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101.
Temperature Stability of Lead‐Free Niobate Piezoceramics with Engineered Morphotropic Phase Boundary 下载免费PDF全文
Ruiping Wang Ke Wang Fangzhou Yao Jing‐Feng Li Florian H. Schader Kyle G. Webber Wook Jo Jürgen Rödel 《Journal of the American Ceramic Society》2015,98(7):2177-2182
The temperature dependence of piezoelectric properties (direct piezoelectric coefficient d33, converse piezoelectric coefficient d33(E = 0), strain S and electromechanical coupling coefficient kp) for two niobate‐based lead‐free piezoceramics have been contrasted. 0.92(Na0.5K0.5)NbO3–0.02(Bi1/2Li1/2)TiO3–0.06BaZrO3 (6BZ/2BLT/92NKN) has a morphotropic phase boundary (MPB) between rhombohedral and tetragonal at room temperature and 0.92(Na0.5K0.5)NbO3–0.03(Bi1/2Li1/2)TiO3–0.05BaZrO3 (5BZ/3BLT/92NKN) features an MPB engineered to be located below room temperature. At 30°C, d33, d33(E = 0), S (at 2 kV/mm), and kp are 252 pC/N, 230 pm/V, 0.069%, 0.51 for 5BZ/3BLT/92NKN; and 348 pC/N, 380 pm/V, 0.106%, 0.57 for 6BZ/2BLT/92NKN, respectively. With increasing temperature, the piezoelectric properties decrease. At 200°C, d33, d33(E = 0), S (at 2 kV/mm), and kp are 170 pC/N, 160 pm/V, 0.059%, 0.36 for 5BZ/3BLT/92NKN; and 181 pC/N, 190 pm/V, 0.061%, 0.39 for 6BZ/2BLT/92NKN. It is found that the electromechanical coupling coefficient has a better temperature stability than the piezoelectric coefficient in the studied system due to a large temperature‐dependent compliance change. The results demonstrate that engineering an MPB is highly effective in tailoring temperature stability of piezoceramics. 相似文献
102.
Gerardo del Cerro Santamaría 《Journal of the American Planning Association. American Planning Association》2013,79(1):101-102
In this article, we review three microcomputer programs for assessing regional economic impacts. The programs are ADOTMATR, GRIMP, and REMI, which we discuss in terms of their suitability for policy analysis and planning practice. We assess the programs in terms of range of applicability, flexibility and ease of use in conducting impact analyses, quality of output, and cost. ADOTMATR and GRIMP are similar; however, GRIMP is easier to use but less flexible and more limited than ADOTMATR. Although REMI is more sophisticated than the other two programs, it is more expensive and more limited in application. 相似文献
103.
Effect of polymerization catalyst technology on the melt processing stability of polyethylenes,Part 3: Additives blends performance 下载免费PDF全文
Karmele del Teso Sánchez Norman S. Allen Christopher M. Liauw Michelle Edge 《乙烯基与添加剂工艺杂志》2016,22(2):117-127
This article considers the interaction between additives that occur during the stabilization process. The simultaneous effects of the additives and associated interactions on melt processing stability and processing discoloration were of particular interest. Melt stability is an important factor to consider because physical changes in the processed polymer can occur during the compounding and fabrication steps. Furthermore, discoloration is one of the most important problems affecting commercial polymers. Most discoloration manifests itself as yellowing, especially in the case of polyolefins. Although yellowing can often be associated with degradation processes caused by various agents, such as light or heat, this is not always the case; yellowing can also be due to the interaction of additives in the stabilizer packages. Blends of primary antioxidants (AOs), secondary AOs, and hindered amine light stabilizers have been studied with the intention of further improving stabilization performance together with cost reduction of the stabilized polymer. Although synergism between AOs and a stabilizer is fairly common, antagonism was also observed in terms of melt flow protection and in color stability in some of the AOs tested. The effects of a range of thermal and light stabilizers on the melt stability (investigated via multiple pass extrusion) and color stability of three different polyethylenes (PEs) were examined. The PEs varied in terms of the catalyst system used to synthesize the polymers and included a high‐density polyethylene (HDPE) produced by using a chromium‐based Phillips catalyst and two linear low‐density polyethylenes (LLDPEs) produced via chromium‐based metallocene and titanium‐based Ziegler‐Natta catalysts. The apparent lack of influence of polymerization catalyst system on the mode of stabilizer interaction should lead to the reassessment of stabilizer formulation strategies in relation to PE type/catalyst system and associated commercial/economic considerations. J. VINYL ADDIT. TECHNOL., 22:117–127, 2016. © 2014 Society of Plastics Engineers 相似文献
104.
Jiadong Zang Ming Li Derek C. Sinclair Wook Jo Jürgen Rödel 《Journal of the American Ceramic Society》2014,97(5):1523-1529
The electrical and dielectric properties of (1 ? x)(0.94Bi1/2Na1/2TiO3–0.06BaTiO3)–x(K0.5Na0.5NbO3) with x = 0, 0.03, 0.09, 0.18 have been investigated by impedance spectroscopy over a wide temperature range. The dc conductivity of the ceramics follows the Arrhenius law with an activation energy ranging from ~1.20 to 1.50 eV. Measurements under different atmospheres show the materials exhibit n‐type semiconducting behavior at elevated temperatures. The presence of a highly polarizable phase for all compositions is revealed by electric modulus (M″) spectra. The Burns temperature decreases with increasing KNN content. The change in temperature‐dependent permittivity with composition is explained by the difference in thermal evolution of polar nanoregions induced by the addition of KNN. 相似文献
105.
Yo‐Han Seo Jurij Koruza Andreja Benčan Barbara Malič Jürgen Rödel Kyle G. Webber 《Journal of the American Ceramic Society》2014,97(5):1582-1588
The influence of second phase zirconia particles on the electrical properties and fracture behavior of various polycrystalline soft Pb(Zr1?xTix)O3 (PZT) compositions was investigated. PZT composites with yttria‐stabilized tetragonal zirconia particles exhibited enhanced crack resistance in comparison to monolithic compositions, regardless of the PZT composition. The addition of zirconia, however, was found to change the PZT composition through the diffusion of zirconium, resulting in variations in the observed piezoelectric and ferroelectric responses. Through the tailoring of the PZT matrix composition, the large electromechanical response and enhanced fracture toughness could be retained. The variation in both small and large signal properties is contrasted to fracture results and crystal structure changes, as determined by X‐ray diffraction. 相似文献
106.
R. Salgado M. A. del Valle B. G. Duran M. A. Pardo F. Armijo 《Journal of Applied Electrochemistry》2014,44(12):1289-1294
Poly(3,4-ethylenedioxythiophene) nanowires (nw-PEDOT), between 6.7–13.8 nm diameter, were obtained by electrochemical methods utilizing modified electrodes with silicon oxide as a template to afford a Pt/nw-PEDOT electrode. Dopamine electro-polymerization was next accomplished upon this electrode (Pt/nw-PEDOT/PDA). The Pt/nw-PEDOT/PDA assembly is capable of hindering interfering signals such as those from ascorbic and uric acid, enabling thus the selective detection of dopamine. Amperometric determination studies allowed limit of detection and limit of quantification limits of 0.47 and 1.59 µM, respectively, to be established. These limits were lower than those obtained with the same conducting polymer but without a nanowire structure. 相似文献
107.
López Steven R.; Lara Ma. del Carmen; Kopelowicz Alex; Solano Susana; Foncerrada Hector; Aguilera Adrian 《Canadian Metallurgical Quarterly》2009,77(4):763
The authors developed and tested a 35-min psychoeducational program with the goal of increasing Spanish-speaking persons’ literacy of psychosis. The program uses popular cultural icons derived from music, art, and videos, as well as a mnemonic device—La CLAve (The Clue)—to increase (a) knowledge of psychosis, (b) efficacy beliefs that one can identify psychosis in others, (c) attributions to mental illness, and (d) professional help-seeking. Assessments were conducted before and after administering the program to both community residents (n = 57) and family caregivers of persons with schizophrenia (n = 38). For community residents, the authors observed increases across the 4 domains of symptom knowledge, efficacy beliefs, illness attributions, and recommended help-seeking. For caregivers, increases were observed in symptom knowledge and efficacy beliefs. La CLAve is a conceptually informed psychoeducational tool with a developing empirical base aimed at helping Spanish-speaking Latinos with serious mental illness obtain care in a timely manner. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
108.
Food traceability is essential to preserve the identity of unique quality traits against frauds or commercial disputes. Therefore, there is a growing demand of new traceability systems for the collection of information related to units/batches of food ingredients and products. 相似文献
109.
In this work, we give a complete picture of the behavior of the low intensity bootstrap of linear statistics. Our setup is given by triangular arrays of independent identically distributed random variables and different normalizations related to the rates of bootstrap intensities. We show that the behavior of this low intensity bootstrap coincides with that of partial sums of a number of summands equal to the bootstrap resampling size. Agreement on the limit laws for different (small) bootstrap sizes is thus shown to be closely related to domains of attraction of α-stable laws. As a byproduct, we obtain local distributional properties of Lévy processes. 相似文献
110.
Julia Romero‐Pastor José Vicente Navarro Marian del Egido Miguel Ortega‐Huertas 《Journal of the American Ceramic Society》2013,96(7):2132-2140
We studied ancient enamels on gilded copper from a collection of archeological horse harness pendants of the Museo Instituto Valencia de Don Juan (Madrid, Spain) to test the benefits of a new, nondestructive analytical methodology based on chemometric analysis (i.e., Principal Component Analysis, PCA) on micro‐ATR‐FTIR spectral data and chemical quantification using SEM‐EDS. The novelty of this approach was threefold: (i) PCA allowed the discrimination of the different harness pendants of known origin and attributed to the 14th and 15th centuries according to the chemical complex composition, nanostructure, glass weathering, and/or coloring mechanisms of each colored enamel, separately (i.e., red, purple, blue, and white), (ii) it is a cheap, easily available and nondestructive methodology that enables us to (iii) draw archeological conclusions about the quality of the manufacturing process, reassess the chronology of these objects and attempt to attribute them to different workshops according to the different traditional recipes identified. In particular, the enamels were made of alkali and/or alkaline earth lead‐glass with a wide range of chemical compounds in the form of pigments or opacifiers. Two types of coloring mechanisms were identified, colloidal particles such as copper‐ruby for red enamels, and ionic mechanisms such as Fe(II) and Co(II) to achieve a blue pigments; Mn(III) in the purple pigment; and two kind of white enamels were identified, i.e., tin oxide as an opacifier and uranium oxide. In addition, we established the reason for the poor state of conservation of some of the enamels by means of the identification of depolymerization and ion exchanges, well‐known harmful effects of glass weathering, and finally a chronology was assigned for some of these pieces according to the enamel composition. 相似文献