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941.
942.
943.
Non‐intrusive characterization of particle size changes in fluidized beds using recurrence plots
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Chiya Savari Rahmat Sotudeh‐Gharebagh Reza Zarghami Navid Mostoufi 《American Institute of Chemical Engineers》2016,62(10):3547-3561
An on‐line method is developed for monitoring of mean particle size in fluidized beds using pressure fluctuations (PFs) and acoustic emissions (AE) signal by recurrence plot (RP) and recurrence quantification analysis (RQA). PFs and AE signals of a lab‐scale fluidized bed were measured simultaneously at various superficial gas velocities and mean particle sizes. Although the AE signals are often very complicated due to many different acoustic sources in the bed, applying RP analyses showed that small changes in mean particle size can be detected by visual comparison of AE‐RP structures, while this cannot be distinguished by graphical RP analysis of PFs. Moreover, the hydrodynamics of the bed was inspected through RQA analysis of both signals. For this purpose, recurrence rate, determinism, laminarity, average length of diagonal and vertical lines were extracted from RPs showing the effect of an increase in the mean particle size. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3547–3561, 2016 相似文献
944.
Scaling Effects in Perovskite Ferroelectrics: Fundamental Limits and Process‐Structure‐Property Relations
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![点击此处可从《Journal of the American Ceramic Society》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Jon F. Ihlefeld David T. Harris Ryan Keech Jacob L. Jones Jon‐Paul Maria Susan Trolier‐McKinstry 《Journal of the American Ceramic Society》2016,99(8):2537-2557
Ferroelectric materials are well‐suited for a variety of applications because they can offer a combination of high performance and scaled integration. Examples of note include piezoelectrics to transform between electrical and mechanical energies, capacitors used to store charge, electro‐optic devices, and nonvolatile memory storage. Accordingly, they are widely used as sensors, actuators, energy storage, and memory components, ultrasonic devices, and in consumer electronics products. Because these functional properties arise from a noncentrosymmetric crystal structure with spontaneous strain and a permanent electric dipole, the properties depend upon physical and electrical boundary conditions, and consequently, physical dimension. The change in properties with decreasing physical dimension is commonly referred to as a size effect. In thin films, size effects are widely observed, whereas in bulk ceramics, changes in properties from the values of large‐grained specimens is most notable in samples with grain sizes below several micrometers. It is important to note that ferroelectricity typically persists to length scales of about 10 nm, but below this point is often absent. Despite the stability of ferroelectricity for dimensions greater than ~10 nm, the dielectric and piezoelectric coefficients of scaled ferroelectrics are suppressed relative to their bulk counterparts, in some cases by changes up to 80%. The loss of extrinsic contributions (domain and phase boundary motion) to the electromechanical response accounts for much of this suppression. In this article, the current understanding of the underlying mechanisms for this behavior in perovskite ferroelectrics is reviewed. We focus on the intrinsic limits of ferroelectric response, the roles of electrical and mechanical boundary conditions, grain size and thickness effects, and extraneous effects related to processing. In many cases, multiple mechanisms combine to produce the observed scaling effects. 相似文献
945.
Effect of P2O5 on the Structural and Magnetic Properties of Magnetite‐Based Glass‐Ceramics
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Viorel Sandu Simona Greculeasa Andrei Kuncser Victor Kuncser 《Journal of the American Ceramic Society》2016,99(12):4013-4021
The specific morphology and magnetic properties of magnetite‐based glass‐ceramics obtained by crystallization of Fe‐containing borosilicate glassmelts in the presence of P2O5 as nucleating agent are investigated. We found that the distribution of the tiny nanoparticles of magnetite determines the low temperature response to magnetic field. The observed effects are discussed with respect to the following factors: (1) the existence of a multimodal size distribution of the tiny grains as revealed by Mössbauer spectroscopy, magnetometry, and high‐resolution electron microscopy; (2) the existence of a disordered layer at the grain surface which is driven by field in a magnetically ordered state; and (3) the interplay between the relaxation mechanisms in different temperature ranges. 相似文献
946.
Characterization and Formation of Yttrium Disilicate Nanocrystalline Powders by EDTA–Citric Acid Complexing Process
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![点击此处可从《International Journal of Applied Ceramic Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Yong Hong Wang Zhong Shang Wang Yan Jiang Xu Wang Ji Gui Cheng 《International Journal of Applied Ceramic Technology》2016,13(4):736-742
A new route for the synthesis of yttrium disilicate (mainly α‐Y2Si2O7) powders was reported as ethylenediaminetetraacetic acid (EDTA)–citric acid (CA) complexing process. The thermal decomposition, phase composition, and microstructure of sample were characterized by thermogravimetry–differential thermal analyses, X‐ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and field emission scanning microscopy, respectively. The EDTA–CA complexation mechanism was further discussed, and the selected condition to get nanocrystalline Y2Si2O7 powders was the precursor with pH 9.38 and heat treatment at around 1050°C. The prepared powders were well crystallized with average crystalline size ca. 50 nm. 相似文献
947.
合成了3种不同晶粒尺寸的ZSM-5分子筛,并制得MTP催化剂,对ZSM-5分子筛催化剂在MTP反应中的性能进行系统研究。采用XRD、SEM、N2物理吸附和TGA等对ZSM-5分子筛催化剂进行表征,发现小晶粒的ZSM-5分子筛具有良好的抗积炭性能,在MTP反应中具有较高的稳定性。采用小晶粒分子筛制成的催化剂,考察反应工艺条件对催化剂催化性能的影响,结果表明,丙烯选择性随反应温度和空速提高而增加,降低反应压力和提高水醇质量比也有利于提高丙烯选择性,为调整MTP工艺的产物分布和优化反应工艺条件提供了技术依据。 相似文献
948.
949.
目前,铜键合丝广泛用于集成电路、电子封装等领域,但是铜丝在制造和键合的过程中受到的局部应力和摆动,会不可避免地产生疲劳问题。通过一套以自激振动为原理组装的微结构疲劳试验装置,对不同直径的微米级铜键合丝进行对称弯曲疲劳性能测试。试验结果表明:该试验装置能够成功地对微米级铜丝进行对称弯曲疲劳性能试验;无论是屈服强度、抗拉强度还是弹性模量,直径20μm的铜丝均高于直径30μm、40μm的铜丝,表现出明显的尺寸效应;所有铜丝的疲劳寿命集中在4.5×104~1×107;在相同应力条件下,铜丝的疲劳寿命随着铜丝直径的增加而减小;直径20μm、30μm、40μm的铜丝对应的疲劳强度(N=106)分别为147 MPa、97 MPa、70 MPa。从扫描电子显微镜的断口分析结果可以看出拉伸断口为凿峰状,断口周围表面出现许多相间的条状拉拔痕迹;疲劳断口为平齐正断,两条裂纹起源于试样表面,瞬断区为窄条状。 相似文献
950.