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41.
Jian Guo Zhenhai Ning Dongyan Fu Jinrong Cheng Jianguo Chen 《International Journal of Applied Ceramic Technology》2020,17(3):1348-1353
The xBiFeO3-(1-x)Ba(Zr0.02Ti0.98)O3 + 1.0 mol% MnO2 (xBF-BZT) lead-free piezoelectric ceramics were prepared by conventional solid-state reaction method. The structure, dielectric, and piezoelectric properties were studied. X-ray diffraction (XRD) analysis showed that xBF-BZT ceramics exhibited pure perovskite structure with the coexistence of tetragonal and rhombohedral phases (0.66 ≤ x ≤ 0.74). The Curie temperature Tc, the dielectric constant εr (1 kHz), dielectric loss tanδ (1 kHz), piezoelectric constant d33, coercive field Ec (80 kV/cm), and remnant polarization Pr (80 kV/cm) of 0.7BF-0.3BZT-Mn ceramics were 491°C, 633, 0.044, 165 pC/N, 35.6 kV/cm, and 22.6 μC/cm2, respectively. The unipolar strain of 0.7BF-0.3BZT reached up to 0.20% under the electric field of 60 kV/cm, which is larger than that (0.15%) of BiFeO3–BaTiO3 ceramics. These results indicated that the xBF-BZT ceramics were promising candidates for high-temperature piezoelectric materials. 相似文献
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光纤布拉格光栅的无源温度补偿 总被引:3,自引:1,他引:2
分析了通过施加应变补偿光纤布拉格光栅(FBG)中心波长随温度漂移的原理,给出了一种新型的无源温度补偿的方法和相应的实验结果。该方法采用了两种不同热膨胀系数的金属,对光栅先施加预应变。在0-60℃范围内,中心波长仅偏移了0.02nm。 相似文献
44.
Rheological properties of MR fluids under large step strain shear are presented in this paper. The experiments were carried out using a rheometer with parallel-plate geometry. Under the large step strain shear, MR fluids behave as nonlinear viscoelastic properties, where the stress relaxation modulus, G(t, γ), shows a decreasing trend with step strain. The experimental results indicate that G(t, γ) obeys time-strain separability. Thus, a mathematical form based on finite exponential serials is proposed to predict MR behavior. In this model, G(t, γ) is represented as the product of a linear stress relaxation, G(t), and the damping function, h(γ), i.e. G(t, γ)=G(t) h(γ). G(t) is simply represented as a three-parameter exponential serial and h(γ) has a sigmoidal form with two parameters. The parameters are identified by adopting an efficient optimization method proposed by Stango et al. The comparison between the experimental results and the model-predicted values indicates that this mathematical model can accurately predict MR behavior. 相似文献
45.
The analysis of 124 curves obtained in short-term tensile tests demonstrate that they can be described by varying strain hardening and softening characteristics. Different stress–strain curves can be produced at invariable yield strength and ultimate strength and interrelated proportional variations of the above characteristics. To determine some specific stress–strain curve, it is necessary to take account of yield strength and ultimate strength as well as strain corresponding to the latter. The relations between yield strength, ultimate strength and hardening and their practically complete absence between these parameters and softening were statistically established. 相似文献
46.
Effect of Strain Rate on Discontinuous Flow and Mechanical Characteristics of High-Nitrogenous Steel
Experimental study on the effect of strain rate on discontinuous flow and mechanical characteristics of the high-nitrogenous steel Kh23AG19F has been performed. Within the range of strain rates from 4.62 · 10-5 to 1.85 · 10 -4 s-1, discontinuous flow, reflected by serration on the tensile diagram, is chiefly determined by intergranular deformation mechanisms. Under strain rates over 1.85 · 10-2 s-1, combined deformation modes prevail, which cause a change in the character of discontinuous flow and transform a serrated tensile diagram into a wavy graph, with the yield stress of steel increased significantly. 相似文献
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采用Cole-Hopf变换法,将平板光波导导模所满足的二阶常微分方程(Helmholtz方程)变换成一阶常微分方程(Riccati方程),用较简单且有效的方法分析导模的特性。给出了多层阶跃型及渐变型平板波导导模的精确解析解和数值解法及实例;给出了非线性平板波导传播特性的数值计算法及实例。 相似文献
50.
机械力化学作用对低介硅灰石瓷料的相变和相组成的影响 总被引:1,自引:0,他引:1
采用X射线衍射仪(XRD)、差热分析(DTA)手段详细研究了由氧化物粉末制备硅灰石陶瓷时,机械力化学作用及后续热处理对硅灰石陶瓷相组成和相变过程的影响,分析了机械力化学在球磨过程中的作用机理主要是细化晶粒、使晶格畸变、晶格缺陷增多、非晶化和诱导低温化学反应。结果表明:高能球磨中的机械力化学作用能够有效地降低硅灰石陶瓷的烧成温度(11160~11220℃)。探明了经高能球磨的样品在烧成过程中的晶相转变规律。瓷料最终的晶相为单一的-硅灰石(高温变体)。 相似文献