Search

Exploring polymer-based composites with a high dielectric constant and energy density simultaneously, as well as low dielectric loss, is of crucial importance because of their potential applications in modern electronics and electric power systems. Here, a multilayer-structured Ti3C2Tx MXene/poly(vinylidene fluoride) (PVDF) film with a high dielectric constant and ultralow dielectric loss is fabricated via spin coating, spray coating and hot-press methods. 4MXene/5PVDF (namely four layers of MXene and five layers of PVDF) exhibits a high dielectric constant (41) and an ultralow dielectric loss (0.028, smaller than that of pure PVDF) at 1 kHz. Surprisingly, the MXene/PVDF films show good broadband dielectric behaviors and the dielectric constant of 4MXene/5PVDF can reach up to 32.2 at 1 MHz, which can remain as high as 78.4% of that at 1 kHz. Based on the crystalline phase transformation and temperature dependence of electrical modulus results, the excellent dielectric properties are attributed to the enhanced interfacial polarization. The multilayered structure can efficiently prevent the formation of a conductive network across the entire film, leading to suppressed dielectric loss, a comparative breakdown strength with pure PVDF and a maximum discharge energy density of 7.4 J cm−3. This work provides a promising design paradigm to construct polymer films with a high dielectric constant and low dielectric loss.

Introducing conductive nanofillers into a dielectric polymer is the most common way to tailor percolative composites with high dielectric constant. However, it usually contributes to large increase of dielectric loss, thereby restricting the improvement of practical energy storage capability. In this study, by regulating the conjugation degree of graphene derivatives and their interfacial interactions with polymer matrix, high dielectric constants were achieved for graphene/polymer composites and the loss was suppressed at a relatively low level. Electrochemical exfoliated graphene with high conjugation degree modified with a carboxyl-riched perylene derivative via π-π stacking interaction was used as a conductive nanofiller. Due to the high conjugation degree of graphene and carboxyl groups-induced high interfacial interactions with PVDF matrix, a high dielectric constant (e = 480) was obtained at a low filler content of 0.74 vol% and the dielectric loss was suppressed as low as 0.27. The enhanced dielectric properties could be reasonably explained by a proposed model. This research provides a new and promising route for researchers to construct graphene/polymer composites with good dielectric properties for applications in modern electronics and electric power systems.

Poly(vinylidene fluoride) (PVDF)-based ferroelectric polymers with excellent flexibility and tuneable ferroelectric performance characteristics have attracted continuous attention for high energy storage applications. To produce ideal novel ferroelectric polymers to enhance released energy density and reduced hysteresis loss, smaller ferroelectric domains are necessary. In this study, we prepared poly(vinylidene fluoride-co-trifluoroethylene)-graft-poly(methyl methacrylate) (P(VDF-TrFE)-g-PMMA) graft copolymers via the pre-irradiation process, achieving the transition from normal ferroelectric performance to either antiferroelectric-like or linear behaviour. Compared to the atom transfer radical polymerization (ATRP), this method is attractive due to its unique merits, such as user-friendly control, short processing time and catalyst-free reaction. By using the nanoconfinement effect concept, grafted-PMMA with fairly strong intermolecular interactions was miscible with P(VDF-TrFE) in an amorphous phase, which effectively impeded the formation of large lamellar crystals. Compared to pristine film, the best performance was achieved for the irradiated grafting film with dielectric loss reduced by 67% (from 0.27 to 0.09) at 1 MHz, released energy density increased by 77% (from 2.2 to 9.5 J/cm3) and released energy efficiency improved by 80% (from 0.15 to 0.75 J/cm3). This work provides a simple and efficient strategy for the fabrication of novel dielectrics for high released energy density and low loss application.

It is a challenge to intentionally prepare the pure PVDF film containing exclusive γ-phase (γ-PVDF film). In this study, the γ-PVDF film containing extremely rare β-phase was prepared by solution casting method. γ-PVDF films were then irradiated with 2.5 MeV electron beam in vacuum at 92, 442 and 993 kGy, respectively. Modifications of γ-PVDF films by the irradiation were detailedly investigated by FTIR, DSC, TGA and XPS measurements. FTIR results show that the irradiation does not induce the crystal phase transition and carbon-carbon double bonds (C=C bonds) are obviously formed for γ-PVDF films when irradiated at high dose of 442 and 993 kGy. In addition, the evolution process of chemical structures was proposed for γ-PVDF films by the irradiation at different dose based on FTIR and XPS analyses. For thermal properties, the irradiation decreases the melting and crystallization temperatures, and thermal decomposition temperature for γ-PVDF film due to the irradiation-induced damage effects. The sample irradiated at 92 kGy has the maximum melting and crystallization enthalpies. However, the irradiation increases the residual yield at high temperature (> 500 °C) of γ-PVDF film due to the formation of crosslinked network structures in the irradiated samples.

In recent years, high energy density polymer capacitors have attracted a lot of scientific interest due to their potential applications in advanced power systems and electronic devices. Here, core–shell structured TiO2@SrTiO3@polydamine nanowires (TiO2@SrTiO3@PDA NWs) were synthesized via a combination of surface conversion reaction and in-situ polymerization method, and then incorporated into the poly(vinylidene fluoride) (PVDF) matrix. Our results showed that a small amount of TiO2@SrTiO3@PDA NWs can simultaneously enhance the breakdown strength and electric displacement of nanocomposite (NC) films, resulting in improved energy storage capability. The 5 wt% TiO2@SrTiO3@PDA NWs/PVDF NC demonstrates 1.72 times higher maximum discharge energy density compared to pristine PVDF (10.34 J/cm3 at 198 MV/m vs. 6.01 J/cm3 at 170 MV/m). In addition, the NC with 5 wt% TiO2@SrTiO3@PDA NWs also demonstrates an excellent charge–discharge efficiency (69% at 198 MV/m). Enhanced energy storage performance is due to hierarchical interfacial polarization among their multiple interfaces, the large aspect ratio as well as surface modification of the TiO2@SrTiO3 NWs. The results of this study provide guidelines and a foundation for the preparation of the polymer NCs with an outstanding discharge energy density.

In this work, the thermal stability, rheological properties and mechanical properties of ethylene-tetrafluoroethylene copolymer (ETFE)/poly(vinylidene fluoride) (PVDF) blends were investigated by thermogravimetric analysis, rheometer and the tensile test. Thermal results indicated that blends had better thermal oxidation resistance than pure ETFE. Particularly, the initial thermal decomposition temperature (T d 0) and the temperature at maximum decomposition rate (T d max) of PVDF/ETFE (10/90 wt%) blends were at 374.49°C and 480°C, which were 52.6°C and 34°C higher than pure ETFE. The activation energy of thermal degradation (E d ) of ETFE was 66 kJ/mol, while the PVDF/ETFE (10/90 wt%) blends presented a higher E d , near 187 kJ/mol. Furthermore, rheological measurements demonstrated that the shear-thinning tendency of blends became stronger with increasing PVDF content. PVDF/ETFE (10/90 wt%) blends had somewhat lower mechanical properties than ETFE, which was still high enough for various applications. Blends with PVDF provided an efficient method to extend the application area of ETFE.

Polymer-based composites with excellent dielectric and thermal conductive properties attract ever-increasing attentions from researchers due to the irreplaceable role in energy storage system and electrical devices. Herein, poly(vinylidene fluoride) (PVDF)-based ternary composites were fabricated by adding small amount of poly(dopamine) coated boron nitride (DBN) and electrochemical exfoliated graphene (EEG) into PVDF matrix. Due to the high degree of π-conjugation and good dispersity of EEG, high dielectric constant could be achieved with a very small addition. Meanwhile, after a small amount of DBN was introduced into the EEG/PVDF system, high dielectric constant, low dielectric loss and excellent thermal conductivity were integrated into the EEG/DBN/PVDF ternary composites due to the synergistic effect of DBN and EEG. Compared with the dielectric constant of 591 and loss of 1.21 for EEG(2.0%)/PVDF, the dielectric constant of the DBN(3.1%)/EEG(2.0%)/PVDF can reach up to 6655 and the dielectric loss can be suppressed below 0.83 at 102 Hz. In addition, the thermal conductivity of the ternary composite film can reach up to 1.33 W m-1 K-1, which is 5.68 times more than that of pure PVDF (0.234 W m-1 K-1). This work provides a simple and efficient strategy to exploit novel polymer based composites with excellent dielectric and thermal conductive properties for extensive applications in electronics and energy storage systems.

Integration of the excellent attributes of high dielectric constant and low dielectric loss in flexible polymer-based nanocomposites has attracted increased research attention because of their extensive applications in modern electronic and electric industry. In this study, to obtain the optimized dielectric constant and loss, the fabrication and properties of a three-phase nanocomposites, including poly(vinylidene fluoride) (PVDF) and two nanofillers, namely, surface-modified multi-wall carbon nanotubes (mCNTs) and barium titanate nanoparticles (mBTs), are investigated in detail. The mCNTs and mBTs were obtained via the hydrolysis of 3-aminopropyltriethoxysilane (AMEO) and condensation reactions between the AMEO and nanofillers. The three-phase nanocomposites are fabricated by a phase-separation and hot-pressing process. The mCNTs and mBTs can be uniformly dispersed within the PVDF polymer matrix because of the enhanced hydrogen bonding interaction and compatibility with the polymer matrix. The percolation threshold (as low as 0.50 vol%) of the two-phase mCNTs/PVDF nanocomposites is adopted to optimize the dielectric properties of the three-phase mCNTs/mBTs/PVDF nanocomposites. At the frequency of 102 Hz, a high dielectric constant of 109 and low loss of 0.06 are obtained for the three-phase nanocomposites with only 0.41 vol% mCNTs and 2.8 vol% mBTs, respectively. Meanwhile, owing to the low percolation threshold and enhanced surface compatibility between the nanofillers and PVDF, the tensile strength of the three-phase nanocomposites is greater than that of PVDF by a factor of greater than 1.5. Owing to their high dielectric constant, low dielectric loss and good mechanical properties, these PVDF-based ternary nanocomposites show potential for applications in electronic devices and energy storage systems.

A mid-infrared BaGa

Herein, through a solution and coagulation method, biodegradable poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [P(3HB-co-4HB)]/graphene nanocomposites were prepared. The nonisothermal melt crystallization peak temperature values and overall isothermal melt crystallization rates in the nanocomposites are greater than in neat P(3HB-co-4HB), indicating a nucleating effect of graphene; however, the crystallization mechanism of P(3HB-co-4HB) remains unchanged in the nanocomposites, regardless of graphene level and crystallization temperature. The nonisothermal and melt crystallization processes of the nanocomposites are found to vary with the graphene loading, exhibiting a maximum at 1 mass% graphene loading. The incorporation of graphene obviously increases spherulites nucleation density values of the nanocomposites and does not modify the crystal structure of P(3HB-co-4HB) in the nanocomposites. The storage modulus has been apparently improved in the nanocomposites compared to neat P(3HB-co-4HB). Moreover, the enzymatic hydrolytic degradation rates have been enhanced obviously in the P(3HB-co-4HB)/graphene nanocomposites than in neat P(3HB-co-4HB).

Reading Ulysses, all kinds of sounds impinge on our ears from all sides. They may be human or nonhuman, loud or low, soft or rough, funny or ridiculous. This paper will explore the different symbolic or metaphorical implications of two distinctive sounds: the church bells and the jingling sound. It seems that few Joycean scholars have attended to Joyce’s manipulating of sounds and their unique stylistic and aesthetic effects, and this paper from a perspective of cognitive phonetics and cognitive psychology, finds that the church bells are the overtone of death, and the jingling sound as well as the tapping sound reveals one major theme of the novel: sexuality.

We experimentally demonstrate a ZnGePsub2/subbased optical parametric oscillator (ZGP-OPO) with a record of the optical-to-optical conversion efficiency. To improve the conversion efficiency, we design and construct a double-pass pumped high-gain OPO and a matched large-sized high-peak-power pump beam to suppress the spatial walk-off and conversion. Pulse energy of 19 mJ with pulse width of 27.8 ns at 5 Hz in the mid-infrared 3-5 μm waveband is obtained in the doubly resonated ZGP-OPO, the beam quality Msup2/supis about 9.6, and the corresponding optical-to-optical conversion efficiency reaches up to 75.7%.

An electro-optically Q-switched high-energy Er:YAG laser with two polarizers is proposed. By using two Al(2)O(3) polarizing plates and a LiNbO(3) crystal with Brewster angle, the polarization efficiency is significantly improved. As a result, 226 mJ pulse energy with 62 ns pulse width is achieved at the repetition rate of 3 Hz, the corresponding peak power is 3.6 MW. To our knowledge, such a high peak power has not been reported in literature. With our designed laser, in-vitro teeth were irradiated under Q-switched and free-running modes. Results of a laser ablation experiment on hard dental tissue with the high-peak-power laser demonstrates that the Q-switched Er:YAG laser has higher ablation precision and less thermal damage than the free-running Er:YAG laser.

We developed a new approach to test the single-photon emissions of semiconductor quantum dots (QDs) in the optical communication band. A diamond-anvil cell pressure device was used for blue-shifting the 1.3 μm emissions of InAs/GaAs QDs to 0.9 μm for detection by silicon avalanche photodiodes. The obtained g((2))(0) values from the second-order autocorrelation function measurements of several QD emissions at 6.58 GPa were less than 0.3, indicating that this approach provides a convenient and efficient method of characterizing 1.3 μm single-photon source based on semiconductor materials.

In Ulysses, there is a whole repertoire of linguistic inventiveness, creativity and play in the form of new words and odd constructions, which calls for our close reading. Lexical Inventiveness, as I argue, best characterizes Joyce’s lexical revolution in which both creativity and playfulness of language are fully stressed. To have a better understanding of them, this chapter is to investigate special conversions, unusual compounds and comic word-play by means of classification and comparison. Our studies show: (1) Joyce’s defamiliarized lexis is more motivated than arbitrary as he made the best use of the accepted lexical resources; (2) As for various word formations, we find that Joyce’s verb conversion follows fairly well the word-formation rules, his compounds deviate a lot from the rules and his jumbled compounds are, in its true sense, what Bakhtin calls “linguistic carnivalization”; (3) Semantically, neologisms, though fleeting, are terse, lively, exciting, expressive, and above all true to life. (4) Perfect truth was perfect language.” (French, 1982). The point with his linguistic inventiveness is to make full use of the visual and auditory textures of words, including their musical nature, and to increase the expressive power of literary language, and thus to achieve the special artistic effects of “defamiliarization” by increasing the difficulty of reading and lengthening their time of perception, and it is in grappling with linguistic deviation, creativity and indeterminateness that lies much of the pleasure of reading Ulysses. So Joyce’s linguistic inventiveness is part of his artistic ingenuity in fiction and calls for further studies.

B y employing Sara Mill’s feminist-stylistics approach, this paper explores the thematic relationship between transitivity system and the male - dominance theme of Lawrence’s Lady Chatterley’s Lover . B y analyzing the transitivity choice, we find that material process dominate s over other verb processes and in most cases Mellors, the hero, serves as an active dominating role in their daily life, particularly in their sexual love , and Connie, the heroine, always takes a passive obedient role in an episode of their love affair. This paper shows that Lawrence holds a chauvinist ic idea towards women and male dominance is easily seen all over his novel.

Knowledge of dynamical structure of protein is an important clue to understand its biological function in vivo. Temperature-jump (T-jump) time-resolved transient mid-IR absorbance spectroscopy is a powerful tool in elucidating the protein dynamical structures and the folding/unfolding kinetics of proteins in solution. A home-built setup of T-jump time-resolved transient mid-IR absorbance spectroscopy with high sensitivity is developed, which is composed of a Q-switched Cr, Tm, Ho:YAG laser with an output wavelength at 2.09 μm as the T-jump heating source, and a continuous working CO laser tunable from 1580 to 1980 cm(-1) as the IR probe. The results demonstrate that this system has a sensitivity of 1 × 10(-4) ΔOD for a single wavelength detection, and 2 × 10(-4) ΔOD for spectral detection in amide I' region, as well as a temporal resolution of 20 ns. Moreover, the data quality coming from the CO laser is comparable to the one using the commercial quantum cascade laser.

The phonological figures in Ulysses have been the weakest aspect in Joycean studies, calling for a systematic scrutiny. From a cognitive phonological perspective, this article aims at a brief survey of those phonological figures in Ulysses and illustrates how much phonological figures have contributed to the poetic texture of the novel. Taking as the point of departure the phonological figures in Ulysses, by means of a revised model of phonological figures by Plett, this article explores some 15 phonological figures concerning phonemic deviations and phonemic enforcement, and their stylistic effects. These figures have contributed much to the musicality and playfulness, and also to the textual cohesion and coherence of the novel, and in some contexts they may produce synaesthesia in the reader’s mind and carry an obvious interpersonal function. Moreover, they have played an important part in the linguistic poeticity of the novel.

We propose an approach to tune the emission of a single semiconductor quantum dot (QD) to couple with a planar cavity using hydrostatic pressure without inducing temperature variation during the process of measurement. Based on this approach, we studied the influence of cavity mode on the single-photon purity of an InAs/GaAs QD. Our measurement demonstrates that the single-photon purity degrades when the QD emission resonates with the cavity mode. This negative influence of the planar cavity is mainly caused by the cavity feeding effect.

We report an experimental study on the optical properties of the self-organized 1.55-μm InAs/InGaAsP/InP quantum dots (QDs) under hydrostatic pressure up to 9.5 GPa at 10 K. The obtained pressure coefficients of emissions from InGaAsP to InAs QDs are 92 meV/GPa and 76 meV/GPa, respectively. Their photoluminescence intensities are found to decrease significantly with increasing pressure due to the pressure-induced Γ-X mixing of InGaAsP at about 8.5 GPa. The lifetime of excitonic emission from QDs decreases from about 1.15 at zero pressure to about 1.05 ns at 7.41 GPa. The wavelength of QD emission was tuned from 1.55 to 0.9 μm by applying a pressure of 8 GPa, displaying the feasibility for indirectly characterizing the individual InAs/InGaAsP/InP QDs of 1.55-μm emission (at zero pressure) under high-pressure using silicon avalanche photodiode.