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121.
Microwave Studies on Strontium Ferrite Based Absorbers 总被引:1,自引:0,他引:1
Single layer microwave absorbers based on strontium ferrite-epoxy composites have been fabricated and their reflection loss characteristics studied in the X-band (8–12.4 GHz) of microwave frequencies. Permittivity (r – jr) and permeability (r – jr) of Co and Ti added strontium ferrite SrCo
x
Ti
x
Fe12 – 2x
O19 (x = 0.1 to 0.9 in steps of 0.2), have been measured. Thickness of the absorber is an important criterion influencing the absorption characteristics. Composites of 3 mm thickness are found to absorb over a reasonable range of X-band frequencies. A minimum reflection loss of –36.5 dB is observed for the composite with x = 0.3. 相似文献
122.
S. Rodewald N. Sakai K. Yamaji H. Yokokawa J. Fleig J. Maier 《Journal of Electroceramics》2001,7(2):95-105
The effect of the electrode material on the high voltage stoichiometry-polarization (electrocoloration) of Fe-doped SrTiO3 single crystals has been studied. For different electrode materials (150-nm Ag/15-nm Cr and 150-nm Au/15-nm Cr) secondary ion mass spectrometry (SIMS) was used to measure the depth profile of the 18O-isotope after high-field stress. The results were compared with spatially resolved impedance measurements on electrocolored Fe-doped SrTiO3 single crystals. For Au/Cr as well as Ag/Cr electrodes a large dc voltage leads to moving color fronts which are usually correlated with a pronounced stoichiometry polarization of the samples due to electrodes blocking the ionic current. However, the local impedance measurements demonstrate that the conductivity profiles near the cathode depend on the electrode material. This finding is in accordance with the SIMS measurements which indicate that the Ag/Cr-electrodes are, in contrast to Au/Cr-electrodes not completely inactive for the oxygen incorporation into the Fe-doped SrTiO3. The results are discussed in terms of defect chemical models. 相似文献
123.
Magnetic properties and intergranular action in bonded hybrid magnets,based on NdFeB and strontium ferrite powders were investigated.The long-range magnetostatic interaction and short-range exchange coupling interaction existed simultaneously in bonded hybrid magnets,and neither of them could be neglected.Some magnetic property parameters of hybrid magnets could be approximately obtained by adding the hysteresis loops of two magnets pro rata. 相似文献
124.
以传统陶瓷制备工艺制备了Y掺杂Ba0.6Sr0.4TiO3基半导体陶瓷材料,分析了不同Y掺杂量与材料PTC特性之间的关系。研究结果表明:Y^3+作为施主掺杂可使Ba0.6Sr0.4TiO3陶瓷材料的室温电阻率明显降低。在-60℃到室温附近的温度区间内,Y掺杂Ba0.6Sr0.4TiO3陶瓷材料的电阻率较为稳定,当高于室温以上的某-一温度Tx时,电阻率随温度的变化呈线性增加趋势,表现出较好的PTC特性。复阻抗测试结果表明,Y掺杂可以同时降低Ba0.6Sr0.4TiO3陶瓷材料的晶粒电阻和晶界电阻。 相似文献
125.
潘义川 《武汉理工大学学报(材料科学英文版)》2007,22(1):74-76
The grain refining process of an AZ91D Mg alloy by Sr addition was studied and the heterogeneous nucleating particles of α-Mg were investigated by electron probe microanalysis (EPMA). With 0.6 wt% Sr addition, the mean grain size of AZ91D alloy was refined from 235.4μm to 52.5 μm at the one-half radius of the ingot. The morphology of primary crystal changed from a sixford symmetrical shape to a petallike shape, Mg-Sr-Al-Fe-Mn heterogeneous nucleating particles were observed at the grain centers and Sr solute atoms presented segregation along the grain boundaries. Grain refinement was facilitated by both the Mg-Sr-Al- Fe-Mn nucleating particles and the Sr solute atoms, and the former played a dominate role in the process. 相似文献
126.
采用固相反应法制备了掺杂不同量氧化镁(MgO)的钛酸锶钡(BST)微波铁电材料。采用SEM、EPMA、XRD等测试手段,分析研究了烧结产物的微观形貌特征、相组成、微区成分等特点,结果表明:MgO总是以单独相存在,Mg^2+没有取代Ba^2+(Sr^2+)或Ti^4+离子而进入BST晶格。 相似文献
127.
Dispersion conditions for slip (slurry) formulation of a powder mixture of lanthanum strontium manganite (La0.84Sr0.16MnO3 - LSM) and carbon (pore former) in water was studied through detailed zeta-potential and rheological measurements. The zeta potential variation with pH for the aqueous suspensions of only LSM or carbon exhibited a maximum value in alkaline medium (−40 mV to −50 mV at a pH of 10-11), establishing the pH window for their co-dispersion for slurry formulation. A study of the viscosity variation with shear rate for the slurries with varying solid content (in the range of 45-65 wt.%) exhibited pseudo-plastic flow behavior, indicating presence of flocculates in them. The yield stress values obtained from the Casson equation reduced with decreasing solid content, indicating reduction in the flocculate strength. The slip with solid content of 50 wt.% exhibited optimum flow characteristics to form long tubes with uniform wall thickness (wall thickness 2-4 mm and length of 150-200 mm). The tubular specimens formed after controlled carbon burn out and sintering at 1400 °C for 1 h possessed about 35% open porosity. The porosity remained the same upon further sintering at 1400 °C for 8 h. 相似文献
128.
129.
Barbara Koodziejska Natalia Stpie Joanna Kolmas 《International journal of molecular sciences》2021,22(12)
Osteoporosis is a chronic disease characterized by low bone mass caused by increased bone turnover and impaired bone microarchitecture. In treatment, we use antiresorptive or anabolic drugs, which usually have a unidirectional effect, i.e., they inhibit the activity of osteoclasts or stimulate the effect of osteoblasts. Strontium ranelate is an anti-osteoporosis drug with a unique mechanism of action (used primarily in postmenopausal women). Unlike other medicines, it has a multidirectional effect on bone tissue, intensifying osteoblastogenesis while inhibiting osteoclastogenesis. It turns out that this effect is demonstrated by strontium ions, an element showing physical and chemical similarity to calcium, the basic element that builds the mineral fraction of bone. As a result, strontium acts through the calcium-sensing receptor (CaSR) receptor in bone tissue cells. In recent years, there has been a significant increase in interest in the introduction of strontium ions in place of calcium ions in ceramics used as bone replacement materials for the treatment of bone fractures and defects caused by osteoporosis. The aim of this study was to summarize current knowledge about the role of strontium in the treatment of osteoporosis, its effects (in various forms), and the ways in which it is administered. 相似文献
130.
Abbas Saeed Hakeem Jekabs Grins Saeid Esmaeilzadeh 《Journal of the European Ceramic Society》2007,27(16):4783-4787
Vickers hardness and refractive index have been determined for a series of La-Si-O-N oxy-nitride glasses containing 30–62 e/o of La and 9–68 e/o of N. The hardness varies between 7.7 and 11.5 GPa at a load of 1 kg and is dependent of the N content, while the La content does not influence it significantly. The increase of the hardness with N content is, contrary to reported findings for other oxy-nitride glasses, found not to be linear over the whole compositional range. The refractive index varies between 1.8 and 2.3 and increases non-linearly with increasing N content. The compositional variations of hardness and refractive index are compared with previously published results. 相似文献