Bending Beam Method Research Articles

Tunable fiber Bragg grating filters realized by chirp rate tuning with a cantilever beam

An efficient scheme to change the chirp rate of a fiber Bragg grating (FBG) has been developed based on a specially-designed cantilever beam with the beam-bending method. It allows, to date, the largest tuning range of 36 nm in reflection bandwidth of a chirped-FBG (CFBG) while keeping the center wavelength nearly fixed during the tuning process. Using this method, bandwidth-tunable fiber grating filters with tunable chromatic dispersion or differential group delay have been demonstrated. Channel spacing-tunable multi-wavelength filters based on both sampled- and superimposed-CFBGs have also been realized. Moreover, tuning of the bandwidth and channel spacing is continuous with this scheme that makes the achieved devices more flexible.

Refractive error correction for in situ curvature measurement using laser beam deflection method

Stoney’s equation allows one to calculate the internal stress in a thin film deposited on a thick substrate from the curvature of the bilayer beam. The curvature measurement is thus critical in the bending beam method, which is based on this equation. When an optical technique is used in curvature measurement, the refraction at optical boundaries needs to be corrected. An approximate correction to Stoney’s equation accounting for refractive error in the bending beam method in electrochemical applications was reported previously. This paper revisits the derivation. A set of diagrams for optical paths in in situ curvature measurement using the laser beam deflection method are presented. These diagrams allow us to establish the triangular relationships among the incident angles of the light beam and the deflection angle of the cantilever beam. Correction solutions are derived for three possible optical arrangements with the consideration of the travel distance of the light beam in liquid and in the container wall. In its approximated form, the correction derived in this paper differs from the previous formula by a factor of 2. It was discovered that an incorrect relationship for curvature was used in the previous derivation.

一种通道数可变的光纤光栅梳状滤波器

An in-fiber Mach-Zehnder interferometer filter based on a pair of long-period fiber gratings (LPGs) had been operated in the reflection mode by incorporating a broadband chirped-fiber Bragg grating (CFBG) or an optical fiber mirror reflector.As a result,the extinction ratio has been nearly doubled and,by tuning chirp rate,i.e.reflection bandwidth of the CFBG using a beam-bending method,channel number of the formed optical comb filter can be easily changed.In our experiment,two comb filters with channel numbers being changed among odd ones from 1 to 5 and 3 to 9 have been achieved,respectively.Even channel filtering can also be achieved if the center wavelength of the chirped fiber grating is changable.

The condition for the evolution of extra current peak in the cyclic voltammogram of Li xMn 2O 4 investigated by in situ bending beam method

The condition for the occurrence of extra current peak near 3.7 ∼ 3.9 V in CV and the relationship between the intensity of the extra current peak and the volume of phase transformation from tetragonal to cubic phase was investigated using in situ bending beam method. It was found that the extra current peak evolved when the sample was subject to the 3 V range and its intensity increased as the excursion depth to the 3 V range was increased. The in situ bending beam method data revealed that the extra current peak accompanied the tensile strain variation which is due to the phase transformation of a residual tetragonal phase to a cubic phase. Further, it was found that the amount of the phase transformation increased as the excursion depth to the 3 V range increased, i.e. the volume of the phase transformation was proportional to the intensity of the extra current peak. It seems that the phase transformation from tetragonal phase to cubic phase cannot be completed during the voltage sweep at the 3 V peak. On the contrary, the voltage excursions to 4 V range did not affect the evolution of the extra current peak.

Increasing Superplasticity and Strong Dynamic Behaviour of Zr—Cu—Ni—Al Bulk Metallic Glass

The plasticity and the dynamic fragility of bulk metallic glass of a Zr62Cu18Ni10Al10 alloy are studied by three-point beam bending methods. We find that the alloy behaves super plastic not only at room temperature, but also at high temperatures. More importantly, it is found that the superplasticity increases with increasing temperature. In addition, the dynamic fragility parameter m for the supercooled liquid of this alloy is measured to be 34.87 and the supercooled liquid of Zr62Cu18Ni10Al10 alloy behaves as a strong liquid.

Changes in Surface Stress of Au Electrode during Underpotential Deposition of Bi and Pb.

The changes in surface stress of Au electrode (mainly oriented to (111) plane) during underpotential deposition (UPD) of Bi and Pb were measured by a bending beam method to investigate the relation between surface stress and structure of the adlayer. The surface stress changed to the compressive direction as Bi- or Pb-UPD proceeded. The changes in surface stress to the compressive direction responded sensitively to the structural changes of the Bi- or Pb-adlayer. The biaxial modulus of (p x root 3)-2Bi monolayer or hexagonal close-packed Pb monolayer on Au (111) electrode was estimated from the relation between the changes in surface stress and the surface elastic strain of the monolayer obtained by surface X-ray scattering. The factors influencing the changes in surface stress during UPD of Bi or Pb were discussed in connection with the structural changes of the adlayer.

Viscosity properties and strong liquid behavior of Pr60Ni25Al15 bulk metallic glass-forming liquids

Pr60Ni25Al15 bulk metallic glass in a cuboid form with dimensions of 2 mm × 2 mm × 55 mm by copper mold casting method was cast. The dynamic viscosity near the glass transition region for Pr60Ni25Al15 was measured by three-point beam bending methods. The fragility parameter m and activation energy for viscous flow of the liquid sample were calculated to be: m = 31.66, E = 10689.17 K, respectively. It was shown that the supercooled liquid of Pr60Ni25Al15 alloy behaved much closer to strong glasses. The variation of active energy with temperature in supercooled liquid was analyzed. It was found that Kivelson’s super-Arrhenius equation is not suitable for description of the activation energy in a supercooled region of Bulk metallic glass, and there is a direct proportion between activation energy crystallization and activation energy of viscous flow.

Sealing Properties of Ceramic Fiber Composites for SOFC Application

For the sealing of solid oxide fuel cells (SOFCs), mid-term (~1,000 h) sealing performance was examined using composite seals prepared with mixtures of a glass and alumino-silicate ceramic fiber. Leak rate could be reduced to < ~0.04 sccm/cm when using a composite seal with 60 vol% glass. Viscosity of the glass at the seal operating temperature of 650 was 2.0×108 dPa·s (log η = 8.3) as estimated by beam-bending method, and found to be suitable for sealing operation.

Long-term stable device for tuning fiber Bragg gratings

It is demonstrated that with a proper choice of embedding material, the composite beam bending method constitutes an effective and reliable approach for tuning fiber Bragg gratings. A long-term stable device is presented with a dynamic range of 80 nm, which exhibits insertion losses smaller than 0.28 dB and small variations of the full width at half-maximum.

Changes in surface stress of gold electrode during underpotential deposition of copper

The changes in surface stress of the evaporated gold electrode (mainly oriented to the (111) plane) during underpotential deposition (UPD) of copper in 0.1 M sulfuric acid medium or 0.1 M perchloric acid medium with and without sulfate or chloride were measured using a bending beam method. The surface stress maximum of gold electrode appeared during Cu-UPD. The co-adsorption of (bi)sulfate or chloride ions with copper atoms induced the compressive surface stress to promote the Cu-UPD. The factors influencing the surface stress or surface elastic strain were discussed in relation to the Cu-UPD structure.

Thin film stress measurement by instrumented optical fibre displacement sensor

Residual stress can adversely affect the mechanical, electronic, optical and magnetic properties of thin films. This work describes a simple stress measurement instrument based on the bending beam method together with a sensitive non-contact fibre optical displacement sensor. The fibre optical displacement sensor is interfaced to a computer and a Labview programme enables film stress to be determined from changes in the radius of curvature of the film–substrate system. The stress measurement instrument was tested for two different kinds of thin film, hard amorphous carbon nitride (CN) and soft copper (Cu) films on silicon substrates deposited by RF magnetron sputtering. Residual stress developed in 500 nm thick CN thin films deposited at substrate temperatures in the range 50–550 °C was examined and it was found that stress in CN films decreased from 0.83 to 0.44 GPa compressive with increase of substrate temperature. Residual stress was found to be tensile (121 MPa) for Cu films of thickness 1500 nm deposited at room temperature.

Changes in mass and stress during anodic oxidation and cathodic reduction of the Cu/Cu 2O multilayer film

The anodic oxidation and cathodic reduction processes of the Cu/Cu 2O multilayer film and pure Cu film in pH 8.4 borate buffer solution were analyzed by electrochemical quartz crystal microbalance (EQCM) for gravimetry and bending beam method (BBM) for stress measurement. The mass loss of the multilayer film during anodic oxidation at 0.8 V (SHE) in the passive region was less than that of the pure Cu film. The comparison between current transients and mass changes during anodic oxidation has succeeded in separating the anodic current density into two partial current densities of oxide film growth, i O 2 - , and of Cu 2+ dissolution through the passive film, i Cu 2 + . As a result, in the case of the pure Cu film, the anodic current density was mainly due to i Cu 2 + , while in the case of the multilayer film, i Cu 2 + was almost equal to i O 2 - . The compressive stress for the multilayer film was generated during anodic oxidation, while the tensile stress for the pure Cu film was generated. The mass loss of the multilayer film during cathodic reduction at a constant current density ( i c = −20 μA cm −2) was significantly less than that estimated from coulometry, suggesting that H 2O produced by cathodic reduction remained in the multilayer film. The compressive stress was generated during cathodic reduction of the multilayer film, which was ascribed to H 2O remained in the multilayer film.

Structural Changes in Li[sub x]Mn[sub 2]O[sub 4] at 3.7 V Induced by Voltage Excursions below 3.0 V

The 3.7 V peak observed in the cyclic voltammogram of Li x Mn 2 O 4 was investigated using the in situ bending beam method and synchrotron X-ray diffraction (XRD). The cyclic voltammogram (CV) at different cutoff voltages revealed the 3.7 V peak during the anodic scan only when the sample was subjected to the 3 V range. The differential strain curves (ds/dt) obtained simultaneously with the CV indicated the presence of tensile strain in the vicinity of 3.7 V suggesting sample volume contractions due to a phase transformation. Synchrotron XRD confirmed that the material underwent a tetragonal to cubic phase transformation.

Onset Mechanism of Jahn-Teller Distortion in 4 V LiMn2O4 and Its Suppression by LiM0.05Mn1.95O4 (M = Co , Ni) Coating

There have been several causes for the capacity fading of reported by many authors, which include Mn dissolution into the electrolyte, and the onset of a Jahn-Teller distortion. One of the main remedies suggested to combat those causes has been doping with other transition-metal ions. However, most of the deterioration reactions take place on the surface. In this study, was coated with a doped-spinel oxide to combat the causes of capacity fading in , which modifies only the surface of the electrodes, and its effect was diagnosed using the bending beam method (BBM). The doped-spinel coated showed an excellent cycle performance. From the BBM data, it was confirmed that this excellent performance was largely due to the suppression of the Jahn-Teller distortion, which takes place at the end of the cathodic sweep in the 4 V range. Furthermore, the mechanism for the onset and suppression of Jahn-Teller distortion in 4 V is proposed based on the strain variations of the stoichiometric, doped, and doped-spinel coated spinel electrodes.

Changes in Surface Stress of Gold Electrode during Underpotential Deposition of Pb

The changes in surface stress of a gold film electrode during underpotential deposition (UPD) of lead in pH 3.0, solution containing or were measured by a bending beam method to investigate the relation between surface stress and structural change of the Pb-UPD layer. A maximum in the surface stress vs. potential curve like an electrocapillary curve emerged at the onset of the UPD. Moreover, a hump in the surface stress vs. potential curve also emerged in the range of surface coverage of Pb from to 0.8 during the UPD process. The changes in surface stress were plotted vs. cathodic charge required for Pb-UPD. Two linear and one plateau region appeared in the surface stress vs. the cathodic charge curve. The plateau region corresponded to the hump in the surface stress vs. potential curve. It was deduced from the comparison with the scanning tunnel microscopy, atomic force microscopy, and surface X-ray scattering spectroscopy results in the literature that the plateau region is associated with the change in rotation angle from to 2.5° of incommensurate hexagonal close-packed Pb layer. Particularly, it was emphasized that the hump resulted from the release of compressive surface stress due to the change in rotation angle of the UPD layer. © 2004 The Electrochemical Society. All rights reserved.

Effect of target self-bias voltage on the mechanical properties of diamond-like carbon films deposited by RF magnetron sputtering

Diamond-like carbon (DLC) thin films were deposited by RF magnetron sputtering under different target self-bias voltages from −290 to −1090 V. Mechanical properties of these films in terms of hardness, Young's modulus, elastic recovery, and plastic resistance parameter ( H/ E) under different target self-bias voltages were analysed by the nanoindentation technique. Hardness and Young's modulus were found to increase in the range of 11–22 and 110–152 GPa, respectively, with increase of target self-bias voltage. The Korsunsky composite hardness model was used in order to determine the true hardness of DLC films from measurement on the film/substrate system. Residual stress in the films, measured using the bending beam method, was found to be compressive and increased with the increase of target self-bias voltage. The variation of intensity ratio, I d/ I g and the position of G-band of the DLC films with respect to target self-bias voltage were also investigated by Raman spectroscopy.

Investigations into capacity fading as a result of a Jahn–Teller distortion in 4 V LiMn 2O 4 thin film electrodes

This study reports the onset of the Jahn–Teller distortion in 4 V LiMn 2O 4 thin film electrodes that was investigated using an in situ bending beam method (BBM). The phase transformation during lithium insertion/extraction could be detected using the BBM technique. The phase transformation between the cubic and tetragonal phases was depicted by the larger value of the compressive or tensile differential strain, which is consistent with a well-known phase transformation between those phases in 3 V LiMn 2O 4. The cyclic deflectograms and cyclic voltammograms were obtained simultaneously. The potential ranges responsible for the Jahn–Teller distortion in 4 V range, which takes place at the electrode surface, was determined by the charge versus. differential strain (d ε/d Q) curve. The onset of the Jahn–Teller distortion was observed at the end of the cathodic scan, and the relaxation of the Jahn–Teller distortion was observed at the beginning of anodic scan. Furthermore, the onset of the Jahn–Teller distortion was found to be dependent on the lithium ion insertion rate, which was controlled by the scan rate.

Nondestructive measurements of the compact strength and the particle-size distribution after milling of roller compacted powders by near-infrared spectroscopy

Compact strength and the particle-size distribution of milled roller compacted compacts were correlated to the slope of the best-fit line through near-infrared spectra for samples prepared under different roll speeds and feed rates. The above correlations were found to hold for compacts prepared from microcrystalline cellulose powder as well as from a typical direct compression pharmaceutical powder blend containing tolmetin sodium dihydrate, microcrystalline cellulose, and dicalcium phosphate dihydrate. Near-infrared spectra were also collected real time for the compacts prepared from the tolmetin powder blend. The real-time slope values for the spectra showed good agreement with the off-line data. The strength of compacts was determined using three-point beam bending method and the particle-size distribution of the milled compacts was determined using sieve analysis. The results suggest that the real-time values of the slope of the best-fit line through the near-infrared spectrum offers a robust, yet simple and fast quality control tool to monitor/control manufacturing and scale-up processes involving dry granulation by roller compaction.

Suppression of Structural Fatigue by Doping in Spinel Electrode Probed by In Situ Bending Beam Method

The onset of a Jahn-Teller effect at the surface of particles during cycling in the 4 V range was previously reported to be one of the causes for the capacity fading. Furthermore, it has been reported that the Jahn-Teller effect in the 4 V range may be suppressed by the substitution of the Mn ions by either Li or other transition metal ions. However, no direct evidence has yet been reported. This study provides evidence for the onset of a Jahn-Teller effect in thin film 4 V and its suppression caused by substituting the Mn ions with and ions using in situ bending beam method (BBM). The deflectograms are measured simultaneously with galvanostatic charge/discharge or cyclic voltammograms, and the onset of the Jahn-Teller effect is investigated by means of the differential strain peak which is observed at around 3.90-3.95 V during cyclic voltammetry, and the slope variation observed in the strain curves during galvanostatic charge/discharge. The suppression of the Jahn-Teller effect in the doped spinel leads to the magnitude of the differential strain peak resulting from the Jahn-Teller effect being reduced in comparison with the other two pairs of peaks, which correspond to the current peaks of the cyclic voltammogram. © 2004 The Electrochemical Society. All rights reserved.

Determination of the potential range responsible for the replacement of surface film on LiMn 2O 4

This study determined the potential range where the dissolution of a surface film on a thin film LiMn 2O 4 electrode, which forms during electrode synthesis, and the formation of a new surface film during cycling at room temperature using an in situ bending beam method (BBM) and an in situ electrochemical quartz crystal microbalance (EQCM) technique with cyclic voltammetry and a galvanostatic charge/discharge cycle. The electrolytes used were LiClO 4/EC-DEC, LiClO 4/PC and LiPF 6/EC-DMC. The deflectogram and massogram showed large peaks during the anodic scan only in the first cycle. These phenomena, were observed regardless of the electrolytes and scan rate used. The tensile strain and the mass reduction in the early stage of the strain peak and the mass peak are related to the dissolution of the initial surface film. In addition, the compressive strain and the mass increase are related to the formation of a new surface film during cycling. The potential ranges where the formation of the new surface film begins ranged from 4.03 to 4.1 V, which appears to terminate at the end of the first anodic scan, and was also observed during the galvanostatic charge/discharge cycle in the same potential range.