纳秒激光加工生成硅量子点的发光性质研究

该文报道氧气、氮气或空气等不同氛围中用纳秒脉冲激光在硅基上加工生成量子点结构,发现这些样品在700 nm波长附近均有增强的光致发光(Photoluminescence,PL),且各样品的PL峰很相似;经适当退火处理后,在某些样品上观察到随机受激发光.通过第一性原理计算,发现各种量子点结构表面的成键类型与密度是形成PL发光增强的关键,并由此提出相应的物理模型.     

ns脉冲激光作用下K9玻璃的等离子体谱图研究

建立一套激光等离子体光谱测量实验装置,以Nd：YAG调Q倍频固体激光器为激发光源,作用K9玻璃。通过对K9的等离子体谱图的分析发现,K9玻璃等离子体谱强度的变化与激光器输出能量呈线性关系。同时利用显微镜观察K9玻璃的表面损伤形貌,并进行理论分析。     

Imaging surface structure of purple membrane partly dissolved by CHAPS with atomic force microscope

Atomic force microscope was employed to study the surface structure of purple membrane (PM) using contact mode in liquid. The surface structures of native PM and PM partly dissolved by detergent CHAPS were com- pared. Results show that 6 mmol/L CHAPS could induce some cracks and holes in PM. While Bateriorhodopsin (BR) was still presented as trimers in the two-dimensional hex- agonal structure. We assume that it was caused by the inter- action between CHAPS micellar and PM. Both absorption spectra and flash photolysis kinetic spectra indicated that BR抯 biochemical functions have been changed.     

纳秒激光制备钛表面纹理结构及其润湿性研究

激光加工技术可在材料表面形成多种纹理结构,为了研究激光加工所得不同纹理结构对材料润湿性的影响,通过纳秒激光加工技术在金属钛表面分别加工直线、网格和点阵的表面纹理结构。采用扫描电子显微镜、接触角测量仪、粗糙度分析仪和X射线光电子能谱分别对激光加工后的钛表面进行表面形貌、接触角、粗糙度与化学成分的表征与分析。结果表明:初经激光纹理加工后试样表面的粗糙度较激光加工前均显著提高,但此时3种纹理结构试样表面接触角均小于90°;随着时间的推移,被加工材料表面化学成分的改变带来了材料表面自由能的变化,进而使被加工表面接触角总体呈现上升趋势;待试样表面化学成分稳定后接触角也基本保持不变,并且对于每种纹理结构而言,其接触角随粗糙度的增加而升高。直线、网格和点阵纹理结构试样表面接触角最终可达157.2°,153.1°和134.6°,从而实现了钛表面润湿性由亲水性向疏水性的转变。     

盐生盐杆菌S9营养条件及紫膜分离的初步研究

目的　为获得紫膜,研究了盐生盐杆菌(Halobacteriumhalobium)S9的最适营养条件和紫膜的分离。方法通过该菌的培养特征、不同培养基、细胞色素的测定等,利用正交试验法对NaCl、酪蛋白氨基酸、MgSO4·7H2O和甘油这4个重要因素进行了优化。结果　最适营养和浓度分别是:NaCl200g/L,酪蛋白氨基酸10g/L,MgSO4·7H2O25g/L,甘油10g/L。该菌株在光照条件下,38℃摇瓶培养6d,可用高速冷冻离心、透析袋、蔗糖密度梯度纯化、超速离心等得到紫膜。结论优化了盐生盐杆菌S9的最适营养条件,并确定了所获紫膜的基本性质,可指导用于分子电子器件,今后将继续对其作定量研究。     

Investigation of structural change of purple membrane in storage by transmission electron microscope and atomic force microscope

The structural change of purple membrane during storage has been investigated by means of transmis sion electron microscope and atomic force microscope. It is found that many liposomes have spontaneously evolved from the purple membrane sheets isolated three years ago. The membrane proteins on the liposomes, bacteriorhodopsin, are still presented as trimers in 2-D hexagonal structure, which is the same as that in natural cell membrane. However, the cytoplasmic surface of purple membrane faced outside on the liposomes.     

单脉冲激光热弹超声脉冲特性理论研究

对梯形激光脉冲入射到半无限弱吸收媒质中热弹激发的超声应力脉冲进行了理论研究,给出了媒质表面束缚和自由两种情况下的超声应力脉冲表达式及其理论曲线.分析表明,表面束缚时应力脉冲为单极性,表面自由时为双极性;应力脉冲比激光脉冲宽,其特性受激光脉冲形状的影响.     

室温工作的射频放电激励板条CO激光器

研究了在室温工作下射频放电激励板条CO激光器的工作特性.采用81 MHz的射频放电,利用并联谐振技术获得均匀的射频放电.激光器电极大小为86 mm(宽)×700 mm(长),间距为1.7 mm.激光器谐振腔为输出耦合系数为8%的负支共焦谐振腔.研究了激光器的脉冲工作特性,以及不同脉冲情况下脉冲的时间特性.获得了峰值功率约为600 W的激光输出.测量了激光器输出的光谱特性以及输出功率稳定性.     

Covariance analysis of the Coulomb explosion of ammonia induced by intense nanosecond laser at 532 nm

The Coulomb explosion of ammonia clusters induced by nanosecond laser at 532 nm with an intensity of ～1012 Wcm^-2 has been studied by time of flight mass spectrometry. The dominant multiply charged ions are N^3＋ and N^2＋ with kinetic energies of 110 and 50 eV respectively. The electrons generated from the multiphoton ionization are heated through inverse bremsstrablung by tbe laser field when colliding with neutral or ionic particles. When their energies surpass the corresponding ionization potentials of the molecules or ions, the subsequent electron impact ionization may take place thus resulting in multi-charged nitrogen ions. Covariance analysis is made to study the possible pathways of the Coulomb explosion.     

脉冲激光加热下材料的温度场研究

通过改变多种参数对单脉冲激光加热下材料温度场进行研究.     

Ionization and dissociation of acetonitrile by intense femtosecond laser pulse

Photoionization and photodissociation of CH3CN were studied by a linear time of flight mass spectrometer coupled with 800 nm, 50 fs laser pulses at intensities of 6.3×1013-1.2×1014 W/cm2. The laser power dependences for principal ions CH3CN+, CH2CN+, CHCN+ and CCN+ were measured, which are consistent with the numbers of photons required to produce the ions via multiphoton ionization and dissociation. The results show that eight-photon non-resonant multiphoton ionization is the main photoionization mechanism of the parent ion CH3CN+, while the fragment ions were produced through the dissociation of the molecules in the super-excited states.     

用减压膜蒸馏测定对流传热系数的研究

介绍了应用减压膜蒸馏技术测定膜组件对流传热系数的理论方法, 并通过实验测定了膜组件的对流传热系数。实验结果得到的关联式与Dittus-Boelter方程基本一致。     

Chromosome microdissection by laser microbeam, chromosomal fragment isolation and amplificationin vitro in barley (Hordeum vulgare L.)

A method for microdissection, isolation and amplification of plant chromosomal fragments using laser microbeam and a glass microneedle was established. Firstly, 7H chromosome of barley (Hordeum vulgare L.) was dissected by Nd: YAG laserbeam with suitable parameters and the fragment comprising a satellite was isolated with a glass microneedle which was fixed on a micromanipulator. Then, the chromosomal fragment DNA was amplified by LA_PCR (linker adaptor PCR) for two rounds. The size of the DNA fragments of PCR products varied from 500-3 000 bp and the PCR products originated from the genome of barley were verified by Southern hybridization. Compared with previous reports, there are some advantages in this research. The performance is easier, the dissection is more precise and the cost is low. It also permits efficient amplification with only one single chromosome fragment. Laser microbeam_glass microneedle method may be useful in the microdissection of special chromosome regions, especially in plants with middle or small chromosomes.     

Anisotropy of nickel-based superalloy K418 fabricated by selective laser melting

Selective laser melting (SLM) is a promising additive manufacturing (AM) technology for fabricating the near net-shaped parts by selectively melting and solidifying a thin powder layer with a high-intensity laser beam according to the CAD data for arbitrary components. In this work, Ni-based superalloy K418 samples were fabricated by selective laser melting (SLM). To evaluate the anisotropic mechanical behavior of the SLM processed K418 samples with layer-by-layer melting, the samples were manufactured parallel (transverse specimens) and vertical (longitudinal specimens) to the building direction on the substrate. The microstructural anisotropy analysis was performed by optical microscopy (OM) and scanning electron microscopy (SEM). Electron backscatter diffraction (EBSD) analysis was used to identify their crystallographic preferred orientation (texture) and to correlate the anisotropy of the mechanical strength with the texture of the material. The results showed that the transverse specimens had slightly higher yield strength, but much significantly higher ductility than that of the transverse specimens with the elongated columnar grains along the building direction.     

采用膜生物反应器处理丁基黄药废水

为了寻找经济适用、无二次污染的选矿药剂废水的处理方法,利用膜生物反应器(MBR)技术对较高浓度的丁基黄药模拟废水(简称黄药废水)进行处理研究,分别考察外加C源投加量、水力停留时间、反应温度对MBR去除黄药和COD效果的影响,并探索黄药的生物降解途径.结果表明,最佳的试验条件为外加C源无水乙酸钠的投加质量浓度为0.5 g/L、水力停留时间24 h、反应温度30℃.MBR运行至稳定状态后,出水COD和黄药的去除率分别大于94.0％和99.7％,出水COD的平均质量浓度为91.89 mg/L;出水的黄药质量浓度介于1.048～2.101mg/L之间,达到较好的处理效果.研究结果为浮选药剂废水的生物净化处理提供了理论依据.     

靶衬间距对脉冲激光沉积薄膜均匀性的影响

以国产脉冲激光沉积设备(PLD-Ⅲ型)在玻璃衬底上沉积Ti O2薄膜为例,研究了PLD法制膜过程中靶衬间距对薄膜均匀性的影响.实验过程中,以Ti O2陶瓷片作为靶材,玻璃作为衬底,保持其他工艺条件(如单脉冲能量、脉冲频率、沉积脉冲总数、衬底温度等)不变,专门考察了不同靶衬间距下,Ti O2薄膜在整个衬底台平面区域的沉积分布状况.结果表明,按样品的表观灰度划分,薄膜沉积的相对均匀区可分为2～3个轴对称区域,分别对应不同的沉积速率和厚度;在一定范围内调节靶衬间距(3.00～7.00 cm),可使高速率沉积区逐渐由轴对称的圆环状变为中心大圆斑(直径约2.20 cm).结合PLD沉积原理与靶衬之间的几何关系,分析了导致上述结果的机理.     

脉冲激光处理硅钢片导热方程有限差分解

建立温度场的数学物理模型，采用有限差分法求解材料在脉冲激光热源作用下具有复杂边界条件温度分布，研究激光与材料相互作用的温度时空特性，对于分析材料的热吸收效应和处理硅钢片具有理论和指导意义。