sol-gel法制备氧化锌铝陶瓷靶材及其性能研究

为提高常压烧结法制备的掺铝氧化锌(AZO)靶材性能,以sol-gel法制备的Al-ZnO复合纳米粉末为原料,对制备工艺参数进行了优化.结果表明:湿法球磨对生坯的密度均匀性有利;随成型压力提高靶材致密度先升后降,电阻率呈相反趋势;增加烧结保温时间,晶粒尺寸变大,致密度与电阻率改善不明显;采用2 MPa成型压力,在1 25...     

Saturation energy density and line profile of the atomic iodine laser transition at high pressure

The saturation energy density of an iodine laser amplifier is proportional to the homogeneous medium linewidth and inversely proportional to the Einstein coefficient. For good energy extraction high values of the saturation energy density are needed, thus also requiring large values of the medium linewidth, especially when the Einstein coefficient increases with pressure, as inferred from fluorescence measurements recently reported in the literature. In order to check this conclusion, we measured the saturation energy density in the pressure range between 0.5 and 4 bar for the buffer gases Ar, SF6, and Xe and also the medium linewidth at a pressure of 2 bar for Ar, SF6, and Xe. It is found that, at least in this pressure range, the Einstein coefficient is constant and does not change with pressure. This is in contrast to the results published in the paper mentioned earlier. From our experimental data an optimum pressure range for high-power iodine laser amplifiers of large extraction efficiency is also inferred.     

Revision on the calculation of optically pumped FIR laser spectrum with Doppler broadening and pressure broadening effects

By means of iteration method and also taking into account Doppler broadening and pressure braodening effect of IR pumping laser, the output power density of optically pumped NH₃ molecules FIR laser is calculated by solving density matrix equations of three-level system. The results of theoretical calculation shows that, in comparison with the FIR laser under the assumption of ideal monochromatic IR pumping, the output power density of FIR laser in the case of Doppler broadening and pressure broadening IR pumping decreases much more. Meanwhile, via the revision of Doppler broadening and pressure broadening effect, the theoretical value of optimum operating gas pressure reduces, which is in better agreement with the experimental value. Further study shows that the revision of Doppler broadening effect is more fit for the conventional FIR laser with a 2m sample tuble and the revision of pressure broadening effect is much more suitable for the miniature FIR laser with a short sample tube of 5 to 20cm in length.     

层流病房表面擦拭消毒的效果观察

利用压电陶瓷技术,设计并制备球面阵列压力传感器,并用于爆炸冲击波压应力的测试.结果表明,阵列传感器可测试爆炸冲击波的的压应力及其分布、体密度分布、面密度分布等参数,测试结果证明爆炸过程产生+的冲击波存在空间分布不均匀性.球面阵列压电陶瓷传感器的性能:测试单元数为136个,呈球面密排分布;不同单元的介电常数分布偏差小于±2.5%;压电常数分布偏差小于±2%;动态响应频率约为1 MHz;冲击破坏阈值为100 MPa量级.     

Cylindrical pin-fin fan-sink heat transfer and pressure dropcorrelations

New pressure drop/flow rate measurements coupled with a previously reported heat transfer database have resulted in new friction factor and heat transfer correlation equations for fan-driven impinging flow through square arrays of cylindrical cross section pin-fins. The correlation equations include the effect of coolant flow rate, pin-fin density and pin-fin height. A comparison with a similar jet-driven impingement flow configuration shows that the heat transfer/pressure drop characteristics. of the two flow configurations are fundamentally different. When the same arrays are compared at the same coolant flow rate, the fan-driven configuration will result in a lower pressure drop and heat transfer rate. An analysis shows that different optimal pin-fin configurations (fin height and fin density) result, depending on the design criteria imposed on the flow     

Evaluation of the hydrostatic pressure effect on Mn/p-Si Schottky barrier diode electrical parameters and interface states

Mn/p-Si Schottky barrier diode (SBD) electrical parameters and interface state density have been investigated with current–voltage (I–V) characteristics and Cheung's functions employing hydrostatic pressure. The interface state density of the diodes has an exponential growth with bias from the midgap towards the top of the valance band. We have seen that the Schottky barrier height (SBH) for Mn/p-Si SBD has a pressure coefficient of 1.61 meV/kbar (16.1 meV/GPa). We have reported that the p-type barrier height exhibited a weak pressure dependence, accepting that the Fermi level at the interface do not shift as a function of the pressure.     

Relationship Between the Number Density and the Phase Shift in Microwave Interferometry for Atmospheric Pressure Plasmas

Diagnosing atmospheric pressure discharges requires more sophisticated techniques than for low pressure plasmas. The plasma number density is a crucial parameter in several applications. Langmuir probe as a number density measuring technique is not applicable at high pressures because the electron mean free path is shorter than the Debye distance. Microwave interferometry appears to be an effective diagnostic technique in this case. However, because of the high collisionality of atmospheric pressure plasmas, the relationship between the phase shift, as measured by a microwave interferometer, and the plasma number density is not straightforward, as is the case in collisionless plasmas. For the special case of a uniform discharge, the plasma number density is found to depend on the square root of the phase shift.     

缓冲气压对CO2激光Al靶等离子体参量的影响

为了研究缓冲气压对激光等离子体参量的影响,利用CO2,激光烧蚀A1靶产生等离子体,缓冲气压变化范围为10-4Pa～2103Pa,激光脉冲能量为180mJ/脉冲,在局域热平衡和光学薄等离子体假设下,采用发射光谱法计算了等离子体的电子温度和电子密度,并研究了缓冲气压对这些参量的影响。结果表明,等离子体的电子温度和电子密度分别在1.05eV～2.47eV与1.951016cm-3～10.5 1016cm-3范围内,Al等离子体的电子温度随气压的增大而减少;低缓冲气压时,电子密度随气压增大而减小,当气压达到600Pa时,激光脉冲会击穿空气形成等离子体,电子密度又开始上升,当气压超过3000Pa时,空气等离子体会屏蔽激光脉冲能量,使到达靶面的激光能量急剧下降,Al原子的特征谱线也随之减弱而几乎消失。这一结果对理解缓冲气压对激光与物质相互作用过程的影响是有帮助的。     

Shubnikov-de Haas oscillations in HgSe〈Fe〉 and HgSe〈Co〉 under hydrostatic pressure

Shubnikov-de Haas oscillations have been studied in the gapless semiconductors HgSe〈Fe〉 and HgSe〈Co〉 under hydrostatic pressure. It is shown that in HgSe〈Fe〉 an increase in pressure results in a decrease in the electron density, which fits within the framework of the Kane model with constant Fermi energy. In contrast, in HgSe〈Co〉 the electron density is independent of the pressure, i.e., Fermi-level pinning is absent. Fiz. Tekh. Poluprovodn. 31, 318–322 (March 1997)     

压力对W-Cu合金电场快速烧结的影响

采用Gleeble—3500D热模拟机,用电场快速烧结的方法制得W-Cu合金。通过对烧结压坯的密度、显微结构以及硬度的分析,研究了压力对W-Cu合金烧结的影响。结果表明:W-Cu合金在800℃、3 min内快速烧结可获得晶粒较细小、显微组织较均匀的烧结体;在10~30 MPa范围内加压能有效促进烧结体的致密化,可获得相对密度为92.60%~94.84%的W-Cu合金烧结体。但是随着压力的增加,烧结体的相对密度增加不明显。压力可使该烧结体显微硬度增高。     

Cu HyBrID laser kinetics: optimization of HBr partial pressure and buffer-gas flow rate

A detailed investigation into the dependence of the densities of the principal plasma species in the laser discharge on the buffer-gas operating parameters is reported. Simple expressions for the densities of the Cu, Br, and H species are derived by considering their major mechanisms for production and loss. These predict that the atomic Cu and Br densities are proportional to the HBr mass flow rate, whereas the density of H species (i.e., H and H/sub 2/) is proportional to the added HBr partial pressure. The theory agrees well with "Hook" method measurements of Cu density in a 25-mm bore diameter device; the Cu density increases approximately in proportion to the HBr mass flow rate, whereas it depends only weakly on the HBr partial pressure. Measurements of the fraction of Cu atoms excited by the discharge pulse, the rate of regrowth of the ground-state Cu density during the inter-pulse period, and the pre-pulse plasma impedance, are also explained in accordance with the theory. The results show that the plasma conditions for maximum laser output, which are remarkably similar to those of other "halogen enhanced" Cu lasers, can be achieved more directly by adjusting the overall buffer flow rate with the partial pressure of the added HBr fixed at 1-2 mbar. The theory is also useful for predicting optimum buffer-gas conditions for a wide range of Cu HyBrID laser dimensions and operating conditions.     

Laser-produced shocks and their relation to material damage

This paper presents data on the shock pressure transmitted to metallic targets and to single crystal potassium chloride targets by CO2TEA laser pulses with microsecond and submicrosecond durations. Scaling relations are established for the effect of variable laser power density and ambient air pressure. The relation of the shock pressure to catastrophic mechanical damage in the potassium chloride is described.     

激光诱导Al等离子体中电子密度和温度的实验研究

激光烧蚀等离子体在微量元素分析方面有着重要的应用背景，而缓冲气体的种类及压力对激光等离子体的特性有重要影响。报道了以氦气、氩气、氮气和空气作为缓冲气体，实验测定了不同气压下Nd：YAG激光烧蚀Al靶产生的等离子体中的时间分辨发射光谱，利用发射谱线的Stark展宽和相对强度计算了等离子体中的电子密度和温度，得到了在不同缓冲气体中激光诱导Al等离子体的电子密度随延时、气压的演化规律，同时得到了电子温度的时间演化特性。实验结果表明，电子密度的数量级约为10^17cm^-3，电子温度测量值约为10000K，二者都是在激光脉冲后随时间快速衰减，直到4μs以后达到一个较低的水平并缓慢变化，其中以氩气作为缓冲气体时等离子体中的电子密度最大。     

分布Er:YAG激光对皮肤光致热分解作用数值分析

为了计算分布Er:YAG激光皮肤治疗中微尺寸调Q Er:YAG对皮肤组织光致热分解作用中的压力曲线,采用分布Er:YAG激光皮肤软组织光致热分解作用的数学模型进行数值计算,得到将激光功率密度控制在合适范围内,能使皮肤组织快速汽化而不碳化,且在该功率密度范围内受照皮肤组织内部形成很短持续时间强大压力的结果。结果表明,合适的功率密度的分布调Q Er:YAG激光皮肤治疗,能达到皮肤周围组织损伤小、手术疼痛感少的效果。该计算结果与国外的实验报道基本吻合。     

压力对NiO晶体结构及电子结构影响的理论研究

采用密度泛函理论的方法研究了不同压力条件下立方结构NiO氧化物的晶格结构、稳定性和电子结构。计算结果表明,NiO氧化物的晶格参数逐渐减小,键长变小,对称性保持不变;体系费米能先降低后增加;零压力下其存在着0.46eV的间接带隙,费米能级附近的状态密度较低,随着外压力的增加,带隙先减小再增大,费米能级附近的态密度先增大再减小。分析结果表明,随着外压力的增加,NiO氧化物价带顶附近的载流子有效质量先增大再减小;导带底的载流子有效质量均较小。外界加力还改变了NiO体系的电子分布情况。     

流体静压力下应变闪锌矿(111)取向GaN/AlGaN量子阱中受屏蔽激子的结合能

结合变分法与自洽计算方法研究了流体静压力下应变闪锌矿(111)取向GaN/AlχGa1-χN量子阱中受电子-空穴气体屏蔽的激子结合能.计算中,考虑了沿(111)取向生长多层结构时存在压电极化引起的内建电场.计算结果表明,考虑压力对双轴及单轴应变的调制以及禁带宽度、有效质量和介电常数等参数的压力效应时,激子结合能随压力的增大近似线性增加;且当电子-空穴气体密度大时,这一效应更加显著.当给定压力时,随着电子.空穴气面密度的增加,激子结合能先缓慢增加,但当密度达到大约1011cm-2时结合能开始迅速衰减.此外,当减小垒的厚度时,由于内建电场减弱,激子结合能显著增加.     

等离子体冕区电子密度陡变和凹陷的研究

从等离子体二维流体方程出发,假定在柱对称电子密度分布的等离子体中,在激光辐射场的区域内,径向电子热压与径向有质动力在稳态情况下平衡,推导出了由有质动力引起的临界密度面附近轴向电子密度轮廓陡变和有场区径向电子密度凹陷结构的解析结果,此结果与266.0nm紫外激光探针所测到的实验结果相符合。     

脉冲供电的空心阴极放电中电子的能量和密度

空心阴极放电具有电子能量大和密度高等优点,特别是脉冲供电的空心阴极放电,它能给出比直流供电的空心阴极放电中高好几个数量级的电子密度,而且高能电子的比例也很高。这对于激发原子的高激发态,尤其是获得双电子激发态是相当适合的。然而,目前对于脉冲供电的空心阴极放电,尤其是对极短波长受激辐射最重要的电子的能量和密度以及随放电参数变化的关系等问题,有待深入研究。 在一个脉冲供电的空心阴极放电装置上,用圆柱型双探针系统测量了氩气电子的能量和密度以及随放电参数变化的关系。并与直流放电的结果作了比较。发现在脉冲放电的条件下电子的密度比在直流放电的条件下约高4个数量级,而电子的能量提高约4～13eV。     

流体静压力下应变闪锌矿(111)取向GaN/AlGaN量子阱中受屏蔽激子的结合能

结合变分法与自洽计算方法研究了流体静压力下应变闪锌矿(111)取向GaN/AlχGa1-χN量子阱中受电子-空穴气体屏蔽的激子结合能.计算中,考虑了沿(111)取向生长多层结构时存在压电极化引起的内建电场.计算结果表明,考虑压力对双轴及单轴应变的调制以及禁带宽度、有效质量和介电常数等参数的压力效应时,激子结合能随压力的增大近似线性增加;且当电子-空穴气体密度大时,这一效应更加显著.当给定压力时,随着电子.空穴气面密度的增加,激子结合能先缓慢增加,但当密度达到大约1011cm-2时结合能开始迅速衰减.此外,当减小垒的厚度时,由于内建电场减弱,激子结合能显著增加.     

Enhanced Photoluminescence and Photoresponsiveness of Eu3+ Ions-Doped CsPbCl3 Perovskite Quantum Dots under High Pressure

Metal halide perovskite quantum dots (QDs) have garnered tremendous attention in optoelectronic devices owing to their excellent optical and electrical properties. However, these perovskite QDs are plagued by pressure-induced photoluminescence (PL) quenching, which greatly restricts their potential applications. Herein, the unique optical and electrical properties of Eu³⁺-doped CsPbCl₃ QDs under high pressure are reported. Intriguingly, the PL of Eu³⁺ ions displays an enhancement with pressure up to 10.1 GPa and still preserves a relatively high intensity at 22 GPa. The optical and structural analysis indicates that the sample experiences an isostructural phase transition at approximately 1.53 GPa, followed by an amorphous state evolution, which is simulated and confirmed through density functional theory calculations. The pressure-induced PL enhancement of Eu³⁺ ions can be associated with the enhanced energy transfer rate from excitonic state to Eu³⁺ ions. The photoelectric performance is enhanced by compression and can be preserved upon the release of pressure, which is attributed to the decreased defect density and increased carrier mobility induced by the high pressure. This work enriches the understanding of the high-pressure behavior of rare-earth-doped luminescent materials and proves that high pressure technique is a promising way to design and realize superior optoelectronic materials.