（Ti,Al）N Film on Normalized T8 Carbon Tool Steel Prepared by Pulsed High Energy Density Plasma Technique

Under optimized operating parameters, a hard and wear resistant （Ti,Al）N film is prepared on a normalized T8 carbon tool steel substrate by using pulsed high energy density plasma technique. Microstructure and composition of the film are analysed by x-ray diffraction, x-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning electron microscopy. Hardness profile and tribological properties of the film are tested with nano- indenter and ring-on-ring wear tester, respectively. The tested results show that the microstructure of the film is dense ahd uniform and is mainly composed of （Ti,Al）N and A1N hard phases. A wide transition interface exists between the film and the normalized T8 carbon tool steel substrate. Thickness of the film is about lO00nm and mean hardness value of the film is about 26 GPa. Under dry sliding wear test conditions, relative wear resistance of the （Ti, Al）N film is approximately 9 times higher than that of the hardened T8 carbon tool steel reference sample. Meanwhile, the （Ti,Al）N film has low and stable friction coefficient compared with the hardened T8 carbon tool steel reference sample.     

脉冲放电脱硫反应器中高能电子密度分布的光谱研究

脉冲流光放电产生的大于等于11.2 eV的高能电子能将处于基态的氮分子激发到N₂(C3Π_u)态,测试脉冲流光放电时的N₂(C3Π_u→B3Πg)发射光谱相对强度可以得出脉冲流光放电产生的高能电子的密度。实验在室温常压下研究了空气中线-板式脉冲流光放电脱硫反应器内高能电子密度分布情况,并研究了脉冲电压、反应器的线线间距对反应器内高能电子密度分布的影响。实验结果表明,反应器内的高能电子主要集中在放电线附近高电场区内,随着离放电线的距离增大,高能电子密度减小;脉冲电压对高能电子密度有很大影响,随着电压的升高,高能电子密度基本呈线性增大;线板间距固定,线线间距为线板间距的0.6～1倍时,反应器内高能电子密度分布较为均匀。     

脉冲激光沉淀制备锂电池LiMn_2O_4薄膜技术(英文)

LiMn_2O_4 thin films were deposited by pulsed laser deposition techniques, two types of substrates were used: LaAlO_3 (100) monocrystalline and stainless steel.XRD and SEM results show that the film grown on LaAlO_3 (100) shown very good preferred orienta…     

The Effect of the Ion Assistance Energy on the Electrical Resistivity of Carbon Films Prepared by Pulsed Plasma Deposition in a Nitrogen Atmosphere

Physics of the Solid State - Thin carbon films prepared by pulsed plasma ion-assisted deposition of graphite in an atmosphere of a mixture of argon and nitrogen are studied. The results of...     

The Nonstationary Behaviour of the Electron Current Density in the Weakly Inonized Plasma at High Field Frequencies

Based upon former studies concerning the nonstationary electron kinetics in collision dominated, weakly ionized plasmas the phase delay between the ac electric field component and the resultant ac electron current density has been analysed, theoretically and experimentally, under the specific conditions of a microwave field superimposed to a dc discharge plasma column. The complex plasma conductivity and thus the phase delay has been calculated by solving an appropriate electron kinetic equation. The same quantities have been experimentally determined by using the microwave cavity which operates with different resonator modes. A comprehensive comparison between calculated and measured quantities for different neon discharge plasmas leads to a complete confirmation of the theoretical expectations.     

脉冲激光器输出能量对薄膜损伤阈值测试的影响

薄膜损伤阈值是薄膜抗强激光作用的关键参数，而脉冲激光器的输出能量直接决定了激光薄膜损伤闲值测试结果及其测试精度。激光器的工作电压、频率以及传输距离是影响能量的重要因素。根据脉冲激光器的工作原理，建立了能量与电压、能量与频率和能量与传输距离的数学模型。在激光器工作电压范围内（300～1100V）进行了实验研究，结果表明：不同频率下建立的能量与电压的数学模型不同；同一工作频率下，激光输出能量与电压有两个线性区域；能量稳定性最好的区域其RMS值小于0．025，PV值小于0．07；输出能量随着探测距离的增加而减小。该结果为激光薄膜损伤阂值测试精度的提高提供了可靠的理论依据。     

磁约束电感耦合等离子体增强溅射沉积Co掺杂ZnO薄膜及其光学特性

采用磁约束电感耦合等离子体增强溅射法(ICP-PVD)在Si(100)和石英玻璃衬底上沉积了Zn_0.95Co_0.05O薄膜。XRD谱显示薄膜具有较强的(002)衍射峰,表明Zn_0.95Co_0.05O薄膜为c轴择优取向生长;透过光谱显示Zn_0.95Co_0.05O薄膜具有良好的透过性,其在可见光和红外波段的平均透过率大于80%,吸收光谱表明Co²⁺取代了Zn²⁺处于四配位晶体场中;喇曼光谱证明Zn_0.95Co_0.05O薄膜具有良好的六方纤锌矿结构;室温PL谱测量发现在可见光的蓝光波段和绿光波段存在较宽的发光带,却没有发现本征的近紫外光发射,这是由于Co掺杂后引入较多的缺陷导致的。     

Pulsed Emission of Very High Energy Gamma-Rays From Crab Pulsar

We present here the results of observation of- very high energy(VHE) gamma-ray emission from Crab Pulsar with Beijing Atmospheric Cerenkov Telescopes, named ACT2 and ACT3, for the duration of the fall 1995-spring 1996 season. The data are based on 168 hours (ACT2) and 125 hours (ACT3) of exposure over the period of observation in tracking model. After conversion the event time to the solar barycenter, the data have been searched for evidence of pulsed emission at 33ms period of Crab Pulsar, We found no steady emission of VHE Gamma-ray with 33ms period at the scale of month or night. But there are two evidences of sporadic emission over an hour duration with the same period as the one at radio frequency.     

蟹状星云脉冲星的TeV γ射线周期发射

利用自行研制的两台大气切伦科夫望远镜(ACT2和ACT3),在1995年秋至1996年春的观测季节对蟹状星云脉冲星进行了168小时(ACT2)和126小时(ACT3)的跟踪观测.分析这些数据没有发现有月或天时间尺度稳定的33ms周期的TeVγ射线发射,但发现两段持续几十分钟的暴发样本具有33ms周期.     

Nuclear Level Density at High Spin and Excitation Energy

The intensive studies of equilibrium processes in heavy-ion reaction have produced a need for information on nuclear level densities at high energies and spins. The Fermi gas level density is often used in investigation of heavy-ion reaction studies. Some papers have claimed that nuclear level densities might deviate substantially from the Fermi gas predications at excitations related to heavy-ion reactions. The formulae of calculation of the nuclear level density based on the theory of superconductivity are presented, special attention is paid to the dependence of the level density on the angular momentum. The spin-dependent nuclear level density is evaluated using the pairing interaction. The resulting level density for an average spin of 52 ħ is evaluated for ¹⁵⁵Er and compared with experimental data. Excellent agreement between experiment and theory is obtained.     

核物质对称能的高密行为研究

同位旋物理的主要任务之一是通过放射性核束引起的核反应来探索介质中有效核子-核子相互作用的同位旋依赖性,尤其是同位旋相关的核物质状态方程, 即密度依赖的核物质对称能。由于对称能,尤其是其高密行为,对核物理学和天体物理学具有重要意义,密度依赖的对称能在过去10年一直是中能重离子物理研究领域的主要焦点之一。近年来,低密对称能的研究已经取得了重要进展, 而对称能的高密行为仍然很不确定。在理论方面,人们提出了许多对高密对称能敏感的观测量。 实验方面, 关于对称能高密行为研究的实验计划已经展开,世界各地正在建造的放射性核束装置为对称能的高密行为研究提供了新的机遇。基于IBUU输运模型综述了研究对称能高密行为的一些敏感观测量及其最新进展, 以及所面临的挑战与机遇。One of the major tasks of studying isospin physics via heavy ion collisions with neutron rich nuclei, is to explore the isospin dependence of in medium nuclear effective interactions and the equation of state of neutron rich nuclear matter, i.e., the density dependence of nuclear symmetry energy. Because of its great importance for understanding many phenomena in both nuclear physics and astrophysics, the study of the density dependence of nuclear symmetry energy has been the main focus of the intermediate energy heavy ion physics community during the last decade. Nowadays significant progress has been achieved in studying the low density behavior of nuclear symmetry energy, but the high density behavior of nuclear symmetry energy is still very uncertain. Theoretically, a number of observables have been proposed as sensitive probes to the high density behavior of nuclear symmetry energy. With new opportunities provided by the various radioactive beam facilities being constructed around the world, studies of the high density behavior of nuclear symmetry energy is expected to be one of the main forefront research areas in nuclear physics in the near future. In this report, based on the transport model IBUU we have reviewed the major progress achieved in studying the high density behavior of nuclear symmetry energy and discussed future challenges in this field.     

Microstructure and Properties of Cr3Si/γ-Fe Composite Coating Prepared by Plasma Transferred Arc Cladding Technique

Under optimized operating parameters, a wear and corrosion resistant Cr3 Si/γ-Fe composite coating is fabricated on a normalized 0.45% carbon steel substrate by using the plasma transferred arc （PTA） cladding technique with Fe-Cr-Si elemental powder blend as the precursor material. Mierostructure, microhardness, dry-sliding wear resistance and electrochemical corrosion characteristic of the coating are evaluated. Test results show that the composite coating is mainly composed of primary Cr3Si dendrites and the interdendritic supersaturated iron-base solid solution γ-Fe. Between the Cr3Si/γ-Fe composite coating and the normalized 0.45% carbon steel substrate, there is a narrow metallurgical bonding zone. The Cr3Si/γ-Fe composite coating exhibits high microhardness, excellent wear and corrosion resistance under test conditions.     

Prediction of Superhard BN_2 with High Energy Density

Considering that pressure-induced formation of short,strong covalent bonds in light-element compounds can produce superhard materials,we employ structure searching and first-principles calculations to predict a new class of boron nitrides with a stoichiometry of BN₂,which are stable relative to alpha-B and alpha-N₂ at ambient pressure.At ambient pressure,the most stable phase has a layered structure(h-BN₂) containing hexagonal BN layers between which there are intercalated N₂ molecules.At 25 GPa,a three-dimensional P4₂/mmc structure with single N-N bonds becomes the most stable.Dynamical,thermal,and mechanical stability calculations reveal that this structure can be recovered under ambient conditions.Its calculated stress-strain relations demonstrate an intrinsic superhard nature with an estimated Vickers hardness of ~43 GPa.This structure has a potentially high energy density of ~4.19 kJ/g.     

激光制备类金刚石膜技术研究

现有技术制备的类金刚石(DLC)膜由于含氢、硬度低、内应力大、附着力差等特点,严重限制了其光学工程应用.激光法是近年发展的一种制备DLC膜的新方法,相比其他制备方法具有诸多优点.综合分析了激光制备DLC膜过程中,激光波长、脉宽、功率密度、衬底温度和偏压等因素对薄膜质量的影响规律.采用氧气氛辅助沉积、元素掺杂和双波长激光...     

Microstructure evolution of WC/steel composite by laser surface re-melting

WC/steel composites fabricated by electro-slag melting and casting were re-melted by transverse flow CO₂ laser. Optical microscopy, scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction and transmission electron microscopy were used to analyze the microstructure evolution in laser melted layer. It was found that the laser-affected zone has three distinguished zones, the melted, transient and heat affected zone. The phases of the melted zone were composed of WC, Fe₃W₃C, (Cr,Fe)₇C₃, martensite and retained austenite. The microstructure evolution in the melted zone was represented by the transformation of three parts including the steel matrix, WC particles cluster and dispersed carbides. A significant reactant was herringbone eutectic carbide of Fe₃W₃C. The effect of laser scanning rate was mainly behaved in affecting the melt depth, microstructure of transient zone and dissolution of medium carbides. In comparison with the substrate, the melted zone has much higher microhardness.     

飞秒脉冲激光沉积钕掺杂薄膜特性研究

采用脉冲激光沉积(PLD)技术在Si(100)衬底上生长了Nd∶YAG薄膜以及Nd∶Glass薄膜,利用扫描电子显微镜(SEM)、能谱仪(EDS)、傅里叶变换红外光谱仪(FTIR)、光学掺量振荡器(OPO)以及光栅光谱仪等测试装置分析了薄膜的表面和断面结构形貌、组成成分、光学吸收谱以及光致发光谱。结果表明：在室温衬底温度下生长的Nd∶YAG薄膜以及Nd∶Glass薄膜均呈无规则非定型结构,没有明显的取向性微晶生长;PLD生长的Nd∶YAG薄膜中存在0.15 at.%化学计量比的Nd元素;Nd∶YAG块体靶材在750和808 nm有两个明显的吸收峰,而薄膜没有明显的吸收峰;Nd∶YAG薄膜在808 nm波长泵浦光下没有明显的光致发光谱峰,而Nd∶Glass薄膜在877和1 064 nm波长处有明显的光致发光谱峰。说明在室温衬底温度下生长的Nd∶Glass薄膜中Nd元素以Nd3+光学活性离子形式掺杂进玻璃基质中,而Nd∶YAG薄膜中的Nd元素没有以Nd3+光学活性离子形式掺杂进YAG基质中。