陶瓷/VDF-TrFE 0-3型铁电复合物的三阶非线性介电系数

在自建的非线性介电测试装置上测得了PT,BT、PZT和VDF-TrFE共聚物形成的0-3型铁电复合物厚片的三阶非线性介电系数ε3.研究发现,三种复合物的ε3都随陶瓷组分含量的上升而增大.测试场强升高,测得的ε3值减小,但对高陶瓷含量(φ＞0.4)的BT/VDF-TrFE和PZT/VDF-TrFE复合物则在6MV/m场强下出现极小值.二相都被预极化的复合物小于仅陶瓷相被预极化的ε3值.PZT/VDF-TrFE复合物的温度依赖关系显示了与(-阶)介电系数类似的表观热滞后现象.高PZT含量的复合物在相变区出现较大的ε3值.     

0—3型PZT／P[VCF（77）—TrFE（23）]铁电复合物的非线性介电系数

用自建的非线性介电测试装置测得了０－３型ＰＺＴ／Ｐ「ＶＤＦ（７７）－ＴｒＦＥ（２３）」铁电复合物厚片在不同场强和温度下的线性和非线性介电系数。对于ＰＺＴ体积含量Φ〉０．３的复合物,介电系数ε１随测试场强的升高显著增大。在Φ〈０．１时,可用Ｍａｘｗｅｌｌ－Ｇａｒｎｅｔｔ方程拟合实验结果。     

《113》轴向取向稀土超磁致伸缩材料的制备与性能

利用低温度梯度水平炉, 成功地生长了113轴向取向的稀土超磁致伸缩材料, 该材料在低磁化场下具有很高磁致伸缩应变, 在10 MPa压应力、 80 kA*m-1磁场下的磁致伸缩应变λ=1540×10-6. 113轴向取向材料的高磁致伸缩应变来源于材料良好的取向; 定向生长的大晶粒; 施加磁场时较多的可转动磁矩.     

介电弹性体致动器的结构设计及应用

介电弹性体作为一种新型的电活性高分子聚合物,当受到电场的激励时会产生变形,撤销电场后能够恢复原状,具有将电能直接转换为机械能的特点。通过将其设计成具有不同结构的致动器,能够提高变形能力,并且满足不同的应用需求。本文介绍了介电弹性体致动器的致动机理,阐明了它们是能够以直线方式产生运动的线性致动器,在此基础上可设计出不同结构的致动器,主要归纳了各种介电弹性体致动器,从它们的性能特征、加工技术和潜在应用等方面进行了讨论。     

树脂基稀土-铁系超磁致伸缩复合材料的制备与压应力效应研究

采用粉末粘结-磁场成型法制备了树脂基稀土-铁系超磁致伸缩复合材料(Giant magnetostrictive particle composite,GMPC),并对样品在不同压应力下的磁致伸缩系数进行了测量,当样品中的TeDyFe合金颗粒尺寸为0~200μm、质量分数为90%时,其磁致伸缩系数于外加磁场达到266 kA.m-1时即已趋近饱和,饱和磁致伸缩系数达623×10-6;当施加在样品纵向方向上的预压应力为5 MPa时,此时样品的饱和磁致伸缩系数最高,为662×10-6,比未加预压应力时样品的饱和磁致伸缩系数高39×10-6,表明所制得的实验样品具有一定的压应力效应,并且压应力效应在较低压力下起积极作用,在较大压力下则产生消极作用。     

0-3型PZT/P[VDF(77)-TrFE(23)]铁电复合物的非线性介电系数

用自建的非线性介电测试装置测得了０ － ３ 型ＰＺＴ／Ｐ［ＶＤＦ（７７） － ＴｒＦＥ（２３）］ 铁电复合物厚片在不同场强和温度下的线性和非线性介电系数。对于ＰＺＴ 体积含量Φ＞ ０ ．３ 的复合物,介电系数ε１ 随测试场强的升高显著增大。在Φ＜ ０ ．１ 时,可用Ｍａｘｗｅｌｌ－ Ｇａｒｎｅｔｔ 方程拟合实验结果。Ｂｒｕｇｇｅｍａｎ 方程适合于低电场（ ＜ １ ＭＶ／ｍ ） 下复合物介电系数的预测。随着退极化场系数Ｌｚ 的改变,用Ｙａｍａｄａ 模型可拟合不同场强下复合物介电系数随Φ的变化关系。ε１ 的温度依赖性显示了明显的热滞后效应。Φ值增大导致升温过程的居里温度Ｔｃ 降低。Φ＜ ０ ．３ 时,三阶非线性介电系数ε３ 随测试场强的升高而减小,而Φ＞ ０ ．４ 试样的ε３ 在６ＭＶ／ｍ 场强下出现极小值。高Φ值的复合物具有较大的ε３ 。高ＰＺＴ 含量的复合物在相变区出现较大的ε３值。ε３ 温度谱同样显示了与ε１ 类似的表观热滞后现象。     

溶剂散逸自组装法制备具有电致收缩性能的聚苯胺/聚氨酯凹透镜阵列

以水珠为模板,采用溶剂散逸自组装法制备了表面具有特殊形貌的有序多孔膜. 以此多孔膜为模板制备了聚苯胺/聚氨酯（PANI/PU）的凹透镜阵列. 采用红外光谱（FTIR）和扫描电子显微镜（SEM）对界面聚合得到的PANI/PU纳米复合物的结构和凹透镜阵列的形貌进行了表征,研究了不同合成条件对纳米复合物导电性能的影响,并对PANI/PU凹透镜阵列的电学和光学性能进行了研究. 结果表明,PANI/PU凹透镜阵列同时具有导电性、电致收缩性和光衍射性质;其收缩率与外加电压成反比,而透光率与收缩率成正比.     

CdS纳米晶@碳点复合物膜的电致化学发光

采用热解柠檬酸法制备碳点(CDs),并将之与表面无包裹剂的CdS纳米晶(CdS NCs)超声复合制备CdS纳米晶@碳点(CdS NCs@CDs)复合物。研究了复合物膜阴极电致化学发光(ECL),探讨了CDs对CdS纳米晶膜ECL增强的机理。CDs分散性良好、尺寸在1.5~4 nm之间;与粒径约为4 nm的CdS纳米晶按体积比2∶3复合后,在360 nm光激发下复合物具有最强的荧光发射且表现为CDs的荧光。同时,复合物膜产生归属于激发态CdS纳米晶的最强的ECL发射,且ECL发光峰起置电势正移至-1.05 V。复合物膜的ECL发射是pH依赖的,在pH值为6时,复合物膜具有最大的ECL强度,为CdS纳米晶膜ECL强度的19倍。这种ECL增强源于CDs能束缚大量电子产生局域电场从而促进近邻CdS纳米晶激发态的形成与弛豫。     

具有电致变色作用的聚合物材料

电致变色现象是指在外加偏电压感应下，材料的光吸收或光散射特性的变化。这种颜色的变化在外加电场移去后仍能完整地保留。显然，它与液晶显示有着实质性的区别。电致变色材料不仅具有变色及多重变色的功能，而且种类多样。最早被研究的是一些氧化物，如     

纤维素基电致驱动器结构可能性与影响因素分析

验证了电致驱动纸(Electro-Active Paper-EAPap)作为驱动器的可能性,同时对其驱动影响因素进行了讨论。EAPap驱动器以纤维素基材料-纸制品作为基体,在基体两面层压了银质电极构成。当在电极上施加一个适当的电压时,EAPap驱动器将产生伸缩、弯曲等位移。实验结果表明,EAPap的驱动性能依赖于样品形式的选取,适宜的驱动电压和驱动频率,同时环境因素对驱动器性能的影响至关重要。另外,在对EAPap驱动器的驱动影响因素的研究中发现,胶的品种也对EAPap驱动器的驱动效果有一定的影响。研究结果表明,EAPap驱动器的电致驱动效应属于电致收缩效应。由于EAPap很容易制造而且轻便,很多领域可以得到应用,如柔性扬声器、活性吸音材料和智能成型控制元件等。     

Polyamide-11/lead zirconate titanates—a novel composite material with high dielectric properties

Polymeric composites gain increasing interest in materials research and practice applications due to combining excellent electric property of piezoelectric ceramic and flexibility of polymer matrix. A novel decoupling capacitor with high dielectric constant has been developed by mixing polyamide-11 (PA11) with ferroelectric ceramic lead zirconate titanates (PZT). The composite demonstrates high dielectric constant, with better frequency stability and low dielectric losses. The dependence of the dielectric constant on frequency and polymer fraction was investigated. The excellent dielectric constant of 100 and the dielectric loss of 0.1 can be obtained at a PA11 volume fraction of 0.4. The enhanced dielectric behavior originates from good connection between ferroelectric ceramic and PA11 Dielectric losses of the PZT/PA11 composites change slightly with the test frequency. Our findings suggest that the created polymeric composites with relatively high dielectric constant represent a novel type of material that is flexible and easy to process. Moreover, is suited to applications in advanced decoupling capacitors and flexible electronics.     

Electrorheology and characterization of acrylic rubber and lead titanate composite materials

Oxide one‐pot synthesis was used to synthesize a polymer precursor to lead titanate, PbTiO₃. Perovskite lead titanate, PbTiO₃, was synthesized via the sol–gel process. The dielectric constant, electrical conductivity and loss tangent of our acrylic rubber (AR71)–lead titanate (PT) composite material (AR/PT_8) were 14.15, 2.62 × 10^?7/Ω m, and 0.093, respectively, measured at 27 °C and 1000 Hz. SEM micrographs of composites between the AR71 elastomer and PbTiO₃ showed that the particles were reinforced within the matrix. The electrorheological properties of the AR71/PT composites were investigated as functions of electric field strength from 0 to 2 kV/mm and PbTiO₃ particle volume fraction. The storage modulus increased linearly with particle volume fraction, with or without an electric field. Without an electric field, the particles merely acted as a filler to absorb or store additional stress. With the electric field on, particle‐induced dipole moments were generated, leading to interparticle interactions, and thus a substantial increase in storage modulus. With PbTiO₃ particle volume fractions as small as 10^?4 embedded in the elastomer matrix, the modulus increased by nearly a factor of 2 as the electric field strength varied from 0 to 2 kV/mm. Copyright © 2008 John Wiley & Sons, Ltd.     

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     

Synergistic effects on polyurethane/lead zirconate titanate/carbon black three-phase composites

Synergistic processes in hybrid composites have frequently been described in the literature over the past few years, opening doors to new studies and applications for this type of material. In this study, three-phase composites were obtained using polyurethane (PU) as the matrix, lead zirconate titanate (PZT) as the ferroelectric ceramic and carbon black (CB) as the conductive phase. The discussion is primarily focused on a comparison of the electrical, thermal and dielectric properties of three-phase composites with those of PU_CB and PU_PZT biphasic composites. The study describes a synergistic effect between the PU/PZT/CB phases involved in the generation of charges between the particles, implying better homogeneity of the composites as well as influence over the PU crystallization. The PU_CB conductivity profile showed a phenomenon of multi-step percolation thresholds attributed to the molecular structure and repulsive surface charge of CB particles. The surface charge phenomenon restricted the percolation curve analysis of the three-phase composites by means of classic percolation theory, shown by distortion of the critical exponents. The dielectric constant three-phase composites increased gradually as a function of CB in accordance with the percolation profile.     

All‐organic nanocomposites of functionalized polyurethane with enhanced dielectric and electroactive strain behavior

For a dielectric elastomer, increasing its dielectric constant substantially could lead to a high electric field induced strain under a low operation field. In this work, high dielectric constant nanocomposites were developed by chemically bonding copper phthalocyanine oligomer (CuPc), a high dielectric constant organic semiconductor, to polyurethane (PU). Transmission electron microscope‐observed morphologies revealed that the sizes of CuPc particles in a nanocomposite of PU attached with 8.78 vol.% of CuPc were in the range of 10–20 nm, much smaller than the sizes (250–600 nm) in physical blend of PU with the same volume fraction of CuPc. At 100 Hz, the nanocomposite film exhibited a dielectric constant of 391, representing a more than 60 times increase with respect to the neat PU. The enhanced dielectric response in the nanocomposite makes it possible to induce a high electromechanical response. A strain of 17.7% and an elastic energy density of 0.927 J/cm³ were achieved under an electric field of 10 V/µm. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of filler content on the stress relaxation behavior of fly ash/polyurea composites

In this study, fly ash/polyurea (FA/PU) composites of various fly ash volume fractions were fabricated. The time-domain stress relaxation behaviors of pure polyurea and the FA/PU composites were measured by dynamic mechanical analysis (DMA) in tension mode at various temperatures. Both temperature and volume fraction of fly ash can affect the segmental motion of polyurea as well as the interaction between fly ash hollow spheres and polyurea matrix, which constitutes the intrinsic mechanism of stress relaxation. Master curves of relaxation modulus were constructed and compared for PU and FA/PU composites. A model was proposed to relate the relaxation modulus and volume fraction of fillers based on three-parameter fractional derivative model and Mori-Tanaka model. The numerical predictions obtained from the model are found to be in good agreement with the experimental results.     

粘度法研究明胶在聚氨酯弹性体表面的吸附

根据文献以异佛尔酮二异氰酸酯（IPDI）为原料制备了具有较好机械性能的聚氨酯弹性体胶条（PU）,并在胶条表面接枝肝素,得到肝素化聚氨酯胶条（PU-Hep）。将聚氨酯胶条浸泡在明胶稀溶液中,测量溶液粘度随时间、溶液浓度和温度的变化,并采用具有界面校正的粘度方程从实验相对粘度数据计算明胶在聚氨酯表面的吸附量。研究发现明胶分...     

钛酸铅/聚[偏氟乙烯(70)-三氟乙烯(30)]复合物的非线性介电性质

用自建的非线性介电测试装置研究了陶瓷相被极化 (B1 )以及陶瓷相和共聚物相都被极化 (B2 )的钛酸铅 /聚 [偏氟乙烯 ( 70 ) 三氟乙烯 ( 3 0 ) ](PT/P[VDF( 70 ) TrFE( 3 0 ) ]) 0 3型铁电复合物厚片在不同测试场强下的非线性介电系数 .对于PT含量 >0 3的复合物 ,介电系数ε1随场强的升高明显增大 .在 <0 1时 ,可用Maxwell Garnett方程拟合实验结果 .Bruggeman方程适合于低电场 ( <1MV/m)下复合物介电系数的预测 .通过Lz 的变化 ,用Yamada模型可拟合不同场强下复合物介电系数随的变化关系 .二阶非线性介电系数ε2 随的升高而增大 ,B2的ε2 大于B1 ,说明B2具有较高的剩余极化 .三阶非线性介电系数ε3 随场强的升高而减小 ,且高值的复合物具有较大的ε3 .两相都被极化试样的ε3 小于仅陶瓷相被极化的试样 .     

Ferroelectric polymer nanocomposite alignment layer in twisted nematic liquid crystal devices for reducing switching voltage

Twisted nematic liquid crystal device (TNLCD) was fabricated using a ferroelectric zinc oxide (ZnO)-doped polyimide alignment layer. The ferroelectric nanoparticle can produce a local electric field, which can trigger the orientation of liquid crystal molecule and reduces the switching voltage. The uniform dispersion of ferroelectric ZnO nanoparticles in the alignment layer was studied using field emission scanning electron microscopy and atomic force microscopy. The ferroelectric property of ZnO-doped polyimide was investigated using dynamic contact electrostatic force microscopy. An increased local electric field due to the presence of nano ZnO was confirmed with the help of scanning tunnelling microscopy. An augmentation of capacitance was observed with an increase in concentration, which substantiates the reduction of switching voltage of TNLCD with the modification of ferroelectric nanoparticle-doped alignment layer.     

Polarization inscription in ferroelectric (111) PZT and (100) SBT films

Ferroelectric thin films form an equilibrium domain structure compatible with their respective crystallographic symmetry. In tetragonal (111) PZT, 90° domains prevail; in (pseudo-tetragonal) (100) SBT both 90° and 180° domains are present. The size of 90° domains has been measured for e.g., PZT as slabs of 15 nm width. Domain size is a result of stress minimization in the film during the paraelectric (PE) → ferroelectric (FE) transition. A precise and regular domain pattern for (111) PZT and (100) SBT films has been investigated in detail by TMSFM. Single domains can be addressed mechanically with the tip of an AFM. Such single domain switching corresponds to a data storage density of 200 Gbit/inch². Applications of ferroelectric and high- paraelectric materials for e.g., non-volatile data storage replacing DRAM devices or as sensors in infrared cameras are increasingly becoming popular.