电子式真空阴极弧离子镀引弧器的研制

研制了电子式真空阴极弧离子镀引弧器 ,分析了其工作原理及工作时序 ,给出了它的关键部分的电路 ,介绍了它的离子镀引弧器的性能及特点。     

激光剥离技术制备GaN/metal/Si的结构和光学特性研究

采用激光剥离技术结合金属熔融键合技术将生长在蓝宝石衬底上的GaN外延层转移到Si衬底上.GaN和Si表面分别用电子束蒸发Al/Ti/Au和Ti/Au/In后,在氮气环境下200℃加压实现GaN和Si的键合.采用脉冲宽度30 ns、波长248 nm的准分子脉冲激光透过蓝宝石衬底辐照GaN薄膜,在脉冲激光能量密度为380 mJ/cm2的条件下将蓝宝石衬底剥离下来,实现GaN薄膜向Si衬底的转移.样品截面显微镜和扫描电镜(SEM)照片说明经过键合工艺形成了致密的GaN/Al/Ti/Au/In/Au/Ti/Si结构.对转移衬底后的GaN薄膜进行原子力显微镜(AFM)和光致发光谱(PL)测试,结果表明金属熔融键合和激光剥离工艺没有对GaN薄膜的结构和光学特性带来明显的不利影响.     

Emissivity of rough sea surface for 8-13 num: modeling and verification

The emissivity model for rough sea surface [Remote Sensing Environ. 24, 313-329 (1988)] is inspected in light of the measured surface emissivity. In the presence of moderate wind (5 m/s or less), the emissivity model is found to be adequate for small to moderate view angles. For large view angles, the discrepancy between the computed and the measured emissivity is large, but one can reduce this considerably by incorporating the reflected sea surface emission into the emissivity model. In addition, examination of the spectral variation of the observed and computed emissivity suggests the need for refined measurements of the complex refractive index. An improved model is constructed to calculate the rough sea surface emissivity that can be used to provide accurate estimates of sea surface skin temperatures from remotely sensed radiometric measurements. An important feature of the improved model is that the computed sea surface emissivity is only weakly dependent on wind speed for most view angles used in practice.     

球磨La2Mg17与Ni复合合金的电化学贮氢性能研究

利用机械合金化法制备了La2Mg17+200%(质量分数)Ni复合储氢合金,并对不同球磨时间时合金的微观结构和电化学性能进行研究。结果发现,在球磨过程中Ni粉诱导了La-Mg-Ni非晶/纳米晶结构的形成。XRD和HRTEM结果共同表征了球磨80h时,合金中有Ni金属的存在,且XRD衍射峰强度较低,宽化严重,SAD为宽化的多环,表明形成非晶结构。电化学及其反应动力学测试结果发现,不同球磨时间的电化学反应的动力学控制机理是不同的。球磨60和80h后合金中不仅存在La-Mg-Ni非晶相,同时也有催化剂金属Ni,使合金的表面电荷转移反应电阻较小,氢在合金体相内的扩散系数D和极限电流密度I L均最大,最终导致80h的放电容量为最大值948.3mAh/g。然而,当合金的球磨时间为100和120h时,合金粉化到纳米级,100h的电荷转移反应电阻R ct最大,合金表面电化学反应缓慢,且合金体相内的极限电流密度和氢扩散系数均最小,属于合金电解液表面间的电荷转移和氢向体相内扩散联合控制的过程,必然导致其放电比容量较小。     

Protein crystallization in space

The microgravity environment of space is an ideal place to study the complicated protein crystallization process and to grow good-quality protein crystals. A series of crystal growth experiments of 10 different proteins was carried out in space on a Chinese re-entry satellite FSW-2 in August, 1992. The experiments were performed for about two weeks at a temperature of 18.5 +/- 0.5 degrees C using a tube-like crystallization apparatus made in the Shanghai Institute of Technical Physics, Academia Sinica. More than half of 48 samples from 6 proteins produced crystals, and the effects of microgravity on protein crystal growth were observed, especially for hen-egg white lysozyme and an acidic phospholipase A2 from the venom of Agkistrodon halys Pallas. Analyses of the crystallization of these two enzymes in this mission showed that the microgravity environment in space may be beneficial to improve size, external perfection, morphology, internal order, and nucleation of protein crystals. Some of these positive microgravity effects were also demonstrated by the growth of protein crystals in gelled solution with the above two enzymes. A structural analysis of the tetragonal lysozyme crystal grown in space is in progress.     

Microstructure and photoluminescence studies of Sb-doped SnO2 zigzag nanobelts

SnO2 zigzag nanobelts were successfully Sb-doped by a simple vapor deposition method. Field emission scanning electron microscope (FESEM), high resolution transmission electron microscope (HRTEM), and X-ray diffraction (XRD) were used to characterize these Sb-doped nanobelts. The Sb doping in SnO2 nanobelts was confirmed by Energy Dispersive X-ray spectrum (EDS) and X-ray photoelectron spectroscopy (XPS). It is found that there is no apparent lattice distance difference between the pure SnO2 and the 0.705 at% Sb doped SnO2 nanobelts. A slight blue-shift in the photoluminescence (PL) spectra was shown with the increase of Sb doping concentration and a reasonable explanation was given.     

Piezoelectric and dielectric properties of PZN-BT-PZT solid solutions

Pb(Zn_1/3Nb_2/3)O₃ ceramics with the perovskite structure can be stabilized by substituting 6–7 mol % BaTiO₃ (BT). Piezoelectric and dielectric properties of the pseudo-binary system (1–x)(0.94PZN-0.06BT) -xPb(Zr_(1–y)Ti_y)O₃ were studied, and the effects of Zr/Ti ratios and thermal annealing process on the piezoelectric and dielectric properties were also discussed. The results show that the piezoelectric properties of this ceramic system are very good when x is about 0.50 and y is about 0.47 with K_p = 70%, d₃₃=560 pC/N, _m #x2248;23,000. These ceramics are favorable to piezoelectric actuators.