gas separation performance with O2 permeability of 206 barrer and O2/N2 selectivity of 5.2. A higher O2 permeability of 320 barrer and lower O2/N2 selectivity of 4.2 were observed for a fresh CTB1-DMN film due to its higher surface area and less tightly packed structure as indicated by weaker charge-transfer complex interactions. Physical aging over 60 days resulted in reduction in gas permeability and moderately enhanced selectivity. CTB2-DMN exhibited notable performance with gas permeation data located between the 2008 and 2015 permeability/selectivity upper bounds for O2/N2 and H2/CH4.

  15. Correlations of norbornenyl crosslinked polyimide resin structures with resin thermo-oxidative stability, resin glass transition temperature and composite initial mechanical properties

    Science.gov (United States)

    Alston, William B.

    1988-01-01

    PMR (polymerization of monomeric reactants) methodology was used to prepare 70 different polyimide oligomeric resins and 30 different unidirectional graphite fiber/polyimide composites. Monomeric composition as well as chain length between sites of crosslinks were varied to examine their effects on resin thermo-oxidative stability and glass transition temperature (Tg) of the cured/postcured resins. A linear correlation of decreasing 316 C resin weight loss/surface area versus (1) decreasing aliphatic content, or (2) increasing benzylic/aliphatic content stoichiometry ratio over a wide range of resin compositions was observed. An almost linear correlation of Tg versus molecular distance between the crosslinks was also observed. An attempt was made to correlate Tg with initial composite mechanical properties (flexural strength and interlaminar shear strength). However, the scatter in mechanical strength data prevented obtaining a clear correlation. Instead, only a range of composite mechanical properties was obtained at 25, 288, and 316 C. Perhaps more importantly, what did become apparent during the correlation study was (1) the PMR methodology could be used to prepare composites from resins containing a wide variety of monomer modifications, (2) that these composites almost invariably provided satisfactory initial mechanical properties as long as the resins formulated exhibited satisfactory processing flow, and (3) that PMR resins exhibited predictable rates of 316 C weight loss/surface area based on their benzylic/aliphatic stoichiometery ratio.

  16. Novel 6FDA-based polyimides derived from sterically hindered Tröger's base diamines: Synthesis and gas permeation properties

    KAUST Repository

    Ghanem, Bader

    2016-04-30

    Two novel Tröger\\'s base-based di-o-substituted diamine monomers were synthesized and used to prepare two intrinsically microporous 6FDA-based polyimides (PIM-PI-TB-1 and PIM-PI-TB-2) with high molecular weight, high thermal stability and excellent solubility in common organic solvents. Compared to previously reported methods for preparing TB-based diamines, which are based on reduction of dimerized nitro-substituted anilines or condensation of phenylenediamine derivatives with dianhydrides, the novel protocol can be used to prepare different functionalized TB-based diamine monomers from a wide variety of aniline derivatives. PIM-PI-TB-1 (made from 6FDA and dibromo-tetramethyl-substituted TB diamine) and PIM-PI-TB-2 (made from 6FDA and tetramethyl-substituted TB diamine) are intrinsically microporous polymers with high BET surface areas of 440 m2/g and 580 m2/g, respectively. Pure-gas permeability coefficients of He, H2, N2, O2, CH4, and CO2 were measured at 35 °C and 2 bar for fresh and 180 days aged films. Both TB-based polyimides exhibited high gas permeability with moderate selectivity. The gas permeability dropped significantly coupled with a moderate increase in selectivity after long-term physical aging of 180 days.

  17. Photo-aligned blend films of azobenzene-containing polyimides with and without side-chains for inducing inclined alignment of liquid crystal molecules

    Science.gov (United States)

    Usami, Kiyoaki; Sakamoto, Kenji

    2011-08-01

    We have succeeded in controlling the pretilt angle of liquid crystal (LC) molecules over the whole range of 0 to 90° by using photo-aligned blend films of two azobenzene-containing polyimides (Azo-PIs) with and without side-chains. The Azo-PIs were synthesized from pyromellitic dianhydride and a mixture of 4,4'-diaminoazobenzene and 4-(4'-propylbi(cyclohexan)-4-yl)phenyl 3,5-diaminobenzoate (PBCP-DABA). PBCP-DABA is a diamine to introduce a side-chain structure into the polyimide. Defect-free uniform LC alignment was obtained in the pretilt angle (θp) ranges of θp ≤ 11° and θp ≥ 78°. Previously, we reported that the pretilt angle can be controlled using pure photo-aligned films of Azo-PIs with different molar fractions of PBCP-DABA. For the pure photo-aligned films, the defect-free pretilt angle ranges were θp < 5° and θp ≥ 85°. These results suggest that the azimuthal anchoring strength of the blend Azo-PI film is stronger than that of the pure films of Azo-PIs with side-chains, at least for the pretilt angle range from 5 to 11°. We found that the defect-free pretilt angle range can be extended by using the blend Azo-PI films instead of the pure Azo-PI films.

  18. Environmental strategy

    DEFF Research Database (Denmark)

    Zabkar, Vesna; Cater, Tomaz; Bajde, Domen

    2013-01-01

    Environmental issues and the inclusion of environmental strategies in strategic thinking is an interesting subject of investigation. In general, managerial practices organized along ecologically sound principles contribute to a more environmentally sustainable global economy. From the managerial...... perspective, appropriate environmental strategies in compliance with environmental requirements aim at building competitive advantages through sustainable development. There is no universal “green” strategy that would be appropriate for each company, regardless of its market requirements and competitive...... situations. Instead, managers undertake careful consideration of the circumstances in which their company operates, paying special attention to their customers’ environmental preferences....

  19. Preliminary Evaluation of Techniques to Fabricate Beryllium, Polyimide, and Ge-doped CH/CD Ablator Materials

    Energy Technology Data Exchange (ETDEWEB)

    Cook, B; Letts, S; Nikroo, A; Nobile, A; McElfresh, M; Cooley, J; Alexander, D

    2004-11-08

    This report including appendices provides information to complete this deliverable. It summarizes the important features of each ablator material, with particular focus to its usefulness for ignition capsules. More detailed discussions of each ablator type are in the Appendix. Included at the end of each separate discussion in the Appendix is a list of all published work with an ICF focus on that ablator type. This report is organized into Be based and polymer (C) based ablators. We summarize status, outstanding issues, and how we plan to address them. Details are in the Appendix. For Be there are two fabrication routes, one by machining bulk pieces into hemi-shells which are then bonded together, and the other by sputtering Be with Cu dopant onto spherical plastic mandrels to build up a wall. This method allows for radial variation in the Cu dopant concentration, while the machining approach is best suited to a uniform doping level. For plastic, we have already made a down select, eliminating polyimide because its performance as an ablator has been seen to be significantly different from that predicted by simulations. The other polymer, GDP (glow discharge polymer or sometimes called plasma polymer) comes in both a normal (hydrogenated) and deuterated form. There are differences between them (besides the H or D) and these will be detailed. The choice between them will be determined in part by cryogenic measurement of the IR absorption spectrum of DT scheduled to occur in the next few months. An initial list of specifications for ignition targets exists. However these specifications are continuing to evolve. This is due to evolving plans for NIF's deliverable energy and to more refined design simulations. Many requirements are not well specified due to lack of knowledge of the effect on the implosion. These requirements include: grain size and texture, fill hole size, fill tube size, bond joint thickness, allowable porosity (size and number), diameter and wall

  20. Stable Economic Cooperation : A Relational Approach

    NARCIS (Netherlands)

    Gilles, R.P.; Lazarova, E.A.; Ruys, P.H.M.

    2008-01-01

    We consider a relational economy in which economic agents participate in three types of relational economic activities: autarkic activities; binary matching activities; and plural cooperative activities. We introduce a stability notion and characterize stable interaction structures, both in the

  1. On Stable Marriages and Greedy Matchings

    Energy Technology Data Exchange (ETDEWEB)

    Manne, Fredrik; Naim, Md; Lerring, Hakon; Halappanavar, Mahantesh

    2016-12-11

    Research on stable marriage problems has a long and mathematically rigorous history, while that of exploiting greedy matchings in combinatorial scientific computing is a younger and less developed research field. In this paper we consider the relationships between these two areas. In particular we show that several problems related to computing greedy matchings can be formulated as stable marriage problems and as a consequence several recently proposed algorithms for computing greedy matchings are in fact special cases of well known algorithms for the stable marriage problem. However, in terms of implementations and practical scalable solutions on modern hardware, the greedy matching community has made considerable progress. We show that due to the strong relationship between these two fields many of these results are also applicable for solving stable marriage problems.

  2. Bartolome Island, Galapagos Stable Oxygen Calibration Data

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Galapagos Coral Stable Oxygen Calibration Data. Sites: Bartolome Island: 0 deg, 17'S, 90 deg 33' W. Champion Island: 1 deg, 15'S, 90 deg, 05' W. Urvina Bay (Isabela...

  3. Allan Hills Stable Water Isotopes, Version 1

    Data.gov (United States)

    National Aeronautics and Space Administration — This data set includes stable water isotope values at 10 m resolution along an approximately 5 km transect through the main icefield of the Allan Hills Blue Ice...

  4. Stable isotope deltas: Tiny, yet robust signatures in nature

    Science.gov (United States)

    Brand, Willi A.; Coplen, Tyler B.

    2012-01-01

    Although most of them are relatively small, stable isotope deltas of naturally occurring substances are robust and enable workers in anthropology, atmospheric sciences, biology, chemistry, environmental sciences, food and drug authentication, forensic science, geochemistry, geology, oceanography, and paleoclimatology to study a variety of topics. Two fundamental processes explain the stable isotope deltas measured in most terrestrial systems: isotopic fractionation and isotope mixing. Isotopic fractionation is the result of equilibrium or kinetic physicochemical processes that fractionate isotopes because of small differences in physical or chemical properties of molecular species having different isotopes. It is shown that the mixing of radioactive and stable isotope end members can be modelled to provide information on many natural processes, including 14C abundances in the modern atmosphere and the stable hydrogen and oxygen isotopic compositions of the oceans during glacial and interglacial times. The calculation of mixing fractions using isotope balance equations with isotope deltas can be substantially in error when substances with high concentrations of heavy isotopes (e.g. 13C, 2H, and 18O ) are mixed. In such cases, calculations using mole fractions are preferred as they produce accurate mixing fractions. Isotope deltas are dimensionless quantities. In the International System of Units (SI), these quantities have the unit 1 and the usual list of prefixes is not applicable. To overcome traditional limitations with expressing orders of magnitude differences in isotope deltas, we propose the term urey (symbol Ur), after Harold C. Urey, for the unit 1. In such a manner, an isotope delta value expressed traditionally as−25 per mil can be written as−25 mUr (or−2.5 cUr or−0.25 dUr; the use of any SI prefix is possible). Likewise, very small isotopic differences often expressed in per meg ‘units’ are easily included (e.g. either+0.015 ‰ or+15 per meg

  5. Stable isotope deltas: tiny, yet robust signatures in nature.

    Science.gov (United States)

    Brand, Willi A; Coplen, Tyler B

    2012-09-01

    Although most of them are relatively small, stable isotope deltas of naturally occurring substances are robust and enable workers in anthropology, atmospheric sciences, biology, chemistry, environmental sciences, food and drug authentication, forensic science, geochemistry, geology, oceanography, and paleoclimatology to study a variety of topics. Two fundamental processes explain the stable isotope deltas measured in most terrestrial systems: isotopic fractionation and isotope mixing. Isotopic fractionation is the result of equilibrium or kinetic physicochemical processes that fractionate isotopes because of small differences in physical or chemical properties of molecular species having different isotopes. It is shown that the mixing of radioactive and stable isotope end members can be modelled to provide information on many natural processes, including (14)C abundances in the modern atmosphere and the stable hydrogen and oxygen isotopic compositions of the oceans during glacial and interglacial times. The calculation of mixing fractions using isotope balance equations with isotope deltas can be substantially in error when substances with high concentrations of heavy isotopes (e.g. (13)C, (2)H, and (18)O ) are mixed. In such cases, calculations using mole fractions are preferred as they produce accurate mixing fractions. Isotope deltas are dimensionless quantities. In the International System of Units (SI), these quantities have the unit 1 and the usual list of prefixes is not applicable. To overcome traditional limitations with expressing orders of magnitude differences in isotope deltas, we propose the term urey (symbol Ur), after Harold C. Urey, for the unit 1. In such a manner, an isotope delta value expressed traditionally as-25 per mil can be written as-25 mUr (or-2.5 cUr or-0.25 dUr; the use of any SI prefix is possible). Likewise, very small isotopic differences often expressed in per meg 'units' are easily included (e.g. either+0.015 ‰ or+15 per meg

  6. Environmental Measurement

    Science.gov (United States)

    Environmental measurement is any data collection activity involving the assessment of chemical, physical, or biological factors in the environment which affect human health. Learn more about these programs and tools that aid in environmental decisions

  7. Environmental Modeling

    Science.gov (United States)

    EPA's modeling community is working to gain insights into certain parts of a physical, biological, economic, or social system by conducting environmental assessments for Agency decision making to complex environmental issues.

  8. Regularity of Tor for weakly stable ideals

    Directory of Open Access Journals (Sweden)

    Katie Ansaldi

    2015-05-01

    Full Text Available It is proved that if I and J are weakly stable ideals in a polynomial ring R = k[x_1, . . ., x_n], with k a field, then the regularity of Tor^R_i (R/I, R/J has the expected upper bound. We also give a bound for the regularity of Ext^i_R (R/I, R for I a weakly stable ideal.

  9. Highly stable flexible thermistor properties of spinel Mn-Co-Ni oxide films on silver/carbon micro-pinecone array composite electrodes

    Science.gov (United States)

    Nakajima, Tomohiko; Hanawa, Satomi; Tsuchiya, Tetsuo

    2017-10-01

    We fabricated flexible Mn1.56Co0.96Ni0.48O4 (MCN) thermistors with stable electrical properties by precisely optimizing precursors and electrodes. The composite Ag and carbon micro-pinecone (CMP) arrays were fabricated with a KrF laser directly from polyimide sheets containing silica nanoparticles and functioned well as electrodes with high bending resistance. The electrical resistance was stable even after 10 000 bending test cycles. The well-crystallized MCN film thermistors were fabricated on the Ag/CMP composite electrodes by KrF laser irradiation at 55 mJ.cm-2 for 600 pulses to optimize the precursor films consisting of MCN nanoparticles and amorphous Mn-Co-Ni oxides. The MCN film thermistors showed high thermistor constants at 3633 K, low electrical resistivity at 10.7 kΩ.cm at 37 °C, and remarkably good stability during 10 000 bending cycles (the change in resistance was only 0.6%). The MCN film thermistors also had excellent temperature cycle resistance at 20-150 °C (3000 cycles). Thus, we improved the reliability of flexible thermistors for application in various kinds of wearable devices.

  10. Environmental Performance

    DEFF Research Database (Denmark)

    Lindelof, Anja Mølle; Schmidt, Ulrik; Svabo, Connie

    2017-01-01

    as its starting point to investigate liveness within a specific kind of contemporary performance: ‘environmental performances’. Environmental performances are arts practices that take environmental processes as their focus by framing activities of non-human performers such as clouds, wind and weeds - key...

  11. Appendix to Health and Safety Laboratory environmental quarterly report. [Fallout radionuclides deposited and in surface air at various world sites; /sup 137/Cs and /sup 90/Sr in milk and drinking water in New York City; and stable Pb in surface air

    Energy Technology Data Exchange (ETDEWEB)

    Hardy, E.P. Jr.

    1977-07-01

    Tabulated data are presented on the deposition of fallout /sup 89/Sr and /sup 90/Sr at various world land sites through 1976; the ..gamma.. spectra and content of /sup 7/Be, /sup 95/Zr, /sup 137/Cs, /sup 144/Ce, /sup 90/Sr, /sup 210/Pb, /sup 238/Pu, /sup 239/Pu, and stable Pb in samples of surface air collected during 1966 at various world sites; and the content of fallout /sup 137/Cs and /sup 90/Sr in samples of drinking water and milk collected in New York City through 1976. (CH)

  12. Local Search Approaches in Stable Matching Problems

    Directory of Open Access Journals (Sweden)

    Toby Walsh

    2013-10-01

    Full Text Available The stable marriage (SM problem has a wide variety of practical applications, ranging from matching resident doctors to hospitals, to matching students to schools or, more generally, to any two-sided market. In the classical formulation, n men and n women express their preferences (via a strict total order over the members of the other sex. Solving an SM problem means finding a stable marriage where stability is an envy-free notion: no man and woman who are not married to each other would both prefer each other to their partners or to being single. We consider both the classical stable marriage problem and one of its useful variations (denoted SMTI (Stable Marriage with Ties and Incomplete lists where the men and women express their preferences in the form of an incomplete preference list with ties over a subset of the members of the other sex. Matchings are permitted only with people who appear in these preference lists, and we try to find a stable matching that marries as many people as possible. Whilst the SM problem is polynomial to solve, the SMTI problem is NP-hard. We propose to tackle both problems via a local search approach, which exploits properties of the problems to reduce the size of the neighborhood and to make local moves efficiently. We empirically evaluate our algorithm for SM problems by measuring its runtime behavior and its ability to sample the lattice of all possible stable marriages. We evaluate our algorithm for SMTI problems in terms of both its runtime behavior and its ability to find a maximum cardinality stable marriage. Experimental results suggest that for SM problems, the number of steps of our algorithm grows only as O(n log(n, and that it samples very well the set of all stable marriages. It is thus a fair and efficient approach to generate stable marriages. Furthermore, our approach for SMTI problems is able to solve large problems, quickly returning stable matchings of large and often optimal size, despite the

  13. Towards a climatology of orographic induced wave drag in the stable boundary layer over real terrain

    NARCIS (Netherlands)

    Kleczek, M.A.; Steeneveld, G.J.; Nappo, C.J.; Holtslag, A.A.M.

    2012-01-01

    The stable boundary layer (SBL) is of particular interest for numerous environmental issues as air quality, aviation, fog forecasting, wind energy engineering, and climate modelling. Unfortunately the current understanding of the SBL is still rather poor, and progress is slow. The relatively poor

  14. (Environmental technology)

    Energy Technology Data Exchange (ETDEWEB)

    Boston, H.L.

    1990-10-12

    The traveler participated in a conference on environmental technology in Paris, sponsored by the US Embassy-Paris, US Environmental Protection Agency (EPA), the French Environmental Ministry, and others. The traveler sat on a panel for environmental aspects of energy technology and made a presentation on the potential contributions of Oak Ridge National Laboratory (ORNL) to a planned French-American Environmental Technologies Institute in Chattanooga, Tennessee, and Evry, France. This institute would provide opportunities for international cooperation on environmental issues and technology transfer related to environmental protection, monitoring, and restoration at US Department of Energy (DOE) facilities. The traveler also attended the Fourth International Conference on Environmental Contamination in Barcelona. Conference topics included environmental chemistry, land disposal of wastes, treatment of toxic wastes, micropollutants, trace organics, artificial radionuclides in the environment, and the use biomonitoring and biosystems for environmental assessment. The traveler presented a paper on The Fate of Radionuclides in Sewage Sludge Applied to Land.'' Those findings corresponded well with results from studies addressing the fate of fallout radionuclides from the Chernobyl nuclear accident. There was an exchange of new information on a number of topics of interest to DOE waste management and environmental restoration needs.

  15. Environmental spaces

    DEFF Research Database (Denmark)

    Larsen, Henrik Gutzon

    Using the development of intergovernmental environmental cooperation in the Baltic Sea area as a concrete example, the aim of this study is to explore how the 'environment' in situations of environmental interdependence is identified and institutionalised as political-geographical objects....... 'Environmental interdependence' is to this end conceptualised as a tension between 'political spaces' of discrete state territories and 'environmental spaces' of spatially nested ecosystems. This tension between geographies of political separateness and environmental wholeness is the implicit or explicit basis...... for a large and varied literature. But in both its critical and problemsolving manifestations, this literature tends to naturalise the spatiality of environmental concerns: environmental spaces are generally taken for granted. On the suggestion that there is a subtle politics to the specification...

  16. Temperature and Humidity Control in Livestock Stables

    DEFF Research Database (Denmark)

    Hansen, Michael; Andersen, Palle; Nielsen, Kirsten M.

    2010-01-01

    The paper describes temperature and humidity control of a livestock stable. It is important to have a correct air flow pattern in the livestock stable in order to achieve proper temperature and humidity control as well as to avoid draught. In the investigated livestock stable the air flow...... is controlled using wall mounted ventilation flaps. In the paper an algorithm for air flow control is presented meeting the needs for temperature and humidity while taking the air flow pattern in consideration. To obtain simple and realisable controllers a model based control design method is applied....... In the design dynamic models for temperature and humidity are very important elements and effort is put into deriving and testing the models. It turns out that non-linearities are dominating in both models making feedback linearization the natural design method. The air controller as well as the temperature...

  17. On some topological properties of stable measures

    DEFF Research Database (Denmark)

    Nielsen, Carsten Krabbe

    1996-01-01

    Summary The paper shows that the set of stable probability measures and the set of Rational Beliefs relative to a given stationary measure are closed in the strong topology, but not closed in the topology of weak convergence. However, subsets of the set of stable probability measures which...... are characterized by uniformity of convergence of the empirical distribution are closed in the topology of weak convergence. It is demonstrated that such subsets exist. In particular, there is an increasing sequence of sets of SIDS measures who's union is the set of all SIDS measures generated by a particular...... system and such that each subset consists of stable measures. The uniformity requirement has a natural interpretation in terms of plausibility of Rational Beliefs...

  18. Stable isotope dilution assays in mycotoxin analysis.

    Science.gov (United States)

    Rychlik, Michael; Asam, Stefan

    2008-01-01

    The principle and applications of stable isotope dilution assays (SIDAs) in mycotoxin analysis are critically reviewed. The general section includes historical aspects of SIDAs, the prerequisites and limitations of the use of stable isotopically labelled internal standards, and possible calibration procedures. In the application section actual SIDAs for the analysis of trichothecenes, zearalenone, fumonisins, patulin, and ochratoxin A are presented. The syntheses and availability of labelled mycotoxins for use as internal standards is reviewed and specific advances in food analysis and toxicology are demonstrated. The review indicates that LC-MS applications, in particular, require the use of stable isotopically labelled standards to compensate for losses during clean-up and for discrimination due to ion suppression. As the commercial availability of these compounds continues to increase, SIDAs can be expected to find expanding use in mycotoxin analysis.

  19. Stable isotope dilution assays in mycotoxin analysis

    Energy Technology Data Exchange (ETDEWEB)

    Rychlik, Michael; Asam, Stefan [Universitaet Muenchen, Lehrstuhl fuer Lebensmittelchemie der Technischen, Garching (Germany)

    2008-01-15

    The principle and applications of stable isotope dilution assays (SIDAs) in mycotoxin analysis are critically reviewed. The general section includes historical aspects of SIDAs, the prerequisites and limitations of the use of stable isotopically labelled internal standards, and possible calibration procedures. In the application section actual SIDAs for the analysis of trichothecenes, zearalenone, fumonisins, patulin, and ochratoxin A are presented. The syntheses and availability of labelled mycotoxins for use as internal standards is reviewed and specific advances in food analysis and toxicology are demonstrated. The review indicates that LC-MS applications, in particular, require the use of stable isotopically labelled standards to compensate for losses during clean-up and for discrimination due to ion suppression. As the commercial availability of these compounds continues to increase, SIDAs can be expected to find expanding use in mycotoxin analysis. (orig.)

  20. Synthesis and effect of physical aging on gas transport properties of a microporous polyimide derived from a novel spirobifluorene-based dianhydride

    KAUST Repository

    Ma, Xiaohua

    2015-02-17

    A novel generic method is reported for the synthesis of a spirobifluorene-based dianhydride (SBFDA). An intrinsically microporous polyimide was obtained by polycondensation reaction with 3,3′-dimethylnaphthidine (DMN). The corresponding polymer (SBFDA-DMN) exhibited good solubility, excellent thermal stability, as well as significant microporosity with high BET surface area of 686 m2/g. The O2 permeability of a methanol-treated and air-dried membrane was 1193 Barrer with a moderate O2/N2 selectivity of 3.2. The post-treatment history and aging conditions had great effects on the membrane performance. A significant drop in permeability coupled with an increase in selectivity was observed after long-term aging. After storage of 200 days, the gas separation properties of SBFDA-DMN were located slightly above the latest Robeson upper bounds for several gas pairs such as O2/N2 and H2/N2.