Ag Nanoparticle-Incorporated Natural Rubber for Mechanical Energy Harvesting Application

The energy conversion performance of the triboelectric nanogenerator (TENG) is a function of triboelectric charges which depend on the intrinsic properties of materials to hold charges or the dielectric properties of triboelectric materials. In this work, Ag nanoparticles were synthesized and used to incorporate into natural rubber (NR) in order to enhance the dielectric constant for enhancing the electrical output of TENG. It was found that the size of Ag nanoparticles was reduced with the increasing CTAB concentration. Furthermore, the CTAB surfactant helped the dispersion of metallic Ag nanoparticles in the NR-insulating matrix, which promoted interfacial polarization that affected the dielectric properties of the NR composite. Ag nanoparticle-incorporated NR films exhibited an improved dielectric constant of up to almost 40% and an enhanced TENG performance that generated the highest power density of 262.4 mW/m².     

Self-templated synthesis of single-crystal and single-domain ferroelectric nanoplates

Free-standing single-crystal PbTiO(3) nanoplates were synthesized by a facile hydrothermal method. A "self-templated" crystal growth is presumed to lead to the formation of the PbTiO(3) nanoplates, which have ferroelectric single-domain structures, whose polarization areas can be manipulated by writing and reading. The nanoplates are also effective catalysts for the oxidation of carbon monoxide.     

类钙钛矿新铌酸盐Ba5NdTi2Nb3O18的合成、结构与介电特性

为满足现代通信技术的小型化、集成化与高可靠性的迫切要求,探索具有高介电常数、低介电损耗与低温度系数的微波介电材料引起了材料科学、化学、物理、电子等领域科学工作者的广泛关注,并已开发出复合钙钛矿结构Ba(Zn_(1/3)Ta_(2/3))O_3、钨青铜结     

溶胶-凝胶法制备掺锰钛酸钡纳米粉体及其陶瓷

The Mn-doped barium titanate nanosized powders and ceramics were prepared via the sol-gel process. The powders and ceramics were characterized by XRD， SEM and TEM. The dielectric properties of the ceramics were also measured. The influences of calcination temperature and Mn concentration on the microstructure， dielectric properties and phase composition of BaTiO₃ nano-powders and ceramics were discussed. The results indicated that the BaTiO₃-based powders doped with 1.0mol% Mn were mainly in cubic BaTiO₃ phase， but the tetragonal phase became more evident when the calcination temperature increased. After sintering， Mn-doped ceramics were mainly composed of cubic BaTiO₃. Specially， a new phase of hexagonal crystal BaTiO₃ and BaMnO₃ existed in the ceramics doped with 5.0mol% Mn and the ceramic grains were in ‘clintheriform’. The structure of ‘clintheriform’ led to the poor densification of ceramics， reducing the dielectric constant obviously. The dielectric constants of BaTiO₃ ceramics first increased and then decreased as the Mn concentration increased. The room temperature dielectric constant was 2 290 and the lowest dielectric loss was 0.004 when the Mn concentration was 0.5mol%.     

Effect of the Different Sr Dopant Contents on NiO Ceramic

Sr - doped NiO ceramic was studied. The effect of composition variation of Ni_(1-x)Sr_xO where x = 0, 0.01, 0.02, 0.03, 0.05 and 0.10 mole % was prepared by using solid state method. The calcination temperature used at 950 °C for 4 hours and the sintering temperature used at 1200 °C for 3 hours. The results depict the microstructures increase in grains size (0.43 - 3.30 μm) by increase of Sr dopant contents. The density and porosity testing support the result of microstructures analysis. The larger grains size led to increase in density and lower in porosity. The dielectric properties is observed in a wide frequency range of (1 - 1 000 MHz). The increase of dielectric constant is associated with the decrease of dielectric loss. The optimum composition was obtained for the x = 0.03 mole % sample with highest dielectric constant (3.24 x 10³) and lowest dielectric loss (1.42) at 1 MHz.     

Preparation of polyimide/BaTiO3‐nanocrystal hybrid thin films and their dielectric property

High dielectric constant is highly desirable in capacitors and memory devices. In this work, oleic acid (OA)‐capped BaTiO₃ nanocrystals were synthesized by a two‐phase approach. Polyimide (PI)/BaTiO₃‐nanocrystal composite thin films with high dielectric constant have been successfully fabricated. The morphologies and dielectric properties of the hybrid films were exploited. The results showed that BaTiO₃ nanocrystals can be uniformly dispersed in the PI thin films owing to the surface modification of OA‐capped BaTiO₃ nanocrystals. It was found that the dielectric constant of composite film varies with the volume fraction of BaTiO₃ nanocrystals and sintering temperatures and reaches a maximum value of 44.1, which is around 13 times higher than that of pristine PI thin film (3.2). These results demonstrated that PI/BaTiO₃‐nanocrystal composite films have considerable application potential in microelectronic fields.     

高耐热、低介电常数含氟聚酰亚胺材料的合成与性能研究

合成了一系列新型含氟耐高温、低介电常数聚酰亚胺 (PI)材料 ,并对其进行了热性能、电性能等方面的测试 .结果表明 ,这类分子结构中含吡啶环单元的材料可保持PI固有的耐热性能 ,其在氮气下的热分解温度为 5 4 5～ 6 0 1℃ ;而侧链的双三氟甲基取代结构一方面使分子具有较高的氟含量 ,另一方面增大了分子的自由体积 ,这两方面的共同作用使得这类材料具有优良的介电性能 ,其介电常数为 2 86～ 2 91;击穿电压为15 0 4～ 197 3kV mm .     

Influence of CTAB/alkanol/cyclohexane w/o microemulsions on the basic hydrolysis of crystal violet

The basic hydrolysis of crystal violet has been studied in w/o microemulsions of the CTAB/alkanols/cyclohexane system (alkanols: 1-butanol and 1-hexanol). The reaction can be considered to occur in the water phase of the droplets and from the rate constant the apparent dielectric constant of the water phase was determined. The cyclohexane incorporation in the system produces a decrease in the effective dielectric constant of the water phase and in the specific conductivity.     

Study on polyvinylidene fluoride as alignment layer in twist-nematic liquid crystal display

The material with high dielectric constant can significantly affect the distribution of the electric field, so this kind of material has great potential in liquid crystal display. In this paper, polyvinylidene fluoride (PVDF) as alignment layer in liquid crystal display was analysed. The optical property, mechanical property, thermal stability and electrical property of PVDF were measured. Experiments show that the absorbance of PVDF material is 0.2 (or less) in visible light, which is better than the conventional alignment material polyimide (PI). The alignment effect can be generated by mechanical friction and the liquid crystal molecules are ordered or aligned, and PVDF can maintain good thermal stability as temperature is lower than 400°C. Since the dielectric constant of PVDF is usually between 6.0 and 8.0, it has significant effect on the distribution of the electric field in the liquid crystal display, and its dielectric loss is also less than PI. The lower operating voltage and the faster response time are obtained from the experiment. It can be confirmed by the experiments that PVDF could be used in liquid crystal display (LCD) as the alignment layer to improve LCD’s characteristics.     

新铌酸盐Sr5NdTi3Nb7O30的合成与介电特性

一些铁电铌酸盐具有优良的电光性能和非线性光学性能,因此该类化合物的人工合成、结构与性能的研究受到了重视,其中钨青铜结构的系列晶体(例如SBN、KNSBN、SCNN)在材料的制备和器件的设计方面都取得了很大进展,它们在实时全息存储、集成     

Low dielectric materials from fluorinated polybenzoxazines

Fluorinated monomers containing a benzoxazine moiety have been synthesized successfully by preparing the benzoxazines from fluorinated amines (4‐fluoroaniline, 2,4‐difluoroaniline, and 2,3,4‐trifluoroaniline). These monomers were polymerized by step curing process following a cure cycle of 100, 150, 200 and 250°C for 1 h at each temperature. The molecular structure of the monomers and their polymers was characterized by Fourier transform infrared and nuclear magnetic resonance techniques. The synthesized fluorinated polybenzoxazines were able to reduce the dielectric constant to 2.0 for polybenzoxazine from 2,3,4 trifluoroaniline (PTF)‐Bzo at a frequency of 1 MHz. Moreover, they possess high thermal stability and low moisture absorption, which makes it suitable for high‐temperature process of interlayer dielectrics. Copyright © 2014 John Wiley & Sons, Ltd.     

Ag负载KTa1-xNbxO3-BaTiO3颗粒掺杂P(VDF-TrFE-CTFE)复合材料的制备及介电性能

通过光照还原法制备了银颗粒负载的铌钽酸钾-钛酸钡复合粉体（Ag/KTN-BT）,并将其与聚偏氟乙烯-三氟乙烯-三氟氯乙烯（P（VDF-TrFE-CTFE））聚合物复合,获得Ag/KTN-BT聚合物基复合材料。研究发现,Ag/KTN-BT填料颗粒在聚合物基体中分散均匀,复合材料结构致密,无明显气孔和裂纹,且具有较好的柔韧性。银纳米颗粒的负载,一方面在复合材料中引入了额外的界面,导致界面极化作用增强,明显提高复合材料的介电常数;另一方面银纳米颗粒的量子尺寸效应和库伦阻塞效应使得复合材料保持较低的介电损耗。当填充体积分数为20%的Ag/KTN-BT颗粒时,聚合物基复合材料的介电常数大幅提升,从聚合物的37提升到125（100 Hz）,介电损耗仅为0.12。与KTN-BT基复合材料对比,Ag/KTN-BT基复合材料也显示出较好的介电性能。     

Temperature dependence of physical constants in binary-fluorinated liquid crystal mixtures

The temperature dependence of dielectric constants and splay elastic constants for fluorinated phenyl bicyclohexane (PBC) binary liquid crystal (LC) mixtures is reported. The results show that the proportions of the constituent elements of binary mixtures strongly influence their anisotropic dielectric constants. For mixtures in which meta-para- and ortho-para-fluorine-substituted molecules are in equal proportion, the effectiveness of the anisotropic dielectric is equal to that with a single para-fluorine- substituted compound. The proportions of a mixture seldom affect the threshold voltage and splay elastic constants in an anti-parallel measurement cell.     

Structure and Shape Control of Hydrothermally Synthesized PbTiO3--Effects of pH and Complexing Agents

Tabular PE-PbTiO3,spherical PY-PbTiO3,and acicular PX-PbTiO3 powders were hydrothermally synthesized from triethanolamine(TEA)-complexed precurso;clubbed PE-PbTiO3 powders were obtained from diethanolamine(DEA)-complexed precursor,The effects of pH of the hydrolyzation as well as complexing agents including TEA,DEA,and MEA(monoethanolamine) on the structure and the morphology of PbTiO3 powders are discussed.The optimal conditions for hydrothermal Synthese of acicular and clubbed PbTiO3 powders have been established.The products were characterized by means of XRD.TEM and other techniques.     

Synthesis and characterization of polyimides from bis(3‐aminophenyl)‐4‐(1‐adamantyl)phenoxyphenyl phosphine oxide

A novel diamine, bis(3‐aminophenyl)‐4‐(1‐adamantyl)phenoxyphenyl phosphine oxide (mDAATPPO), was synthesized via the Williamson ether reaction of 4‐(1‐adamantyl)phenol and bis(3‐nitrophenyl)‐4‐fluorophenyl phosphine oxide, followed by reduction. The phenol group was prepared by the Friedel–Crafts reaction of 1‐bromoadamantane and phenol, whereas the phosphine oxide group was synthesized by the Grignard reaction of 1‐bromo‐4‐fluorobezene and diphenyl phosphinic chloride, followed by nitration. The monomer and its intermediate compounds were characterized with Fourier transform infrared, NMR, and melting‐point apparatus. The monomer was then used to prepare polyimides with 2,2‐bis(3,4‐dicarboxyphenyl)hexafluoropropane dianhydride, 3,3′,4,4′‐benzophenonetetracarboxylic dianhydride, 4,4′‐oxydiphthalic dianhydride, and pyromellitic dianhydride by the conventional two‐step synthesis: the preparation of poly(amic acid) followed by solution imidization. The molecular weights of the polyimides were controlled to 20,000 g/mol by off‐stoichiometry, and the synthesized polyimides were characterized with Fourier transform infrared, NMR, gel permeation chromatography, thermogravimetric analysis, and differential scanning calorimetry. In addition, the solubility, intrinsic viscosity, dielectric constant, and birefringence of the polyimides were evaluated. Novel polyimides with mDAATPPO exhibited good solubility, high glass‐transition temperatures (290–330 °C), excellent thermal stability (>500 °C), low dielectric constants (2.77–3.01), low refractive indices, and low birefringence values (0.0019–0.0030). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2567–2578, 2006     

The origin of DC electrical conduction and dielectric relaxation in pristine and doped poly(3‐hexylthiophene) films

We present here the evidence for the origin of dc electrical conduction and dielectric relaxation in pristine and doped poly(3‐hexylthiophene) (P3HT) films. P3HT has been synthesized and purified to obtain pristine P3HT polymer films. P3HT films are chemically doped to make conducting P3HT films with different conductivity level. Temperature (77–350 K) dependent dc conductivity (σ_dc) and dielectric constant (ε′(ω)) measurements on pristine and doped P3HT films have been conducted to evaluate dc and ac electrical conduction parameters. The relaxation frequency (f_R) and static dielectric constant (ε₀) have been estimated from dielectric constant measurements. A correlation between dc electrical conduction and dielectric relaxation data indicates that both dc and ac electrical conductions originate from the same hopping process in this system. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 1047–1053, 2010     

Novel epoxy nanocomposite of low Dk introduced fluorine‐containing POSS structure

A nanoporous additives, polyhedral oilgomeric silisesquioxane containing eight functional hexafluorine groups, octakis(dimethylsiloxyhexafluoropropyl ether)silsesquioxane (OF) has been synthesized and blended with the UV‐cured epoxy resin. The OF containing (10%) epoxy has significantly lower dielectric constant (2.65) than the plain epoxy (3.71). The incorporation of fluorine containing additives is well‐known to reduce dielectric constant due to lower its polarizability. In addition, the presence of the bulky POSS structure is able to create additional free space or pores and further reduces the dielectric constant of the epoxy matrix. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 502–510, 2007     

Origins of Giant Dielectric Properties with Low Loss Tangent in Rutile (Mg1/3Ta2/3)0.01Ti0.99O2 Ceramic

The Mg²⁺/Ta⁵⁺ codoped rutile TiO₂ ceramic with a nominal composition (Mg_1/3Ta_2/3)_0.01Ti_0.99O₂ was synthesized using a conventional solid-state reaction method and sintered at 1400 °C for 2 h. The pure phase of the rutile TiO₂ structure with a highly dense microstructure was obtained. A high dielectric permittivity (2.9 × 10⁴ at 10³ Hz) with a low loss tangent (<0.025) was achieved in the as-sintered ceramic. After removing the outer surface, the dielectric permittivity of the polished ceramic increased from 2.9 × 10⁴ to 6.0 × 10⁴, while the loss tangent also increased (~0.11). The dielectric permittivity and loss tangent could be recovered to the initial value of the as-sintered ceramic by annealing the polished ceramic in air. Notably, in the temperature range of −60–200 °C, the dielectric permittivity (10³ Hz) of the annealed ceramic was slightly dependent (<±4.4%), while the loss tangent was very low (0.015–0.036). The giant dielectric properties were likely contributed by the insulating grain boundaries and insulative surface layer effects.     

固相剪切碾磨方法制备聚丙烯/钛酸钡高介电常数复合材料

采用固相剪切碾磨方法(S3M)制备高介电常数聚丙烯/钛酸钡复合材料。当钛酸钡体积分数φBaTiO3=0.50时,体系的介电常数由纯聚丙烯的2.3增加到108.7(1 kHz)。复合材料断面的SEM照片显示,粒径约100 nm的钛酸钡粒子均匀分散在聚丙烯基体中。复合粉体的SEM、TGA和FT-IR分析表明固相剪切碾磨产生的强大剪切、挤压、摩擦等作用在聚合物相引起多种复杂的物理及化学变化,聚合物粒径变小,粒子比表面积增大,表面能大幅增加,与具有较高表面活性的钛酸钡粒子形成较强的界面相互作用。     

Effect of droplet size on the dielectric properties of PDLC films

Polymer dispersed liquid crystal (PDLC) films (5CB/PMMA, 60/40) of different droplet size were prepared by a solvent-induced phase separation method under different N₂ flow speeds. The effects of droplet size on the thermal transitions of the LC and various dielectric properties such as dielectric constant, conductance, dielectric loss, and the electric field induced in a droplet were examined. The configuration of the LC in the film with smaller droplets can be identified by comparing the dielectric constant of the film with the one predicted by Boettcher's mixture formula. In addition, the effect of droplet size on the electro-optical response of the PDLC film was investigated. Variations of the conductance and the dielectric constant of the film were analyzed under various AC frequencies, with the purpose of elucidating the polarization mechanism of the LC molecules in the droplet. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35 : 1373–1381, 1997