Small-angle neutron scattering study on microstructure of poly(N-isopropylacrylamide)-block-poly(ethylene glycol) in water

By employing small-angle neutron scattering (SANS), we investigated the microstructures of, poly(N-isopropylacrylamide) (PNIPA)-block-poly(ethylene glycol) (PEG) (NE) in deuterated water D₂O, as related to macroscopic behaviors of fluidity, turbidity and synerisis. SANS revealed following results: (i) microphase separation occurs at around above 17 °C in a temperature range of transparent sol below 30 °C. In the microdomain appeared in the transparent sol state, both block chains of PNIPA and PEG are swollen by water; (ii) for the NE solution of polymer concentration W_p > 3.5% (w/v), corresponding to opaque gel above 30 °C, a percolated structure, i.e., network-like domain is formed by NE as a result of macrophase separation due to dehydration of the PNIPA chains. As the temperature increases toward 40 °C, the network domain is squeezed along a direction parallel to the NE interface, which leads to increase of the interfacial thickness given by swollen PEG chains and to the macroscopic synerisis behavior.     

Accelerate ageing of PZT-type ceramics

Accelerate ageing of lead zirconate–titanate ferroceramics (PZT) by fast neutron irradiation is investigated. The ferroelectric behavior of Pb_1−wM_w(Zr,Ti)O₃, where w < 0.5 wt%, M = Li, Nb, Cr, Bi, Mn, Sb, La for Zr/Ti ratio = 51.5/48.5, prepared by solid state reaction, is strongly affected by fast neutron irradiation at Φ_i = (10¹³ ÷ 10¹⁸) n/cm² integrated fluxes. Structural investigations (XRD and SEM) reveal modifications of the microstructure, porosity and elementary cell parameters. High irradiation levels induce tetragonal-cubic at the same time with a ferro–paraelectric transition. The micrographs show the evolution of 90° and 180° walls as well as herringbone structure typical for tetragonal distortions with irradiation level. A relation between macroscopic characteristics (piezoelectric and dielectric) and microscopic properties (crystallographic parameters, porous structure and grain morphology) as function of irradiation doses can be established using a model based on microstructural parameters. These results offer opportunities to understand the fundamentals of radiation effects upon piezoelectric ceramics.     

Dielectric and Pyroelectric Properties of Compositionally Graded Pb(Zr1-xTix)O3 Thin Films Prepared by Sol-gel Process

"Compositionally graded ferroelectric lead zirconate titanate Pb(Zr1-xTix)O3 (PZT) thin films were grown on Pt/Ti/SiO2/Si substrates by using a sol-gel process. The final structure consists of six layers, up-graded graded films starting from PbZrO3 on the Pt electrode to the top PZT(50) layer, it consists of no Ti, 10%Ti, 20%Ti, 30%Ti, 40%Ti, and 50%Ti respectively. Whereas films with opposite gradient are called down-graded graded films. Structure and dielectric properties of the graded films was investigated by X-ray diffraction, Auger electron spectroscopy and by impedance analysis. The up-graded and down-graded PZT films annealed at 600 o, exhibited the remanent polarization values of 18.0 and 24.2 1C/cm2, respectively. The typical small signal dielectric constants and loss tanffi at a frequency of 100 Hz were 523 and 0.018, 544, and 0.020, respectively, for up-graded and down-graded PZT thin films. The temperature dependence of pyroelectric coeoients of the graded PZT films was measured by a dynamic technique. From 20 o to 82 o, the pyroelectric coeoients of the up-graded and down-graded PZT films up to 374 and 407 1C/m2K, respectively."     

Micropatterning of the Ferroelectric Phase in a Poly(vinylidene difluoride) Film by Plasmonic Heating with Gold Nanocages

Polymer thin films with patterned ferroelectric domains are attractive for a broad range of applications, including the fabrication of tactile sensors, infrared detectors, and non‐volatile memories. Herein, we report the use of gold nanocages (AuNCs) as plasmonic nanostructures to induce a ferroelectric–paraelectric phase transition in a poly(vinylidene fluoride) (PVDF) thin film by leveraging its photothermal effect. This technique allows us to generate patterned domains of ferroelectric PVDF within just a few seconds. The incorporation of AuNCs significantly enhances the pyroelectric response of the ferroelectric film under near‐infrared irradiation. We also demonstrate the use of such patterned ferroelectric films for near‐infrared sensing/imaging.     

Structure analysis and the standard molar enthalpy of formation of a coordination polymer [Co(TO)2Cl2]n (TO = 1,2,4-triazole-5-one)

A coordination polymer was synthesized by the reaction of CoCl₂ with 1,2,4-triazole-5-one (TO) and charaterized by means of IR and TG–DTG. Single-crystal structure analysis showed that the complex crystallized in the monoclinic space group C2/c: a = 23.105(9) Å, b = 3.5683(2) Å, c = 13.589(6) Å,  = 90°, β = 124.038(4)°, γ = 90°, V = 928.4(7) Å³, Z = 4. The standard molar enthalpy of formation of the complex was determined to be (−1034.28 ± 0.95) kJ mol⁻¹.     

Sulfonated poly(arylene thioether phosphine oxide)s copolymers for proton exchange membrane fuel cells

High molecular weight sulfonated poly(arylene thioether phosphine oxide)s (sPATPO) with various sulfonation degrees were prepared directly by aromatic nucleophilic polycondensation of 4,4′-thiobisbenzenethiol with sulfonated bis(4-fluorophenyl) phenyl phosphine oxide and bis(4-fluorophenyl) phenyl phosphine oxide. sPATPO in the acid form with sulfonation degrees of 60–100% exhibits a glass transition temperature higher than 230 °C and a 5% weight loss temperature above 400 °C, indicating high thermal stability. sPATPO with a high sulfonation degree shows high proton conductivity and good resistance to swelling as well. For instance, sPATPO-70 displays the conductivity of 0.0783 S/cm and a swelling ratio of 11.6% at 90 °C. TEM micrographs showed that sPATPO membranes with a high sulfonation degree could form continuous ion channels, which are favorable for improving the proton conductivity but harmful to remaining the mechanical property. The membranes are expected to show good performances in fuel cell applications.     

Nanoscale phenomena in synthetic functional oxide heterostructures.

This paper reviews nanoscale phenomena such as polarization relaxation dynamics and piezoelectric characterization in model ferroelectric thin films and nanostructures using voltage-modulated scanning force microscopy. Using this technique we show the three-dimensional reconstruction of the polarization vector in lead zirconate titanate (PZT) thin films. Second, the time-dependent relaxation of remanent polarization in epitaxial PZT ferroelectric thin films, containing a uniform two-dimensional grid of 90 degrees domains (c-axis in the plane of the film), has been investigated extensively. The 90 degrees domain walls preferentially nucleate the 180 degrees reverse domains during relaxation. Relaxation occurs through the nucleation and growth of reverse 180 degrees domains, which subsequently coalesce and consume the entire region as a function of relaxation time. In addition we also present results on investigation of the relaxation phenomenon on a very local scale, where pinning and bowing of domain walls has been observed. We also show how this technique is used for obtaining quantitative information on piezoelectric constants and by engineering special structures, and how we realize ultrahigh values of piezoconstants. Last, we also show direct hysteresis measurements on nanoscale capacitors, where there is no observable loss of polarization in capacitors as small as 0.16 microm2 in area.     

PZT/P(VDF-TrFE)7030 0-3型复合材料的非等温结晶和居里相变行为

采用DSC研究了PZT P(VDF TrFE) 70 30复合材料的非等温结晶和居里相变过程 .结果表明 ,PZT粒子对共聚物基体的结晶行为 ,包括结晶温度、结晶速率和结晶度等影响不大 ;然而共聚物的居里相变过程则受到PZT粒子的影响 ,随PZT粒子含量的增大 ,共聚物基体的居里相变热焓与熔体结晶热焓的比值减小 ,而且其中对应从顺电性的高温相 (HT)转变为铁电性的过冷相 (CL)的相变热焓含量减小 ,意味着PZT粒子的存在能够抑制共聚物铁电晶体中旁式构象缺陷的形成 ,从而提高铁电晶体的完善度     

Fabrication of Poly(L‐lactide)‐block‐Poly(ethylene glycol)‐block‐Poly(L‐lactide) Triblock Copolymer Thin Films with Nanochannels: An AFM Study

This paper aims to report the fabrication of biodegradable thin films with micro‐domains of cylindrical nanochannels through the solvent‐induced microphase separation of poly(L ‐lactide)‐block‐poly(ethylene glycol)‐block‐poly(L ‐lactide) (PLA‐b‐PEG‐b‐PLA) triblock copolymers with different block ratios. In our experimental scope, an increase in each of the block lengths of the PLA and PEG blocks led to both a variation in the average number density (146 to 32 per 100 µm²) and the size of the micro‐domains (140 to 427 nm). Analyses by atomic force microscopy (AFM) and fluorescence microscopy indicated that the hydrophilic PEG nanochannels were dispersed in the PLA matrix of the PLA‐b‐PEG‐b‐PLA films. We demonstrated that the micro‐domain morphology could be controlled not only by the block length of PEG, but also by the solvent evaporation conditions.

     

Thermally stimulated depolarization current in electron‐irradiated poly(vinylidene fluoride‐trifluoroethylene) (56/44 mol %) copolymers

The effect of electron irradiation on poly(vinylidene fluoride‐trifluoroethylene) (56/44 mol %) copolymers was studied with dielectric constant measurements, differential scanning calorimetry (DSC), X‐ray diffraction, thermally stimulated depolarization current (TSDC) spectroscopy, and polarization hysteresis loops. The dielectric relaxation peaks, obeying the Vogel–Fulcher law, indicated that the copolymers were transformed from a normal ferroelectric to a relaxor ferroelectric. The X‐ray and DSC results showed that both the crystalline and polar ordering decreased after irradiation, indicating a partial recovery from trans–gauche bonds to local trans bonds (polar ordering). Moreover, the peak temperature decreased with the irradiation dose in the TSDC spectra; this demonstrated fewer dipoles and crystalline regions in the irradiated copolymer films during the ferroelectric–paraelectric transition and was consistent with polarization hysteresis loop measurements. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1099–1105, 2004     

Microwave-assisted extraction of pyrethroid insecticides from semi permeable membrane devices (SPMDs) used to indoor air monitoring

A rapid and environmentally friendly methodology was developed for the extraction of pyrethroid insecticides from semi permeable membrane devices (SPMDs), in which they were preconcentrated in gas phase. The method was based on gas chromatography mass–mass spectrometry determination after a microwave-assisted extraction, in front of the widely employed dialysis method. SPMDs were extracted twice with 30 mL hexane:acetone, irradiated with 250 W power output, until 90 °C in 10 min, this temperature being held for another 10 min. Clean-up of the extracts was performed by acetonitrile–hexane partitioning and solid-phase extraction (SPE) with a combined cartridge of 2 g basic-alumina, deactivated with 5% water, and 500 mg C₁₈.

Pyrethroids investigated were Allethrin, Prallethrin, Tetramethrin, Bifenthrin, Phenothrin, λ-Cyhalothrin, Permethrin, Cyfluthrin, Cypermethrin, Flucythrinate, Esfenvalerate, Fluvalinate and Deltamethrin. The main pyrethroid synergist compound, Pyperonyl Butoxide, was also studied. Limit of detection values ranging from 0.3 to 0.9 ng/SPMD and repeatability data, as relative standard deviation, from 2.9 to 9.4%, were achieved. Pyrethroid recoveries, for spiked SPMDs, with 100 ng of each one of the pyrethroids evaluated, were from 61 ± 8 to 103 ± 7% for microwave-assisted extraction, versus 54 ± 4 to 104 ± 3% for dialysis reference method. Substantial reduction of solvent consumed (from 400 to 60 mL) and analysis time (from 48 to 1 h) was achieved by using the developed procedure.

High concentration levels of pyrethroid compounds, from 0.14 to 7.3 μg/SPMD, were found in indoor air after 2 h of a standard application.     

Synthesis and properties of oxynitrides (La,Sr)Ti(O,N)3 thin films

We report on the synthesis, optical and electrical properties of thin films of La_xSr_(1−x)Ti(O,N)₃, x = 0, 0.25, 0.50, 0.75 and 1. The films were grown by a soft chemistry process from polymeric precursor solutions, which were deposited by spin coating on 100-oriented SrTiO₃ substrates. After drying, the organic matrix was burned at 400 °C. These steps were repeated six times to obtain a reasonable thickness of the films. Afterwards, the samples were heated in a tube furnace at 950 °C in flowing ammonia. The oxynitride films showed different colours from red-orange for LaTiO₂N to greenish-blue for SrTiO₃:N. The films were characterised by X-ray diffraction, scanning electron microscopy, atomic force microscopy, UV–vis spectroscopy, secondary ion mass spectrometry and electrical measurements. The results show that the films are polycrystalline and have the perovskite structure. Their thickness is about 440 nm and the average roughness value is 7.5 nm. UV–vis transmittance measurements showed a strong decrease in the band gap values for the oxynitrides compared to the respective oxides. The values change from approximately 3.2 eV for the oxides to an average value of 2.4 eV for the oxynitrides. The electrical measurements indicate a change in the electrical behaviour from insulator for LaTiO₂N to semiconductor for SrTiO₃:N.     

Ferroelectric and Pyroelectric Properties of Highly (111)-oriented Nanocrystalline Pb(Zr0:95Ti0:05)O3 Thin Films

"Lead zirconate titanate Pb(Zr0:95Ti0:05)O3 (PZT95/5) antiferroelectric thin films with 300 nm thickness were grown on Pt/Ti/SiO2/Si substrates by a sol-gel method with rapid thermal annealing processing. The X-ray diffraction results showed that the highly (111)-oriented pervoskite PZT95/5 thin films were grown on Pt/Ti/SiO2/Si substrates when annealed at 600-700 oC. Electrical measurements were conducted on PZT95/5 films in metal-ferroelectric-metal capacitor configuration. The PZT95/5 thin films annealed at 600-700 oC showed well-saturated hysteresis loops at an applied voltage of 20 V. At 1 kHz, the dielectric constant and dielectric loss of the films were 519 and 0.028, 677 and 0.029, 987 and 0.025, respectively for the thin films annealed at 600, 650, and 700 oC. The average remanent polarization (Pr) and the coercive electric field (Ec) obtained from the P-E hysteresis loops, were 19.1 1C/cm2 and 135.6 kV/cm, 29.31C/cm2 and 88.57 kV/cm, 45.3 1C/cm2 and 102.1 kV/cm, respectively for PZT95/5 thin films annealed at 600, 650 and 700 oC for 10 min in the oxygen atmosphere. This showed a good ferroelectricity of the prepared PZT95/5 films on Pt/Ti/SiO2/Si substrates by the simple sol-gel processing. The pyroelectric coeocient (p) of antiferroelectric PZT95/5 films was measured by a dynamic technique. At room temperature, the p values of the antiferroelectric PZT95/5 films at 1 kHz were 274, 238, and 212 1C/m2K."     

Magnetostatic Coupling in CoFe2O4/Pb(Zr0.53Ti0.47)O3 Magnetoelectric Composite Thin Films of 2-2 Type Structure

CoFe₂O₄/Pb(Zr_0.53Ti_0.47)O₃ (CFO/PZT) magnetoelectric composite thin films of 2-2 type structure had been prepared onto Pt/Ti/SiO₂/Si substrate by a sol-gel process and spin coat-ing technique. The structure of the prepared thin film is substrate/PZT/CFO/PZT/CFO. Two CFO ferromagnetic layers are separated from each other by a thin PZT layer. The upper CFO layer is magnetostatically coupled with the lower CFO layer. Subsequent scan-ning electron microscopy (SEM) investigations show that the prepared thin films exhibit good morphologies and compact structure, and cross-sectional micrographs clearly display a multilayered nanostructure of multilayered thin films. The composite thin films exhibit both good magnetic and ferroelectric properties. The spacing between ferromagnetic layers can be varied by adjusting the thickness of intermediate PZT layer. It is found that the strength of magnetostatic coupling has a great impact on magnetoelectric properties of composite thin films, i.e., the magnetoelectric voltage coefficient of composite thin film tends to increase with the decreasing of pacing between two neighboring CFO ferromagnetic layers as a result of magnetostatic coupling effect.     

Effects of electron irradiation on poly(vinylidene fluoride–trifluoroethylene) copolymers studied by solid‐state nuclear magnetic resonance spectroscopy

The effects of electron irradiation on the molecular chemical structure, conformation, mobility, and phase transition of vinylidene fluoride (VDF) and trifluoroethylene (TrFE) copolymer have been investigated with variable‐temperature, solid‐state ¹⁹F nuclear magnetic resonance (NMR). It has been found that electron irradiation converts all‐trans conformations of both VDF‐rich and TrFE‐containing segments into dynamically mixed trans–gauche conformations accompanied by a simultaneous ferroelectric‐to‐paraelectric (or amorphous) transition. The variable‐temperature ¹⁹F magic‐angle‐spinning spectra results show that the paraelectric phase melts at much lower temperatures in irradiated films than in an unirradiated sample. Moreover, ¹⁹F NMR relaxation data (spin–lattice relaxation times in both the laboratory and rotating frames) reveal that electron irradiation enhances the molecular motion in paraelectric regions, whereas the molecular motion in a high‐temperature amorphous melt (>100 °C) is more constrained in irradiated films. Besides these physical changes, electron irradiation also induces the formation of several CF₃ groups. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 1714–1724, 2006     

Measurement of glass transition temperature by mechanical (DMTA), thermal (DSC and MDSC), water diffusion and density methods: A comparison study

Glass transition measured by DMTA from the change in slope in storage modulus was 55 °C, which was 10.5 °C lower than the value measured by tan δ peak. Initial glass transition measured by DSC, increased exponentially and reached a constant value of 55 °C at or higher heating rate of 30 °C/min. Transition temperature, measured by MDSC, remained constant up to heating rate 15 °C/min and then decreased. The glass transition values determined from reversible heat flow was 60 °C. The break in diffusivity and density (i.e. volume) was observed at 50 °C below the glass transition temperature measured by thermal and mechanical methods.     

Structures of 3,3′-dicarbometoxy-2,2′-bipyridine complexes with silver(I) and copper(II) cations

The structures of 3,3′-dicarbometoxy-2,2′-bipyridine (dcmbpy) complexes with copper(II) and silver(I) cations have been determined using single crystal X-ray-diffraction. The crystals of Cu(dcmbpy)Cl₂ are monoclinic, C2/c, a = 16.966(3), b = 18.373(3), c = 13.154(2) Å, β = 126.543(3)°. The crystals of Ag(dcmbpy)NO₃ · H₂O are also monoclinic, C2/c, a = 16.7547(13), b = 11.0922(9), c = 18.7789(18) Å, β = 100.228(7)°. The results have been compared with the literature data on the complexes of dcmbpy and its precursors: 2,2′-bipyridine (bpy) and 3,3′-dicarboxy-2,2′-bipyridine (dcbpy). Two types of complexes of 3,3′-carboxy derivatives of bpy are distinguished: (1) with metal atom bonded to two N atoms of the same molecule and (2) with metal atom bonded to two N atoms of two different molecules. The Cu(dcmbpy)Cl₂ complex belongs to the first type, whereas Ag(dcmbpy)NO₃ · H₂O belongs to the second type.     

Stability of workroom air volatile organic compounds on solid adsorbents for thermal desorption gas chromatography

The storage stability of the occupationally frequently occurring compounds, methylethylketone, methylisobutylketone, benzene, toluene, tetrachloroethylene, n-butylacetate, -pinene, β-pinene, limonene and n-decane, has been investigated on the adsorbents Tenax TA, Chromosorb 106 and Carbotrap using thermally desorbable tube type samplers, commonly utilized in ambient and workroom atmospheric measurements. Fifty and 500 ng of each compound were loaded on the various adsorbents tubes, stored at both ambient (20 °C) and refrigerated (4 °C) temperatures and analysed by means of thermal gas chromatography with mass spectrometric detection on days 0, 7, 14 and 28 after exposure. A 90% storage recovery was chosen as acceptance criteria for storage stability, and statistical testing by Student's t-test, analysis of variance and Bonferroni post hoc tests were employed to investigate the effect of the categorical variables storage time, storage temperature and analyte loading on the different adsorbents. Chromosorb 106 showed the overall best behaviour with recoveries of 90% or better for all analytes during the 28-day test period. Tenax TA and Carbotrap yielded lower recoveries and were more influenced by variations in storage time, storage temperature and analyte loading. Refrigerated temperatures were best avoided for storage on Tenax TA, but may increase the recovery of some compounds on Carbotrap (e.g. n-butylacetate). The blank build-up on the adsorbents was also investigated, and Carbotrap and Tenax TA showed no signs of artefact development over time. Chromosorb 106, however, contained inherently more artefacts that build up over time, which in spite of the excellent storage capability, may limit its use in field studies where long storage times are normal.     

LaNiO3衬底上Pb(ZrxTi1－x)O3铁电薄膜及梯度薄膜的制备和研究

报道了在镍酸镧 (LaNiO₃, 简称LNO)衬底上锆钛酸铅 [Pb(Zr_xTi_1－x)O₃, 简称PZT]铁电薄膜及其成分梯度薄膜的结构、介电性能、铁电性能以及热释电性能. 首先通过金属有机化合物热分解(MOD)法在Si(100)基片上制备出LaNiO₃, 薄膜, 再通过溶胶-凝胶(sol-gel)法, 在LNO/Si(100)衬底上制备出Pb(Zr_0.80Ti_0.20)O₃, [PZT(80/20)]和Pb(Zr_0.20Ti_0.80)O₃, [PZT(20/80)]铁电薄膜及其成分梯度薄膜. 经俄歇微探针能谱仪(AES)对制备的梯度薄膜进行了成分深度分析, 结果证实成分梯度的存在. 经XRD分析表明, 制备的梯度薄膜为四方结构和三方结构的复合结构, 但其晶面存在一定的结构畸变. 经介电频谱测试表明, 梯度薄膜的介电常数比每个单元的介电常数要大, 但介电损耗相近. 在10 kHz下, 梯度薄膜的介电常数和介电损耗分别为317和0.057. 经电滞回线的测试表明, 梯度薄膜的剩余极化强度比每个单元都大, 而矫顽场却明显较小. 梯度薄膜的剩余极化强度和矫顽场分别为29.96 μC•cm^-2 和54.12 kV•cm^－1. 经热释电性能测试表明, 室温下梯度薄膜的热释电系数为5.54×10-8 C•cm^－2•K^－1, 高于每个单元的热释电系数.