PDC材料烧结过程中钴在金刚石层中的扩散熔渗迁移机制

 讨论了PDC材料烧结过程中钴在金刚石层中的固相扩散、钴液熔渗、两次钴高浓度峰的“波浪”式迁移过程中的运动规律及其作用机制,并根据实验观测的数据进行了有关计算。结果表明：在5.8 GPa、1 300 ℃条件下,钴的扩散系数D≈1.6×10^-7 cm²/s,是一般常压及相同温度条件下钴固相扩散系数（3×10^-10 cm²/s）和相同压力条件下钴的液相扩散系数（5×10^-5 cm²/s）的中间值;对于粒度W≥10 μm的金刚石烧结体系,钴液熔渗作用时间非常短暂,略大于0.5 s,而对于W≤1 μm的超细金刚石烧结体系而言,钴熔渗作用时间为28 s,比粒度W≥10 μm的金刚石烧结要长得多;两次钴高浓度峰的迁移速度分别约为50 μm/s和100 μm/s。     

激光产生蒸汽羽的干涉研究

 根据拍摄1.06 μm长脉冲钕玻璃激光与LY12铝靶耦合产生蒸汽羽的干涉分幅照片，测出在t<50 μs空气冲击波速度约为473 m/s而蒸汽羽阵面扩散速度约为162 m/s。运用蒸汽羽等离子体的有关热力学特性方程组，得到蒸汽羽等离子体的电子密度、电子温度、电离度和吸收系数的最大值分别为N_e≈3.1×10¹⁷ cm^-1，T≈6 096 K，η≈0.014，α_(1.06μm)≈0.03 cm^-1的结果。     

SiC1-xGex/SiC 异质结光电二极管特性的研究

使用二维器件模拟软件Medici, 对SiC_1-xGe_x/SiC异质结的光电特性进行了模拟.设计了N型重掺杂SiC层的厚度为1 μm, P型轻掺杂SiC_1-xGe_x层厚为0.4 μm, 二者之间形成突变异质结.在反向偏压3 V、光强度为 0.23 W/cm²的条件下, p-n+ SiC_0.8Ge_0.2/SiC和p-n+ SiC_0.7Ge_0.3/SiC敏感波长λ分别可以达到0.64 μm和0.7 μm, 光电流分别为7.765×10^－7 A/μm和7.438×10^－7 A/μm; 为了进一步提高SiC_1-xGe_x/SiC 异质结的光电流, 我们把p-n+两层结构改进为p-i-n三层结构.在同样的偏压、光照条件下, p-i-n SiC_0.8Ge_0.2/SiC和p-i-n SiC_0.7Ge_0.3/SiC的光电流分别达到1.6734×10－6 A/μm和1.844×10－6 A/μm.     

强激光辐照下纯铝的力学响应和层裂的实验测量与分析

 采用速度干涉（VISAR）测试技术,对强激光辐照下纯铝的动态力学响应和层裂特性进行了实验测量和分析。样品厚度分别为200 μm 和485 μm,激光脉冲的半高宽约为10 ns,功率密度变化范围为10¹⁰~10¹¹ W·cm^-2。实测了样品自由面速度波形,反映了强激光加载作用下材料损伤演化过程以及损伤对材料动态响应的影响。计算得到了冲击波强度(2.0~13.4 GPa) 和不同拉伸应变率下铝的层裂强度(1.6~2.3 GPa)。在所采用的实验条件和1维近似下,激光辐照产生的冲击波强度与激光功率密度之间成线性关系。最后讨论了层裂强度与拉伸应变率之间的关系,显示层裂强度随着拉伸应变率的增加而增大。     

利用侧向阴影照相技术探测靶的飞行速度

 建立起一套侧向阴影照相的光学系统,利用可见光作为探测光,在状态方程实验中对靶的飞行速度进行探测。在天光KrF准分子激光装置上进行激光打靶实验,激光波长为248.4 nm。在激光功率密度为8.3×10¹¹ W/cm²的条件下,测得50 μm厚铝靶的飞行速度为3.28 km/s;在激光功率密度为4.7×1010¹¹ W/cm²的条件下,测得带100 μm厚烧蚀层的13 μm厚铝靶的飞行速度为2.52 km/s。最后进行了误差分析计算,实验中探测激光与靶表面偏离角度最大不会超过2.06°,偏离角对实验精度产生的影响可以被忽略。     

延迟质子先驱核33Ar、49Fe的实验研究

用65 MeV的¹²C束轰击²⁴Mg、⁴⁰Ca靶, 通过(¹²C, 3n)反应, 产生了延迟质子先驱核³³Ar及⁴⁹Fe, 观测了它们的β⁺延迟质子谱, 其主峰能量分别在3.28±0.07 MeV与1.98±0.04 MeV, 截面分别为0.4±0.08 μb与0.7±0.14 μb, 测得³³Ar的半衰期为167±24 ms.     

能量为6×1014~5×1016eV的宇宙线能谱研究

1982年, 作者在悉尼大学对能量为6×10¹⁴~5×10¹⁶eV的高能宇宙线的能谱进行了实验研究. 实验采用了快速、高效率的电子仪器, 并用电子计算机进行控制, 实现了高度自动化. 研究结果表明, 初级宇宙线的积分能谱可表示为I=K.(E/E₀)^－γ, 式中γ的数值在能量E为3×10¹⁵eV附近由1.15±0.04改变为1.19±0.08.     

电子束辐照圆环靶产生动态应变的实验研究

 动态应变是电子束辐照靶结构产生结构响应中的一个重要力学参数。本文叙述了近年来我们在“闪光二号”装置上进行电子束辐照圆环靶产生动态应变的实验研究。靶材为LY-12铝,靶厚为2.5~3 mm,靶上能通量为50~60 J/cm²。实验结果表明,在圆环受照部分内表面中心处应变值可达1.6×10⁴ με,而在圆环两侧内表面处应变值为(0.45~0.65)×10⁴ με。     

对带电轻子质量公式的一些猜测

本文建议轻子电磁自能通过（（δm）/m）=（1/（2π））n^-b 与量子数 n 联系起来,其中 b 为待定常数.并建议动量截断值 M 与引力常数 k 和精细结构常数α的联系为 M=（?）.得到了带电轻子质量公式（?）.利用 e^-和μ^-质量的实验值和α值作输入,给出计算值 k=（6.67231±0.00026）×10^-8 cm³g^-lsec^-2和m_τ=（1782.306±0.078）MeV,与观察值 k=（6.6720±0.0041）×10^-8cm³ g^-1sec^-2和 m_τ=(1782_-4⁺³)MeV 很好符合.公式预言第四个带电轻子质量应为 m=（11725.47±0.51）MeV 可以在最近的实验中检验。本文还对所建议的质量公式和结果进行了讨论.     

Measurement of J/ψ decays into ΛΛ π+π-

Based on 58 million J/ψ events collected by the BESⅡ detector at the BEPC, J/ψ→ΛΛ π⁺π^- is observed for the first time. The branching fraction is measured to be Br(J/ψ→ΛΛ π⁺π^-)=(4.30±0.13±0.99)×10^-3, excluding the decays to intermediate states, namely J/ψ→Ξ^-Ξ⁺, J/ψ→Σ(1385)^-Σ(1385)⁺, and J/ψ→Σ(1385)⁺Σ(1385)^-. The branching fractions for these intermediate resonance channels are measured to be:Br(J/ψ→Ξ^-Ξ⁺)=（0.90±0.03±0.18）×10^-3, Br(J/ψ→Σ(1385)^-Σ(1385)⁺)=(1.23±0.07±0.30)×10^-3,and Br(J/ψ→Σ(1385)⁺Σ(1385)^-)=(1.50±0.08±0.38)×10^-3, respectively. The angular distribution is of the form dN/d(cosθ)α(1+αcos²θ) with α=(0.35±0.29±0.06) for J/ψ→Ξ^-Ξ⁺, α=(-0.54±0.22±0.10) for J/ψ→Σ(1385)^-Σ(1385)⁺, and α=(-0.35±0.29±0.06) for J/ψ→Σ(1385)⁺Σ(1385)^-.     

强激光使铝靶层裂的模拟实验研究

 激光引起的冲击波可能使得靶材料层裂断裂，这个现象取决于光束的功率密度、脉冲持续时间、靶的厚度和靶材料的性能参数。用气炮驱动的平板撞击实验和概念模拟分析了极短持续时间的三角形压缩应力击波在LY-12铝靶中的传播衰减和层裂强度的时间相关性，根据气炮模拟实验结果，估计了厚度小于2 mm的LY-12铝靶产生层裂所需的激光功率密度和能量密度的阈值条件。     

铝靶激光热应力的实验研究

 用高温应变计和热偶计等诊断技术，研究连续波氧碘化学激光（CW/COIL）与铝合金板作用产生的激光热应力。当照射靶面激光强度约1 000 W/cm²时，激光热应力随靶厚的增加而快速减小。当激光辐照靶材厚度h＝1.00 mm、激光强度I＝640~980 W/cm²时，激光热应力随辐照靶面激光强度的增加而增大。两者的激光热应力－时间曲线随靶厚的减薄或随辐照靶面激光强度的增加而变得越来越复杂。当靶厚h≤2.50 mm，辐照靶面激光强度I≥800 W/cm²时，激光热应力强度超过激光辐照区材料断裂强度，萌生许多孔洞裂纹，引起材料断裂破坏。     

Spall in Aluminium with Helium Bubbles under Laser Shock Loading

The spallation behaviors of AI+0.2 wt% ~(10)B targets and neutron irradiated AI+0.2 wt% ~(10)B targets with 5 nm radius helium bubble subjected to direct laser ablation are presented. It is found that the spall strength increases significantly with the tensile strain rate, and the helium bubble or boron inclusions in aluminum reduces the spall strength of materials by 34%. However, slight difference is observed in the spall strength of unirradiated samples compared with the irradiated sample with helium bubbles.     

Resistance to deformation and fracture of aluminum AD1 under shock-wave loading at temperatures of 20 and 600°C

The results of measurements of the dynamic elastic limit and spall strength under shock-wave loading of aluminum samples AD1 of thicknesses between 0.5 and 10.0 mm at room temperature and at temperature increased up to 600°C are presented. The anomalous thermal hardening of aluminum under high strain rate has been confirmed. An analysis of the decay of precursors at temperatures of 20 and 600°C has shown that the change in the main mechanism of drag of dislocations occurs at a strain rate equal approximately to 5 × 10³ s⁻¹, which agrees with the results of measurements by the Hopkinson split bar method. The results of measurements of the spall strength in a wide range of strain rates add the previously obtained data and agree with them.     

Behavior of aluminum near an ultimate theoretical strength in experiments with femtosecond laser pulses

The dynamics of the motion of the free surface of micron and submicron films under the action of a compression pulse excited in the process of femtosecond laser heating of the surface layer of a target has been investigated by femtosecond interferometric microscopy. The relation between the velocity of the shock wave and the particle velocity behind its front indicates the shock compression to 9–13 GPa is elastic in this duration range. This is also confirmed by the small (≤1 ps) time of an increase in the parameters in the shock wave. Shear stresses reached in this process are close to their estimated ultimate values for aluminum. The spall strength determined at a strain rate of 10⁹ s⁻¹ and a spall thickness of 250–300 nm is larger than half the ultimate strength of aluminum.     

High strain rate deformation and fracture of the magnesium alloy Ma2-1 under shock wave loading

This paper presents the results of measurements of the dynamic elastic limit and spall strength under shock wave loading of specimens of the magnesium alloy Ma2-1 with a thickness ranging from 0.25 to 10 mm at normal and elevated (to 550°C) temperatures. From the results of measurements of the decay of the elastic precursor of a shock compression wave, it has been found that the plastic strain rate behind the front of the elastic precursor decreases from 2 × 10⁵ s^?1 at a distance of 0.25 mm to 10³ s^?1 at a distance of 10 mm. The plastic strain rate in a shock wave is one order of magnitude higher than that in the elastic precursor at the same value of the shear stress. The spall strength of the alloy decreases as the solidus temperature is approached.     

Targets for studying the dynamic and radiative properties of material with laser facilities

The technology of target preparation for direct and indirect laser irradiation is developed to study the shock compressibility of materials on the Sokol-2 and Iskra-5 laser facilities. Copper and aluminum films with a density close to that of the bulk materials are prepared by ion-beam deposition. The difference in the densities of the film and bulk materials is 0.8–1.7%, and the accuracy of density measurement is 0.4–1.5%. Processes for the preparation of porous materials (aluminum, copper, nickel, gold, etc.) are also devised. Porous cop-per samples of thickness 10–50 μm, pore size 0.1–5.0 μm, mean density 0.065–0.4 g/cm³, and porosity 20–140 are obtained. The preparation of freely suspended film targets 0.1–0.2 μm thick that are irradiated by picosecondlaser shots on the Progress-P and élas-PS facilities is described.     

Dynamic fracture of copper under the action of a relativistic high-current electron beam

This paper presents the results of investigations of the dynamic spall fracture of bulk (2–6 mm) copper targets under the action of a relativistic high-current electron beam (1.3 MeV electron energy, 50 ns pulse duration, ∼10¹⁰ W/cm² power density) generated by the SINUS-7 accelerator. By numerical simulation with the use of the BETAIN1 software package it has been found that the amplitude of the stress wave formed is 6 GPa and the deformation rate is 5·10⁵ s⁻¹. As established experimentally, there is a practically linear relationship between the thickness of the target and the thickness of the spalled layer. Comparison of the experimental data and the simulation results has shown that the spall strength of copper under the given conditions is 1.3 GPa, which is in good agreement with the data available in the literature. Analysis performed with the use of fractographic teqniques has revealed that in the case of recrystallized copper the size of the spall pits formed inside the grains is four times greater than the size of the pits formed on the grain boundaries. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 69–74, July, 2006.