纳微米PZT/水泥基压电复合材料的研究

采用溶胶-凝胶法合成了锆钛酸铅(PZT)纳微米粉体.XRD与SEM分析结果表明,经700 ℃煅烧的PZT粉体的平均晶粒尺寸约为26.4 nm,粉体团聚体的平均尺寸约为200 nm.采用干压成型-水化法制备了纳微米PZT/水泥基压电复合材料,研究了复合材料的压电及介电性能.SEM结果表明,PZT陶瓷相在基体中呈网状分布.PZT颗粒之间的良好连通性使复合材料具有优良的压电性能.     

Low‐temperature elastic and dielectric properties of K3Na(SO4)2 crystals

Elastic and dielectric properties of glaserite K₃Na(SO₄)₂ single crystal were examined using the method of composite oscillators, Brillouin light scattering methods and dielectric spectroscopy. Measurements were performed in the temperature range from 18 K to 300 K. Anomalies in the temperature dependencies of Brillouin shift and dielectric permittivity at about 70 K confirmed the earlier predicted phase transition at 75 ± 25 K. Temperature dependences of the resonance frequency of the vibrating composite oscillator, Brillouin shift measured in the [110] direction, components of dielectric permittivity tensor reveal an anomaly at about 50 K. Moreover, thermal hysteresis of the dielectric permittivity suggested the presence of an incommensurate state between T ₁ = 50 K and T ₂ = 70 K. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electroactive influence of ferroelectric nanofillers on polyamide 11 matrix properties

Barium titanate ceramic powders have been incorporated in polyamide 11 to form homogeneous dispersion of particles in the matrix. Barium titanate/polyamide 11 nanocomposites have been synthesized using a solvent casting method with ultrasonic stirring to homogeneously disperse inclusions in the matrix. Composites with volume fraction of barium titanate ϕ ranging from 0.01 to 0.4 were elaborated. Films were fabricated using a hot press method. Only the inclusions were poled in the matrix to form a ferroelectric particles/unpoled matrix composite. Interactions between the particles and the matrix, pyroelectric and piezoelectric response were studied as a function of ϕ by dynamic dielectric spectroscopy. Composites show interesting pyro-piezoelectric activity. Pyroelectric merit factor increases linearly and it reaches a limit value of 0.3 for a volume fraction ϕ = 0.1.     

Dielectric relaxation of (N(C2H5)4)2CoCl2Br2 nanocrystallites incorporated into the PMMA matrix

The dielectric properties of tetraethylammonium dibromo-dichloro-cobaltate (N(C₂H₅)₄)₂CoCl₂Br₂ (TEA-CBC) nanocrystallites incorporated into the polymethylmethacrylate (PMMA) matrix were investigated within the spectral range of 3 × 10⁵–3 × 10⁹ Hz in the temperature range of 90–300 K. The considerable difference of the dielectric spectra of the nanocomposite compared to the TEA-CBC crystal and to the pure PMMA matrix was observed. The phenomenon of the ‘negative capacity’ has been found in the considered material. Its dependence on the NC content was investigated. Temperature investigations of the dielectric permittivity for the TEA-CBC NC incorporated into the polymer PMMA matrices have shown the sharp-like resonance dependences of the imaginary part of the dielectric permittivity near 1.2 GHz. The intensity of the corresponding resonance peaks increase sub-linearly with increasing NC content. Taking into account the substantial growth of the imaginary part of the permittivity with increasing NC concentration, one can assume that the main contribution to the effect is given by the interface NC-PMMA regions. Additional experiments were performed to eliminate the influence of ‘geometry factor’.     

Spectral and barrier properties of heterocomposites based on poly (para-phenylene) disposed between the silicon films

ABSTRACT

Within the framework of the methods of the electron density functional and the ab initio pseudopotential, we have obtained the spatial distributions of the valence electrons density, the electron energy spectra and the Coulomb potential for heterocomposites based on poly (para-phenylene) and carbon nanotube disposed between the silicon films.

?It was revealed that the maximal value of the potential barrier was noticed in a composite material from polyparaphenylene filaments placed between silicon films and completed with carbon nanotubes perpendicularly to the surface of the silicon films and along them.     

Conductivity and Optical Properties of a Polyiodine Canal Complex (Benzophenone)9(KI)2I7, CHCl3

Abstract

(Benzophenone)₉(KI)₂I₇, CHCl₃ single crystals have a golden metallic reflection on the surfaces parallel to the polyiodine chain axis. The compound is a member of a large class of channel-like inclusion compounds in which isolated iodine atom chains are the only possible conducting strands in an otherwise insulating matrix. The (contactless) microwave conductivity is ～ 10 Ω^?1 cm^?1 at room temperature with an activation energy of ～0.03 eV down to 70°K, while the dc conductivity is ～10^?-⁶. Conductivity is strongly frequency dependent and contact problems are severe.     

Fe2O3掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3无铅压电陶瓷的制备与性能

采用固相合成法制备了Fe2O3掺杂(Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3(简称BCZT)无铅压电陶瓷。借助XRD、SEM、阻抗分析仪等对该陶瓷的相组成、显微结构以及压电和介电性能进行了研究。结果表明,Fe2O3掺杂降低了BCZT无铅压电陶瓷的烧结温度并使居里温度Tc从85℃提高到95℃;当Fe2O3掺杂为0.02wt%～0.1wt%时,陶瓷样品均为ABO3型钙钛矿结构;少量Fe2O3掺杂促进了陶瓷晶粒的生长,但随着Fe2O3掺杂量进一步增加,陶瓷晶粒随之细化;当Fe2O3掺杂量为0.04wt%时,陶瓷样品具有最优综合电性能,其压电常数d33、机电耦合系数kp、机械品质因数Qm、介电损耗tanδ和介电常数εr分别为400 pC/N,0.40,51,0.023和3482。     

Prediction of piezoelectric properties of crystal-ceramic composites

In the framework of the model of a piezoelectrically active ferroelectric crystal-ceramic composite of the 0–3 type, the concentration dependences of the effective piezoelectric properties of this composite are determined. Two examples of such composites are discussed: the single-domain PbTiO₃ crystal (Pb_{1 ? x}Ca _itx)TiO₃ ceramic and the polydomain PbTiO₃ crystal (Pb_{1 ? x}Ca_x)TiO₃ ceramic. Based on these examples, we analyzed the effect of the 90° domain structure, the form of crystalline inclusions, the remanent polarization of the ceramics, molar Ca concentration (x), and other factors of the effective piezoelectric coefficients e _3j ^* and d _3j ^* and and their anisotropy. The relation between the piezoelectric polarization of the composite to single-domain inclusions and the anisotropy of its piezoelectric coefficients is also studied.     

Dielectric properties of epoxy composites with mixed fillers including graphite nanoplatelets/BaTiO3

Abstract

The electrical properties of L285 epoxy composite materials (CMs) with a mixed filler including graphite nanoplatelets (GNP)/barium titanate(BT) at various GNP concentrations and at 35?wt.% of BT are measured using the AC impedance spectroscopy with frequencies ranging from 1?kHz to 2?MHz. The complex permittivity and its frequency dependence increase with the GNP content. The addition of a BT filler in GNP/L285?CM increases the percolation threshold in addition to a slight increase in the permittivity, allowing a higher GNP content in the composite without the formation of a conductive network. The AC conductivity increases and its dependence on the frequency decreases, as the GNP content increases.     

Design,Synthesis and Physical Properties of New Liquid Crystal Materials for Active Matrix LCD (1)

Abstract

Liquid crystal materials having a decahydronaphthalene ring structure were designed for active matrix LCD and were prepared by hydrogenation of the ocatahydronaphthalenes obtained through the reaction of a fluorinated phenyl magnesium bromide with the 6-alkyl-decahydronaphthalen-2-ones and followed by dehydration. These compounds exhibit wide nematic temperature ranges with low melting points and very low birefringences. These results are useful for design of new liquid crystal mixtures for TFT-displays.     

Synthesis,crystal structure,HF and DFT calculations of 1-(2-chlorobenzyl)-N-(1-(2-chlorobenzyl)-4,5-dihydro-1H-imidazol-2-yl)-1H-benzimidazol-2-amine

The titled compound (1), has been synthesized and characterized by IR and ¹H-NMR spectroscopy, and single crystal X-ray diffraction. The compound crystallizes in the triclinic space group P-1. The crystal structure is stabilized by C-H…π and aromatic π-π interactions. There are also intramolecular N-H…N and C-H…N hydrogen bonds in the molecule. The use of quantum chemical calculations to characterise and optimise the choice of material is illustrated by ab initio treatments. Vibrational frequencies and LUMO-HOMO energy difference of 1 have also been investigated by Density functional theory (DFT) and Hartree-Fock (HF) calculations. Calculated frequencies are in good agreement with the corresponding experimental data.     

Syntheses,Structural, and Biological Studies of Two New Peptide Compounds, 2(s)-(5-fluorouracil-1-aceto)amino-2-isopropyl Acetate Hemihydrate and 2(s)-(5-fluorouracil-1-aceto)amino-2-isopropyl Acetic Acid

Abstract  Two new peptide compounds, 2(s)-(5-fluorouracil-1-aceto)amino-2-isopropyl acetate hemihydrate (1:1/2H ₂ O) and 2(s)-(5-fluorouracil-1-aceto)amino-2-isopropyl acetic acid (2), have been synthesized and characterized by elemental analysis, IR, ¹H- and ¹³C NMR spectroscopy. Two new compounds were structurally characterized by single-crystal X-ray diffraction. The thermal stabilities of compounds 1:1/2H ₂ O and 2 were studied by DSC-TGA techniques. The result of the biological test showed that the compounds 1:1/2H ₂ O and 2 have certain antitumor activities. Index Abstract  Two new peptide compounds, 2(s)-(5-fluorouracil-1-aceto)amino-2-isopropyl acetate hemihydrate (1:1/2H2O) and 2(s)-(5-fluorouracil-1-aceto)amino-2-isopropyl acetic acid (2), have been synthesized and characterized by elemental analysis, IR, 1H-, and 13C NMR spectroscopy. Two new compounds were structurally characterized by single-crystal X-ray diffraction. The thermal stabilities of compounds 1:1/2H2O and 2 were studied by DSC-TGA techniques. The result of the biological test showed that the compounds 1:1/2H2O and 2 have certain antitumor activities.      

Crystal structures of polymeric complexes of zinc(II) bromide and perchlorate with 1,4-diazoniabicyclo [2.2.2]octane-1,4-diacetate

Two zinc(II) complexes containing a flexible double betaine, namely [{Zn(L)Br₂}_n]·nH₂O (1) and [{Zn(L)₂(H₂O)₂}_n](ClO₄)_2n·4nH₂O (2) [L=1,4-diazoniabicyclo [2.2.2]octane-1,4-diacetate,⁻O₂CCH₂N⁺(CH₂CH₂)₃N⁺CH₂CO₂ ⁻], have been prepared and shown to have polymeric structures by single-crystal X-ray analysis. Complex (1) exhibits an infinite zigzag chain in which each zinc(II) atom is coordinated by two unidentate carboxylate oxygen atoms and two bromide ligands in a distorted tetrahedral geometry. Complex (2) consists of an assembly of catonic Zn(L)₂(H₂O)₂ ²⁺ moieties and discrete perchlorate anions as well as lattice water molecules. In (2) each zinc(II) atom is coordinated by two pairs of unidentate carboxylate oxygen atoms and two aqua ligands in a distorted octahedral geometry and cross-linked by skeletons of double betaine ligands to form a corrugated layer structure corresponding to the plane (100).     

Semi-interpenetrating polymer networks based on polyurethane and poly(2-hydroxyethyl methacrylate): Dielectric study of relaxation behavior

The study of molecular dynamics by broadband dielectric spectroscopy (BDS) is presented for polyurethane (PU), poly(2-hydroxyethyl methacrylate) (PHEMA) and for semi-IPNs based on PU and PHEMA synthesized by photopolymerization. The dielectric properties were performed in wide range of frequencies and temperatures with the goal to establish the relation between the relaxations and the structure. Five relaxation phenomena were finally detected for PHEMA : γ-, βsw-, β-relaxations at low temperatures and α-relaxation at 150 °C at high frequencies plus ionic conductivity relaxation which starts at 0 °C. For semi-IPNs the overlapping of γ- and βsw-relaxations of PHEMA (?125/?75 °C), then with increasing the temperature α-relaxation in PU (?75/0 °C), next ionic conductivity relaxation which starts at 0 °C, and finally the α-relaxation of PHEMA (+125/+170 °C) were detected. The α-relaxation of PHEMA in semi-IPNs shifts to lower temperatures and became broader with increasing amount of PU due to incomplete phase separation in the system and formation of interphases. The dielectric relaxation phenomena were fitted with Havriliak–Negami equation. Activation energy, τ_o and α parameters were calculated. For α-relaxations corresponding dielectric characteristics have been determined from Vogel–Fulcher–Tammann equation. The relaxation map for investigated PU, PHEMA and semi-IPNs was built.     

The Interaction of Light with Rb0.73Cr5Te8 and Polymer/Nanoferrite Composites

Abstract

The magnetic and photomagnetic characterizations of two materials are reported: ploymer/nanoferrite composites and the non-stoichiometric crystalline materials Rb0.73Cr5Te8. In the inorganic-organic composite material, the inorganic component is iron oxide and the organic component is the polymer poly(p-ethylphenol) (PEP). The Rb0.73Cr5Te8 material is a new non-stoichiometric formulation of the ACr5Te8 system that exhibits spin glass type magnetic behavior with a spin glass freezing temperature of 175K. The photomagnetism of both compounds has been measured at several temperatures below the spin blocking temperature.     

The relations of sintering conditions and microstructures of [Bi0.5(Na1‐x‐yKxLiy)0.5]TiO3 piezoelectric ceramics

Bismuth sodium titanate (abbreviated as BNT) based solid solution, [Bi_0.5(Na_1‐x‐yK_xLi_y)_0.5]TiO₃ (0 < x + y < 1) ceramics, was invented in our group. These ceramics, which are considered as new candidates for lead‐free piezoelectric materials, were prepared by conventional ceramic sintering technique. The results of X‐ray diffraction show that the ceramics possess a single perovskite phase. The relations of the sintering conditions and the microstructures of the ceramics were studied. It was found that the optimized sintering condition is at 1100‐1150 °C for 2‐3 h, the grains of the ceramics have very regular shape, and the grain size of the ceramics is in the range of 1.3‐2.2 μm. These ceramics with the compositions of high amount of K⁺ and low amount of Li⁺ have relatively large piezoelectric charge constant (d₃₃), and can be put into practical applications. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,characterization and photoluminescence studies of new Cu(II) complex

In the current work, a new coordination complex, [Cu(HL)₂], 1 [H₂L = 2–((E)–(2–hydroxypropylimino)methyl)–4–nitrophenol] was successfully synthesized and characterized by IR, UV-vis and photoluminescence spectroscopic techniques, single crystal and powder X-ray diffraction measurements. In the crystalline structure of complex 1, the aliphatic –OH group of the ligand is not coordinated and points away from the metal coordination zone, and also actively participates in intermolecular bifurcated O?H···O hydrogen bonds which link the molecules to form hydrogen-bonded linear chains. C?H···π and π···π contacts also connect the molecules in the structure which form to 3D structure. This hydrogen bonded polymeric networks lie in the bc-plane and stacks along to the a-axis. Furthermore, complex 1 and its ligand H₂L display an intense navy-blue emission and blue emission in the solid state at room temperature, respectively, when they are excited under UV light.     

Dielectric and pyroelectric response of PVDF loaded with BaTiO3 obtained by mechanosynthesis

Electroactive composites based on ferroelectric ceramic and polymer components are still of interest since their properties can be easily tailored to the requirements of smart structures, sensors and actuators. We studied the dielectric and pyroelectric response of poly(vinylidene fluoride) loaded with BaTiO₃ nanograins obtained by mechanically activated synthesis from BaO and TiO₂. The BaTiO₃ nanopowder was characterized by X-ray diffraction, transmission electron microscopy and NIR Raman scattering. The relaxation processes in the polymer matrix were found to determine the dielectric response of the composites but with higher permittivity values due to the presence of BaTiO₃. The activation energy of the segmental motion of the polymer matrix was found to increase with increasing contents of the filler. The dielectric response of the composites with volumetric fraction of BaTiO₃ equal to and greater than 0.24 was found to be dominated by a broad maximum at ∼320 K, which we relate to the Curie point of the ferroelectric nanograins.     

Synthesis,Characterization and Crystal Structure of 1-Phenyl-3-methyl-4-(salicylidene hydrazide)-phenylethylene-pyrazolone-5

Abstract A new compound 1-phenyl-3-methyl-4-(salicylidene hydrazide)-phenylethylene-pyrazolone-5 (PMPeP-SHZ) has been synthesized and characterized by elemental analysis, IR spectrum, MS and single crystal X-ray diffraction. The compound crystallizes in a monoclinic, space group P2(1)/c with cell parameters: a = 10.8275(19) ?, b = 24.689(4) ?, c = 9.7167(16) ? and β = 95.127(4)°, Z = 4, S = 1.097. In the crystal structure, the compound presents in the diketo form. The structure exhibits both intra- and intermolecular hydrogen bonding and the molecules are interlinked through hydrogen bonds forming an infinite 2D network. The fluorescent result shows blue emission at room temperature in solid state. Graphical Abstract Synthesis, Characterization and Crystal Structure of 1-Phenyl-3- methyl-4-(salicylidene hydrazide)-phenylethylene-pyrazolone-5 Li Zhang, Guan-Cheng Xu, Lang Liu, Guang-Fei Liu, and Dian-Zeng Jia* Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Inclusion property of (R,R)-(-)-trans-2,3,-bis(hydroxydiphenylmethyl)-1,4-dioxaspiro[4,4]nonane for aromatic components

An optically active host molecule, (R,R)-(-)-trans-2,3-bis(hydroxydiphenylmethyl)-1,4- dioxaspiro[4,4]nonane (1), is able to form inclusion complexes with nonpolar aromatic components such as benzene, toluene, p-xylene, mesitylene, and ethylbenzene. The host 1 crystallizes in the monoclinic space group C2 with a = 15.694(2), b = 9.326(2), c = 18.457(1) Å, = 10.34(1)°, and Z = 4. An inclusion complex (1-B) of 1 with benzene crystallizes in the orthorhombic space group P2₁2₁2 with a = 17.007(4), b = 19.670(5), c = 8.634(4) Å, and Z = 4. An inclusion complex (1-X) involving both 1 and p-xylene has the monoclinic space group P2₁ with a = 17.211(3), b = 20.143(3), c = 8.603(3) Å, = 92.64(2)°, and Z = 2. In the inclusion complexes, molecules of 1 are dimerized by intramolecular and intermolecular hydrogen bonds forming eight-membered (OH)₄ rings. The benzene and p-xylene molecules fit into the voids of the crystal packing of 1. In addition, the inclusion complexes are stabilized by van der Waals contacts between the hydrophobic sites. Thermal analysis of the inclusion complexes indicated that the number and the size of the alkyl group of the aromatic components affects the stability of the inclusion complexes.