小焦斑纳秒激光烧蚀铝平面靶的数值研究

用二维辐射流体程序Flash模拟了小焦斑纳秒激光与铝平面靶的相互作用过程,其中入射激光的聚焦半径为25μm,峰值强度约为1013 W/cm2,波长为532nm。模拟发现激光通道上的等离子体出现了密度排空的现象,激光焦斑外侧出现环状的射流结构。激光通道上密度排空现象对电子热输运的计算较为敏感,对比干涉实验测量的密度分布,确定了模拟中限流因子的取值为0.08。通过考察辐射致冷与电子横向热输运对等离子体膨胀运动的影响,对环状射流结构的形成原因给出了物理解释,并在模拟上验证了辐射冷却在其形成过程中的主导作用。     

Self-compliance multilevel storage characteristic in HfO_2-based device

In this paper, the self-compliance bipolar resistive switching characteristic of an HfO_2-based memory device with Ag/HfO_2/Au structure for multilevel storage is investigated. By applying a positive voltage, the dual-step set processes corresponding to three stable resistance states are observed in the device. The multilevel switching characteristics can still be observed after 48 hours. In addition, the resistance values of all the three states show negligible degradation over 104 s,which may be useful for the applications in nonvolatile multilevel storage.     

2 μm mode-locking laser performances of sol-gel-fabricated large-core Tm-doped silica fiber

High-power ultrafast fiber lasers operating at the 2 μm wavelength are extremely desirable for material processing, laser surgery, and nonlinear optics. Here we fabricated large-core(LC) double-cladding Tm-doped silica fiber via the sol-gel method. The sol-gel-fabricated Tm-doped silica(SGTS) fiber had a large core diameter of 30 μm with a high refractive index homogeneity(Δn=2 × 10~(-4)). With the newly developed LC SGTS fiber as the gain fiber, high-power mode-locking was realized. By using a semiconductor saturable absorber mirror(SESAM) as a mode locker, the LC SGTS fiber oscillator generated mode-locked pulses with an average output power as high as 1.0 W and a pulse duration of 23.9 ps at the wavelength of 1955.0 nm. Our research results show that the self-developed LC Tm-doped silica fiber via the sol-gel method is a promising gain fiber for generating high-power ultrafast lasers in the 2 μm spectral region.     

Experimental Identification and Study of Coloured Conical Emission in Quadratic Nonlinear Media

We have explicitly identified coloured conical emission （CCE） and noncollinear optical parametric generation （OPC） by spectrum characterizations. With an experimental setup providing different pump pulse durations, CCE and noncollinear OPG are observed both alternatively and simultaneously. Comparisons between CCE and noncollinear OPC are studied. Accumulation behaviour of modulational instabilities is observed in our two-crystal cascaded configuration, which results in enhancement or depression of the CCE formation.     

神光-ⅡU装置的SBS背向散射角分辨诊断系统

针对双锥对撞点火方案实验中的受激布里渊散射过程,发展了一套门控角分辨全口径背向散射诊断系统。设计了光纤阵列,对神光-ⅡU装置打靶伺服反射镜上的散射信号进行收集,利用其时间特性,通过相对测量的方式,获得了角分辨的背向受激布里渊散射能量份额,发现其角分布敏感依赖于激光在球壳表面的辐照模式,为深入研究双锥对撞点火方案中的受激布里渊散射过程提供了可靠的实验结果。     

高岭石/甲酰胺插层的Raman和DRIFT光谱

用Raman和漫反射红外光谱研究高岭石/甲酰胺插层反应机理及插层作用对高岭石微结构的影响.     

硅藻土表面羟基的漫反射红外光谱(DRIFT)研究

运用傅里叶变换漫反射红外光谱（DRIFT）及氘化技术,研究了硅藻土的表面羟基结构及其在热处理中的变化。     

碳含量对Y-Ni-B-C超导相的形成与临界温度的影响

报道ThCr₂Si₂型结构的四元金属间化合物Y₂Ni₂B₂C_x的形成与超导电性.当碳配比含量x=0.9—1.2时,电弧熔炼的合金结晶为较好的YNi₂B₂C单相.当x＜0.8或x＞1.2时,合金中虽仍以YNi₂B₂C为主相,但杂相明显增加.超导转变温度T_c随碳含量增加明显分为两个台阶.x≤0.8时,T_c约为12.5K;x≥0.9时,T_c约为15K. 关键词：     

温和条件下 Cu-Zn/Al2O3 催化剂上酯加氢制醇

 制备了新型无铬非晶态 Al2O3 负载的 Cu-Zn 催化剂, 并采用 X 射线衍射、透射电镜、程序升温还原和红外光谱进行了表征, 考察了其液相酯加氢制高碳醇的催化性能, 并优化了反应条件. 结果表明, 在 240 °C 和 10 MPa 氢压相对温和的反应条件下, 髙碳醇收率达 86.3%, 远远高于相同条件下传统的 Cu-Cr 基催化剂. 对前体、焙烧后及还原后催化剂的物相进行了研究, 探讨了催化剂组分及表面羟基的作用.     

焙烧温度对酯加氢制醇Cu-Al-Ba催化剂性能的影响(英文)

通过共沉淀法在不同焙烧温度下制备了新型无铬Cu-Al-Ba催化剂.测试了其在高压釜中将棕榈油甲酯加氢制备高碳醇的反应性能.结果表明催化剂的焙烧温度对催化性能有较大影响.在从150℃升至750℃的过程中,高碳醇的收率显示了三个阶段的变化,相应地,催化剂前驱体的热重(TG-DTG)曲线也显示了三个阶段的失重.X射线衍射(XRD)、X射线荧光(XRF),透射电镜-能谱分析-选区电子衍射(TEM-EDS-SAED)、N2物理吸附和程序升温还原(TPR)表征表明,催化剂是由一种孔雀石-勃石-碳酸钡前驱体制得的.在300或550℃焙烧后,催化剂组成为晶态的CuO、BaCO3和非晶态的Al2O3.其中,非晶态的Al2O3为CuO的高分散提供了大的比表面,杆状的BaCO3组分有利于提供微孔结构.在更高的焙烧温度750℃,新物相BaAl2O4的形成破坏了催化剂中的非晶态结构,导致其比表面积和孔容的急剧下降,并引起CuO物种的聚结.550℃焙烧的催化剂显示了最高的高碳醇收率,达到92.3%,这归因于其大的比表面积、大孔容和较高的CuO分散性.