Fe,Ce原子在A1—Fe—Ce非晶合金中的分布

采用Ｘ射线衍射技术研究了Ａ１－Ｆｅ－Ｃｅ合金的非晶结构,发现非晶态合金Ｘ射线强度曲线上都丰在明显的预峰,合金随铁含量增加,预峰和主峰向大角度偏移;合金随铈含量增加,预峰和主峰向小解度偏移。２５０℃时,非晶合金出现铝相晶化,而预峰的形状和位置并未发生改革;４００℃时央预峰消失的位置形成多种化合物相。Ｆｅ原子大部分存在于预峰所对应的Ａ１－Ｆｅ－Ｃｅ原子团簇中,崦Ｃｅ原子大部分无规分布于Ａ１非晶基体中。     

溶胶-凝胶法制备Zn1-xMgxO薄膜及其发光性质

采用溶胶-凝胶工艺在玻璃衬底上制备了Zn1-xMgxO(x=0.1,0.2,0.3,0.4,0.5,0.6,0.7)薄膜。X射线衍射(XRD)谱测试结果发现:在0.10.3时出现MgO立方相。薄膜光致发光谱研究表明紫外发光峰随Mg含量的增加向短波方向移动,且随着退火温度的升高发生明显蓝移,禁带宽度增大。但是退火温度为590℃的样品较560℃样品的发光峰出现红移。     

预注入对Si_(1-x)C_x合金形成的影响

室温下在单晶Si中注入 (0 6— 1 5 )at%的C原子 ,部分样品在C离子注入之前在其中注入2 9Si 离子产生损伤 ,然后在相同条件下利用高温退火固相外延了Si1 -xCx 合金 ,研究了预注入对Si1 -xCx 合金形成的影响 .如果注入C离子的剂量小于引起Si非晶化的剂量 ,在 95 0℃退火过程中注入产生的损伤缺陷容易与C原子结合形成缺陷团簇 ,难于形成Si1 -xCx 合金 ,预注入形成的损伤有利于合金的形成 .随着C离子剂量的增大 ,注入产生的损伤增强 ,预注入反而不利于Si1 -xCx 合金的形成 ,但当注入C原子的浓度超过固相外延的溶解度时 ,预注入的影响可以忽略 .退火温度升高到 10 5 0℃ ,无论预注入还是未预注入样品 ,C含量低的合金相仍然保留 ,而C含量高的合金相大部分消失 .     

GaN1-xPx三元合金的光学与结构特性

对采用金属有机化学气相淀积(MOCVD)技术生长的GaN1-xPx三元合金进行了低温光致发光(PL)和X射线衍射(XRD)测试分析,与来自GaN层的带边发射相比,P的摩尔分数比为0．03,0．11和0．15的GaN1-xPx的光致发光峰分别呈现出了73meV,78meV和100meV的红移,文中将这种红移归因于GaN1-xPx合金具有大的带隙能量弯曲系数。X射线衍射结果表明GaN1-xPx三元合金仍为六方结构晶体,且随着P组份比的增加,GaN1-xPx合金的(0002)衍射峰逐渐向小角度方向移动,即晶格常量变大,同时,(0002)衍射峰谱线不断宽化,说明由于替位式P原子的不规则分布以及部分间隙P原子的影响造成了GaN1-xPx样品的晶格畸变。在GaN1-xPx的光致发光谱及X射线衍射谱中均未观测到相应的有关GaP的峰,表明所生长的高P含量的GaN1-xPx三元合金没有产生明显的相分离。     

非晶态Mg_(70)Zn_(30)合金结构因子的预峰

利用X射线衍射仪对非晶态Mg70 Zn30 合金的结构进行了研究 ,获得了强度曲线、结构因子、双体分布函数和原子间最近邻距离 .结果表明 ,Mg70 Zn30 合金在小Q区间存在强烈的预峰现象 .根据预峰的特性 ,提出了Mg70 Zn30 熔体的结构模型 ,即Mg原子位于中心 ,8个Zn原子位于顶角所形成的简单立方结构模型 .该模型以共享顶点的方式相连接 ,能够满足预峰对Mg—Mg原子间距离的要求 .Mg70 Zn30 非晶合金中预峰的产生是相邻原子团中心Mg原子之间相互关联的表现     

一维Fibonacci系列的X射线衍射峰轮廓的计算

用简单原子层的Fibonacci系列模型,根据振幅-相位关系,计算了其X射线衍射图谱,衍射峰位置在k=2π((m+nτ)/(1+2τ))d^-1,d为平均面间距。衍射峰角宽度β与原子层总厚度D仍满足Scherrer公式:β=0.88λ/Dcosθ。并用振幅-相位图解释了弱衍射峰的强度随原子层数增大时产生起伏的现象。 关键词：     

镁含量和热处理对Zn1-xMgxO薄膜结构和发光性能的影响

采用溶胶-凝胶工艺在玻璃衬底上制备了Zn1-xMgxO(x=0.1,0.2,0.3,0.4,0.5,0.6,0.7)薄膜.X射线衍射谱(XRD)测试结果发现,在0.1相似文献   

烧结β型Ti-Nb合金中由间隙原子引起的Snoek弛豫

用粉末冶金方法制备了不同Nb含量的Ti-Nb合金.用美国TA仪器公司的动力学分析仪Q800以单臂振动模式研究了不同Nb含量和不同热处理以及不同测量参数下的Ti-Nb合金的内耗行为,用X-射线衍射检测了不同样品的微观结构.实验表明,在水淬的和烧结态的Ti-Nb合金的内耗-温度曲线上均发现了弛豫型的内耗峰,这个内耗峰的高度与Nb含量有关,在低Nb含量的Ti-Nb合金样品中不出现,水淬样品内耗峰的最大值出现在Ti-35.4 wt.%Nb (以下称Ti-35.4Nb)的合金中,烧结态样品的内耗峰高度在实验成分范围内单调地随Nb含量而增加.水淬的Ti-35.4Nb合金的弛豫参数分别是激活能H_(wq)=(1.67±0.1) eV和指数前因子τ_(0wq)=1.1×10~(-17±1) s.另外,内耗峰的高度也与热处理有关,水淬的Ti-35.4Nb合金比具有相同成分的烧结态的合金的内耗峰高得多,淬火温度对内耗峰高度也有影响.研究发现,这个内耗峰与Ti-Nb合金中的β相有关,峰高取决于β相的稳定性及其含量,当β相的稳定性降低以及β相的量增加时,峰高增加.水淬Ti-35.4Nb合金中的β相是亚稳状态的β相(β_M),时效时β_M能转变成稳定的α相和稳定β相(β_S),烧结态合金中的β相是β_S.不同热处理状态下Ti-35.4Nb合金样品的微观结构的不同导致了内耗峰高度的差别.从微观结构分析,在淬火的合金中,峰高最大值出现在35 wt.%Nb含量附近的现象是由β相的稳定性和β_M相的量随Nb含量变化引起的.在烧结态的Ti-Nb合金中,峰高单调地随Nb含量的增加而增加的情况是由β_S的量决定的.在循环应力作用下,β_M或β_S相晶格点阵中氧原子的跳动和氧原子与替代原子的相互作用是产生内耗峰的根源.     

基片位置对激光会聚铬原子沉积的影响

为了研究基片位置对激光会聚铬原子沉积的影响,基于原子的粒子运动,采用数值计算对基片切割会聚激光场不同部位时高斯激光驻波场光学势阱、原子运动轨迹和沉积条纹进行了仿真。研究结果充分显示了基片位置对上述三方面的影响。虽然基片会对激光产生衍射,但是无论衍射存在与否,沉积条纹半峰全宽的最小值和中心峰值的最大值都出现在基片表面和激光中轴线重合的位置。此时,衍射将使条纹中心峰值降为非衍射时的0.96倍,同时,半峰全宽增加至非衍射时的1.03倍。另外,仿真结果显示,不管是否考虑衍射,垂直于激光中轴线方向(y方向)上沉积条纹的中心峰值随y值的增加呈现单调减小的趋势,而条纹半峰全宽随y值的增加呈现单调递增的趋势。     

硬币材料特征峰幅度的探究

利用X射线实验仪测量了不同模式下单元素金属及多元素合金次级X射线K_α特征峰峰值随入射角及出射角的变化.当入射角与出射角相同时,单元素金属的次级X射线特征峰峰值不随角度的改变而改变;当入射角不变时,单元素金属的次级X射线特征峰峰值随出射角的增大而增大,验证了X射线一次荧光激发的理论.对于多元素FeZn合金,当入射角与出射角相同时,Fe的总X射线荧光强度随出射角的增大而增大,Zn的总X射线荧光强度随出射角的增大而减小;当入射角不变时,Fe的总X射线荧光强度随出射角的增大而增大,而Zn的总X射线荧光强度随出射角的增大呈现先增加后减小的趋势,验证了X射线二次荧光激发的理论.     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.     

A stereo matching algorithm using multi-peak candidate matches and geometric constraints

Gray cross correlation matching technique is adopted to extract candidate matches with gray cross correla- tion coefficients less than some certain range of maximal correlation coefficient called multi-peak candidate matches. Multi-peak candidates are extracted corresponding to three closest feature points at first. The corresponding multi-peak candidate matches are used to construct the model polygon. Correspondence is determined based on the local geometric relations between the three feature points and the multi-peak candidates. The disparity test and the global consistency checkout are applied to eliminate the remaining ambiguous matches that are not removed by the local geometric relational test. Experimental results show that the proposed algorithm is feasible and accurate.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.     

Optical Pulse Compression Schemes That Use Nonlinear Bragg Gratings

Nonlinear optical pulse compression of picosecond pulses typically requires long lengths of optical fiber and multiple components. Periodic structures, such as fiber Bragg gratings, are highly dispersive at wavelengths outside of the photonic bandgap. This implies that such gratings can be used as very short all-fiber compressors. In this paper a number of such compression schemes are reviewed involving uniform and nonuniform fiber Bragg gratings, relying on both soliton and nonsoliton compression principles. Experimental results supporting the corresponding underlying theory are also presented. Finally, an extension of one of the compression schemes is shown, which allows the generation of adjustable high-repetition rate soliton trains.