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83.
Further Enhancing Piezoelectric Properties by Adding MnO2 in AgSbO3‐Modified (Li,K,Na)(Nb,Ta)O3 Lead‐Free Piezoceramics 下载免费PDF全文
Qing Liu Fang‐Yuan Zhu Lei Zhao Ke Wang Jing‐Feng Li 《Journal of the American Ceramic Society》2016,99(11):3670-3676
This work investigated the effect of MnO2 addition on the phase structure, microstructure, and electrical properties of AgSbO3‐modified (Li,K,Na)(Nb,Ta)O3 (abbreviated as LKNNT‐AS) lead‐free piezoelectric ceramics with an optimized composition endowed with a state of two‐phase coexistence. A small amount (0.1 wt%) of MnO2 can significantly further enhance the piezoelectric property of LKNNT‐AS ceramics, whose piezoelectric constant d33 and converse piezoelectric coefficient d33* as well as planar electromechanical coupling factor kp reach 363 pC/N, 543 pm/V, and 0.49, respectively. The temperature stability of piezoelectricity in MnO2‐modified LKNNT‐AS samples also improved, which is associated with the more uniform and better thermally stable ferroelectric domains that were revealed by piezoresponse force microscopy. 相似文献
84.
Layered Orthorhombic Nb2O5@Nb4C3Tx and TiO2@Ti3C2Tx Hierarchical Composites for High Performance Li‐ion Batteries 下载免费PDF全文
Chuanfang Zhang Seon Joon Kim Michael Ghidiu Meng‐Qiang Zhao Michel W. Barsoum Valeria Nicolosi Yury Gogotsi 《Advanced functional materials》2016,26(23):4143-4151
Engineering electrode nanostructures is critical in developing high‐capacity, fast rate‐response, and safe Li‐ion batteries. This study demonstrates the synthesis of orthorhombic Nb2O5@Nb4C3Tx (or @Nb2CTx) hierarchical composites via a one‐step oxidation —in flowing CO2 at 850 °C —of 2D Nb4C3Tx (or Nb2CTx) MXene. The composites possess a layered architecture with orthorhombic Nb2O5 nanoparticles decorated uniformly on the surface of the MXene flakes and interconnected by disordered carbon. The composites have a capacity of 208 mAh g?1 at a rate of 50 mA g?1 (0.25 C) in 1–3 V versus Li+/Li, and retain 94% of the specific capacity with 100% Coulombic efficiency after 400 cycles. The good electrochemical performances could be attributed to three synergistic effects: (1) the high conductivity of the interior, unoxidized Nb4C3Tx layers, (2) the fast rate response and high capacity of the external Nb2O5 nanoparticles, and (3) the electron “bridge” effects of the disordered carbon. This oxidation method was successfully extended to Ti3C2Tx and Nb2CTx MXenes to prepare corresponding composites with similar hierarchical structures. Since this is an early report on producing this structure, there is much room to push the boundaries further and achieve better electrochemical performance. 相似文献
85.
《钢铁研究学报(英文版)》2016,(5):501-508
Hot deformation behavior of a new type of M3∶ 2 high speed steel with niobium addition made by spray forming was investigated based on compression tests in the temperature range of 950-1 150 ℃ and strain rate of 0. 001-10 s~(-1). A comprehensive constitutive equation was obtained,which could be used to predict the flow stress at different strains. Processing map was developed on the basis of the flow stress data using the principles of dynamic material model. The results showed that the flow curves were in fair agreement with the dynamic recrystallization model. The flow stresses,which were calculated by the comprehensive constitutive equation,agreed well with the test data at low strain rates( ≤1 s~(-1)). The material constant( α),stress exponent( n) and the hot deformation activation energy( Q_(HW)) of the new steel were 0. 006 15 MPa~(-1),4. 81 and 546 kJ·mol~(-1),respectively. Analysis of the processing map with an observation of microstructures revealed that hot working processes of the steel could be carried out safely in the domain( T = 1 050-1 150 ℃,ε = 0. 01- 0. 1 s~(-1))with about 33% peak efficiency of power dissipation( η). Cracks was expected in two domains at either lower temperatures( 1 000 ℃) or low strain rates( 0. 001 s~(-1)) with different cracking mechanisms. Flow localization occurred when the strain rates exceeded 1 s~(-1) at all testing temperatures. 相似文献
86.
采用浸渍法制备了Nb2O5/α-A l2O3催化剂(简称催化剂)并用于环氧乙烷水合制乙二醇的反应,通过控制α-A l2O3载体中致孔剂的含量来调变载体的孔径、孔分布及比表面积;采用吡啶吸附红外光谱、氨程序升温脱附法研究了载体的比表面积及孔径对催化剂酸性及反应性能的影响。实验结果表明,产物的选择性受扩散因素及催化剂酸性的影响,而催化剂的酸量、酸密度可以通过载体的孔径及比表面积的变化加以调控。比表面积较小及孔径较大的载体对催化剂催化环氧乙烷水合制乙二醇的反应较为有利。当载体的比表面积小于0.80m2/g、孔径为4.00~8.00μm时,在反应温度160℃、反应压力1.5M Pa、n(H2O)∶n(EO)=22、液态空速25h-1的条件下,环氧乙烷的转化率大于99.8%,乙二醇的选择性超过89.9%。 相似文献
87.
Hiromichi Ichinose Masanori Taira Sachiko Furuta Hiroaki Katsuki 《Journal of the American Ceramic Society》2003,86(9):1605-1608
Niobium- or vanadium-doped anatase sols were prepared by hydrothermal treatment of 0.1 mol/dm3 peroxotitanium complex aqueous solutions dissolving 0–10 mol% niobium or vanadium at 100°C for 8 h. Niobium-doping caused the increase of lattice constants of anatase and the shape change of anatase crystal from spindle-like to cubic-like structure, but no change of the optical absorbance. Vanadium-doping caused the decrease of lattice constant of c -axis, the miniaturization of anatase crystal and the increase of optical absorbance at the wavelength from 350–700 nm. 相似文献
88.
A fabrication process for niobium-based Josephson superconductive tunnel junctions with a Pb/In alloy top electrode which showed very good mechanical and electrical properties and high oxide uniformity is described. The dependence of the junction parameters on the In-percentage in the alloy is also reported, and the results, in connection with data on the barrier composition, obtained via Auger electron-spectroscopy analysis, are discussed. 相似文献
89.
基于Nb2O5样品溶解困难、测定杂质元素多的特点,研究了全谱电弧发射光谱仪测定Nb2O5样品中18种杂质元素的方法。试验了光谱缓冲剂、电极形状、样品装填方式、分析谱线、信号采集时间等对测定效果的影响。结果表明,石墨粉、氟化钠、氧化镓以94∶5∶1的质量比混合作为光谱缓冲剂;采用孔径4mm、深7mm的孔型石墨电极作为下电极;样品装满电极后下压2mm,并滴加蔗糖溶液;各元素最佳分析谱线在各自特征蒸发时间内采集信号强度,测定结果最优。在选定的工作条件下,各元素检出限均小于1.5μg/g,样品加标回收率在86%~118%之间;对合成校准样品进行测定,测定值与理论值基本一致,各元素10次测定结果的相对标准偏差(RSD)均小于10%。 相似文献
90.
Multifilamentary superconducting conductors, which are usually manufactured by hot extrusion and cold drawing, consist of bundles of small diameter superconducting filaments embedded in a normal conducting matrix. It is most desirable for the magnet designer as well as for the conductor manufacturer to control the uniformity of properties along the length of conductors which will be used in large magnets. In this paper we present a continuous monitoring of the superconducting and normal matrix areas through a non-destructive sampling procedure over the whole length of a superconducting conductor. 相似文献