一种新型主链为偶氮苯的共轭聚合物的合成与性能

以偶氮苯为主链的共轭聚合物可以用常见的原料——间苯二胺、对苯二胺、邻苯二胺和邻氨基苯酚通过重氮化及耦合来合成。不同合成条件获得的产物差别很大,如在亚硝酸钠与原料比例不同的情况下,产物的溶解性和导电性有很大差异。通过对合成的聚合物掺杂碘,研究其导电性,得出控制适量的亚硝酸钠比例和掺杂比例可以提高聚合物的导电性。4种不同原料获得的聚合物中,以邻苯二胺和邻氨基苯酚为基础的聚合物更值得进一步研究,将其由半固体状态进一步固化将使其更有应用前景。这种新型共轭材料成本低廉、合成简单,在光电和光伏器件中将得到广泛应用。     

Examining structure property relationships in coatings based on substituted linear aromatic polycyanurates

Three series of halogenated and non-halogenated polycyanurates are prepared in good yield and purity, and fully characterised. Many of the resulting polymers, formed at room temperature using phase transfer catalysis, can be cast into films with good resilience and high thermal stability (some examples suffer no mass loss when held isothermally at 190 °C and only display appreciable losses when held continuously at 300 °C). Char yields of 35–65% are achieved in nitrogen depending on backbone structure. Some problems were encountered with solubility, particularly with heavily halogenated dichlorotriazines, which limited molecular weights (M_n = 2000–4000 g mol^?1 depending on backbone structure) although when the phase volume ratio was altered to 0.25 higher molecular weights (M_n = 10,000–30,000 g mol^?1) were possible. Best solubility was achieved by using aromatic diols with at least two equivalent phenylene units per dichlorotriazine unit. DSC reveals polymerisation exotherms with maxima at 190–260 °C (ΔH_p = 35–57 kJ/mol) followed by embrittlement and shrinkage (when heated to 300 °C). These phenomena may be due to the formation of poorly formed crystallites (activation energies span 155–380 kJ/mol) combined with thermal isomerisation.     

聚丙烯腈基炭纤维组织结构表征与性能分析

采用扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、X射线衍射(XRD)、激光拉曼光谱(Raman)及化学分析法等测试技术对4种PAN基3K炭纤维(2种国产炭纤维、1种国外原丝国内炭化纤维、一种日本炭纤维)的表面形貌、组织结构及化学组成等方面进行了表征,并分析了材料的微观结构组织与宏观性能的关系。结果表明:相比日本炭纤维,国产炭纤维表面缺陷多、微观结构不完整、R值大、杂质含量多等因素决定了其具有较低的拉伸强度。     

A novel ultralow-loss Sr2CeO4 microwave dielectric ceramic and its property modification

A new ultralow-loss Sr₂CeO₄ microwave dielectric ceramic was prepared via a conventional solid-state method. The X-ray diffraction and Rietveld refinement results demonstrate that pure-phase Sr₂CeO₄ ceramics belong to the orthorhombic structure with a Pbam space group. Scanning electron microscopy analysis reveals dense and homogeneous microstructure. Optimum microwave dielectric properties of ε_r = 14.8, Q × f = 172,600 GHz (9.4 GHz) and τ_f = -62 ppm/°C were obtained as it was sintered at 1270 °C for 4 h. In addition, the substitution of a few amount of Ti⁴⁺ for Ce⁴⁺ was found to have significant influences on the grain morphology, sintering behavior, phase structure and microwave dielectric properties. Among them, the Sr₂Ce_0.65Ti_0.35O₄ ceramic sintered at 1350 °C for 4 h demonstrates near-zero τ_f of -1.8 ppm/°C, ε_r of 20.7 and Q×f of 115,550 GHz (8.1 GHz) because of its two-phase structure, showing large application potentials.     

Synthesis,structure and dielectric constant property of two novel complexes based on protonated 1-aminoadamantane

The reaction of 1-aminoadamantane hydrochloride and divalent metal chloride in concentrated hydrochloric acid medium yields two unusual complexes containing protonated 1-aminoadamantane, (C₁₀H₁₈N)¹⁺₂[ZnCl₄]^2? (1), (C₁₀H₁₈N)¹⁺₂[MnCl₄(H₂O)₂]^2? (2a) and (C₁₀H₁₈N)¹⁺₂[MnCl₄(D₂O)₂]^2? (2b). Their crystal structures have been determined by X-ray crystallography. Both complexes contain molecular network of (C₁₀H₁₈N)⁺ cations and divalent metal chloride polyhedral anions (Mn and Zn site symmetry 2/m). Dielectric constants of both two organic–inorganic hybrid salts were measured at different temperatures and frequencies. Different structures lead to large discrepancy in the dielectric property measurements. In addition, thermal analysis of complex 2 was studied.     

葡聚糖修饰漆酶的制备及其催化特性和稳定性

将经NaIO₄氧化处理的葡聚糖（500×10³）连接在漆酶分子上以提高漆酶在酸性溶液环境中的稳定性。HPLC和SDS-PAGE分析表明葡聚糖修饰漆酶的分子量在200×10³以上。荧光光谱和圆二色性光谱分析表明修饰漆酶保持了天然漆酶的三级和二级结构。酶催化反应显示修饰漆酶与天然漆酶具有类似的底物亲和性和催化活性，而其在酸性条件下的稳定性显著提高。通过葡聚糖修饰使得漆酶在pH 3,50℃下的酶活半衰期从0. 07 h提高到17. 1 h，在含30%（体积）乙腈, pH 3下的酶活半衰期从0. 11 h提高到10. 3 h。在不同pH下测定修饰漆酶在216 nm处的圆二色性光谱，结果显示偶联葡聚糖增强了漆酶分子的结构稳定性，提高了其在高温及有机溶剂存在下的催化活性。     

Structural and dielectric properties of CuO nanoparticles

The DC conduction and dielectric behaviour of copper oxide nanoparticles prepared by sol-gel method and sintered at 950 °C were studied in the temperature range of 200–526 K. The formation of single phase monoclinic CuO was confirmed by x-ray diffraction. Chemical composition of the CuO ceramic was investigated with X-ray photoelectron spectroscopy (XPS) technique. Although XRD analysis shows the formation of single phase CuO, XPS spectra revealed the presence of Cu³⁺ and Cu²⁺. Deviation from linearity ln (σ_DC) vs. 1/T plot at ~390 K was observed, which indicates that DC conduction in the CuO pellet is dominated by two different conduction mechanisms. The results obtained on AC conductivity indicate that AC conduction mechanism could be well explained by the multihopping model at low frequencies, while high frequency AC conductivity data can be described by small polaron tunnelling model. The dielectric relaxation mechanism in the CuO pellet was studied by impedance spectroscopy. It was found that while dielectric constant is an increasing function of temperature, it decreases with increasing frequency. The obtained impedance spectra indicated that the grain boundary effects and intergranular activities play a crucial role on the dielectric relaxation processes.     

Structural,magnetic and dielectric properties of the novel magnetic spinel compounds ZnCoSnO4 and ZnCoTiO4

The transparent semiconductor Zn₂SnO₄ with cubic spinel structure and the isostructural Zn₂TiO₄ have been magnetically doped with Co²⁺. ZnCoSnO₄ and ZnCoTiO₄ exhibit ferrimagnetism below T_N ≈ 13?K and T_N ≈ 17?K. Ferrimagnetic moments are evident in M vs H curves below T_N by small hysteresis. Fits to strictly linear Curie-Weiss plots above T_N give μ_eff ≈ 4.86 μ_B and ≈4.91 μ_B for ZnCoSnO₄ and ZnCoTiO₄, above theoretical predictions. Impedance spectroscopy data from sintered ceramic can be fitted with a standard equivalent circuit model based on two RC elements for bulk and GB areas. The relative dielectric permittivity of the bulk is ≈20 and ≈30 for Zn₂SnO₄ and Zn₂TiO₄. The semiconducting ZnCoSnO₄ and ZnCoTiO₄ceramics exhibit bulk resistivity of ≈1 10⁶?Ω?cm and ≈1 10⁵?Ω?cm at 560?K (287?°C), and bulk activation energies of E_A ≈ 1.2?eV and 1.1?eV.     

Annealing effect on dielectric property of AlN ceramics

Effects of slow-cooling at high temperatures and annealing at intermediate temperatures on dielectric loss tangent of AlN ceramics were explored. Y₂O₃ was added as a sintering additive to AlN powders, and the powders were pressureless-sintered at 1900 °C for 2 h in a nitrogen flow atmosphere. In succession to the sintering, AlN samples were slow-cooled at a rate of 1 °C/min from 1900 to 1750 °C and/or annealed at 970 °C for 4 h. Al₅Y₃O₁₂ was detected in the AlN ceramics obtained by the slow-cooling and AlYO₃ was found in the ceramics cooled at a rate of 30 °C/min. AlN ceramics with a relative density of 0.986 were obtained by the slow-cooling method. On the other hand, very low tan δ values between 2.6 and 4.6 × 10⁻⁴ were obtained when the AlN ceramics were annealed at 970 °C for 4 h.     

Elaboration and dielectric property of modified PZT/epoxy nanocomposites

Composites of lead zirconate titanate (PZT) 50 nm nanoparticles and epoxy resins have been produced with various PZT contents from 0 to 20 wt%. The morphology and thermal properties of prepared composites were characterized using scanning electron microscopy and differential scanning calorimetry. The PZT nanoparticles were found to be well dispersed in the epoxy resin matrix. The glass transition temperature (T_g) value of the nanocomposites increases from 164 to 178°C with increasing the PZT weight fraction. The dielectric composites properties dependences were studied via a wide range of frequency from 10 Hz to 100 kHz. The dielectric constant of PZT/epoxy composite was increased from 5.56 to 6.29 (at f = 1 kHz, T = 30°C), respectively to the incorporated PZT amount, and these values are higher than that the dielectric constant of pure cured epoxy resin, ε = 4.86. POLYM. COMPOS., 37:455–461, 2016. © 2014 Society of Plastics Engineers     

Relation between dielectric property and desulphurization of coal by microwaves

Dielectric properties of various coals and aqueous NaOH solutions were determined to study thermochemical coal desulphurization by microwave irradiation. Aqueous NaOH solutions were used as media for irradiation. The coal samples were placed in a rectangular cavity and irradiated with 2450 MHz microwaves, resulting in 70–80% desulphurization efficiency.     

Morphology of poly(ether sulfone)-modified polycyanurates

Polycyanurates prepared from cure of bisphenol A dicysanate (BPADCy) were modified with either hydroxyl-terminated or cyanated poly(ether sulfone)s (as HPES or CPES, respectively) of different molecular weights. With high molecular weight HPES (or CPES), the resulting resin showed a two-phase morphology in contrast to the single-phase morphology generated from the curing reactions of the low molecular weight HPES (or CPES) and BPADCy as observed from optical microscopy. Results from scanning electron microscopy suggests a discrete-continuous fracture surface for the high molecular weight HPES-modified polycyanurate but for the CPES-modified analogue, a blur interface between particle and matrix was observed. However, this blur interface can also be generated if 1 wt% of catalyst system (n-nonylphenol/cobaltic acetylacetonate) was used during cure of mixtures of high molecular weight HPES and BPADCy. This blur interface in the catalyzed system is attributed to the inter-reactions between the hydroxyl termini in HPES and the cyanate groups in BPADCy.     

Preparation,dielectric property and microwave absorption property of Cu doped SiC nanopowder by combustion synthesis

Abstract

Cu doped SiC nanopowders have been prepared via combustion synthesis, using silicon powder and carbon black as the raw materials, copper powder as the doping source and polytetrafluoroethylene as the chemical activator respectively. The microstructure of prepared nanopowders has been characterised by X-ray diffraction and scanning electronic microscope. The electric permittivities of prepared SiC nanopowders in the frequency range of 8·2–12·4 GHz have been determined. Results show that prepared β-SiC nanopowders have fine spherical particles and narrow particle size distribution, and a quantity of SiC whisker increases with increasing Cu doping content. The Cu₃Si impurity has been generated when Cu content is up to 10%. The β-SiC doped with 10% Cu has the highest real part ?′ and dielectric loss tanδ values. The 5% Cu doped SiC nanopowder with matching thickness of 2 or 2·5 mm exhibits the best microwave absorption properties in the frequency range of 8·2–12·4 GHz.     

Structural,dielectric and transport properties of samarium-doped cobaltites

Cobaltites have gained considerable importance in the field of material science, due to their valuable dielectric, biological and magnetic properties. This work highlights the importance of samarium (Sm) doping to enhance the structural and dielectric properties of bismuth calcium cobaltite. All samples were synthesized using the co-precipitation technique and were sintered at 750 °C for 2 h. X-Ray Diffraction (XRD) analyses, as well as Fourier-transform infrared spectroscopy, are used to realize the monoclinic structure of all samples. In addition, XRD analysis was used to determine the lattice strains, lattice constant, crystallite size, the volume of a unit cell, and dislocation density. This analysis shows that Sm doping increases the dislocation density and lowers the average crystallite size. The AC conductivity, (σ_ac), dielectric constant (ε), and loss tangent tan (δ) for all samples were measured at various fixed frequencies and in the variable frequency range (100Hz – 3 MHz). The obtained results are also discussed using the non-linear modified Debye function and Jonscher's power law. The composition Bi₂Ca_1.95Sm_0.05CoO₆ proves to be the better dielectric material at 350 °C–600 °C as it achieves a high value for dielectric constant while maintaining the lower dielectric loss than that of other compositions. Bi₂Ca_1.95Sm_0.05CoO₆ acquires a higher value for σ_ac than the previously reported σ_ac values of Ca_2-xY_xCo₂O₅. These qualities make the aforementioned specimen highly preferable for energy applications.     

Thermal behavior and dielectric property analysis of boron nitride‐filled bismaleimide‐triazine resin composites

Bismaleimide‐triazine (BT) resin/hexagonal boron nitride (h‐BN) composites are prepared, and the effects of h‐BN content on the thermal and dielectric properties are studied in the view of structure–property relationship. It is found that the introduction of the BN in the BT resin dramatically improve the thermal conductivity of BT resin. The thermal conductivity of the composites is up to 1.11 W/m.K, with an h‐BN concentration of 50 wt %, which is increased by six times compared with the pure BT resin. The BT resin/h‐BN composites also exhibit excellent thermal properties, with the glass transition temperatures above 200°C, and thermal decomposition temperatures over 390°C. Moreover, the composites possess good dielectric properties. Their dielectric constant and loss tangent (tan δ) are less than 4.5 and 0.015, respectively. The results indicate that the BT resin/h‐BN composites are promising as efficient heat‐releasing materials in the high‐density electronic packaging technology. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Enhanced mechanical property and tunable dielectric property of SiCf/SiC-SiBCN composites by CVI combined with PIP

The SiBCN matrix via chemical vapor infiltration (CVI) or/and polymer infiltration pyrolysis(PIP) technologies was orderly introduced to SiCf/SiC composites to ...     

一种新型共轭Schiff碱聚合物的合成与表征

以对苯二甲醛和水合肼为原料,无水乙醇作溶剂合成了一种共轭Schiff碱聚合物,并通过GPC、IR、1 H NMR、紫外-可见吸收光谱和荧光光谱对其分子量和组成结构进行表征。结果表明,该物质为一种分子量较大的共轭Schiff碱聚合物,具有良好的荧光性。     

Characterization of electrosynthesized conjugated polymer-carbon nanotube composite: optical nonlinearity and electrical property

The effects of multi-walled carbon nanotube (MWNT) concentration on the structural, optical and electrical properties of conjugated polymer-carbon nanotube composite are discussed. Multi-walled carbon nanotube-polypyrrole nanocomposites were synthesized by electrochemical polymerization of monomers in the presence of different amounts of MWNTs using sodium dodecylbenzensulfonate (SDBS) as surfactant at room temperature and normal pressure. Field emission scanning electron microscopy (FESEM) indicates that the polymer is wrapped around the nanotubes. Measurement of the nonlinear refractive indices (n(2)) and the nonlinear absorption (β) of the samples with different MWNT concentrations measurements were performed by a single Z-scan method using continuous wave (CW) laser beam excitation wavelength of λ = 532 nm. The results show that both nonlinear optical parameters increased with increasing the concentration of MWNTs. The third order nonlinear susceptibilities were also calculated and found to follow the same trend as n(2) and β. In addition, the conductivity of the composite film was found to increase rapidly with the increase in the MWNT concentration.     

Synthesis and electroluminescent properties of a novel copolymer with short alternating conjugated and non‐conjugated blocks

A new electroluminescent copolymer [poly(1,5‐di(3,5‐dimethyloxystyrylene)naphthalene‐block‐tri(ethylene oxide)) (DSN–TEO)], containing alternating rigid, conjugated light‐emitting units and flexible tri(ethylene oxide) ionic conductive units, was synthesized via the Wittig reaction. The polymer has fairly good solubility in chloroform, tetrahydrofuran, toluene, etc, and excellent film‐forming ability. The decomposition temperature and the glass transition temperature were 409 °C and 42.2 °C, respectively. A light‐emitting diode (LED) device with configuration ITO/PEDOT–PSS/DSN–TEO/Ca(Al) and light‐emitting electrochemical cell (LEC) device with ITO/DSN–TEO + PEO (LiTf)/Al were prepared, and the photoluminescence and electroluminescence (EL) properties were investigated. Efficient blue‐green light emission (EL maximum emissive wavelength at 508 nm) was found with onset voltage at 6 V. The maximum light efficiency was 0.107 cd A^?1 at 20 V for LED, and the onset voltage 2.5 V and the maximum light efficiency was 4.2 cd A^?1 at 2.8 V for LEC, respectively. The response time of the LEC was less than 5 s. The EL efficiency of LEC device was improved by 44 as compared with the relative LED device. © 2003 Society of Chemical Industry     

多级孔硅铝酸盐的结构特性及其除湿性能

采用水热法制备出具有深度除湿功能（RH<20%）、高饱和吸附量和中低温快速脱附性能（<100℃）的除湿轮用多级孔硅铝酸盐吸附剂。采用N₂-吸附脱附、XRD、透射电镜、FT-IR和NMR等技术表征吸附剂的微观结构;采用动态水汽吸附分析仪（DVS）测试其吸附-脱附性能。结果发现,通过控制制备前体的微晶温度,可调控吸附剂在中低湿度工况下的除湿性能：微晶温度是通过影响吸附剂微观结构中有序介孔和类微孔结构的比例,来影响吸附剂的深度除湿功能;升高微晶温度会提高吸附剂中类微孔和骨架Al比例从而强化其深度除湿能力,但会显著降低介孔有序度及总孔容,削弱其饱和吸附量及脱附性能;过高的类微孔和骨架Al比例会提高吸附剂的脱附再生温度,增大除湿能耗。