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1.
V. S. Sangawar R. J. Dhokne A. U. Ubale P. S. Chikhalikar S. D. Meshram 《Bulletin of Materials Science》2007,30(2):163-166
The electrical conductivity of naphthalene doped polystyrene (PS) films (≈61·58 μm thick) was studied as a function of dopant
concentration and temperature. The formation of charge transfer (CT) complexes and strong concentration dependence of carrier
mobility point out that the current carriers are transported through doped polymer system via hopping among sites associated
with the dopant molecules. The activation energy, E
a, was calculated from the graph of log σ vs 103/T plot within low and high temperature regions. 相似文献
2.
目前对于介电材料的研究与应用一般集中于电子产品及其相关领域,高介电陶瓷材料应用于油品精制领域还是一个新的尝试。首先简要介绍了介电力学精制工艺装置,并重点讨论了介电陶瓷在其中的应用及基本原理,最后选用几种不同介电常数的介电陶瓷材料在装置中进行了实验,实验证明,高介电陶瓷材料对油品有较好的精制效果,并且对于所选用的几种介电材料而言随着介电常数的增加精制效果也提高。 相似文献
3.
The feasibility of studying ionic motion in glass using thermally stimulated polarization (TSPC)/depolarization current (TSDC)
techniques was investigated with 4Na2O-96SiO2 and 30PbO-70SiO2 (mol %) glasses. The TSPC peaks in these glasses were dependent on glass composition and attributed to bulk polarization.
The high temperature background TSPC is shown to be due to the d.c. conductivity, whereas the TSPC/TSDC peaks in the 4Na2O glass are attributed to shorter range Na+ motion. 相似文献
4.
A concentric cylinder capacitor has been used to measure the orthobaric liquid dielectric constants of multicomponent mixtures of the major components of liquefied natural gas (LNG) to an accuracy of approximately ± 0.05% at temperatures from 110 to 130 K. These mixtures ranged from a ternary mixture containing nitrogen, methane, and normal butane to four to eight component methane rich (74 to 90 mol %) mixtures containing up to 5 mol % of nitrogen, 16 mol % of ethane, 7 mol % of propane, 5 mol % of the butanes, and 0.44 mol % of the pentanes. Some of these mixtures were prepared to simulate commercial LNG compositions. Experimental densities previously reported for these mixtures have been combined with the mixture dielectric constant data to calculate values of the Clausius-Mossotti (CM) function and the excess CM function. Pure component experimental CM functions for LNG components except for propane and isobutane have been combined with the mixture data in the development of a simple calculational technique for the prediction of LNG densities to an uncertainty of approximately ± 0.15% based on a knowledge of the composition and dielectric constant of the liquid mixtures. In fitting the data, pseudo values of the CM function are derived for the slightly polar components, propane and isobutane, while constraining the mixture excess CM function to be zero. 相似文献
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通过4,4’-二(4-烯丙氧基苯甲酸)苯酯与POSS分子的硅氢化反应,合成了POSS交联聚合物。用FTIR、XRD对聚合物结构进行了表征,利用椭偏仪测量了薄膜的折射率和介电常数。通过改变单体与POSS投料摩尔比,可制备出k<2.5的低介电常数薄膜。 相似文献
8.
采用溶胶-凝胶结合二次煅烧的方法制备了高介电常数BaTiO3陶瓷,通过X射线衍射分析得到所制备的体系为四方相和立方相共存结构,从扫描电镜的图像中能观察其晶粒尺寸为1μm。通过TF2000铁电分析仪得到其介电常数在煅烧温度为1310℃,保温时间为4h,室温、测试频率为100Hz、测试电压为100V的条件下最大值为38306。研究了BaTiO3铁电陶瓷的反转电流随温度、频率和电压的影响规律,研究发现随着温度的升高反转电流缓慢降低,而随着电场和频率的增加反转电流迅速升高。从能量的观点也能进一步分析温度和电场对于反转电流的影响。 相似文献
9.
Thermally stimulated currents have been studied in solution grown pure and doped polyvinyl alcohol films polarised at different temperatures. The TSC spectra have been used to calculate relaxation time, activation energy, capture cross section, charge and the attempt-to-escape frequency in films doped with different impurities. The electrical conductivity, charge-retaining capability and other parameters are found to be dependent on the doping. The results are explained in terms of the energy levels created by the dopants and charge transfer through a tunnelling mechanism. 相似文献
10.
C. J. De Oliveira J. A. C. De Paiva P. C. Barbosa J. Mendes Filho J. C. P. De Oliveira A. Sergio Bezerra Sombra N. Aranha L. C. Barbosa O. L. Alves 《Journal of Materials Science》1993,28(16):4305-4310
Niobophosphate glasses (P2O5-PbO-Nb2O5-K2O-XFe2O3), were studied using thermally stimulated depolarization currents and Mössbauer spectroscopy in samples of different iron concentrations, and were subjected to oxidation and reduction processes. The use of both techniques provided new information about the distribution of iron and niobium between tetrahedral and octahedral sites. 相似文献
11.
Single crystal of potassium pentaborate (KB5) has been grown by solution growth technique. FTIR and laser Raman measurements
are carried out to make a qualitative analysis on KB5 crystal. Dielectric behaviour of the KB5 crystal has been studied in
the microwave region using K-band microwave bench equipped with the Gunn Oscillator guided with rectangular wave-guide. To
confirm the suitability of this crystal as electro optic device, its dielectric behaviour with the change of frequency has
also been investigated. Photoconductivity studies were also carried out on this material. It was interesting to observe that
the KB5 crystal exhibited negative photoconductivity. 相似文献
12.
Cellular (foamed) glasses are a prime candidate for certain structural applications, such as support of the silvered glass concentrator mirrors in solar thermal energy systems. An economical nondestructive measurement of strength-limiting defects in these materials would permit development of designs in which the material is subjected to a higher working stress level and maintains the same probability of failure. This would result in weight and cost savings for any application. A method of measuring the capacitance of well-defined regions of a specimen was investigated. Large voids were found to produce significant localized changes in the capacitance of the specimen. The feasibility of locating the large, strength limiting defects in this porous material has been demonstrated for one type of cellular glass. Means of producing an image from this type of data and an implementation scheme for on-line production measurements are discussed. 相似文献
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DC resistivity of extruded ethylene propylene rubber (EPR) samples with various Pb concentration have been measured under
wet conditions as a function of electrical field at selected temperatures in a range from 20 to 100°C. The temperature and
electrical field coefficients of resistivity have been calculated. Thermally stimulated discharge current (TSDC) has also
been measured and a broad positive peak has been observed for three EPR samples. It has been found that the resistivity of
EPR is not sensitive to the Pb concentration within the range of 0 to 5 parts per hundred base resin (phr). The results show
that the resistivity of EPR varies non-linearly with both temperature and electrical field. The temperature coefficient of
resistivity α of EPR has been measured to be ∼0.1 K−1 for all the samples with various Pb concentration. The electrical field coefficient of resistivity β of EPR at room temperature
is small and increases with temperature. Increasing Pb content increases slightly the electrical field coefficient β of resistivity.
Based on a space charge limited conduction model, the trap depth of EPR has been estimated. TSDC measurements indicate that
doping with Pb increases both the density of charge carriers and the number of deep traps simultaneously. The broad TSDC peak
reveals that there must be a distribution rather than just a single value of the trap depth. 相似文献
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Dielectric constant, dielectric loss and conductivity of Bi4(GeO4)3 and Bi4(SiO4)3 single crystals have been measured as a function of frequency and in the temperature range from liquid nitrogen temperature
to 400° C. The values of the static dielectric constant at room temperature are 16·4 and 13·7 for Bi4(GeO4)3 and Bi4(SiO4)3 respectively. The plots of log (σ) against reciprocal temperature at different frequencies of these crystals merge into a straight line beyond 250°C and the
activation energies calculated in this region are found to be 0·95 eV and 1·2 eV for Bi4(GeO4)3 and Bi4(SiO4)3 respectively. 相似文献
16.
Cu
x
Zn1−x
Fe2O4 samples exhibit dispersion of dielectric constant, tanδ and resistivity in the frequency range of 1 kHz to 50 MHz. The dispersion
exhibited is in general accord with Koops’ model. However, the details of the conducting and non-conducting regions must be
taken into account when composition tends to change interrelationship between the elementary capacitor resistor circuits.
On quenching these samples from 800°C the dielectric constantε
1 showed an increase for CuFe2O4 and Cu0·8Zn0·2Fe2O4 samples. The dielectric constant of the remaining samples showed no influence on quenching. The compositional variation showed
that the dielectric constant has higher value for the ferrite Cu0·4Zn0·6Fe2O4
The results are explained on the basis of cation transfer. 相似文献
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Dielectric constant (ɛ), dielectric loss (tan δ) and conductivity (σ) for K2Zn2(SO4)3 and (NH4)2 Mg2(SO4)3 have been measured over the frequency range 100 Hz — 100 kHz and in temperature range 30°C — 400°C. The values of static
dielectric constant at room temperature are 7.67 and 4.80 for K2Zn2(SO4)3 and (NH4)2 Mg2(SO4)3 respectively. The plots of log σ against reciprocal temperature at different frequencies of these samples merge into a straight
line beyond 250°C and the activation energies calculated in this region are found to be 0.67 eV and 1.98 eV for K2Zn2(SO4)3 and (NH4)2 Mg2(SO4)3 respectively. 相似文献
20.
采用紫外光辐照超低介电常数多孔SiCOH薄膜,研究不同照射时间对薄膜结构和性能的影响。采用动态纳米压入技术测量薄膜的力学性能,发现随照射时间增加,薄膜的模量(Er)和硬度(H)不断提高。当辐照时间增至6h时,薄膜力学强度分别达到Er约7.4GPa,H约1.0GPa。傅里叶变换红外光谱(FT-IR)、X射线光电子能谱(XPS)分析表明紫外辐照处理能够使薄膜样品中发生键的断裂与重新结合,从而改变了薄膜骨架的交联密度和刚性,进而提高力学性能。但介电性能并未受到明显影响,紫外辐照6h后,k值仅从2.0增至2.2。 相似文献