Thermal stability and spectroscopic properties of Er3+-doped niobium tellurite glasses for broadband amplifiers

Three Er3+-doped tellurite glasses with compositions of 70TeO(2)-30ZnO, 70TeO(2)-20ZnO-10Nb(2)O(5) and 70TeO(2)-20ZnO-5BaO-5Nb(2)O(5) have been investigated for developing fiber and planar broadband amplifiers and lasers. The optical spectroscopic properties and thermal stability of Er3+-doped tellurite glasses have been discussed. The results show that the incorporation of Nb2O5 increases the thermal stability of Er3+-doped tellurite glasses significantly, Er3+-doped niobium tellurite glasses 70TeO(2)-20ZnO-10Nb(2)O(5) and 70TeO(2)-20ZnO-5BaO-5Nb(2)O(5) exhibit the good thermal stability (DeltaT > 150degreesC), the large emission cross-section (>10 x 10(-21) cm(2)) and broad full width at half maximum (similar to65 nm), will be preferable for broadband Er3+-doped fiber amplifiers. (C) 2004 Elsevier B.V. All rights reserved.

TeO2-Nb2O5-YF3玻璃系统的形成区及性质研究

制备了一种新型的氧卤碲酸盐玻璃：TeO2-Nb2O5-YF3,给出并研究了TeO2-Nb2O5-YF3三元系统的玻璃形成范围。测试了玻璃的密度、折射率、差热(DTA)、拉曼光谱、红外透射光谱以及紫外吸收光谱,通过光谱分析研究了组分含量的变化对玻璃结构及红外透射特性的影响。实验结果表明,TeO2-Nb2O5-YF3玻璃系统具有优良的成玻璃性能和热稳定性等特性,而且在2.8～3.3 μm区域内无明显的[OH]基团吸收,在中红外3～5 μm区域具有优良透射性能,因此在中红外透射方面具有潜在应用价值。

Bi2O3-B2O3-TiO2系统玻璃的形成能力研究

采用传统的玻璃熔融方法，研究了Bi2O3-B2O3-TiO2-RmOn四元系统的玻璃形成区（RmOn分别为La2O3、Sb2O3、ZrO2、SiO2和Nb2O5氧化物），给出了上述四元系统的玻璃形成范围。研究发现：Bi2O3-B2O3-TiO2-La2O3系统的玻璃形成范围最大，当TiO2的摩尔含量超过25％时，上述五个系统均不能形成玻璃。分剐熔制了摩尔分数55Bi2O3-35B2O3—5TiO2—5RmOn的玻璃（RmOn分别为La2O3、Sb2O3、ZrO2、SiO2和Nb2O5），测定了其红外吸收光

Modelagem computacional aplicada na estimação de parâmetros cinéticos em processos químicos e cromatográficos

A estimação de parâmetros cinéticos em processos químicos e cromatográficos utilizando técnicas numéricas assistidas por computadores tem conduzido para melhoria da eficiência e o favorecimento da compreensão das fenomenologias envolvidas nos mesmos. Na primeira parte deste trabalho será realizada a modelagem computacional do processo de produção de biodiesel via esterificação, sendo que, o método de otimização estocástica Random Restricted Window (R2W) será correlacionado com os dados experimentais da produção de biodiesel a partir da esterificação do ácido láurico com etanol anidro na presença do catalisador ácido nióbico (Nb2O5). Na segunda parte do mesmo será realizada a modelagem computacional do processo de cromatografia de adsorção (batch process) onde serão correlacionados os dados provenientes dos modelos cinéticos de HASHIM, CHASE e IKM2 com os dados experimentais da adsorção de amoxicilina com quitosana, e também serão correlacionados os dados experimentais da adsorção de Bovine Serum Albumin (BSA) com Streamline DEAE com os dados provenientes de uma nova aplicação do método R2W mediante a implementação de um modelo cinético reversível. Ademais, as constantes cinéticas para cada processo supracitado serão estimadas levando em consideração o valor mínimo da função resíduos quadrados.

Structure and optical properties of Nb2O5 sculptured thin films by glancing angle deposition

Nb2O5 sculptured thin. films deposited by electron beam evaporation with glancing angle deposition were prepared. Nb2O5 sculptured thin. films with tilted columns are optical anisotropy. XRD, SEM, UV-vis-NIR spectra are employed to characterize the microstructure and optical properties. The maximum of birefringence (Delta n) is up to 0.045 at alpha = 70 degrees with packing density of 0.487. With increasing the deposition angle, refractive index and packing density of Nb2O5 STF are decreasing. The relationship among deposition parameter, microstructure and optical properties was investigated in detail. (C) 2008 Elsevier B. V. All rights reserved.

热带亚热带季风气候条件下表生成矿地球化学－以个旧和老挝Nameung、Boloven地区为例

在前人对热带亚热带季风型气候条件下云南个旧砂矿、老挝Xaymomboun特区Ban Nameung铜多金属矿和Champasak省Boloven高原玄武岩等研究成果基础上，采用典型表生矿床实证解剖思路，选择个旧白云岩风化剖面、锡铅砂矿、锰结核、砂矿重选流程、Ban Nameung硫化氧化矿和Boloven玄武岩风化壳等对象，通过岩矿鉴定、主量微量元素地球化学、稀土元素地球化学、人工重砂、化学物相和微区分析等研究手段，研究这些矿床表生成矿物质来源、成矿机理、矿床地球化学特征和矿物工业可利用性等内容，并探索热带亚热带季风型气候条件下典型矿床表生成矿三个问题：（1）Sn、Pb、Mn、Ag、REE、Nb、Ta、Ga和Cd等元素表生富集成矿（矿化）规律；（2）上述元素成矿机理和工业利用可能性；（3）典型矿床其他20几种元素表生贫化与富集规律。研究获得如下主要认识： 1. 个旧地区燕山期以来持续抬升和亚热带季雨林的表生环境，使个旧地区大面积出露的碳酸盐岩风化形成强烈岩溶地貌，碳酸盐岩风化过程中CaO和MgO大量淋失，为砂矿提供了巨大容矿空间，同时碳酸盐地区碱性环境有利于原生硫化矿分解。含矿或不含矿白云岩、花岗岩、玄武岩、夕卡岩和原生硫化矿石等风化形成粘土矿物和铁锰氧化物，释放出Sn、Pb、Mn、Ga、Cd、Ag、In、Cu和Zn等元素，难风化重矿物如锡石表生残留富集，而粘土矿物和铁锰氧化物对成矿元素吸附是砂矿表生成因机理之一。 2. 个旧地区岩溶型砂矿形成机理为：（1）原生重矿物残留富集成矿，如锡石、磁铁矿。（2）金属硫化物残留成矿，如砂矿中残存大量方铅矿、黄铜矿、黄铁矿，是原生硫化物残留结果。（3）表生矿物富集成矿，如白铅矿、孔雀石、自然铅和自然铜等富集。（4）铁锰氧化物吸附和包裹成矿，如铁锰氧化物吸附Pb和Ga等元素，包裹含Pb和Zn微粒矿物。（5）锰结核吸附包裹成矿，锰结核吸附和包裹Sn、Pb和Cu等元素和微粒矿物。（6）类质同象成矿，如Ga和Al类质同象，Cd和Zn等类质同象成矿。（7）岩溶作用成矿，岩溶落水洞或溶洞内水流冲刷使锡石等重矿物富集成矿。元素表生成矿不仅是单一成矿作用结果，而是综合作用结果，如Pb有表生矿物富集成矿，也有铁锰氧化物吸附成矿。 3. 砂矿中锰结核是锰铁结核，主要成分为Fe2O3 、Al2O3、SiO2和MnO等，包裹了赤铁矿、方解石、云母、石英、蒙脱石、高岭石、白云石、钾长石等和锡石、白铅矿等矿物。锰结核中Mn、Sn、Pb、Ag、Ga、Cd和In富集成矿，Cu和Zn富集矿化，锰结核比砂矿更富集Mn、Pb和REE，其成矿机理应是吸附和包裹成矿元素或矿物使其富集成矿。 4. 个旧表生砂矿共生伴生组分复杂，有用矿物有锡石、方铅矿、白铅矿、黄铜矿、自然铅、自然铜、孔雀石、软锰矿、白钨矿、磁铁矿和褐铁矿等。模拟岩溶作用自然过程中砂矿矿物流向的源兴采选车间砂矿重选流程结果表明，锡铅精矿中Pb、Ga、Mo、Cd、In、Cu和Zn等金属总实收率仅为3.03％～6.44％，绝大部分金属留在了尾矿中。一段床和矿泥床分析中，Ag和Mn回收率低于0.66％～0.29％，Ag富集在硫化物态中，没有富集在铁锰氧化物态中；Mn富集在碳酸盐态中，没有铁锰氧化物态中。整个流程中Pb、Mn、Cu和Zn等富集在碳酸盐态矿物中，没有富集在硫化物态中。选矿流程没有利用具有潜在利用价值矿物如磁铁矿。重选流程解释了岩溶过程能富集Pb、Mn、Cu和Zn的碳酸盐矿物，不能富集这些元素的硫化矿物。 5. 老挝Ban Nameung硫化矿氧化初期，风化产物中Ag、Pb、Zn和Cu淋失，SiO2、K2O和CaO富集，风化后期Ag、Fe和Mn富集。硫化矿风化过程中，Au硫化物态部分变为有机态和铁锰氧化物态；Ag硫化物态部分变为铁锰氧化物态和有机态；Cu硫化物态部分变为铁锰氧化物态和碳酸盐态；Pb硫化物态、吸附态、碳酸盐态和铁锰氧化物态部分变为铁锰氧化物态、碳酸盐态和有机态；Zn硫化物态变为部分铁锰氧化物态、有机态、碳酸盐态和吸附态矿物。随着风化作用加强，上述几种相态比例还会改变。 6. 老挝Boloven新生代亚碱性玄武岩富Nb、Ta和Ga等微量元素，风化壳中REE、Nb、Ta和Ga已富集成矿，∑REE最高775×10-6～1003×10-6，（Nb2O5＋Ta2O5）最高642×10-6~656×10-6，Ga最高81.6 ×10-6。风化壳中达到边界品位的（Nb2O5＋Ta2O5）厚度有2m以上。REE可能存在于含P和Ti矿物中，也可能形成REE独立矿物。Nb、Ta和Ga应赋存在Ti、U、Zr和Th矿物中，其成矿应是重矿物表生残留富集结果，与粘土矿物吸附和三水铝石关系不紧密。

Optimization of the Mechanical and Optical Properties of Tunable Optical Sensor Arrays (TOSA) for a Nanospectrometer in the Visible and Near Infrared Spectral Range

Tunable Optical Sensor Arrays (TOSA) based on Fabry-Pérot (FP) filters, for high quality spectroscopic applications in the visible and near infrared spectral range are investigated within this work. The optical performance of the FP filters is improved by using ion beam sputtered niobium pentoxide (Nb2O5) and silicon dioxide (SiO2) Distributed Bragg Reflectors (DBRs) as mirrors. Due to their high refractive index contrast, only a few alternating pairs of Nb2O5 and SiO2 films can achieve DBRs with high reflectivity in a wide spectral range, while ion beam sputter deposition (IBSD) is utilized due to its ability to produce films with high optical purity. However, IBSD films are highly stressed; resulting in stress induced mirror curvature and suspension bending in the free standing filter suspensions of the MEMS (Micro-Electro-Mechanical Systems) FP filters. Stress induced mirror curvature results in filter transmission line degradation, while suspension bending results in high required filter tuning voltages. Moreover, stress induced suspension bending results in higher order mode filter operation which in turn degrades the optical resolution of the filter. Therefore, the deposition process is optimized to achieve both near zero absorption and low residual stress. High energy ion bombardment during film deposition is utilized to reduce the film density, and hence the film compressive stress. Utilizing this technique, the compressive stress of Nb2O5 is reduced by ~43%, while that for SiO2 is reduced by ~40%. Filters fabricated with stress reduced films show curvatures as low as 100 nm for 70 μm mirrors. To reduce the stress induced bending in the free standing filter suspensions, a stress optimized multi-layer suspension design is presented; with a tensile stressed metal sandwiched between two compressively stressed films. The stress in Physical Vapor Deposited (PVD) metals is therefore characterized for use as filter top-electrode and stress compensating layer. Surface micromachining is used to fabricate tunable FP filters in the visible spectral range using the above mentioned design. The upward bending of the suspensions is reduced from several micrometers to less than 100 nm and 250 nm for two different suspension layer combinations. Mechanical tuning of up to 188 nm is obtained by applying 40 V of actuation voltage. Alternatively, a filter line with transmission of 65.5%, Full Width at Half Maximum (FWHM) of 10.5 nm and a stopband of 170 nm (at an output wavelength of 594 nm) is achieved. Numerical model simulations are also performed to study the validity of the stress optimized suspension design for the near infrared spectral range, wherein membrane displacement and suspension deformation due to material residual stress is studied. Two bandpass filter designs based on quarter-wave and non-quarter-wave layers are presented as integral components of the TOSA. With a filter passband of 135 nm and a broad stopband of over 650 nm, high average filter transmission of 88% is achieved inside the passband, while maximum filter transmission of less than 1.6% outside the passband is achieved.

All solid-state electrochromic devices with gelatin-based electrolyte

6 x 8cm(2) electrochromic devices (ECDs) with the configuration K-glass/EC-layer/electrotype/ion-storage (IS) layer/K-glass, have been assembled using Nb2O5:Mo EC layers, a (CeO2)(0.81)-TiO2 IS-layer and a new gelatin electrolyte containing Li+ ions. The structure of the electrolyte is X-ray amorphous. Its ionic conductivity passed by a maximum of 1.5 x 10(-5) S/CM for a lithium concentration of 0.3g/15ml. The value increases with temperature and follows an Arrhenius law with an activation energy of 49.5 kJ/mol. All solid-state devices show a reversible gray coloration, a long-term stability of more than 25,000 switching cycles (+/- 2.0 V/90 s), a transmission change at 550 nm between 60% (bleached state) and 40% (colored state) corresponding to a change of the optical density (Delta OD = 0. 15) with a coloration efficiency increasing from 10cm(2)/C (initial cycle) to 23cm(2)/C (25,000th cycle). (c) 2007 Elsevier B.V. All rights reserved.

Síntese e caracterização de CuNb2O6 e CuNbC através de reação sólido- sólido e gás- sólido a baixa temperatura

The refractory metal carbides have proven important in the development of engineering materials due to their properties such as high hardness, high melting point, high thermal conductivity and high chemical stability. The niobium carbide presents these characteristics. The compounds of niobium impregnated with copper also have excellent dielectric and magnetic properties, and furthermore, the Cu doping increases the catalytic activity in the oxidation processes of hydrogen. This study aimed to the synthesis of nanostructured materials CuNbC and niobium and copper oxide from precursor tris(oxalate) oxiniobate ammonium hydrate through gas-solid and solid-solid reaction, respectively. Both reactions were carried out at low temperature (1000°C) and short reaction time (2 hours). The niobium carbide was produced with 5 % and 11% of copper, and the niobium oxide with 5% of copper. The materials were characterized by X-Ray Diffraction (XRD), Rietveld refinement, Scanning Electron Microscopy (SEM), X-Ray Fluorescence Spectroscopy (XRF), infrared spectroscopy (IR), thermogravimetric (TG) and differential thermal analysis (DTA , BET and particle size Laser. From the XRD analysis and Rietveld refinement of CuNbC with S = 1.23, we observed the formation of niobium carbide and metallic copper with cubic structure. For the synthesis of mixed oxide made of niobium and copper, the formation of two distinct phases was observed: CuNb2O6 and Nb2O5, although the latter was present in small amounts

Desenvolvimento de um protótipo para alimentação de pós para aspersão térmica em tocha de plasma

The nanometric powders have special features that usually result in new properties, originating applications or expanding them in various fields of knowledge. Because having a high area/volume ratio, phenomena such as superficial strength of adsorption becomes greater than the weight of the powder which makes more difficult its handling. The high power of agglomeration of these powders requires study and development of equipments to enable its management into the plasma torch. The objective of this work is to develop a powder feeder which can solve the mainly problems about insertion of powder into the thermal spray developed in the laboratory of plasmas, which are carried out with plasma torch arc not transferred (plasma spray). Therefore, it was made a aluminum s powder feeder and tests were performed to verify their operation and determine its rate of deposition by spraying powders of niobium pentoxide (Nb2O5) and titanium dioxide (TiO2) with particle sizes less than 250 mesh (<0.063 mm). We used masses of 0.5 g - 1.0 g and 1.5 g of each powder in tests lasting 15 seconds - 20 to 25 seconds for each mass. The tests were performed in two ways: at atmospheric pressure using argon gas with a flow of 9 l / min as carrier gas and through a Venturi pipe also using argon gas with a flow of 9 l / min as carrier gas and with a flow of 20 l/min as the feed gas passing through the Venturi pipe. The powder feeder developed in this paper is very easy to be handling and building, resulting in feeding rate of 0.25 cm3/min - 1.37 cm3/min. The TiO2 showed higher feeding rates than the Nb2O5 in all tests, and the best rates were obtained with tests using mass 1.5 g and time of 15 seconds, reaching feeding rate of 1.37 cm3/min. The flow of feed had low interference in feeding rate during the tests

Obtenção de pós de Nb a partir da redução aluminotérmica com ignição por plasma

The aluminothermic reduction consists in an exothermic reaction between a metallic oxide and aluminum to produce the metal and the scum. The extracted melted metal of that reaction usually comes mixed with particles of Al2O3 resulting of the reduction, needing of subsequent refine to eliminate the residual impure as well as to eliminate porosities. Seeking to obtain a product in powder form with nanometric size or even submicrometric, the conventional heat source of the reaction aluminothermic , where a resistor is used (ignitor) as ignition source was substituted, for the plasma, that acts more efficient way in each particle of the sample. In that work it was used as metallic oxide the niobium pentoxide (Nb2O5) for the exothermal reaction Nb2O5 + Al. Amounts stoichiometric, substoichiometric and superestoichiometric of aluminum were used. The Nb2O5 powder was mixed with aluminum powder and milled in planetarium of high energy for a period of 6 hours. Those powders were immerged in plasm that acts in a punctual way in each particle, transfering heat, so that the reaction can be initiate and spread integrally for the whole volume of the particle. The mixture of Nb2O5 + Al was characterized through the particle size analysis by laser and X-ray diffraction (DRX) and the obtained product of reaction was characterized using the electronic microscopy of sweeping (MEV) and the formed phases were analyzed by DRX. Niobium powders with inferior sizes to 1 mm were obtained by that method. It is noticed, through the analysis of the obtained results, that is possible to accomplish the aluminothermic reduction process by plasma ignition with final particles with inferior sizes to the original oxide

Síntese de Fischer-Tropsch sobre perovskitas LayCu0,4Fe0,6O3

The current natural gas production of 52 Mm3d-1 and the large projects for its expansion has been setting new boundaries for the Brazilian industry of oil and gas. So far, one of the biggest challenges regards to the logistics for gas transportation from offshore fields. Therefore, the transformation of natural gas into gasoline, diesel and/or olefins via Fischer-Tropsch synthesis would be an alternative to this matter. In this work, the production of hydrocarbons by Fischer-Tropsch synthesis in a slurry reactor was investigated and a perovskite-type catalyst (LayCu0,4Fe0,6O3 ± d) was used with y varying from 0 to 1 on a molar basis. In addition, Nb2O5 support was also applied in order to observe the selectivity of the produced hydrocarbons by the Fischer-Tropsch process. It is shown that the hydrogen conversion was influenced by the support as well as the different phases of the samples. The kinetic results for the CO2 production suffered great influence with the introduction of the Nb2O5 support throughout the series of samples studied. The catalysts allowed obtaining welldefined cuts of hydrocarbons in the range of C1-C6 and C17-C28, and these results were clearly influenced by the support and the lanthanum content. The higher olefin/paraffin ratio obtained was 1.8 when using a non-supported perovskite with y equal to 0.8. This would indicate the suitability of using this material for the production of olefins

Preparation and characterization of cellulose/hydrous niobium oxide hybrid

A composite of cellulose extracted from bagasse with Nb2O5 center dot nH(2)O in three different proportions (16.67, 37.5 and 50.0 wt%) was prepared using the co-precipitation method. The materials were characterized by X-ray diffractometry (XRD), Fourier transform infra-red spectroscopy (FTIR), thermogravimetric analysis (TG/DTG), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). TG data obtained show that the presence of inorganic material influenced slightly the stability of the hybrid material. The precipitation of 16.67 wt.% of oxide was sufficient to inhibit the combustion peaks present in the DSC curve of cellulose. This work will help find new applications for these materials. Published by Elsevier Ltd.

Synthesis of KNbO3 nanostructures by a microwave assisted hydrothermal method

One-dimensional nanostructures of KNbO3 have attracted a great interest in the scientific community, mainly because of their promising application as nanoelectromechanical systems (NEMS). However, the synthesis of KNbO3 structures becomes complex due to the natural tendency to form non-stoichiometric potassium niobates. In this context, we report on the crystallization of one-dimensional KNbO3 nanostructures through the reaction between Nb2O5 and KOH under microwave-assisted hydrothermal synthesis (M-H). The use of this synthesis method made possible a very fast synthesis of singlecrystalline powders. Based on SEM, TEM and XRD characterizations, the influence of the synthesis time and the reactants concentration in the structure and morphology of the resultant KNbO3 was established. The conditions that favor the crystallization of nanofingers were determined to be small amounts of Nb2O5 and short reaction times. (C) 2008 Elsevier B.V. All rights reserved.

Microwave-assisted hydrothermal synthesis of structurally and morphologically controlled sodium niobates by using niobic acid as a precursor

There are many advantages to using a microwave as a source of heat in hydrothermal reactions. Because it is a quick and homogeneous way to crystallize ceramic powders, it was used in this work for the production of antiferroelectric sodium mobate (NaNbO3) in a cubic-like form and its intermediary phase, disodium diniobate hydrate (Na2Nb2O6 center dot H2O), with a fiber morphology. The syntheses were carried out by treating niobic acid (Nb2O5 center dot nH(2)O) with NaOH. By changing the reaction time and the concentration of the reactants, particles with different structures and different morphologies could be obtained. The structural evolution of the products of this reaction was elucidated on the basis of the arrangement of the NbO6 octahedral units. Conclusive results were obtained with morphological and structural characterizations through XRD, TEM, MEV, and NMR and Raman spectroscopy. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).