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超声辐照乳液聚合研究进展 总被引:11,自引:0,他引:11
综述了超声辐照乳液聚合的特点,聚合成核机理,影响因素及反应动力学特点,简要介绍了超声辐照无皂乳液聚合,超声辐照微乳液聚合,超声辐照乳液共聚和纳米粒子存在下的超声辐照乳液聚合。 相似文献
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N. L. Singh Anita Sharma V. Shrinet A. K. Rakshit D. K. Avasthi 《Bulletin of Materials Science》2004,27(3):263-267
The effect of high-energy (50 MeV) Li3+ ion beam irradiation on polypropylene (PP) film has been studied in the fluence range 2.4 × 1012−l.5 × 1014 ions/cm2. The a.c. electrical properties of PP films were measured in the frequency range from 0.05– 100 kHz, and at temperature range
between 30 and 140°C. This study indicates two peaks at 60°C and 120°C with comparatively high magnitudes. There is an exponential
increase in conductivity with log of frequency and the effect is significant at higher fluences. The loss factor (tan δ) vs
frequency plot suggests that PP film based capacitors may be useful below 10 kHz. The capacitance is constant over a wide
temperature range up to 130°C. FTIR spectra of the PP films before and after irradiation indicate that intensity of C-H stretching
vibration at 2900 cm−1 is modified. The presence of many new peaks with the increase of fluence suggests the formation of alkanes and alkynes which
might be responsible for the observed changes in the dielectric and electrical properties of PP films. 相似文献
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The electrical and dielectric behaviour of a gadolinium-based zirconium fluoride glass have been studied over a wide temperature (23–275 °C) and frequency (100 Hz–1 MHz) range. The conductivity at 200 °C was of the order of 10–6 (ohm-cm)–1 and the activation energy was 0.75 eV. The dielectric constant measured at 1 kHz was 14 and was independent of frequency at low temperatures. The observed dielectric dispersion has been attributed to the conduction mechanism. 相似文献
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《Materials science & engineering. C, Materials for biological applications》2006,26(2-3):571-573
In this work, we have studied the frequency effect on the metal/polysilicon/oxide/silicon (MSPOS) structure. We present the capacitance–voltage (C–V) characteristics at four frequencies (10 kHz, 100 kHz, 400 kHz and 1 MHz). The results show that the C–V curves have dispersion when the frequency decreases. The increase of the frequencies translates the CT(V) curve towards negative voltages and causes the decrease of the minimum value of capacitance. The variation of the capacitance for low frequencies is less important compared to that of the high frequencies. 相似文献
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D. Schmoranzer M. La Mantia G. Sheshin I. Gritsenko A. Zadorozhko M. Rotter L. Skrbek 《Journal of Low Temperature Physics》2011,163(5-6):317-344
We report on experimental investigations of acoustic emission by quartz tuning forks resonating at frequencies 32 kHz, 38 kHz, 77 kHz and 100 kHz immersed in cold gaseous 4He and its normal and superfluid liquid phases. Frequency dependence of the observed low-drive-linewidth at 350 mK together with the temperature and pressure dependences (1.3 K < T < 4.2 K, 0 < p < 25 bar) of the observed damping of the high frequency (77 and 100 kHz) resonators measured in normal liquid 4He and its superfluid phase provide strong and direct evidence of the importance of sound emission by these tuning forks. Three analytical models of acoustic emission by vibrating tuning forks are developed and compared with the experimental results. We also discuss the importance of sound emission for experiments with the commonly used 32 kHz tuning forks as well as other oscillating structures??spheres, wires, grids and various micromachined sensors. We compare the relative importance of dissipative losses due to laminar viscous/ballistic drag and acoustic emission in liquid and superfluid 4He. 相似文献
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Our ultimate objective is to design a combined frequency standard for optical as well as radio frequencies. A mode-locked laser provides frequency components that can be used as a ruler to measure any unknown optical source through direct beating. The frequency spacing of a pair of teeth of this comb is in itself a radio frequency reference. Fast control and correction for both the average frequency and the repetition rate of a mode-locked Ti : sapphire laser are achieved by locking the laser to a reference cavity of ultra-low expansion quartz with equal mode spacing. We measure an optical frequency with a mean square deviation of 700 Hz, instability limited by the radio-frequency sources used to count the repetition rate. As a reference standard to achieve absolute accuracy, we use the Λ transition 5S1/2 (F = 1) → 5D5/2 (F = 3) → 5S1/2 (F = 2) of rubidium. The theory for this coherent interaction shows that, with one mode resonant with the two-photon 5S1/2 (F = 1) → 5D5/2 (F = 3) transition, the fluorescence goes through a resonance for a change in repetition rate of less than 10 kHz. These results suggest that, by locking to the peak of that resonant feature, optical stability and absolute accuracy better than 1 kHz can easily be achieved. 相似文献
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Andrzej Skumiel 《International Journal of Thermophysics》2010,31(3):546-555
This article describes the magnetic and hyperthermic investigation of a concentrated magnetic fluid on the basis of a transformer
mineral oil with magnetite particles. The structure of a ferrofluid and general magnetic parameters of a medium were determined
from vibrating sample magnetometer measurements. The hyperthermic experiments were carried out at a frequency f = 1500 kHz for various magnetic field amplitudes. The analysis of calorimetric results allowed an estimate of the contribution
of relaxational and hysteresis loss mechanisms in total energy losses in the hyperthermic effect under the influence of an
alternating magnetic field. Additional calorimetric measurements were also performed (at H
C = 1500 A · m−1) versus frequency in the range from 50 kHz to 2 MHz which indicated that for f
o = 653 kHz the heating process is the most effective. 相似文献
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Dongxiang Zhou Liangbin Hao Shuping Gong Qiuyun Fu Fei Xue Gang Jian 《Journal of Materials Science: Materials in Electronics》2012,23(12):2098-2103
This paper presents the structural, ferroelectric, ferromagnetic, resonance and magnetoelectric (ME) properties of multilayered ME composites fabricated using tape casting method. The compositions corresponding to CoFe2O4 (CFO) with particle size of ~150?nm and BaTiO3 (BTO) with particle size of ~100?nm were chosen as ferromagnetic and ferroelectric phases, respectively. Delamination was found at the interface between CFO and BTO layers, which was related to the residual stress due to the difference in thermal expansion coefficient between the two layers. The largest direct magnetoelectric and converse magnetoelectric coefficients of the multilayered ME composite were, respectively, 36?μV/cm?Oe at a bias magnetic field of 2,800?Oe and 1.16?×?10?3?G/V at a frequency of 30?kHz. In addition, the corresponding interfacial coupling coefficient was calculated to be 3.2?×?10?5. For the multilayered ME composite, a resonance frequency of 4.96?MHz and a bandwidth of 40?kHz were obtained using capacitance-frequency spectrum method. 相似文献
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A. Casey R. Schanen C. P. Lusher B. P. Cowan J. Saunders 《Journal of Low Temperature Physics》2004,134(1-2):649-654
Pulsed NMR measurements have been performed on 3He films adsorbed on an exfoliated graphite sample of area 2 m2. The spectrometer is constructed using a DC SQUID with additional positive feedback, operating in flux locked loop mode with a bandwidth of 3.4 MHz. The input circuit, is a superconducting flux transformer, and so is intrinsically broadband. This spectrometer can therefore operate from typical frequencies used in conventional NMR down to otherwise inaccessible low kHz frequencies. With this system studies at the “ferromagnetic anomaly” have been undertaken at frequencies from 2 kHz to 100 kHz (0.06 to 3.09 mT), with the static magnetic field oriented normal to the nominal direction of the graphite platelets. At 50 and 100 kHz, measurements of the susceptibility are fit by high temperature series expansions between 100 mK and 5 mK, to determine an exchange constant J=1.86 mK. Below 1.3 mK the dipolar frequency shift increases linearly with temperature down to 0.3 mK, extrapolating to 10 kHz, close to our calculated value of 9.6 kHz, for fully polarised spins with an assumed lattice spacing of 0.392 nm for the second layer solid. Below 1.5 mK, a significant field dependence to the magnetisation and dipolar frequency shift appears at fields comparable to the characteristic dipolar field, below which the equilibrium alignment of the magnetization is field dependent. Assuming the frequency shift, in applied fields of 1.54 and 3.09 mT, to be proportional to the sample polarisation we find that it is not possible to fit the observed temperature dependence by 2D ferromagnetic spin-wave theory, with a consistent set of parameters for both fields. The theory is applied in the range 0.15>T/J>0.5, takes into account the Zeeman gap and finite system size, and includes the k=0 spin wave term. At present, the data provide no unambiguous evidence for a finite ordering temperature induced by the anisotropic dipolar interaction. 相似文献
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A high-temperature superconducting magnetometer with double modulation at frequencies of 50 kHz and 5 MHz, which uses the nonlinear properties of a ceramic superconductor, is described. The magnetometer has a noise level of 2.3 nA/(m·Hz1/2) in the 0–14.5 kHz frequency band. 相似文献