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131.
在5% H2+95% N2(V/V)还原气氛中1 500℃烧结4 h制备La0.1BixSr0.9-xTiO3(x=0、0.05、0.075、0.1)陶瓷,并对其组成、显微结构和热电性能进行研究。结果表明:掺Bi试样的主晶相均为SrTiO3,当Bi掺杂量大于0.075时,样品中出现少量Bi2O3杂相;掺Bi试样的晶粒发育完全,形状规则,结合紧密,显示出Bi2O3良好的助烧效果。另外,Bi元素掺入使La0.1Sr0.9TiO3陶瓷的电导率和Seebeck系数绝对值显著增加,说明Bi元素的掺入可有效提高材料的载流子浓度和载流子迁移率。其中,x=0.075时试样的功率因子最大,在400℃时为692 μW·m-1·K-2。虽然其热导率比未掺杂Bi试样有所提高,x=0.075时试样的ZT值在500℃时仍可达0.172,比未掺杂Bi试样提高了130%。 相似文献
132.
在Ca O-Mg O-Si O2作为复合烧结助剂降低氧化铝陶瓷温度的前提下,研究不同添加量的稀土氧化物Nd2O3对陶瓷烧结温度、磨损率、显微结构的影响。通过设计Nd2O3在六铝酸钙中固溶和Nd2O3在Al2O3单晶表面扩散的实验,探索Nd2O3对氧化铝陶瓷耐磨性能影响的机理。结果表明:加入过量的Nd2O3会破坏晶界结合强度,导致陶瓷的耐磨性能变差;而少量Nd2O3的加入能有效提高晶界间结合强度和陶瓷的致密度,改善耐磨性能,耐磨性提高幅度约42.7%。 相似文献
133.
Microstructure and Properties of Cr3Si/γ-Fe Composite Coating Prepared by Plasma Transferred Arc Cladding Technique 下载免费PDF全文
Under optimized operating parameters, a wear and corrosion resistant Cr3 Si/γ-Fe composite coating is fabricated on a normalized 0.45% carbon steel substrate by using the plasma transferred arc (PTA) cladding technique with Fe-Cr-Si elemental powder blend as the precursor material. Mierostructure, microhardness, dry-sliding wear resistance and electrochemical corrosion characteristic of the coating are evaluated. Test results show that the composite coating is mainly composed of primary Cr3Si dendrites and the interdendritic supersaturated iron-base solid solution γ-Fe. Between the Cr3Si/γ-Fe composite coating and the normalized 0.45% carbon steel substrate, there is a narrow metallurgical bonding zone. The Cr3Si/γ-Fe composite coating exhibits high microhardness, excellent wear and corrosion resistance under test conditions. 相似文献
134.
Anatase nanoparticles modified by sulfate groups were synthesized using hydrothermal method. The particles were controlled to large sizes by simply adjusting the amount of H2O2, in which HOO^- ions replaced the surface sulfate groups and reduced the steric effect to promote the grain growth. The size-induced microstructural changes of the as-prepared nanoparticles were characterized using powder XRD, FT-IR, TG. and UV-vis analyses. The sulfate groups existed on anatase surface in unidentate and bidentate coordination forms. With the particle size reduction, bandgap energies of the as-prepared anatase nanoparticles decreased, and the desorption temperature of sulfate groups shifted towards lower temperatures. 相似文献
135.
重金属铜、锌、铅、镉对小形月牙藻生长及亚显微结构的影响 总被引:8,自引:0,他引:8
周宏 《浙江大学学报(理学版)》1998,25(2):85-92
本文研究了重金属铜、锌、铅、镉对小形月牙藻(Selenastrum minutum )生长的影响, 以及小形月牙藻对重金属的吸收富集情况, 并着重研究了四种重金属对小形月牙藻的亚显微结构的影响.从电镜观察可见, 四种重金属对小形月牙藻的毒性症状首先表现在叶绿体, 其呈平行排列的、片状的类囊体受毒害后,变成指纹状排列、条索状排列、甚至不规则的波纹状;四种重金属对液泡的影响也很明显, 随着重金属浓度的增加, 原来的多数小液泡变成一个或几个大液泡;细胞壁变得结构松散, 重金属浓度高时, 外层呈剥落状.根据本实验结果, 四种重金属对小形月牙藻的毒性顺序是:Cd >Cu>Pb>Zn .本实验结果还表明, 小形月牙藻对重金属铜、锌、铅、镉都有一定的吸收富集能力, 尤其对铅和锌有更大的耐受力, 能够大量吸收水体中的铅和锌. 相似文献
136.
采用磁控溅射方法在(100)YSZ基底上沉积了YBa2Cu3O7/SrTiO3/YBa2Cu3O7异质外延三层膜。利用交流磁化率和四引线电阻测量的方法确定了三层膜的超导性能,利用X射线衍射和透射电子显微镜研究了三层膜的结构特征。研究结果表明,膜层的结晶质量较好,临界转变温度Tc在83.5K和86.7K之间。YBCO膜层中的绝大多数甚至全部)晶粒为c取向,在有些膜中只存在少量的a或b取向的YBCO晶 相似文献
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139.
Boundary Conditions of Wigner-Seitz Cell in Inner Crust of Neutron Stars with Relativistic Mean Field Approach 下载免费PDF全文
The microscopic structure of the Wigner-Seitz (W-S) cell in the inner crust of neutron stars is investigated with the relativistic mean field (RMF) approach. The W-S cell is composed of a cluster of neutrons and protons localized in a region around the centre and surrounded by a neutron gas of approximately uniform density. In order to generate the density of the W-S cell, appropriate boundary conditions in the calculation of the single-particle wavefunctions are necessary. We emphasize on the choice of the boundary conditions in the RMF approach. Three kinds of boundary conditions are suggested. The properties of the W-S cell with the three kinds of boundary conditions are investigated. The neutron density distributions in the RMF and Hartree-Fock-Bogoliubov (HFB) models are compared. It is found that the neutron gas densities of the W-S cell in the RMF model is higher than those obtained in the HFB model. 相似文献
140.
Internal friction of nanocrystalline nickel is investigated by mechanical spectroscopy from 360 K to 120 K. Two relaxation peaks are found when nanocrystalline nickel is bent up to 10% strain at room temperature and fast cooling. However, these two peaks disappear when the sample is annealed at room temperature in vacuum for ten days. The occurrence and disappearance of the two relaxation peaks can be explained by the interactions of partial dislocations and point defects in nanocrystalline materials. 相似文献