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排序方式: 共有298条查询结果,搜索用时 15 毫秒
1.
2.
Effect of Zwitterionic Surfactants on Interparticle Forces, Rheology, and Particle Packing of Silicon Nitride Slurries 总被引:1,自引:0,他引:1
William A. Ducker Erik P. Luther David R. Clarke Fred F. Lange 《Journal of the American Ceramic Society》1997,80(3):575-583
Phosphocholine (PC) zwitterionic surfactants, with different hydrocarbon chain lengths (C6 C6 PC to C9 C9 PC), were absorbed on the surface of silicon nitride near the isoelectric point (pH 6). Adsorption of the surfactants changed the lateral and normal surface forces, the rheology, and the consolidation behavior of the particles. The normal force between two silicon nitride surfaces as a function of separation and the lateral (friction) forces were measured using an atomic force microscope (AFM). These measurements indicated that surfactant adsorption reduced the magnitude of the long-range attractive van der Waals force and produced a repulsive short-range force. Although the adsorbed layers provided a barrier to particle contact, they could be ejected with a critical force that increased with the hydrocarbon chain length. The effect of an adsorbed layer on the viscosity and consolidation of slurries was also measured. The viscosity of all slurries decreased with increasing shear rate, indicative of attractive particle networks. The highest viscosity was observed for slurries formulated at the isoelectric point without added surfactant. Much lower viscosities were observed when the surfactant concentration was greater than the critical micelle concentration (cmc). A relative density of 0.46 was obtained via pressure filtration at 4 MPa without a surfactant, and between 0.46 to 0.59 (C6 C6 PC to C9 C9 PC, respectively) for surfactant concentrations greater than the cmc. Comparing force measurements with rheology and packing density provides a basis for discussing the role of interparticle forces in ceramic powder processing via colloidal routes. 相似文献
3.
Erik E Luther Fred F. Lange Dale S. Pearson 《Journal of the American Ceramic Society》1995,78(8):2009-2014
Two different methods are used to coat silicon nitride particles with an alumina precursor to make Si3 N4 behave like Al2 O3 in aqueous slurries. The first method involves the precipitation of an aluminum hydroxycarbonate from dissolved Al(NO3 )3 during the decomposition of urea. In the second method, dry silicon nitride powder is reacted with aluminum tri- sec -butoxide in hexane at room temperature. Both methods produce a coated powder in which the electrophoretic and rheological properties of aqueous slurries mimic those of alumina. When salt is added to slurries consisting of coated Si3 N4 powder, all rheological evidence suggests the presence of a short-range repulsive potential that produces a weakly attractive particle network similar to that previously reported for Al2 O3 powder. Although electrophoretic and rheological data showed that the coated powder behaved like Al2 O3 , consolidation data indicated that slurries of coated powder with added salt did not pack to high density. In addition, these bodies were not plastic as found for bodies consolidated from dispersed and salt-added Al2 O3 slurries. 相似文献
4.
We present a method depending on matrix continued fractions and Sturm's comparison theorem to obtain verified inclusions for eigenvalues of the underlying boundary value problem of the first-order phase locked loop equation $pu'' + (\lambda + \tilde g)u = 0$ ,p = 1/SNR with general phase detector characteristic $\tilde g(\phi )$ . 相似文献
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During the years 1985 up to 1995 53 patients between 18 and 80 years of age (mean age 54.7 years) with histologically and clinically proven Zoon's balanitis were treated by circumcision. The majority of patients had symptoms for more than 12 months. In five cases they had lasted for 8, 10, 16, 17 and 47 (!) years. 30 patients were investigated by means of physical examination and questionnaire in this retrospective study. Lesions involved glans in all patients, while in 17 of 30 patients both glans and prepuce were involved. None of the patients showed lesions of the prepuce only. In most cases Zoon's balanitis was successfully treated by circumcision in a period of two to four weeks. In four cases, psoriatic lesions, and in one case lichen ruber was diagnosed. In the remaining patient, whose circumcision was inadequate, a small area of balanitis persisted in the sulcus coronarius still covered by the foreskin. The curative effect of adequate circumcision in 100% of patients suggests that Zoon's balanitis is a relatively non-specific reactive balanitis caused by a disturbed "preputial-ecology". It is remarkable that other distinct inflammatory diseases of glans and prepuce can show features which are identical to those Zoon's balanitis. 相似文献
7.
Luther B.M. Yong Wang Larotonda M.A. Alessi D. Berrill M. Rocca J.J. Dunn J. Keenan R. Shlyaptsev V.N. 《Quantum Electronics, IEEE Journal of》2006,42(1):4-13
We discuss the demonstration of gain-saturated high repetition rate table-top soft X-ray lasers producing microwatt average powers at wavelengths ranging from 13.9 to 33 nm. The results were obtained heating a precreated plasma with a picosecond optical laser pulse impinging at grazing incidence onto a precreated plasma. This pumping geometry increases the energy deposition efficiency of the pump beam into the gain region, making it possible to saturate soft X-ray lasers in this wavelength range with a short pulse pump energy of only 1 J at 800-nm wavelength. Results corresponding to 5-Hz repetition rate operation of gain-saturated 14.7-nm Ni-like Pd and 32.6-nm line Ne-like Ti lasers pumped by a table-top Ti:sapphire laser are reported. We also discuss results obtained using a 1 /spl omega/1054-nm prepulse and 2 /spl omega/527-nm short pulse from a Nd:glass pump laser. This work demonstrates the feasibility of producing compact high average power soft X-ray lasers for applications. 相似文献
8.
Xiaoyu Li Thomas Scott Shao Yang Chris Cromer Marla Dowell 《Journal of research of the National Institute of Standards and Technology》2004,109(4):429-434
We briefly explain the fundamentals of detector nonlinearity applicable to both electrical and optical nonlinearity measurements. We specifically discuss the attenuation method for optical nonlinearity measurement that the NIST system is based upon, and we review the possible sources of nonlinearity inherent to thermal detectors used with high-power lasers. We also describe, in detail, the NIST nonlinearity measurement system, in which detector responsivity can be measured at wavelengths of 1.06 µm and 10.6 µm, over a power range from 1 W to 1000 W. We present the data processing method used and show measurement results depicting both positive and negative nonlinear behavior. The expanded uncertainty of a typical NIST high-power laser detector calibration including nonlinearity characterization is about 1.3 %. 相似文献
9.
Low Loss,High NA Chalcogenide Glass Fibers for Broadband Mid‐Infrared Supercontinuum Generation 下载免费PDF全文
Bin Zhang Wei Guo Yi Yu Chengcheng Zhai Sisheng Qi Anping Yang Lei Li Zhiyong Yang Rongping Wang Dingyuan Tang Guangming Tao Barry Luther‐Davies 《Journal of the American Ceramic Society》2015,98(5):1389-1392
High‐purity Ge–As–Se and Ge–As–S chalcogenide glasses were prepared by modified physical and chemical purification techniques. Using the purified glasses, step‐index fibers with a small core (~5.5 μm) and large numerical aperture (~1.3) were fabricated. When a 13.5‐cm‐long fiber was pumped with 320 fs pulses at a repetition rate of 10.5 MHz at 4.1 μm, supercontinuum spanning from ~1.8 to ~9.8 μm with a dynamic range of ±10 dB and an average power of ~3 mW was generated. 相似文献
10.
High Brightness 2.2–12 μm Mid‐Infrared Supercontinuum Generation in a Nontoxic Chalcogenide Step‐Index Fiber 下载免费PDF全文
Bin Zhang Yi Yu Chengcheng Zhai Sisheng Qi Yuwei Wang Anping Yang Xin Gai Rongping Wang Zhiyong Yang Barry Luther‐Davies 《Journal of the American Ceramic Society》2016,99(8):2565-2568
An environment friendly nonlinear chalcogenide glass fiber with a Ge‐Sb‐Se core and a Ge‐Se cladding is fabricated for bright broadband mid‐infrared (MIR) supercontinuum (SC) generation. The fabricated Ge‐Sb‐Se/Ge‐Se fiber with a core diameter of 6 μm shows zero group velocity dispersion at ~4.2 μm and ~7.3 μm. By pumping the fiber with a length of 11 cm at 4.485 μm with 330 fs pulses, we achieve a SC covering the 2.2–12 μm spectral range and with an output average power of ~17 mW. This bright broadband SC source is promising for high‐resolution MIR spectroscopy. 相似文献