使用Pb1-xGexTe材料提高红外薄膜光学器件温度稳定性

提高薄膜光学器件温度稳定性的一条途径是根据光学薄膜器件的稳定性理论,选择两种具有相反折射率温度系数的材料组成膜系,使材料随温度变化引起的位相变化相互抵消.但很难找到折射率温度系数可以完全相互抵消的两种材料,因此有必要找到一种折射率温度系数可以调节的材料.研究表明:红外长波材料Pb1-xGexTe的折射率温度系数可以随Ge组分x的改变而改变.研究结果证明使用Pb1-xGexTe材料,薄膜光学器件温度稳定性得到了很大的提高.     

使用Pb1-xGexTe材料提高红外薄膜光学器件温度稳定性

提高薄膜光学器件温度稳定性的一条途径是根据光学薄膜器件的稳定性理论,选择两种具有相反折射率温度系数的材料组成膜系,使材料随温度变化引起的位相变化相互抵消.但很难找到折射率温度系数可以完全相互抵消的两种材料,因此有必要找到一种折射率温度系数可以调节的材料.研究表明:红外长波材料Pb1-xGexTe的折射率温度系数可以随Ge组分x的改变而改变.研究结果证明使用Pb1-xGexTe材料,薄膜光学器件温度稳定性得到了很大的提高.     

使用Pb_(1-x)Ge_xTe材料提高红外薄膜光学器件温度稳定性

提高薄膜光学器件温度稳定性的一条途径是根据光学薄膜器件的稳定性理论 ,选择两种具有相反折射率温度系数的材料组成膜系 ,使材料随温度变化引起的位相变化相互抵消。但很难找到折射率温度系数可以完全相互抵消的两种材料 ,因此有必要找到一种折射率温度系数可以调节的材料。研究表明 :红外长波材料 Pb1-x Gex Te的折射率温度系数可以随 Ge组分 x的改变而改变。研究结果证明使用 Pb1-x Gex Te材料 ,薄膜光学器件温度稳定性得到了很大的提高。     

利用Pb1-xGexTe材料的折射率异常性质改善红外光学薄膜的低温性能

红外薄膜干涉滤光片性能在低温下的变化是空间遥感系统中的一个关键性问题。经研究表明IV-VI族半导体PbTe和GeTe的赝二元合金Pb1-xGexTe在铁电相变点具有折射率异常—相应于铁电相变,Pb1-xGexTe薄膜呈现出最大折射率值。用Pb0.94Ge0.06Te材料代替PbTe材料,制作了一个红外薄膜干涉滤光片。测试结果表明:其中心波长漂移从0.48nm/K改进到0.23nm/K,在所测量的80K～300K的温度范围,用Pb0.94Ge0.06Te材料制作的滤光片的峰透过率高于用PbTe材料制作的滤光片约3%,从而极大地改善了光学薄膜器件在深低温环境下的稳定性和可靠性。     

类金刚石薄膜的光学性能的研究

利用脉冲真空电弧镀的方法,在硅基底上沉积类金刚石薄膜,研究薄膜的光学性能、光学常数和离子能量关系。结果表明:不同的离子能量可以得到不同折射率的薄膜,无氢类金刚石薄膜的折射率在2.5～2.7之间变化;通过改变工艺条件来制备不同折射率的薄膜,和不同折射率的基底材料相互匹配;折射率和光学能隙随离子能量具有相反的变化趋势,和理论预测的趋势相一致;对于硅、锗等红外材料,要求的薄膜应具有1.8～2.1左右的折射率,因此提出一种基于物理汽相沉积和化学汽相沉积两种相互结合的方法,来降低薄膜的折射率,以达到和硅、锗等材料的折射率匹配。     

超导纳米线单光子探测器的光耦合结构

为了提高超导纳米线单光子探测系统(SNSPD)的探测效率,搭建了超导纳米线单光子探测系统,研究了该系统的光耦合结构及该结构随温度降低而发生的变化.首先,测量了SNSPD在不同电流下的量子效率,确定了器件的性能.然后,提出了两种不同的光纤直接对准的器件封装方法,这些方法可以在室温下自主控制光纤端面与器件表面的距离(gap).考虑封装材料的热胀冷缩,gap在温度变化时有很明显的变化,研究了温度变化对gap的影响.最后,提出通过改变入射光的波长来观察器件表面反射光光强的周期性波动,从而精确测量不同温度下gap的大小.实验结果表明,对于两种不同的光耦合结构,gap在温度降低270 K以后分别减小了4.1 μm和17 μmm.理论计算和实验数据基本吻合,可为未来器件封装和新型封装结构的设计提供参考依据.     

用于温度测试的光纤SPR传感器特性研究

表面等离子体波共振效应（SPR）对液体折射率变化非常敏感，而温度变化又会导致液体折射率和金膜复介电常数的改变。利用这一原理，可以考察温度变化对SPR共振效果的影响。采用相对光谱检测技术，获得相应的SPR反射光谱，并详细分析了共振波长和共振强度等参数随温度变化的特性曲线。定义耦合系数η，还可实现对不同液体温度下共振效应强度的评估。通过这些研究，进一步扩展了此类传感器的应用领域。     

一种改进的绝热材料导热系数测控系统的设计

介绍了一种在传统防护热板法双平板装置基础上改进的测量绝热材料导热系数的设计方法,既可以测出在给定温度范围内材料的平均导热系数,又可以得到导热系数随温度的变化曲线,同时还可以对材料非稳态下的传热特性进行测定.本系统采用内部集成了24位高精度Δ-∑ADC且拥有改进的8051内核的高集成混合信号元器件MSC1210进行信号的采集和处理,利用PWM方式进行功率控制,人机对话界面友好,具有测试精度高、稳定性好、易于操作等优点.     

高灵敏度长周期光纤光栅温度传感器的设计

为提高光纤光栅温度传感器的灵敏度,文中采取纤芯弹光系数大于包层弹光系数的长周期光纤光栅且在其包层外面涂覆一层随温度的升高折射率减小的薄膜材料,同时采用热膨胀系数大的金属封装光栅三种增敏措施。计算表明,增敏后的温度传感器其灵敏度系数为0.2375nm/℃,温度测量分辨力小于0.1℃。     

表面等离子体共振理论仿真研究

为了掌握影响激发表面等离子体共振(SPR)现象的因素,文中以薄膜光学理论为基础,利用Winspall软件模拟研究Kretschman结构下,金膜厚度、待测介质折射率以及三棱镜类型对表面等离子体共振吸收峰位变化的影响,得出了最佳膜厚以及影响激发SPR现象的棱镜折射率和待测物质折射率随共振角度变化的规律,为SPR传感器的设...     

Cylindrical specimens for KIC of rocks

Stress intensity factors for pairs of diametrically opposite radial cracks on the inside of a jacketed pressurized hole in a thick cylinder have been calculated by using finite element technique. Burst tests on thick cylinder rock samples under above conditions have been performed and the K_IC values for Antrim Shale and Limestone determined. The method is very convenient for rocks whose samples are often available in form of cylindrical bars drawn as cores from underground drilling.     

Electron and light microscopy studies on the domain structures of Zn3B7O13Cl, Zn3B7O13Br and Zn3B7O13I ferroic boracites

The domain structures of Zn₃B₇O₁₃Cl, Zn₃B₇O₁₃Br and Zn₃B₇O₁₃I boracite single crystals were studied by means of polarized light in conjunction with electron microscopy. Single crystals of the three compositions were grown by chemical transport reactions in closed quartz ampoules, at a temperature of 900 °C and were examined by polarizing optical microscopy (PLM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). For both PLM and SEM, the same as‐grown samples were used without having to resort to metallization of the crystal faces. For TEM the single crystals were crushed and mounted on holey carbon films. Comparative electron microscope images were useful for revealing the domain structure of these ferroelectric/ferroelastic materials previously observed between the crossed polars of an optical microscope. X‐ray diffraction analysis of the pulverized crystals was performed for this triad of halogen boracites containing zinc as a common metal.     

GT/CAD/CAPP/PDM/ERP系统集成研究

研究ETO生产方式下以成组技术为基础的CAD/CAPP/PDM/ERP的集成方法,包括面向CAD/CAPP/PDM/ERP的集成的成组信息编码,基于成组编码的CAD/PDM集成、CAPP/PDM集成和PDM/ERP集成.提出了基于成组技术的CAD/CAPP/PDM/ERP集成框架,研究了贯穿于CAD、CAPP、PDM与ERP系统的统一的成组编码方案和信息编码方案.     

基于太赫兹光谱的人参和西洋参鉴别

为了快速区分人参和西洋参,依据两者所含的人参皂苷在太赫兹波段具有不同指纹光谱,提出了一种基于人参皂苷的太赫兹光谱鉴别人参和西洋参的方法。采用MATLAB软件识别人参和西洋参的太赫兹光谱,同时根据太赫兹光谱特征并通过标准的主成分分析(PCA)区分出人参、西洋参。实验结果表明,基于太赫兹光谱的主成分分析可精确区分出人参、西洋参,并且还可以应用于其他类似物质的区分中。     

Analysis of the Rk surface roughness parameter proposals

European manufacturers have proposed a set of surface roughness parameters based on an examination of the variation in slope of the bearing ratio curve of a surface profile. It is shown, that the proposed procedure provides no useful information, and indeed is misleading, since the bearing ratio curve of even a normally-distributed random surface profile exhibits the expected variation in slope when plotted on rectangular coordinates. On the other hand, the desired information is readily obtained by a similar examination of the cumulative height distribution of a surface profile (the unity complement of the bearing ratio) when it is plotted on normal probability coordinates.     

永磁同步电机积分滑模观测器控制

对永磁同步电机观测器控制进行研究,针对传统滑模观测器存在控制精度低、系统抖振较大的不足,设计了一种永磁同步电机积分滑模观测器控制。积分滑模控制具有控制精度高、系统抖振小的特点。积分滑模观测器可以有效提高电机控制精度,增强控制系统抗干扰能力。采用饱和函数代替符号函数进行滑模控制律设计,降低控制系统固有抖振,使滑模控制动态性能提高。通过仿真验证了积分滑模观测器控制策略的可行性。     

Characterization of cast Al86Mn3Be11 alloy

An Al₈₆Mn₃Be₁₁ alloy cast into copper mould was subjected to metallographic investigation. The as-cast microstructure consisted of a quasicrystalline icosahedral phase (i-phase), Be₄AlMn phase and, occasionally, a hexagonal phase. Al-rich solid solution represented the dominant phase. The chemical compositions of phases were determined using AES. The composition of the Be₄AlMn slightly deviated from the stoichiometric composition, whereas the composition of the i-phase was approximately Al₅₂Mn₁₈Be₃₀, containing an appreciable amount of Be. The average composition of the hexagonal phase was Al₆₆Mn₂₁Be₁₃. Deep etching and particle extraction provided a deep insight into the three-dimensional morphology of the i-phase and the hexagonal phase, whereas Be₄AlMn was slightly attacked by the etchant. The i-phase was present predominantly in the form of dendrites and a rodlike eutectic phase. The hexagonal phase was primarily in the form of hexagonal platelets, whereas Be₄AlMn was rather irregular in shape. The morphology of the i-phase can be explained by predominant growth in 3-fold directions and the lowest energy of the 5-fold planes, leading to the faceting and adopting a pentagonal dodecahedron shape. The brightnesses of phases in the backscattered electron images were rationalized by determining their backscattering coefficients. TEM investigation showed considerable phason strain in the i-phase, and the polycrystalline nature of the Be₄AlMn phase.     

Investigation on the impact behavior of Al2O3-SiC-MgO nanoceramic/metal laminated composite

Lightweight laminated composites containing a ceramic front layer and a metallic backing layer were used in order to protect people, moving equipment, and mobile vehicles from high velocity impact and the increased mobility of mobile vehicles. In this study, by adding10 vol% SiC and 500 ppm MgO nanoscale particles on the microstructure of Al ₂ O ₃ matrix and applying optimum sintering conditions, ceramic performance against high-speed projectile impact was improved. To perform this investigation, a number of target samples with two different types of front layers (alumina and Al ₂ O ₃-SiC-MgO nanocomposite ceramic) were produced. Impact tests were conducted on these samples using 7.62 mm projectiles with a velocity of 820 ± 15 m/s. The amount of bulge and bending of the backing layer caused by impact tests was measured. The results of the impact tests on the samples made of Al ₂ O ₃-SiC-MgO nanocomposite ceramics and alumina were also compared and analyzed. The results indicate that the substitution of Al ₂ O ₃-SiC-MgO ceramic layer — which is proffered in this paper — instead of pure alumina ceramic layer, decreases the areal-density of the samples by at least 30% and improves mechanical properties by about a 60% increase in flexural strength and 100% growth of the energy distribution factor, which impressively increases impact energy absorption.     

Electron microscopy of crack/particle interactions in Al2O3/SiC nanocomposites

Crack/particle interactions in alumina/silicon carbide nanocomposites have been investigated by scanning electron microscopy and transmission electron microscopy, with cracks induced by Vickers microindentation. Intergranular cracks are frequently deflected into grains by SiC particles on grain boundaries inclined to the average direction of crack propagation. This mechanism is proposed to explain the change in the fracture mode from intergranular fracture for monolithic alumina to predominantly transgranular fracture for the nanocomposites. Neither stress-induced microcracking around SiC particles nor significant crack deflection by intragranular particles was found to occur in the nanocomposites. It is argued that an addition of nanoparticles may not be a promising approach for increasing the toughness of alumina.     

Near-field second harmonic imaging of the c/a/c/a polydomain structure of epitaxial PbZrxTi1–xO3 thin films

Near-field optical second harmonic microscopy has been applied to imaging of the c/a/c/a polydomain structure of epitaxial PbZr _x Ti_{1– x} O₃ thin films in the 0 <  x  < 0.4 range. Comparison of the near-field optical images and the results of atomic force microscopy and X-ray diffraction studies show that an optical resolution of the order of 100 nm is achieved. Symmetry properties of the near-field second harmonic signal allow us to obtain good optical contrast between the local second harmonic generation in c- and a-domains. Experimentally measured near-field second harmonic images have been compared with the results of theoretical calculations. Good agreement between theory and experiment is demonstrated.