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1.
弥补激光棒热透镜的最佳端面研磨半径理论计算 总被引:1,自引:0,他引:1
从激光晶体的热效应理论出发,把棒状激光晶体等效为梯度折射率棒.利用梯度折射率光学理论,由梯度折射率棒的光焦度公式,推导了更为精确的激光棒端面研磨半径公式.并把它与通常使用的端面研磨半径公式进行了比较.结果发现,它们的曲线在激光棒耗散功率比较大时,吻合的比较好(≥450w);在小耗散功率时,两曲线差别很大(〈450W);并且在耗散功率为某一定值时(420W左右),有一个无穷点.最后理论分析了它们差异的原因. 相似文献
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理想自聚焦棒透镜和Maxwell鱼眼微球透镜对有限远物点成像及球差 总被引:2,自引:0,他引:2
本文用变折射率介质中的光线理论研究了具有双曲正割折射率分布的理想自聚焦棒透镜对有限远物点成像的像距及其纵、横向球差的计算公式。并将它与Maxwell鱼眼微球透镜对有限远物点的成像作对比。严格的数值计算结果表明:两类透镜的纵、横向球差都随折射率梯度的增强而减小。弱梯度时棒透镜比球镜的球差小;但强梯度短物距时球透镜可达到比棒透镜的球差小一、两个数量级。 相似文献
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基于光束扫描法的光纤预制棒折射率测试仪主要适用于直径和长度在一定范围内的圆柱形样品折射率分布的测试。提出一种套管辅助法可实现更短长度、更细直径和变直径样品的折射率测试。该方法将待测样品居中放置于一个尺寸符合测试要求的圆柱形套管内,并在套管内注入折射率匹配油,使其没过待测样品后按常规步骤进行测试。对比实验结果表明,套管辅助法与直接测量法的偏差与仪器的测量误差相当。采用套管法,获得了预制棒拉丝终止后变径区不同位置折射率的径向分布,可为拉丝过程的研究提供参考。 相似文献
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<正> 一、序言用公式(1)可表示塑料梯度折射率棒的梯度折射率(GRIN).折射率的分布规律用于宽带光通信纤维和新式微型光学元件(棒透镜),这种梯度折射率棒正在受到极大的注视。 相似文献
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利用金纳米棒在光照射下激发表面等离激元的性质,实验研究了其在不同介电环境下的吸收光谱.通过分析纵向等离子体共振吸收峰峰位随介质折射率的变化,获得了金纳米棒表面等离激元探针测量介质折射率的经验公式为n=(385.59)-1(λ/nm-290.56).利用金纳米棒表面等离激元探针的高介电灵敏度,测试了一些未知液体的折射率,并与阿贝折射仪测量法的结果相比较.结果与分析表明,本方法较之阿贝折射仪测量介质折射率的方法具有更高的精密度.因此,表面等离探针可用于拓展大学物理实验中的介质折射率测量实验. 相似文献
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Raman spectroscopy is used in this work to reveal an increase in the size of anatase crystallites in the process of drying
of hydrated titanium dioxide gel and ordering of the structure of primary particles of hydrated tin dioxide gel under drying.
Raman spectra are interpreted with account of dimensional effects. It is found that mechanical stresses that arise in the
materials under drying have a great effect on the structural changes found there.
TERMOXIDE Research and Production Company, 624051 Zarechnyi, Sverdlovsk Region, P/O Box 94, Russia. Translated from Zhurnal
Prikladnoi Spektroskopii, Vol. 64, No. 2, pp. 266–268, March–April, 1997. 相似文献
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不同干燥法制备纳米TiO2光催化剂的光谱研究 总被引:5,自引:0,他引:5
本文分别用常态、超临界乙醇和超临界CO2干燥法干燥钛酸正丁酯的醇凝胶,制备纳米TiO2光催化剂。应用XRD,FTIR,FT-Raman和Fluorescent spectrum(FS)等光谱技术对催化剂进行了表征。以光催化降解罗丹明B为模型反应,比较所得样品光催化活性。实验结果表明,不同干燥方法对催化剂的晶相结构、半导体能带结构、光吸收性能、表面性质及光催化活性均产生显著的影响,用超临界CO2干燥法制备的TiO2光催化剂具有较好的光催化活性。 相似文献
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Diphasic gel in the mullite composition was prepared from a colloidal sol of boehmite mixed with a hydrolyzed tetraethoxisilane (TEOS) solution. The boehmite sol was obtained by peptization of a poorly crystallized or very small mean crystallite size (approximately 34 A) precipitate, resulting from the reaction between solutions of aluminum sulfate and sodium hydroxide. Ultrasound was utilized in the processes of the TEOS hydrolysis and the boehmite peptization, and also for complete homogenization of the mixture to gel. The wet gel is almost clear and monolithic. The gel transparency is lost on drying, when syneresis has ended, so that the interlinked pore structure starts to empty and is recovered upon water re-absorption. Cracking closely accompanies this critical drying process. Differential thermal analysis (DTA) and X-ray diffraction (XRD) show that the solid structure of the gel is composed of an amorphous silica phase, as a matrix, and a colloidal sized crystalline phase of boehmite. Upon heat treatment, the boehmite phase within the gel closely follows the same transition sequence as in pure alumina shifted towards higher temperatures. Orthorhombic mullite formation was detected at 1300 degrees C. 相似文献
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Micro-droplets of soft matter solutions have different morphologies upon drying, and can become wrinkled, buckled or cavitated particles. We investigate the morphology evolution of a drying soft matter droplet in this work: at the early stage of drying, wrinkling or cavitation instability can occur in the droplet, depending on the comparison between the critical wrinkling and cavitation pressure; at a later stage of drying, no wrinkles will appear if cavitation happens first, while cavitation can still occur if wrinkling happens first. A three-dimensional phase diagram in the space of elastic length, gel layer thickness and weight loss is provided to illustrate the drying pathways of a soft matter droplet. This diagram can help guide future fabrications of micro-particles with desired morphologies. 相似文献
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Amin Zeinali Zeinab Hosseini Dastgerdi Farshad Kheiri 《Journal of Macromolecular Science: Physics》2020,59(5):263-283
AbstractGelatin/montmorillonite bionanocomposite hydrogels containing 0, 5 and 10?wt.% of montmorillonite were prepared via two different techniques, either a cooling or drying method. In addition, gelatin/polyvinyl alcohol/montmorillonite bionanocomposite hydrogels having gelatin/polyvinyl alcohol ratios of 1/1, 1/2 and 2/1, loaded with 0, 5 and 10?wt.% of montmorillonite, were prepared via a cyclic freezing-thawing technique. The microstructural properties of both types of the prepared bionanocomposite hydrogels were investigated using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The gel fraction, swelling behavior and drying kinetics of all prepared bionanocomposite hydrogels were also studied. The XRD and SEM results showed a porous structure with a possible exfoliated morphology for both types of the prepared bionanocomposite hydrogels. In addition, the gel fraction of the bionanocomposite hydrogels increased and a more entangled and crosslinked network with a decreased pore size was obtained by increasing the loading level of montmorillonite for both types of the bionanocomposite hydrogels. The swelling ratio and drying rate of both types of the bionanocomposite hydrogels could be increased by decreasing the PVA portion or MMT loading level, while the swelling and drying ability of the gelatin/montmorillonite bionanocomposite hydrogels prepared via the cooling method was higher than those of the corresponding samples prepared via the drying method. 相似文献
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On the basis of the investigation of the electronic absorption and fluorescence spectra of porphin introduced into inorganic and organo–inorganic silicate gel matrices, the participation of the surface hydroxyl groups in the formation of the dication form of porphin is shown. The influence of the gel matrix drying process on the reverse process of deprotonation of the porphin dication has been revealed. 相似文献
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E. Gutmann D.C. Meyer A.A. Levin P. Paufler 《Applied Physics A: Materials Science & Processing》2005,81(2):249-259
Alumina-based nanometre films produced by a sol–gel method are investigated by wide-angle X-ray scattering and X-ray reflectometry. Every dipping cycle of the sol–gel route results in formation of an X-ray amorphous film exhibiting a density gradient. Both withdrawal speed and drying temperature used as tuning parameters during coating preparation influence the thickness and density of the sol–gel film. An increase of the withdrawal speed results in a thicker film of a lower mean density. An opposite effect is observed with an increase of the drying temperature. The appearance of multilayer Bragg reflections in the reflectivity curves of successive stacked films is discussed in detail. The thermal stability of the density-modulated aluminium oxide-based nanometre multilayers is investigated in a temperature range of 300–1000 °C. Possible applications as X-ray optical elements are outlined. PACS 61.10.Kw; 68.60.Dv; 81.20.Fw 相似文献
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LiMn2O4 thin films were prepared by a sol–gel method using spin-coating and annealing processes. Anhydrous Mn(CH3COCHCOCH3)3 (manganese acetylacetonate) and LiCH3COCHCO–CH3 (lithium acetylacetonate) were chosen as source materials. The film electrochemical properties depended on the drying temperature even when subjected to the same annealing conditions. The discharge capacity of annealed film increased as the drying temperature was increased. However, the rate of capacity fading during cycling increased as the drying temperature was increased. 相似文献
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以间苯二酚和甲醛为原料,对水相溶胶-凝胶聚合自发成膜技术获得间苯二酚-甲醛(RF)凝胶薄膜进行了研究。主要研究了溶胶-凝胶过程中冰醋酸(HAC)含量和反应温度对凝胶过程的影响,分析了RF有机凝胶自发成膜的形成机理。IR和SEM分析表明,所得到的凝胶膜具有典型的RF有机气凝胶结构,薄膜厚度大约为50 μm,膜由直径10 μm左右的粒子组成,没有观察到明显的孔洞结构。分析认为,在间苯二酚和甲醛占总溶液的质量分数为67%左右及控制pH值在一定的酸性范围,RF凝胶自发成膜过程和机理可以用RF凝胶的收缩机理加以解释,RF自发膜的表面形貌及形成机理与均匀泡沫的连续相分离机理类似。 相似文献
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N. V. Menshutina D. D. Lovskaya A. E. Lebedev E. A. Lebedev 《Russian Journal of Physical Chemistry B, Focus on Physics》2017,11(8):1296-1305
A complex study of the production of sodium alginate aerogel particles by emulsion gelation and dripping methods followed by drying in supercritical carbon dioxide is conducted. The factors that affect the characteristics of the obtained materials are determined. The above-mentioned methods are tested on a semiindustrial level using high-pressure homogenization and spraying through pneumatic nozzles. The resulting gel particles are dried in a supercritical carbon dioxide medium using equipment with the volume of drying vessels of 0.25 and 2 L. The necessary characteristics and quality of the obtained aerogels do not deteriorate in the case of production scale-up. 相似文献