Dielectric and Piezoelectric Properties of PZT Substituted with Samarium

The paper reports influence of samarium substitution on the properties of a PZT composition near MPB. Samarium (Sm) was varied from 0 to 0.02/FU. The samples were prepared by standard double sintering ceramic method. XRD analysis showed all samples to be of single phase. Dielectric properties were studied as a function of temperature and frequency. All the samples show well defined ferroelectric behaviour. Remanence ratio ( P r / P s ) was found to increase with increasing Sm concentration. Piezoelectric change coefficient d 33 decreases with increase in Sm.     

氢化丁腈橡胶／超细全硫化粉末丁腈橡胶共混物的结构与性能研究

采用熔融共混工艺制备了氢化丁腈橡胶（HNBR）／超细全硫化粉末丁腈橡胶（UFPNBR）共混物,研究了共混物相态结构、动态力学性能、力学性能及老化性能,并与HNBR／NBR共混物作了对比。透射电镜观察表明：在HNBR／UFPNBR体系中,HNBR容易形成连续相,UFPNBR为分散相;在HNBR／NBR体系中容易形成双连续相结构。DMA动态力学性能分析表明：2种共混物都只有一个tanδ峰,且相容性较好。HNBR／UFPNBR共混物在玻璃化转变区的tanδ峰值逐渐降低,而HNBR／NBR体系的tanδ峰值先减小后增大。加入适量的UFPNBR能降低HNBR／UFPNBR共混物的压缩永久变形;与常规共混胶相比,HNBR／UFPNBR具有低脆性温度和良好的耐老化性能,但力学性能略低。     

Homogeneous Styrene Butadiene/Acrylonitrile Butadiene Rubber Blends

The graft copolymerization of acrylonitrile (AN) onto butadiene rubber (BR) was carried out in toluene at 80°C, using dibenzoyl-peroxide (BPO) as initiator. The synthesized poly acrylonitrile-grafted-butadiene rubber (AN-g-BR) was characterized by N% elemental analysis and Fourier-transform infrared (FT-IR) spectroscopy. Styrene butadiene rubber/acrylonitrile butadiene rubber (SBR/NBR) blends were prepared with different blend ratios in presence and absence of AN-g-BR, where the homogeneity of such blends were examined with intrinsic viscosity (η) measurements, differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The scanning electron micrographs illustrate disappearance of the macro-scale phase separation of SBR/NBR rubber blend as a result of the incorporation of AN-g-BR into that blend. Viscosity measurements confirm homogeneity of that blend. Differential Scanning Calorimetry traces exhibit shifts in glass transition temperatures (T _g's) of SBR and NBR in their blend, indicating some degree of homogeneity. Physico-mechanical properties of the rubber blend vulcanizates with different blend ratios, in presence and absence of AN-g-BR, were investigated before and after accelerated thermal aging. The SBR/NBR (25/75) homogeneous blend possessed the best physico-mechanical properties after thermal aging, together with the best swelling behavior in motor oil. The physico-mechanical properties of SBR/NBR (25/75) filled blend with different types of inorganic fillers during thermal aging were studied.     

Natural Rubber/Acrylonitrile Butadiene Rubber Blend Membranes: Vapor Permeation Properties

Natural rubber (NR)/Acrylonitrile butadiene rubber (NBR) blend membranes, prepared by using dicumyl peroxide as the crosslinking agent, were tested for their vapor permeation characteristics. The permeation studies were conducted using three chlorinated hydrocarbons, viz. dichloro methane, chloroform, and carbon tetrachloride. The effects of the blend ratio, compatibilizer, penetrant size, and temperature on the vapor permeability of the membranes were investigated. The permeability of the blends was found to decrease with an increase in the NBR content, which has been attributed to the inherent solvent resistant nature of NBR. The permeation behavior of compatibilized blends was compared with those of the uncompatibilized blends. The separation efficiencies of the membranes were also tested using chloroform/acetone mixtures to complement the observations from the vapor permeation experiments.     

顺丁橡胶/有机蒙脱土纳米复合材料的介电性能研究

采用机械混炼法制备了顺丁橡胶/有机蒙脱土(BR/OMMT)纳米复合材料;采用精密电桥对纳米复合材料的介电性能进行了研究。结果表明,纳米复合材料的相对介电系数(ε)随温度的升高逐渐增加,而介电损耗(tanδ)随温度的升高分别出现β峰和α峰。当晶区完全融化后,ε及tanδ随温度的升高而急剧上升;在频率一定时,纳米复合材料的介电损耗随OMMT含量的增加逐渐增加,并且峰值向高温方向移动;在OMMT含量一定时,在相同温度下,复合材料的ε和tanδ均随着频率的升高而下降;随着频率的升高,介电损耗峰向高温方向移动。     

顺丁、丁腈橡胶离聚体改性聚氯乙烯研究

用马来酸酐接枝橡胶和金属离子交联形成离聚体的方法可提高顺丁橡胶(BR)、丁腈橡胶(NBR)、PVC三元共混物的相容性，以交联剂、引发剂、接枝单体为三要素，采用正交试验方法，通过综合评分法，优选了三元离聚体配方，在此基础上用部分硬脂酸锌代替无机氧化锌作离子交联剂，使合金材料获得了满意的性能，与未经改性PVC/BR/NBR三元共混物相比，硬脂酸锌离子交联马来酸酐接枝的三元合金的拉伸强度提高了101％，断裂伸长率增加113％，红外光谱证明了马来酸酐接枝顺丁胶与锌离子的离子交联的存在，且硬脂酸锌的效果优于氧化锌。     

Dielectric Properties of Styrene—Butadiene Rubber/Silicon Dioxide Mixtures

The dielectric constant ?′ and dielectric loss ?″ have been investigated for SBR samples vulcanized with TMTD and loaded with silica in increasing quantities in the frequency range from 60 Hz to 10⁸ Hz at room temperature. Also, the physico-mechanical properties of these samples have been investigated. The results of ?′ and ?″ are analysed using the Cole—Cole method. Two absorption regions are found: a low frequency absorption region with a maximum at about 10 kHz which is attributed to Maxwell—Wagner effect and a high frequency absorption region with a maximum at 10⁷ Hz which is due to the orientation of polar groups. A third absorption region appeared at frequencies below 100 Hz and may be due to absorption of moisture arising from the presence of silica in the sample.     

The Behaviour of Styrene Butadiene Rubber/Acrylonitrile Butadiene Rubber Blends in the Presence of Chlorinated Hydrocarbons

The behaviour of styrene butadiene rubber/acrylonitrile butadiene rubber (SBR/NBR) blends in the environment of chlorinated hydrocarbons, such as carbon tetrachloride, chloroform and dichloromethane, in the temperature range 32–52°C has been investigated. Sulphur, dicumyl peroxide and a mixed system consisting of sulphur and peroxide were used as the vulcanising systems for the matrix. The effects of vulcanising agents, blend composition, solvents and temperature on the sorption characteristics were studied. The sulphur-vulcanised systems exhibited the highest solvent uptake and those with dicumyl peroxide as the vulcanising agent the lowest. This difference has been explained on the basis of the nature of cross links established between the polymer chains during vulcanisation. The solvent uptake increased with an increase in SBR content in the blends when carbon tetrachloride was used as the penetrant, whilst it decreased with SBR content when chloroform and dichloromethane were used as the probes. This behaviour has been explained on the basis of the polarity difference of the solvents. For a given blend system, the solvent uptake was maximum when dichloromethane was used as the solvent and minimum when carbon tetrachloride was used. This has been accounted for in terms of the difference in the size of the penetrants. The intrinsic diffusion coefficient, permeation coefficient, cross link density and interaction parameter were estimated from the sorption data. Thermodynamic parameters such as enthalpy and free energy changes were also calculated. These values indicate that the sorption process in the present systems is exothermic and is more spontaneous in sulphur-vulcanised systems. The experimental results, when compared with different theoretical diffusion models, have been found to be closer to Robeson’s and Maxwell’s models.     

Natural Weathering Test of Styrene Butadiene Rubber and Recycled Acrylonitrile Butadiene Rubber (SBR/NBRr) Blends

The effect of recycled acrylonitrile butadiene rubber (NBRr) content of SBR/NBRr blends on natural weathering was studied. Three different size of NBRr (S1; 117–334 µm, S2; 0.85–15.0 mm and S3; direct sheeted form) were used and the blends were exposed to natural weathering for 3 and 6 months. The results indicated that the SBR/NBRr blends with smallest size of NBRr (S1) show a better retention of tensile properties, which are able to withstand better weathering than coarser size (S2 and S3) of SBR/NBRr blends. The presence of hydroxyl, carbonyl and nitro group after exposure to natural weathering was detected in FTIR analysis, which related to the UV oxidation process of rubber blends. The scanning electron microscopy proved that the SBR/NBRr blends with smallest size of NBRr (S1) with higher content of NBRr, shows a better resistant to natural weathering.     

(Sm1-xLa_x)_2(Zr1-yCe_y)_2O_7陶瓷材料介电性能与热导率

以Sm_2O_3, La_2O_3,ZrO_2和CeO_2等氧化物为原料,采用固相反应法制备双位掺杂(Sm_1-xLa_x)_2(Zr_1-yCe_y)_2O_7(x=0.5;y=0.1,0.2,0.3,0.4)陶瓷材料,研究了其晶体结构、显微组织、介电性能和热导率。结果表明,随着离子掺杂变化,该系列氧化物的结构发生了从焦绿石向萤石的转变。其显微组织比较致密,晶界清洁,但晶粒大小分布不均匀;且随掺杂离子元素含量的增加制备陶瓷材料的介电常数增大,热导率下降,热导率与介电常数成反比。     

Comparison of Properties of Polypropylene (PP)/Virgin Acrylonitrile Butadiene Rubber (NBRv) and Polypropylene (PP)/Recycled Acrylonitrile Butadiene Rubber (NBRr) Blends

The comparison properties of polypropylene (PP)/recycled acrylonitrile butadiene rubber (NBRr) blends and polypropylene/virgin acrylonitrile butadiene rubber (NBRv) blends were investigated. The tensile properties such as tensile strength, tensile modulus and elongation at break of PP/NBRv blends are higher than PP/NBRr blends. However, PP/NBRv blends exhibit lower stabilization torque and higher swelling percentage than PP/NBRr blends. Based on SEM, a finer morphology was observed in PP/NBRv blends in comparison with the PP/NBRr blends. The thermal stability of PP/NBRr is better than that of PP/NBRv blends.     

聚酰亚胺/有机蒙脱土/丁苯橡胶复合材料性能的研究

将聚酰亚胺(PI)与有机蒙脱土(OMMT)混合,制备了PI/OMMT粉状材料;将粉状材料与丁苯胶乳(SBR)混合,制备了颗粒状PI/OMMT/SBR复合材料.SEM照片显示,有机蒙脱土可改善聚酰亚胺与丁苯橡胶的相容性.X射线衍射(XRD)结果表明,聚酰亚胺分子链与丁苯橡胶分子链一起插入有机蒙脱土层间,使层间距变大;有机蒙脱土作为交联点存在.动态力学性能测试结果表明,在频率扫描下,加入PI/OMMT后丁苯橡胶的G′最高,但tanδ较低.     

CNT-MF/硅橡胶泡沫复合材料的制备及介电性能

以碳纳米管(CNT)作为核,密胺树脂(MF)作为壳,苯乙烯马来酸酐共聚物(SMA)为乳化剂,原位聚合制备微胶囊化碳纳米管(CNT-MF),并将包覆后的碳纳米管作为填料添加到硅橡胶泡沫中,制备了CNT-MF/硅橡胶泡沫复合材料。探讨了核/壳质量比对微胶囊化碳纳米管的包覆效果的影响,同时研究了微胶囊化碳纳米管用量对硅橡胶泡沫泡孔结构和介电性能的影响。结果表明,微胶囊化碳纳米管的加入有利于提高复合材料的泡孔结构,大泡孔的存在和泡孔面积有利于材料介电性能的提高。当核/壳质量比为1∶10的微胶囊化碳纳米管添加量为15 phr时,复合材料介电性能表现最佳,此时复合材料在1 kHz的介电常数为26.34,介电损耗仅为0.013 6。     

Reduced dielectric loss and high piezoelectric constant in Ce and Mn co-doped BiScO3-PbCexTi1-xO3-Bi(Zn0.5Ti0.5)O3 ceramics

MnO₂-doped 0.99(0.36BiScO₃-0.64PbTi_1-xCe_xO₃)-0.01Bi(Zn_0.5Ti_0.5)O₃ (BS-PTC-BZT-MnO₂) ceramics are fabricated by the solid-state method. Here, it's firstly reported that Ce element can reduce dielectric loss (tan δ) and suppress the decrease of piezoelectric constant (d₃₃) simultaneously. Effects of Ce contents on the structure and electrical properties of BS-PTC-BZT-MnO₂ ceramics are studied. The ceramics (x?=?0.02) with MPB (rhombohedral-tetragonal) possess low dielectric loss (tan δ?=?1.36%, 1?kHz) and high piezoelectric constant (d₃₃ =?360 pC/N) simultaneously, which is superior to most reported BS-PT. Besides, excellent comprehensive properties including high Curie temperature (T_C =?422?°C), large dielectric constant (?_r =?1324), and high remnant polarization (P_r =?35.1?µC/cm²) are obtained. Asymmetric S-E and P-E hysteresis loops indicate that defects and oxygen vacancies are induced by multi-valence elements (Ce and Mn), which is the origin for reducing tan δ. In addition, good thermal stability of piezoelectric and dielectric properties is observed. These results indicate that Ce and Mn co-doped BS-PTC-BZT-MnO₂ ceramics can be well applied as power electronic devices under high temperature.     

白炭黑/丁苯吡橡胶/顺丁橡胶复合材料的性能研究

对比研究白炭黑填充溶聚丁苯橡胶/顺丁橡胶(BR)、乳聚丁苯橡胶/BR和丁苯吡橡胶(VPSBR)/BR复合材料的性能。结果表明:白炭黑在VPSBR/BR并用胶中的分散较好,相应胶料定伸应力较高,0℃下的tanδ较大,耐磨性能较好;提高VPSBR/BR并用胶中BR用量可降低胶料60℃下的tanδ,且耐磨性能变化不大。     

Dielectric constants of bulk ferroelectric PZT measured by terahertz time-domain spectroscopy

The complex permittivity of bulk ceramic ferroelectric of nominal composition PbZr_0.4Ti_0.6O₃ was measured in the range 0.2–2?THz using transmission time-domain spectroscopy. The results indicate strong absorption and dispersion in this frequency range as often seen in highly disordered and polar materials. The results are compared to equivalent thin film data in the literature, and significant differences in the real and imaginary permittivity suggest that substrate clamping and degree of polarisation of the ferroelectric thin film materials affect dielectric properties even at these high frequencies.     

Dielectric relaxations and ferroelectric behaviour of even-odd polyamide PA 6,9

Thermo Stimulated Current (TSC) combined with Dynamic Dielectric Spectroscopy (DDS) have been applied to the investigation of dielectric relaxation modes of an even-odd Polyamide PA 6,9. The correlation between results obtained by both methods allows us to describe precisely the molecular mobility. At high temperature, the various dielectric relaxation phenomena are separated by applying the dielectric modulus formalism. The comparison between the activation enthalpy values obtained by DDS and TSC leads to the assignment of the so-called α mode to cooperative movements of polymeric sequences. Molecular mobility of PA 6,9 is compared with the one of PA 11. The piezoelectric activity of PA 6,9 is shown and analyzed.     

Mn掺杂对铌钽酸盐无铅压电陶瓷性能的影响

采用传统固相反应法制备了Mn掺杂的(K,Na,Li)(Nb,Ta)O3无铅压电陶瓷,研究其介电和压电性能.实验结果表明,MnCO3的加入使样品的烧结温度降低,提高了陶瓷的致密性和压电性能.当MnCO3的添加质量分数为0.2 %的时候,样品的性能达到最佳.     

Dielectric and structural characterization and effective piezoelectric coefficient of KDP/p-Benzoquinone ceramic composites

A study of the interaction between an inorganic phase, KH₂PO₄ (KDP) and an organic phase C₆H₄O₂ (BZQ) in composites KDP/BZQ is presented here. Studies by X-ray powder diffraction and Raman spectroscopy confirm the interaction by a variation in the volume of the unit cell and new bands identified corresponding to the formation of new hydrogen bonds between KDP and BZQ in the Raman spectra. Relaxation process and conductivity were studied using an impedance analyzer in a wide frequency range (10²–10⁶?Hz) between room temperature and 90?°C allowing seeing the dielectric character of the composites and the proton conductivity behavior. Also the effective piezoelectric coefficient was determined by piezo response microscopy; it was observed a decrement of the KDP coefficient on increasing the concentration of BZQ, probably due to the interaction between them.     

Effects of Microstructure on the Dielectric and Piezoelectric Properties of Lead Metaniobate

In an attempt to obtain dense PbNb₂O₆ ceramics, sintering experiments were conducted using starting powders with various particle sizes and different modifications (rhombohedral and orthorhombic structures). During sintering of rhombohedral powders, the phase transformation to the tetragonal phase promoted grain growth, resulting in poor densification. Sintering of orthorhombic powders, however, yielded dense ceramics through suppression of the phase transformation. Based on these results, ceramics with various densities and different microstructures were prepared, and their dielectric and piezoelectric properties were evaluated. The dielectric constant and Curie temperature were dependent on density, grain size, and crack density. Cracks and intragrain pores severely deteriorated the piezoelectric properties. Dense ceramics with the maximum coupling factors and piezoelectric strain constants were obtained by prolonged heating of a fine powder with orthorhombic structure.