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BaFe12O19 powders with nanocrystaUine sizes were produced by sol-gel auto-combustion method. The precursors were prepared under the molar ratios of citric acid to the metal nitrate of 0.5, 1.0 and 1.5. Appropriate ethylene diamine （C2H8N2） was added in order to adjust pH of 7. The ions distribution of citric acid at different pH explains the effect of citric acid in the starting solution. The XRD patterns of the as-burnt powders and annealing powders show different phases for different citric acid content. In addition, the lattice constants （a, c） derived from X-ray diffraction pattern were changed from 0.58881 nm to 0.58997 nm and 2.32057 nm to 2.32296 nm respectively. The data from VSM indicated that the powder with high citric acid content took on good magnetic properties. Pure single BaFe12O19 of the specific maximum magnetization M（1 T）≈ 49.73 Am^2/kg, the specific remanent magnetization Mr ≈ 30.77 Am^2/kg and the coercive force He≈ 467 kA/m was produced when the molar ratios of citric acid to the metal nitrate was 1.5. 相似文献
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本文详细地阐述了在物理设计性实验《误差分配和实验仪器选择》中进行CAI课件研制的设计思想和内容。通过实践，该课件优化教学过程能有效提高实验课的教学质量。 相似文献
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Single phase Fe5C2 intermetallic compound was prepared by mechanical alloying method. The phase and crystal structure of sample were analyzed with X-ray differaction spectrum. The decomposing temperature of the Fe5C2 compound is 596.4℃ determined by the DSC curve. It is further shown that the size of nanometer crystal grain is an important condition for carrying out the solid state reaction at room temperature and normal pressure. 相似文献
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多功能、开放性电子电工实验中心的实践探索 总被引：7，自引：6，他引：7
探索电子电工实验教学、管理新模式，充分利用实验室的资源，电子电工实验中心由原单一职能转变为多功能实验中心，增设“技能”教学，加快培养学生的动手能力和创新精神，建立“全天候”开放实验室，改变原有的教学模式，让学生自主进行实验，充分调动了学生的学习的积极性和自主性。 相似文献
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1IntroductionIt is well known that the solubility of carbon in Fefor both body-centered-cubic (bcc) and face-centered-cubic (fcc) structures is very low, even in a liquidstate. The maxi mum solubility of carbon in ferrite isonly about 0 .1 atompercent .The difference of atomicradius between Fe and C is so large that C is em-bedded at the interstitial site in the bcc or fcc Fe lat-tice . Hume-Rothery rules suggest that the atomic sizeof the solute and solvent should differ by less than15 %to… 相似文献
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Supersaturated solid solutions Fe1-xCx （0≤x≤0.9 ） of wide composition range have been prepared by mechanical alloying process. Nanocrystalline phase was formed for 0 ≤ x ≤ 0.67 and a large grain phase for 0.75 ≤ x ≤ 0.9. The large fraction of graphite volume puts off formation of nanocrystalline phase for high carbon content. In the large grain phase, magnetization follows simple magnetic dilution, and eoereivity He is mainly due to dissolution of carbon at grain boundaries. In the nanocrystalline phase the alloying effect of carbon is revealed by a distinct reduction of average magnetic moment. The increasing lattice constant with increasing carbon content is observed for x ≤ 0.5, suggesting that the high carbon concentration may enhance diffusion of carbon into the Fe lattice. It shows a discontinuity in the Hc variation with a grain size D of nanocrystalline phase. For small grain D below the critical value, Hc increases with D. For a large grain D, Hc decreases with increasing D. The solubility limit of carbon in a-Fe extended by nanocry- stalline phase formation is discussed. 相似文献
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针对目前高校实验室队伍建设中的实验技术人员待遇不高,职称晋升困难和实验技术人员积极性不高等普遍问题,我校创新性的尝试在实验室队伍建设中设立"实验技术总监、技术主管岗位"系列岗位措施。阐述了设立技术岗位的指导思想和实施办法,并从实验技术岗位的分级、具体考评内容、负责部门及岗位申请条件等6个方面详细介绍了实施办法,通过总结技术岗位的实施情况,说明了设立实验技术岗位在很大程度上提高了实验技术人员待遇,充分发挥了实验技术人员工作积极性,提高了实验技术水平。 相似文献
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溶液凝胶自然燃烧制备的铝掺杂对钡铁氧体晶相和磁性能的影响 总被引：1，自引：0，他引：1
Al-substituted barium ferrite powders were synthesized using the sol-gel auto-combustion method according to the molecular formula BaAlxFe12-xO19 (x=0, 0.1, 0.2, 0.3, 0.4, 0.5, 1.0). Compared with non-substituted barium ferrite annealing at 1000℃, the vibrating sample magnetometer (VSM) measurement manifested that the optimum magnetic properties formation temperature of Al-substituted barium ferrite was 1100℃. The data from X-ray diffractometer (XRD) showed that with increasing x, the lattice constants (a and c) decreased as well as the unit-cell volume Vcell. Magnetic measurement of non-substituted and Al-substituted powders annealed from 900℃ to 1200℃ exhibited that the maximum magnetization M (10 kOe), the remanent magnetization Mr and the coercivity Hc depended strongly on the chemical composition of powder as well as the annealing temperature. When annealing at 1100℃, BaAl0.5Fe11.5019 of high coercivity Hc (6584 Oe) was produced. Meanwhile, M (10 kOe) and Mr were 42.83emu/g and 25.65emu/g, respectively. 相似文献
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介绍了上海大学在实验室队伍建设中设置实验技术总监岗位的背景、思路和做法,包括设岗、待遇、职责及实践的情况,提出了关于实验技术总监的两个关键词:关键、领先。 相似文献
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