第十一届全国周培源大学生力学竞赛个人赛命题总结

对第十一届全国周培源大学生力学竞赛个人赛命题进行了总结,介绍了理论力学和材料力学的命题思路,并提出了一些建议。     

Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95合金的磁性、磁致伸缩和穆斯堡尔谱研究

系统研究了室温下Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95(x=0.05,0.1,0.15,0.2,0.25,0.3)合金中元素Al替代Fe对结构、磁性、磁致伸缩性能和自旋重取向的影响.测量结果发现,x<0.2时Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95合金基本上是纯的单相,x=0.2时出现其他杂相,杂相随Al替代量的增加不断增多.随Al替代量x的增加,点阵常数a接近于线性增大,Curie温度TC逐渐下降,而矫顽力Hc急剧下降.振动样品磁强计(VSM)测量发现,磁化强度M随Al替代量x的变化较为复杂.VSM计和磁致伸缩效应测量共同表明,少量Al的替代有利于降低磁晶各向异性,而且随着Al替代量x的增多磁致伸缩系数快速减小,x>0.15时巨磁致伸缩效应消失.穆斯堡尔效应研究发现,随Al含量的增加Tb0.3Dy0.6Pr0.1(Fe1-xAlx)1.95合金中易磁化轴可能在{110}面逐渐偏离了立方晶体的主对称轴,发生自旋重取向,从而引起合金宏观磁性、磁致伸缩性能的变化.     

光子扫描隧道显微镜的探测场

通过修改光子扫描隧道显微镜探测场的计算模型，推导出比较符合实际的探测场及透射系数的计算公式，并利用这一新计算公式在微机上进行了模拟计算，得到了一些过去未曾发现的现象，对光子扫描隧道显微镜的实际探测具有一定的指导意义。     

铁镍合金纳米管阵列的模板制备和磁性

"在阳极氧化铝模板的孔洞中利用模板浸润的方法成功制备出了铁镍合金纳米管阵列．通过改变所用模板的参数和沉积纳米管的的制备条件,所制备的纳米管的长度、内径和外径的尺寸都可以得到有效控制．利用扫描电子显微镜和透射电子显微镜对所制备的纳米管及其阵列的形貌进行了表征．对铁镍合金纳米管阵列的宏观磁性测量表明样品具有磁各向异性,沿纳米管长轴方向样品更容易被磁化．对纳米管的磁化反转机制和磁矩在纳米管中的静态分布进行了讨论．铁镍合金纳米管的这些性质都是由纳米管的独特结构造成的．"     

Interaction between heat dipole and circular interfacial crack

The heat dipole consists of a heat source and a heat sink. The problem of an interracial crack of a composite containing a circular inclusion under a heat dipole is investigated by using the analytical extension technique, the generalized Liouville theorem, and the Muskhelishvili boundary value theory. Temperature and stress fields are formulated. The effects of the temperature field and the inhomogeneity on the interracial fracture axe analyzed. As a numerical illustration, the thermal stress intensity factors of the interfacial crack are presented for various material combinations and different positions of the heat dipole. The characteristics of the interfacial crack depend on the elasticity, the thermal property of the composite, and the condition of the dipole.     

High-frequency magnetic properties and core loss of carbonyl iron composites with easy plane-like structures

To fully release the potential of wide bandgap(WBG)semiconductors and achieve high energy density and efficiency,a carbonyl iron soft magnetic composite(SMC)with an easy plane-like structure is prepared.Due to this structure,the permeability of the composite increases by 3 times(from 7.5 to 21.5)at 100 MHz compared with to the spherical carbonyl iron SMC,and the permeability changes little at frequencies below 100 MHz.In addition,the natural resonance frequency of the composite shifts to higher frequencies at 1.7 GHz.The total core losses of the composites at 10,20,and 30 m T are80.0,355.3,and 810.7 m W/cm³,respectively,at 500 k Hz.Compared with the spherical carbonyl iron SMC,the core loss at500 k Hz is reduced by more than 60%.Therefore,this kind of soft magnetic composite with an easy plane-like structure is a good candidate for unlocking the potential of WBG semiconductors and developing the next-generation power electronics.     

锰烧结矿中氧化钙和氧化镁的快速测定

锰烧结矿中氧化钙和氧化镁的测定 ,经典分析方法是采用氨水 -过硫酸铵两次沉淀分离法和氯酸钾 -六次甲基四胺 -铜试剂沉淀分离法。由于这些分离法需两次沉淀分离 ,繁琐费时 ,因而不能满足炉前快速分析的要求。炉前分析现场采用的氨水 -过硫酸铵一次沉淀分离法[1] ,虽简便、快速 ,但准确度和精密度都欠佳。本文在详细研究氨水 -过硫酸铵分离方法的共沉淀吸附现象时 ,提出在 p H值 1～ 3的条件下 ,用六次甲基四胺沉淀分离锰、铁、铝等干扰离子 ,残留的痕量金属离子 ,用三乙醇胺和 L-半胱氨酸掩蔽。该法操作简便快速 ,准确度和精密度好 ,应用…     

Microwave reflection properties of planar anisotropy Fe50Ni50 powder/paraffin composites

The reflection properties of planar anisotropy Fe₅₀Ni₅₀ powder/paraffin composites have been studied in the microwave frequency range. The permeability of Fe₅₀Ni₅₀ powder/paraffin composites is greatly enhanced by introducing the planar anisotropy, and can be further enhanced by using a rotational orientation method. The complex permeability can be considered as the superposition of two types of magnetic resonance. The resonance peak at high frequency is attributed to the natural resonance, while the peak at low frequency is attributed to the domain-wall resonance. The simulated results of the microwave reflectivity show that the matching thickness, peak frequency, permeability, and permittivity are closely related to the quarter wavelength matching condition. The Fe₅₀Ni₅₀ powder/paraffin composites can be attractive candidates for thinner microwave absorbers in the L-band (1-2 GHz).     

Magnetic moment distributions in a-Fe nanowire array

With the developing requirement of magnetic recording density, perpendicular magnetic re-cording is an important approach and attracts considerable interest[1,2]. In perpendicular magnetic recording technology, it is expected that the preferred direction of magnetization and magnetic moments are perpendicular to the disk, high remanence, high coercivity and small size are also demanded for the magnetic recording elements[3]. Recently, people have electrodeposited mag-netic metal nanowires into…