国产金属箔式应变片在低温和强磁场下工作特性的研究

HT- 7U超导模型线圈实验中 ,研究了国产金属箔式应变片在低温和强磁场下的工作特性 ;测量了应变片从室温液氮温度液氦温度的输出示应变曲线 ,以及磁场强度从 0 T- 4T时应变片的输出示应变曲线。实验测得 ,对所选用的应变片 ,从室温降至液氮温度 (77.4K)的热输出为 - 3 6 4 7με,降至液氦温度 (4.2 K)的热输出为 - 3 999με,磁场从 0 T升至 4T的输出示应变为2 3 5με。     

Magnetic Properties and magnetic phase diagrams of intermetallic compound GdMn2Ge2

A modified Yafet－Kittle model is applied to investigate the magnetic properties and magnetic phase transition of the intermetallic compound GdMn_2Ge_2. Theoretical analysis and calculation show that there are five possible magnetic structures in GdMn_2Ge_2. Variations of external magnetic field and temperature give rise to the first-order or second-order magnetic transitions from one phase to another. Based on this model, the magnetic curves of GdMn_2Ge_2 single crystals at different temperatures are calculated and a good agreement with experimental data has obtained. Based on the calculation, the H－T magnetic phase diagrams of GdMn_2Ge_2 are depicted. The Gd－Gd, Gd－Mn, intralayer Mn－Mn and interlayer Mn－Mn exchange coupling parameters are estimated. It is shown that, in order to describe the magnetic properties of GdMn_2Ge_2, the lattice constant and temperature dependence of interlayer Mn－Mn exchange interaction must be taken into account.     

A Photonic Bandgap Filter Using Metallic Hilbert Curves

We theoretically suggest that a metallic plate with Hilbert curves can possesses multiple resonances in a linear scale, leading to multiple stop bands and pass bands for electromagnetic waves over a wide frequency range.The forward transmission from a line source nearby a small plate covered by four cells with Hilbert curves is checked by a probe at the far field, the results agree well with the multiple resonance frequencies calculated by the plane wave incidence under a periodic boundary condition, the return loss spectra show that radiations of a line antenna working at 4.5 GHz can be greatly enhanced, which results from the interaction of the antenna and the subwavelength metallic plate. This kind of metallic pattern is very practical in multi-frequency functioned wave devices with sub-wavelength sizes.     

Pd-Si Binary Bulk Metallic Glass Prepared at Low Cooling Rate

We report that binary bulk metallic glasses can be made up to 6ram in diameter in a Pd Si ahoy system by air cooling at slow cooling rate (about 8 K/s). The high stability of the undercooled liquid and the large glass-forming ability (GFA) of the binary alloy are contributed to the removing of heterogeneous impurities in the alloy melt by employing the fluxing technique. It has been found that decreasing cooling rate can increase the supercooled liquid region and thermal stability of the glassy alloy. After fluxing, a wider supercooled liquid region (△T = 58 K) and higher glass-forming ability have been obtained in a Pd81Si19 binary glassy alloy prepared by slow cooling rate.     

Variable Energy Positron Annihilation Spectroscopy of GaN Grown on Sapphire Substrates with MOCVD

Depth profiled Doppler broadening of positron annihilation spectroscopy (DBPAS), which is also called the variable energy positron annihilation spectroscopy (VEPAS), is used in characterization of GaN grown on sapphire substrates with metal-organic chemical vapour deposition (MOCVD). The GaN film and the film/substrate interface are investigated. The VEPFIT (variable energy positron fit) software was used for analysing the data,and the positron diffusion length of the sapphire is obtained. The results suggest that there is a highly defected region near the GaN/sapphire interface. This thin dislocated region is generated at the film/substrate interface to relieve the strain. Effects of implantation dose on defect formation, for the GaN/Sapphire samples, which implanted by Al^ ions, are also investigated. Studies on AI implanted GaN films (not including the interface and sapphire) have revealed that there are two different regions of implantation damage. For the low Al^ implantation dose samples, in the region close to the surface, defects are mainly composed of vacancy pairs with small amount of vacancy clusters, and in the interior region of the film the positron traps are vacancy clusters without micro-voids. For the highest dose sample, however, some positron trap centres are in the form of micro-voids in the second region.     

离子束技术在金属中氦行为研究中的应用

结合我们近期的研究工作，本文介绍和讨论了离子束技术在金属中氦行为研究中的应用，还介绍和讨论了氦在金属中的基本特性，如氦的捕获、迁移和氦泡结构等．     

Zr基金属玻璃电子输运性质的研究

在4—300K 的温度区间内,测量了金属玻璃 Zr_(100-x)Co_x(x=22,28,33.2)和Zr_(66.7)M_(33.3)(M=Fe,Ni,Cu)的电阻温度关系.实验指出,这两组典型的 Zr 基金属玻璃的电子输运性质,有着共同的规律性.分析表明,在10K80K 时,这种规律与现有的理论有较大的偏离,对这种偏离出现的可能起因作了讨论.