喷雾干燥法制备LiCoO2超细粉

本文研究了一种新型的制备锂离子电池正极材料的工艺方法通过喷雾干燥法制备出 Ｌｉ Ｃｏ Ｏ２超细粉试验中, 进行了混合粉体的 Ｄ Ｔ Ａ Ｔ Ｇ Ａ 分析; Ｘ Ｒ Ｄ 谱分析显示, 所得 Ｌｉ Ｃｏ Ｏ２ 为具有α Ｎａ Ｆｅ Ｏ２ 层状结构的 Ｈ Ｔ Ｌｉ Ｃｏ Ｏ２ ; 从 Ｓ Ｅ Ｍ 照片可见, Ｌｉ Ｃｏ Ｏ２ 粉末元素分布均匀, 粒径为几百纳米;电化学性能测试结果表明, 其充电容量为１４８ｍ Ａ·ｈｇ , 放电容量为１３５ｍ Ａ·ｈｇ, 具有优良的电化学性能     

SiC-ZrO2(3Y)-Al2O3纳米复相陶瓷的力学性能和显微结构

本文介绍用非均相沉淀方法制备的纳米ＳｉＣ－ＺｒＯ２（３Ｙ）－Ａｌ２Ｏ３复合粉体经放电等离子超快速烧得到晶内型的纳米复相陶瓷,超快速烧结的升温速率为６００℃／ｍｉｎ,在烧结温度不保温,迅即在３ｍｉｎ内冷却至６００℃以下。     

涂布嘴双腔结构理论分析

本文分析涂布嘴双腔结构里的流体压力波动的传播、反射的叠加过程,给出经腔体衰减的流体压力波动比公式。说明合理的双腔结构不仅在宽度方向上,而且在随时间变化上都将使流体压力波动明显衰减,从而平抑涂布嘴出口流体流速波动,提高涂布纵横向均匀性。     

808nm半导体激光器的腔面反射率设计

通过对不同腔长的808nm半导体激光器单管进行P-I测试,提取出了材料内部参数,如内量子效率,内损耗、透明电流密度、模式增益等.根据得出的内部参数进行了腔面反射率设计,分析腔面反射率与功率转换效率的关系,得出了关系曲线.进行腔面镀膜实验,把实验值与计算值相比较,二者相吻合.通过这种腔面反射率设计方法,可以得到半导体激光器的最大功率转换效率,从而使其工作于优化状态下.     

不耦合装药爆炸扩腔机理研究

在大量现场试验的基础上,通过动光弹实验和理论分析,对敞口条件下岩石的爆炸扩腔机理和规律进行了研究.敞口条件下球形偏心不耦合装药爆炸扩腔初始应力场的动光弹研究结果表明:装药结构对围岩中应力波的产生和发展有显著的影响;围岩中的初始应力分布随药包与腔壁间隙的增大而降低;由于药包的偏心作用,围岩中产生的S波较球形耦合装药显著增强;S波的波阵面与爆扩形成的腔体形状有明显的几何相似特性,表明了围岩的破坏主要是S波作用的结果.在对经典敞口爆扩经验公式和现场试验结果进行分析比较的基础上,提出了敞口条件下多次爆扩的剥落扩腔作用机理:认为敞口条件下多次爆扩的腔体扩大是冲击载荷压缩扩腔和二次冲击剥落扩腔共同作用的结果.     

放电等离子超快速烧结SiC-Al2O3纳米复相陶瓷

本文介绍用非均相沉淀法制备的纳米ＳｉＣ－Ａｌ２Ｏ３复合粉体经放电等离子超快速烧结得到晶内型的纳米复相陶瓷,超快速烧结的升温速率为６００℃／ｍｉｎ在烧结温度不保温,迅即在３ｍｉｎ内冷却到６００℃以下。     

650 MHz超导腔的传导冷却结构设计及数值模拟

为了实现仅依靠小型制冷机和热传导方式带走超导腔热量、抛弃复杂的液氦系统,对超导腔的传导冷却结构展开了研究。根据传热要求为650 MHz超导腔初步设计了5种不同的冷却结构,并使用数值模拟软件进行传热仿真,研究了不同的冷却结构、冷却结构的材料和接触热阻等因素对冷却效果的影响。研究结果表明:设计3个冷头比2个冷头更合理,连接冷头和冷环的热桥长度与超导腔的温度近似成线性关系,束管处的热桥有利于截断束管漏热。热桥材料采用高纯铝的冷却效果好于高纯无氧铜,同时热桥与冷环的接触热阻应控制在10 K·cm²/W以下。     

多模式工作激光器的研究

目的:研究一台激光器多种模式工作的特性以及不同模式之间的转换。方法:设计一台双腔钛宝石激光器,采用双光束泵浦方式,通过锁模和光学元件的替换实现激光器的多模式工作。结果:连续运转状态下,两个激光腔的输出为可调谐连续输出;两个激光腔都进行色散补偿时,锁模激光器输出两列飞秒光脉冲;锁模状态下,只有一个激光腔进行色散补偿时,该激光腔输出飞秒光脉冲,而另外一个激光腔没有进行色散补偿,输出皮秒光脉冲。结论:多种模式工作的激光器适用于多种领域的研究与应用。     

连续挤压铜扁排扩展腔及模具的结构优化设计

为了研究扩展腔结构和定径带长度对模具出口处金属流动的影响,从而优化扩展腔及模具的结构,采用有限元数值模拟方法对扩展腔结构参数以及定径带长度进行正交实验,并对挤压过程中模具入口处的金属流速、应变场和温度场进行有限元分析.结果表明:当扩展腔采用中间宽、边部窄的结构时,其模具出口处的金属流速比扩展腔厚度方向更均匀;影响模具出口处金属流速的扩展腔结构参数中,扩展腔中间厚度(H)最为显著,扩展腔中间宽度(l)的影响次之,其两边厚度h的影响较不明显.本实验条件下生产3 mm×100 mm的扁排,扩展腔组合结构的最佳方案如下:扩展腔中间宽度(l)为62 mm,中间出口厚度(H)为38 mm,两侧厚度(h)为24 mm.在其他条件不变的情况下,选择7 mm的定径带不仅有利于金属成形,还有利于提高扁排质量.     

新型CO2分离膜的结构和性能

研制成功一种对ＣＯ２具有促进传递作用的新型膜材料－聚乙烯胺,将此膜材料覆盖在聚砜膜表面复合膜,考察了复合膜的多层结构,复合膜对ＣＯ２、ＣＨ４、Ｎ２等的吸着性能,及复合膜对ＣＯ２和ＣＨ４的分离进透过性能。结果表明,该复合膜对ＣＯ２有很高的吸着量,而对其他测试气体仅有极微弱的吸着;对ＣＯ２／ＣＨ４体系该复合膜具有良好的分离的能力。     

A High Average Power Dye Laser Powered by a Vortex Stabilized Flashlamp

A flashlamp pumped organic dye laser has recently been operated at an average power output of 114 W. This is the highest average power ever reported for a dye laser. The laser was excited by a high power, vortex stabilized flashlamp. In this type of lamp a fast flow of argon gas is injected near the walls. The gas swirls inward and exits through holes in the electrodes. The fast gas flow provides cooling to allow the lamp to operate at high average power and it also stabilizes the position of the discharge. The lamp was used in an elliptical pumping cavity, with the lamp at one focus. The arc length in the lamp was 10 cm. The dye was circulated through a transverse flow channel at the other focus. The lamp was fired at repetition rates up to 357 Hz and with an energy per pulse of 211 J, i.e. an average power of 75 kW. The laser output pulses had a full width at half maximum of 1·8 μ sec. The average power output increased nearly linearly with repetition rate to a maximum of 114 W at 255 Hz. The achievement of even higher powers was limited by the replacement rate of dye in the channel and a drop in the flashlamp intensity at higher repetition rates. The dye used in these experiments was Rhodamine 6G in an ethanol solution.     

High power single mode output CO2 laser

Abstract

While attempting to reach TEMoo single mode high output power, the transverse discharge method was adopted. The optic axis, the direction of glow discharge and gas flow velocity are all mutually orthogonal. The discharge region has a 2.3 liter medium volume, and 100 m/sec gas flow. This small signal gain exceeds 0.8/m in the local region. We also adopted a stable multi‐path cavity for coordinating the larger volume laser medium. Under auxiliary discharge, the maximum output power can reach 1500W, at an efficiency of 9%.     

Polarization states and output powers of a CO(2) laser with an electro-optic phase retarder

We study the power output and polarization state of a CO(2) laser that contains both passive polarization-sensitive elements (Brewster plates) and an active phase-retarding electro-optic modulator (CdTe crystal). The theoretical threshold condition (i.e., the retardation required to extinguish the laser) is obtained from a cavity round-trip Jones matrix. We show that adding extra Brewster plates may be counterproductive in that the required retardation voltage increases. We calculated the output power, which depends on the saturated gain properties of the active media, by iterative modeling, with the elliptically polarized light propagated repeatedly around the cavity. We compare the theory with results from a folded rf-excited waveguide CO(2) laser (Laser Ecosse Model CM3500). Theory and experiment are in fair agreement for low powers. As expected, at high powers there are extra difficulties in modeling the cavity behavior, probably because of distortions induced in and by the crystal.     

Multiple pass unstable resonator for an annular gain CO2 laser

The design, construction, and operational characteristics of an optical resonator for an annular gain media are described. The system, developed for laser power extraction investigations in a new type of coaxial discharge geometry, features a folded multipass unstable resonator concept, fabricated from lightweight uncoated diamond-turned aluminum substrates. The resulting cw CO2 device incorporates excitation aspects of the nonself-sustained PIE excitation process in addition to a new magnetic discharge stabilization technique. Laser performance and output beam characteristics are presented.     

A Numerical Investigation on a c.w. High-power,Electron-beam,Pre-ionized He : N 2 : CO 2 : CO Laser

We studied some kinetic, fluid-dynamic and electrical problems arising in the numerical modelling of a c.w. TE high power CO₂ laser operating with N₂, He and CO additives. We adapted a five-temperature pulsed laser model to the c.w. case by coupling a set of fluid-dynamic equations to the kinetic set. We added the rate equation for the secondary electron density. We calculated in some detail the ionization term and fitted experimental results to determine attachment and recombination coefficients in the discharge chamber. In order to solve our equations a numerical code has been developed. By this means we investigated the effects of temperature, density and velocity variations in the flowing mixture on the small signal gain of the device. We obtained profiles in the laser chamber of the sustainer current, small signal gain and fluid-dynamic parameters. A simple (Fabry-Perot) optical cavity model has been used to calculate output power and electrical efficiency of the device. A comparison of numerical code predictions and experimental results is presented.     

Design improvement of cooling channel layout for plastic injection moulding

The objective of this research is to propose a method for designing cooling channel layouts for plastic injection moulding; optimization techniques have been adopted to simultaneously reduce moulded defects and cooling cycle times. Using the numerical examples of coolant flow in cooling channels, it is found that curved cooling channels along the cavity significantly affect the temperature of the plastic. Moreover, the differences between cooling channels for 2-D and 3-D models are discussed. Furthermore, the cooling channel layout is designed in two stages on the basis of the results from the numerical examples. In the proposed design procedure, the cooling channel layout is determined after taking into consideration the design factors that are significant for maintaining the required plastic temperature.     

Room-temperature sub-diffraction-limited plasmon laser by total internal reflection

Plasmon lasers are a new class of coherent optical amplifiers that generate and sustain light well below its diffraction limit. Their intense, coherent and confined optical fields can enhance significantly light-matter interactions and bring fundamentally new capabilities to bio-sensing, data storage, photolithography and optical communications. However, metallic plasmon laser cavities generally exhibit both high metal and radiation losses, limiting the operation of plasmon lasers to cryogenic temperatures, where sufficient gain can be attained. Here, we present a room-temperature semiconductor sub-diffraction-limited laser by adopting total internal reflection of surface plasmons to mitigate the radiation loss, while using hybrid semiconductor-insulator-metal nanosquares for strong confinement with low metal loss. High cavity quality factors, approaching 100, along with strong λ/20 mode confinement, lead to enhancements of spontaneous emission rate by up to 18-fold. By controlling the structural geometry we reduce the number of cavity modes to achieve single-mode lasing.     

Sensitive absorption spectroscopy by use of an asymmetric multiple-quantum-well diode laser in an external cavity

We have developed a broadly tunable diode laser system by employing custom-designed asymmetric multiple-quantum-well (AMQW) InGaAsP lasers in an external cavity configuration. Feedback is provided by a diffractive optical element with high coupling efficiency and wavelength selectivity, allowing for single-mode tuning of the output wavelength by varying the external cavity length. This tunable laser system was used experimentally to perform absorption spectroscopy on weak CO(2) lines over a broad wavelength region in the near infrared. An experimental tuning range of 80 nm has been observed for a laser cavity length of 600 mum, which is double the tuning range found with conventional, uncoated quantum-well lasers. We achieved a detection sensitivity of 5 x 10(-6) at 95% confidence over the wavelength range of 1.54-1.62 mum by employing a second-harmonic detection technique. The theoretical predictions of a broad gain profile from an ambipolar rate equation model are found to correspond to the experimentally observed increased tunability of the uncoated AMQW lasers.     

Microstructure and Fracture Behavior of 316L Austenitic Stainless Steel Produced by Selective Laser Melting

Selective laser melting is an additive manufacturing method based on local melting of a metal powder bed by a high power laser beam. Fast laser scans are responsible for severe thermal gradients and high cooling rates which produce complex hydrodynamic fluid flow. These phenomena affect crystal growth and orientation and are believed to be the cause of material spattering and microstructural defects, e.g.pores and incompletely melted particles. In this work, the microstructure and texture of 316 L bars built along two different orientations and the effect of different distribution of defects on their mechanical response and failure mechanisms were investigated. Partially molten powder particles are believed to be responsible for the scattering in elongation to failure, reduced strength, and premature failure of vertical samples.