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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
DOE OSTI2013

Analysis of carrier behavior in C60/P(VDF-TrFE) double-layer capacitor by using electric-field-induced optical second-harmonic generation measurement

By using displacement current measurement (DCM) and electric-field-induced optical second-harmonic generation (EFISHG) measurement, we studied the carrier behavior in the indium-tin oxide (ITO)/Poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE))/C60/Au(or Al) capacitors. Two DCM peaks appeared asymmetrically at around −35.5 V and +30.0 V in the dark. Correspondingly, the EFISHG response from the C60 layer was observed, but the peak positions were different with respect to DCM ones. The results show that the spontaneous polarization of the ferroelectric P(VDF-TrFE) polymeric layer directly affects the electric field in the C60 layer, and thus governs the carrier motion in this layer. As a result, the C60 layer serves like an insulator in the dark, while electrons and holes are captured and released at the interface in response to the turn-over of spontaneous polarization of ferroelectric layer. On the other hand, under white light illumination, C60 layer serves like a conductor due to the increase of photogenerated mobile carriers, and these carriers dominate the carrier motions therein. Our findings here will be helpful for analyzing carrier behaviors in organic electronic devices using ferroelectric polymers.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2014

Dielectric properties of poly(vinylidene fluoride) nanocomposites filled with surface coated BaTiO{sub 3} by SnO{sub 2} nanodots

SnO{sub 2} nanoparticles with an average diameter of about 4 nm were coated on the surface of BaTiO{sub 3} (BT) (∼100 nm) by chemical treatment. With the introduction of BT@SnO{sub 2}, the dielectric permittivity of poly(vinylidene fluoride) (PVDF) composite was significantly increased to 90 at 10{sup 3} Hz, which is ∼40% higher than that of the BT/PVDF composites. It was attributed to the enhanced interfacial polarization in the interlayers between BT and PVDF due to the addition of SnO{sub 2} nanodots. The distance of SnO{sub 2} nanodots on the adjacent BT surfaces is close enough for the electron transport in the matrix by tunneling effect. Besides, the semiconductive SnO{sub 2} leads to the weak insulating-conducting transition close to the percolation threshold.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Effect of roll hot press temperature on crystallite size of PVDF film

Fabrication PVDF films have been made using Hot Roll Press. Preparation of samples carried out for nine different temperatures. This condition is carried out to see the effect of Roll Hot Press temperature on the size of the crystallite of PVDF films. To obtain the diffraction pattern of sample characterization is performed using X-Ray Diffraction. Furthermore, from the diffraction pattern is obtained, the calculation to determine the crystallite size of the sample by using the Scherrer equation. From the experimental results and the calculation of crystallite sizes obtained for the samples with temperature 130 °C up to 170 °C respectively increased from 7.2 nm up to 20.54 nm. These results show that increasing temperatures will also increase the size of the crystallite of the sample. This happens because with the increasing temperature causes the higher the degree of crystallization of PVDF film sample is formed, so that the crystallite size also increases. This condition indicates that the specific volume or size of the crystals depends on the magnitude of the temperature as it has been studied by Nakagawa.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Nanoindentation and thermal characterization of poly (vinylidenefluoride)/MWCNT nanocomposites

We report the preparation, thermal and micro/nanomechanical behavior of poly (vinylidine diflouride) (PVDF)/multiwalled carbon nanotube (MWCNT) nanocomposites. It has been found that the addition of MWCNT considerably enhances the β-phase formation, thermal and mechanical properties of PVDF. Atomic force microscope (AFM) studies have been performed on the composites under stress conditions to measure the mechanical properties. The nanoscale mechanical properties of the composites like Young's modulus and hardness of the nanocomposites were investigated by nanoindentation technique. Morphological studies of the nanocomposites were also studied, observations show a uniform distribution of MWCNT in the matrix and interfacial adhesion between PVDF and MWCNT was achieved, which was responsible for enhancement in the hardness and Young's modulus. Differential scanning calorimetry (DSC) studies indicate that the melting temperature of the composites have been slightly increased while the heat of fusion markedly decreased with increasing MWCNT content.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Ceramic-polymer nanocomposites with increased dielectric permittivity and low dielectric loss

The use of lead free materials in device fabrication is very essential from environmental point of view. We have synthesized the lead free ferroelectric polymer nanocomposite films with increased dielectric properties. Lead free bismuth titanate has been used as active ceramic nanofillers having crystallite size 24nm and PVDF as the polymer matrix. Ferroelectric β-phase of the polymer composite films was confirmed by X-ray diffraction pattern. Mapping data confirms the homogeneous dispersion of ceramic particles into the polymer matrix. Frequency dependent dielectric constant increases up to 43.4 at 100Hz, whereas dielectric loss decreases with 7 wt% bismuth titanate loading. This high dielectric constant lead free ferroelectric polymer films can be used for energy density applications.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Morphological characterization of β phase in poly-(vinylidenefluoride) film prepared by spin cast method

Poly-(Vinylidene fluoride) PVDF film was prepared by spin casting method to control the pore size of the matrix. The morphological spherulitic structure was confirmed Scanning Electron Microscopy (SEM) after gold sputtering and the presence of β phase was ensured in spin cast PVDF film by the FTIR spectroscopy. The β phase is very important in the application because it improve the properties like piezoelectricity by modifying PVDF crystallinity.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Structural phase study in un-patterned and patterned PVDF semi-crystalline films

This work explores the structural phase studies of organic polymer- polyvinylidene fluoride (PVDF) thin films in semi-crystallized phase and nano-patterned PVDF thin films. The nanopatterns are transferred with the CD layer as a master using soft lithography technique. The semi-crystalline PVDF films were prepared by a still and hot (SH) method, using a homemade spin coater that has the proficiency of substrate heating by a halogen lamp. Using this set up, smooth PVDF thin films in semi-crystalline α-phase were prepared using 2-Butanone as solvent. XRD, AFM and confocal Raman microscope have been utilized to study the structural phase, crystallinity and quality of the films.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Study of nano imprinting using soft lithography on Krafty glue and PVDF polymer thin films

The present work reveals soft lithography strategy based on self assembly and replica molding for carrying out micro and nanofabrication. It provides a convenient, effective and very low cost method for the formation and manufacturing of micro and nano structures. Al-layer of compact disc (sony CD-R) used as a stamp with patterned relief structures to generate patterns and structures with pattern size of 100nm height, 1.7 μm wide. In literature, PDMS (Polydimethylsiloxane) solution is widely used to get negative copy of the Al-layer. In this work, we have used inexpensive white glue (Polyvinylacetate + water), 15gm (□5) and PVDF (Polyvinylidene difluoride) spin coated films and successfully transferred the nano patterns of Al layer on to white glue and PVDF films.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Electrospun nanocomposite fibrous polymer electrolyte for secondary lithium battery applications

Hybrid nanocomposite [poly(vinylidene fluoride -co- hexafluoropropylene) (PVdF-co-HFP)/magnesium aluminate (MgAl{sub 2}O{sub 4})] fibrous polymer membranes were prepared by electrospinning method. The prepared pure and nanocomposite fibrous polymer electrolyte membranes were soaked into the liquid electrolyte 1M LiPF{sub 6} in EC: DEC (1:1,v/v). XRD and SEM are used to study the structural and morphological studies of nanocomposite electrospun fibrous polymer membranes. The nanocomposite fibrous polymer electrolyte membrane with 5 wt.% of MgAl{sub 2}O{sub 4} exhibits high ionic conductivity of 2.80 × 10{sup −3} S/cm at room temperature. The charge-discharge capacity of Li/LiCoO{sub 2} coin cells composed of the newly prepared nanocomposite [(16 wt.%) PVdF-co-HFP+(5 wt.%) MgAl{sub 2}O{sub 4}] fibrous polymer electrolyte membrane was also studied and compared with commercial Celgard separator.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Piezoelectricity and ferroelectricity of cellular polypropylene electrets films characterized by piezoresponse force microscopy

Cellular electrets polymer is a new ferroelectret material exhibiting large piezoelectricity and has attracted considerable attentions in researches and industries. Property characterization is very important for this material and current investigations are mostly on macroscopic properties. In this work, we conduct nanoscale piezoelectric and ferroelectric characterizations of cellular polypropylene (PP) films using piezoresponse force microscopy (PFM). First, both the single-frequency PFM and dual-frequency resonance-tracking PFM testings were conducted on the cellular PP film. The localized piezoelectric constant d{sub 33} is estimated to be 7–11pC/N by correcting the resonance magnification with quality factor and it is about one order lower than the macroscopic value. Next, using the switching spectroscopy PFM (SS-PFM), we studied polarization switching behavior of the cellular PP films. Results show that it exhibits the typical ferroelectric-like phase hysteresis loops and butterfly-shaped amplitude loops, which is similar to that of a poly(vinylidene fluoride) (PVDF) ferroelectric polymer film. However, both the phase and amplitude loops of the PP film are intensively asymmetric, which is thought to be caused by the nonzero remnant polarization after poling. Then, the D-E hysteresis loops of both the cellular PP film and PVDF film were measured by using the same wave form as that used in the SS-PFM, and the results show significant differences. Finally, we suggest that the ferroelectric-like behavior of cellular electrets films should be distinguished from that of typical ferroelectrics, both macroscopically and microscopically.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Ferroelectric polymer-ceramic composite thick films for energy storage applications

We have successfully fabricated large area free standing polyvinylidene fluoride -Pb(Zr{sub 0.52}Ti{sub 0.48})O{sub 3} (PVDF-PZT) ferroelectric polymer-ceramic composite (wt% 80–20, respectively) thick films with an average diameter (d) ∼0.1 meter and thickness (t) ∼50 μm. Inclusion of PZT in PVDF matrix significantly enhanced dielectric constant (from 10 to 25 at 5 kHz) and energy storage capacity (from 11 to 14 J/cm{sup 3}, using polarization loops), respectively, and almost similar leakage current and mechanical strength. Microstructural analysis revealed the presence of α and β crystalline phases and homogeneous distribution of PZT crystals in PVDF matrix. It was also found that apart from the microcrystals, well defined naturally developed PZT nanocrystals were embedded in PVDF matrix. The observed energy density indicates immense potential in PVDF-PZT composites for possible applications as green energy and power density electronic elements.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Effect of annealing process on the phase formation in poly(vinylidene fluoride) thin films

This work reports the initial study on the effect of annealing process on the crystalline phase of poly(vinylidene fluoride) (PVDF) thin film. PVDF powder was dissolved in N,N-dimethylformamide before spin-coated onto a glass substrate to form a film. The films were annealed at 30°C, 90°C and 110°C for 5 hrs. The crystalline phase of the powder PVDF as received was investigated by using XRD and FTIR techniques. Moreover, the crystalline phases of thin films after annealing were investigated by using the same techniques. XRD analysis showed that in powder form PVDF exists in α-phase. Each annealed PVDF thin films exhibited identical formation of three-phases material namely γ (as major phase) while α and β phases as the minor phases. The FTIR analysis showed that the powder form of PVDF exists in α and β phases. FTIR measurement further confirmed the XRD results implying that the annealing process has no significant effect on the phase formation in PVDF films.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Preparation and characterization on nano-hybrid composite solid polymer electrolyte of PVdF-HFP /MG49-ZrO{sub 2} for battery application

Initial study on nano composite polymer electrolyte of PVdF-HFP/MG49-ZrO{sub 2} has been done. The zirconium was synthesis via in-situ sol-gel method in a dissolved polymer blends. The effects of different concentrations of zirconium and pH values have been investigated on nano composite polymer (NCP). Analysis impedance show that only at 6 wt. % of zirconium for all pH values show a semi-circle arc which have lowest value of bulk resistance. No ionic conductivity value is obtain due to the absent of ion charge carriers. Analysis of XRD revealed that crystallinity phase of the nano composite polymer was affect by different pH values. However, no significant changes have been observed in IR bands. This could well indicate that different pH medium did not affect the chemical bonding in the structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Reinforced fluropolymer nanocomposites with high-temperature superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y}

Bismuth Strontium Calcium Copper Oxide (Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub y})/Polyvinylidene fluoride (PVDF) nanocomposite was prepared and their thermal properties were analyzed. The composite consists of the polyvinylidene fluoride (PVDF) as an insulating polymer matrix, and homogenously distributed Bismuth strontium calcium copperoxide (2212) nanoparticles. SEM data shows flaky grains of the superconductor coated and linked by polymer. Differential scanning calorimetry (DSC) results indicated that the melting point was not affected significantly by the addition of BSCCO. However, the addition of superconducting ceramic resulted in an extra melting peak at a lower temperature (145°C). Thermogravimetric analysis of the samples shows that the onset decomposition temperature of the PVDF matrix was decreased by the addition of SC filler.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Enhanced piezoelectric response in the artificial ferroelectric polymer multilayers

An actuator with a high piezoelectric response, the ferroelectric polymer multilayer actuator, is described. The ferroelectric polymer multilayers consisting of alternative ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer and relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofloroethylene) (P(VDF-TrFE-CFE)) terpolymer with different periodicities and fixed total thickness are prepared by the Langmuir-Blodgett technique. Both X-ray diffraction and Raman spectroscopic measurements indicate that the structure of the multilayer with thin alternating layer is similar to that of the ferroelectric copolymer. Compared with that of the copolymer, it is found that the piezoelectric coefficient of the multilayer could be improved by 57%. We attributed the enhanced piezoelectric response of the multilayers to the internal electric fields that arises from the electrostatic couplings between different layers.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2015

Fabrication of self-healing super-hydrophobic surfaces on aluminium alloy substrates

We present a method to fabricate a super-hydrophobic surface with a self-healing ability on an aluminium alloy substrate. The coatings are obtained by combining a two-step process (first, the substrate is immersed in a solution of HCl, HF and H{sub 2}O, and then in boiling water) and succeeding surface fluorination with a solution of poly(vinylidene-fluoride-co-hexafluoropropylene) and a fluoroalkyl silane. The morphological features and chemical composition were studied by scanning electron micrometry and energy-dispersive X-ray spectroscopy. The prepared super-hydrophobic aluminium surfaces showed hierarchical structures forming pores, petals and particles with a contact angle of 161° and a sliding angle of 3°.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Great reduction of loss at high electric field in the polyvinylidene fluoride/aromatic polythiourea blend films along with an irreversible phase transition

In this paper, the polarization response of dielectric blend based on the polyvinylidene fluoride (PVDF) and aromatic polythiourea (ArPTU) was investigated. It is found that the conduction loss at high field has been reduced 2–4 times along with an interesting irreversible transition under high electric field. The loss at 700 MV/m can be kept below 20%, which is better than most other polar dielectric polymers. It is proved that the transition is a phase change from glass phase to polar β phase at a critical field. And the highly polar thiourea groups of ArPTU can act as traps for the electrons, reduce conduction loss greatly and prevent dielectric breakdown by stabilizing the electron energy.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Ternary systems based on PVDF, BaTiO{sub 3} and MWCNTs: Fabrication, characterization, electromagnetic simulation

In this work, ternary bulk systems based on polyvinylidene fluoride (PVDF), synthesised barium titanate (BaTiO{sub 3}, BT) nanopowder and multi walled carbon nanotubes (MWCNTs) were fabricated by film stacking technique, starting from solvent cast films. The main purpose was to investigate the influence of BT and MWCNTs addition to the polymeric matrix on its microstructural and dielectrical properties. In order to achieve it, different BT concentrations, ranging between the 60 and 75 %wt, were tested, whereas a MWCNTs content of 2 %wt was maintained constant. The morphology was studied by observation at scanning electron microscopy (SEM), the microstructure and crystalline phases investigated by X-Ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy, and the electromagnetic properties measured in the microwave region (8-12 GHz). The electromagnetic response of the investigated bulk systems was also simulated as function of the sample thickness.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗