Compact high-power TEA N(2) laser

A modification is adopted in the conventional Blumlein excitation system for realizing a simple and compact TEA N(2) laser. Super-radiant laser pulses of approximately 1.0 MW peak power, approximately 0.6 ns duration, and approximately 1.0 mrad divergence have been achieved.     

A compact frequency-stabilized pulse-periodic waveguide CO2 laser for calibration of wavelength meters

A compact pulse-periodic waveguide CO₂ laser with high-frequency excitation with automatic assignment of the 10P (14) line and stabilization of the emission frequency in the middle of this line using a sealed-off optoacoustic cell, which is filled with a mixture of C₂H₄ (0.1%) and nitrogen, was developed. It is shown that the laser-frequency instability is within 3 MHz, thus meeting the requirements that are imposed on the calibration tools for high-resolution wavelength meters that are similar to WS-6IR.     

氧化锆纳微米复合陶瓷材料的性能及显微结构研究

用热压烧结制备ZrO2/[Ti(C,N)/Al2O3]纳微米复合材料.用扫描电镜观察其断口形貌和微观结构.分析纳米四方氧化锆(ZrO2)多晶陶瓷含量对复合材料力学性能的影响.结果表明:当ZrO2体积含量为10%时,其抗弯强度和断裂韧性分别高达625MPa和8.58MPa·m1/2.     

射频激励板条波导CO2激光器远场空间压缩单峰输出模式的研究

从研究射频激励板条波导CO₂激光器远场压窄单峰的理论成因出发,根据实验现象,通过理论分析和数值计算得出宽波导平平腔自再现模,这种自再现模式与无波导壁时不同,其近场具有复杂分布,理论分析表明求出这种模式的远场是压窄单峰强度分布,实验结果证实了这种模式的存在.     

基于微波烧结的Ti(C,N)/Al_2O_3金属陶瓷刀具切削淬硬钢的试验研究

利用微波烧结技术制备了Ti(C,N)/Al_2O_3金属陶瓷刀具(TA),并通过高速干式切削淬硬钢40Cr(50±2HRC)研究刀具的切削性能,同时与硬质合金刀具YT15进行对比。采用正交试验和极差分析法,以切削参数为优化对象,以工件金属去除率、表面粗糙度和刀具寿命为优化目标,确定了刀具的最佳切削用量。试验结果表明,切削淬硬钢40Cr时,刀具TA的最优切削参数为v=120m/min、a_p=0.3mm、f=0.1mm/r。TA刀具的切削时间为66min,比YT15提高了175%。工件平均表面粗糙度为1.27μm,比硬质合金刀具降低了15.9%。刀具的切削性能优于硬质合金刀具,并且可以实现以车代磨。     

A disk RF-excited CO2 laser

The design and performance characteristics of a CO₂ laser with radio frequency discharge excitation and a radiator in the form of a flat disk are described. A hybrid unstable-stable resonator is used in the laser.     

可调谐声光调Q CO2激光器

摘要：利用调Q脉冲激光器速率方程计算了自行设计的声光调Q小型CO2激光器的主要技术参数,分析了影响声光调Q CO2激光器输出的主要因素,提出了优化设计的途径和方法,实验结果与理论计算基本一致。经优化设计的激光器脉冲重复频率达1Hz～50kHz, 1kHz时在获得脉宽180ns,峰值功率4062w的激光输出,并利用光栅实现了激光输出波长的连续调谐,波长调谐范围9.2μm～10.8μm,该激光器在激光测距、环境探测及空间通讯等领域具有广泛的用途。     

High-power CO(2) laser-beam monitor

A diagnostic system for measuring the beam power and quality of a high-power cw CO(2) electro-aerodynamic laser is described. A ZnSe beamsplitter was employed to split off a small fraction (0.5%) of the main laser beam for diagnostic purposes. The low-power beam was split again to provide two beams for power and energy-distribution measurements, concurrent with sample irradiation by the main beam. An electrically calibrated disk calorimeter was used to measure beam power. The temporal and spatial energy distributions were measured by means of a mechanically scanned, one-dimensional pyroelectric array. This provided a 16x16 element two-dimensional map of the beam profile at a rate of up to 10 Hz.     

CO2 laser cutting of stained glass

This paper covers the CO₂ laser cutting of stained glass using a Ferranti MF400 CNC laser cutting machine. The report examines the various laser cutting parameters required to generate a cut surface in glass which will require minimal post-treatment to be carried out, and also investigates the degree of geometrical intricacy that can be attempted, together with the associated limitations, in cutting 2D glass components. The experimental procedure used to obtain the necessary information for a preliminary database on the laser cutting of stained glass is also detailed. Finally, the implications and applications of the investigative work are examined for commercial situations through construction of a simple 2D test artefact.Notation f pulse frequency (Hz) - k thermal conductivity (W/mK) - P laser beam power (W) - Pl pulse duration (10^–5 s) - Pr pulse ratio - Ps pulse separation (10^–5 s) - P shield gas pressure (bar) - R _a surface roughness (m) - t _s substrate thickness (mm) - V cutting speed (mm/min) - V _opt optimum cutting speed (mm/min) - w kcrf width (mm) - angle of deviation (deg.) - wavelength (m) - d perforation depth (mm)     

不同Al2O3含量ZrO2(3Y)/Al2O3纳米复合粉体的制备与表征

采用化学共沉淀法制备了Al2O3数量分数为0%～30%的ZrO2(3Y)/Al2O3纳米复合粉体,研究了Al2O3含量和煅烧温度对粉体相结构、晶粒尺寸和晶格畸变的影响.结果表明800℃×2 h煅烧的复合粉体只出现t-ZrO2相,不出现Al2O3的任何晶相;Al2O3的添加抑制了ZrO2(3Y)晶粒的增长和四方相向单斜相的结构相变,使相变温度显著提高,晶格畸变增大.     

Field emission from multiwall carbon nanotubes in controlled ambient gases,H2, CO,N2 and O2

Adsorption and desorption on clean pentagons at a tip of multiwall carbon nanotube (MWNT) have been investigated by field emission microscopy (FEM) in an atmosphere of various gases, i.e., hydrogen, carbon monoxide, nitrogen and oxygen. A MWNT with clean surface which is obtained by heat treatment gives FEM patterns consisting of six bright pentagonal rings. Adsorbates are recognized as bright spots in the FEM pattern. They reside preferentially on the pentagonal sites where the strong electric field is concentrated, and bring about stepwise increase in the emission current. Heat treatment of the MWNT emitter at about 1300K allows adsorbates to desorb. After the desorption of hydrogen and nitrogen, the original clean surface with pentagons is recovered, while the tip structure is destroyed after the desorption of oxygen.     

Novel electrode adaptation for N2 lasers

A novel electrode design is described and its performance is indicated.     

Compact CO2 laser for infrared heterodyne radar

A compact CO(2) laser has been developed for field use as part of an infrared heterodyne radar. The laser, which contains a separate local oscillator, transmits 10.5 W cw or 7 W average in the electrooptically Q-switched mode at a repetition rate of 50 kHz. The applicability of this laser to active imaging is discussed.     

CO2 laser welding of zinc-coated steel sheets

Welding of zinc-coated steel sheets for the automotive industry has been investigated experimentally and theoretically, using a continuous wave 2 kW CO₂ laser. The specimens of 0.8, 1.0 and 1.2 mm thickness were welded as butt joint and lap joint. Argon gas was shielded co-axially to reduce the plasma and to protect the molten, pool from atmosphere. The mechanical tests of specimens were carried out to investigate the ductility of welds in butt joint and lap joint, using the Erichsen test, ball punch test and tensile shear test. The value of transverse weld pattern is higher than others. The fatigue life of longitudinal weld is superior, but that of circular weld pattern is inferior due to the high tensile residual stresses in the weld. The maximum Erichsen value was obtained as 96% and the deformability of zinc coated steel butt-welded was found to be 80% in the ball punch test. The high pressure formed by vaporization of zinc with the low boiling temperature during laser lap-joint welding splattered the molten pool and created porosities in the weld. The optimum gap was calculated to be 0.1 mm in the lap joint welding of zinc-coated steel sheet which was a good agreement with the experimental result.     

Annular dark-field image simulation of the YBa2Cu3O(7-delta)/BaF2 interface

Scanning transmission electron microscope (STEM) images of the interface of a YBa2Cu3O(7-delta) (YBCO)/BaF2 thin film bilayer show a relatively wide (approximately 40 A) contrasting band at the interface when viewed edge-on. Simulation of annular dark-field (ADF) images of this interface reveal that a significant contribution to this wide band of contrast is due to strain from dislocations oriented perpendicular to the incident beam direction and this contrast cannot be explained using solely a Z-contrast interpretation of ADF images. We believe that these are the first such calculations which predict that the presence of a misfit dislocation network can contribute a significant amount of contrast to cross-section ADF images of an interface.     

CO2 laser pulse shortening by laser ablation of a metal target

A repeatable and flexible technique for pulse shortening of laser pulses has been applied to transversely excited atmospheric (TEA) CO(2) laser pulses. The technique involves focusing the laser output onto a highly reflective metal target so that plasma is formed, which then operates as a shutter due to strong laser absorption and scattering. Precise control of the focused laser intensity allows for timing of the shutter so that different temporal portions of the pulse can be reflected from the target surface before plasma formation occurs. This type of shutter enables one to reduce the pulse duration down to ~2 ns and to remove the low power, long duration tails that are present in TEA CO(2) pulses. The transmitted energy is reduced as the pulse duration is decreased but the reflected power is ~10 MW for all pulse durations. A simple laser heating model verifies that the pulse shortening depends directly on the plasma formation time, which in turn is dependent on the applied laser intensity. It is envisaged that this plasma shutter will be used as a tool for pulse shaping in the search for laser pulse conditions to optimize conversion efficiency from laser energy to useable extreme ultraviolet (EUV) radiation for EUV source development.     

Process parameters selection for laser polishing DF2 (AISI O1) by Nd:YAG pulsed laser using orthogonal design

Mechanisms of laser polishing metals in a continuous scanning mode, as envisaged and analyzed in this paper, are rather complex, and experimental optimization of laser polishing metallic material is very time-consuming and difficult. Aiming at shortening the experimental time in achieving a better surface finishing of DF2 (AISI 01) tool steel by pulse Nd:YAG laser, we used the orthogonal experimental design for selecting the laser operational parameters. The results showed that the orthogonal design (OD) allowed the optimum technological parameters for the laser polishing to be obtained quickly and effectively. According to the OD analysis and experimental data, the attainable optimum laser smoothening/polishing parameters from this study are pulse energy (P)?=?1?J, feed rate?=?300–400?mm/min, pulse duration?=?3?ms, and pulse frequency (f)?=?20–25?Hz. The work in this paper demonstrates the relative superiority of orthogonal design in saving experimental times and providing good laser polishing surface in surface texturing and the smoothening process.     

Al2O3短纤维增强铝基复合材料的抗拉强度及影响因素

用挤压铸造法制备了Al2O3短纤维增强不同成分的铝基复合材料,测定了它们的抗拉强度.用SEM、TEM等观察了复合材料的断裂过程与界面状态.结果表明,复合材料中存在纤维断裂型、界面脱粘型与纤维断裂+界面脱粘混合型三种断裂类型.三种断裂类型对应三种不同的界面状态轻微反应型、细小化合物析出型和粗大化合物析出型.在此基础上分析了基体成分与断裂机制、界面及强度间的关系.     

Al2O3(sf)／Al-5．3Cu复合材料断裂过程与界面

利用ＳＥＭ拉抻装置对Ａｌ２Ｏ３（ｓｆ）Ａｌ－５．３Ｃｕ复合材料微观断裂过程进行了原位观察,并用ＴＥＭ分析了该复合材料的界面状况。研究表明：复合材料的断裂是一种复合断裂机制,界面存在ＣｕＡｌ２化合物。提出了判断合金元素对界面影响的分析方法。     

金属/陶瓷复合材料的原位合成及其结构研究

以铝镁合金、高纯石英棒为原料，采用原位合成法在1473K氮气氛下保温2h制备了Al（Si）／AlN／MgAl2O4复合材料。采用XRD、SEM和EDX等方法分析了所得材料的相组成与显微结构。结果表明：复合材料的物相为MgAl2O4、Al-Si、AlN、Mg2Si和Si；在铝与SiO2界面上形成的Al2O3与基体合金中的镁反应生成块状的MgAl2O4尖晶石晶体，在复合材料内部发现均匀分布的AlN晶须，部分氧、铝、镁、铁形成化合物与硅一起均匀弥散分布于复合材料中。