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1.
Thin buffer layers of hydrogen diffusive metals such as Ti, Nb, and V were inserted between a Mg4Ni thin film and a Pd top layer, which were prepared by DC magnetron sputtering. Their optical, electrochemical properties, and switching durability were investigated using both gasochromic and electrochromic switching methods. It has been proved that Ti, Nb, and V buffer layers can protect the migration of Mg to surface of thin film during the switching processes, and also service as a protection layer against the oxidization of Mg. These metal buffer layers do not affect the hydrogenation of Mg–Ni alloy mirrors system when switching with hydrogen gas or electrochromic, rather, its dehydrogenation speed is accelerated greatly. Switching cyclic number of those metal buffer layer inserted mirrors achieved 400–500 cycles which was enhanced ca. 3 times than non-inserted one.  相似文献   

2.
Palladium-coated magnesium–manganese–nickel films behave as gasochromic switchable mirrors, becoming transparent on exposure to dilute hydrogen, and reverting to a mirror state on exposure to air. The cycling stability of the optical switching depends upon preservation of the integrity of the Pd catalyst overlayer. Alloying between Mg and Pd causes interdiffusion of the two elements, and leads to degradation in switching speed and eventual deactivation. Incorporation of a thin niobium oxide barrier layer between the active magnesium alloy film and the Pd layer substantially improves the cycling stability of the mirror.  相似文献   

3.
We applied magnesium–titanium (Mg–Ti) thin film as the optical switching layer to all-solid-state switchable mirror on plastic sheet (polyethylene terephthalate, PET) in the viewpoint of clear transparency at the transparent state. For the switching speed from the reflective to the transparent states, the PET-device showed a little slower switching speed than the glass-device, and it depended on the sheet resistance of indium tin oxide (ITO). When Mg–Ti thin film was applied to the PET-device, absorption at the visible ray was reduced, resulting in near-colorless state at the transparent state. The PET-device with Mg–Ti thin film showed chromaticity coordinates of x=0.341 and y=0.339 and a luminous transmittance of 42.4% at the transparent state. However, the PET-device had lower durability than that of the glass-device. It seemed to be related with the degradation mechanism of the optical switching layer. When Mg–Ti thin film after the durability test was analyzed by XPS, though the glass-device had much oxidized state of magnesium, the PET-device had mixture states of oxide and hydroxide in the optical switching layer. We suggest that the hydroxide in the layer will be formed by including water in the PET sheet, and the hydroxide might significantly affect the rapid degradation of the PET-device.  相似文献   

4.
Pd-capped Mg-rich Mg-Ni alloy thin film shows excellent reversible switching properties in optical transmittance by the exposure to hydrogen containing gas. However, it shows fast degradation due to the oxidization of magnesium and the switching durability is not good enough for practical applications. To resolve this problem we tried to improve its switching durability of Mg-Ni based switchable mirror by the combined use of metal buffer layer insertion between Pd and Mg-Ni layer and polytetrafluoroethylene (PTFE) protective coating. PTFE thin film has been prepared on the surface of Mg-Ni thin films by RF magnetron sputtering in the Ar and CF4 mixed gas discharge plasma at room temperature and a power of 30 W. The sample of Pd/Ti/Mg4Ni thin film with the protective coating of 900-nm-thick PTFE layer can be switched over 1600 switching cycles, which suppress the degradation by 15% of its initial transmission modulation level.  相似文献   

5.
A multilayer film of Mg and Ni was prepared by dc/ac magnetron sputtering and annealed below 623 K in vacuum to obtain polycrystalline Mg2Ni thin films. The phase transformation during heating process and optical switching properties of the films were investigated. The influence of the original crystalline state of Mg2Ni films on optical switching properties such as transmission, optical band gaps and the cycle times was discussed. The indirect optical band gaps of the fully hydrogenated amorphous Mg2Ni films were estimated by linear extrapolation.  相似文献   

6.
Mg–Li–Al–Ce–Zn and Mg–Li–Al–Ce–Zn–Mn alloys were prepared using a vacuum induction melting method. Their electrochemical oxidation behavior in 0.7 M NaCl solution was investigated by means of potentiodynamic polarization, potentiostatic oxidation, electrochemical impedance technique and scanning electron microscopy examination. Their utilization efficiencies and performances as anode of metal–hydrogen peroxide semi-fuel cell were determined. The Mg–Li–Al–Ce–Zn–Mn exhibited higher discharge activity and utilization efficiency than Mg–Li–Al–Ce–Zn, and gave improved fuel cell performance. The utilization efficiency of Mg–Li–Al–Ce–Zn–Mn is comparable with that of the state-of-the-art magnesium alloy anode AP65. The magnesium–hydrogen peroxide semi-fuel cell with Mg–Li–Al–Ce–Zn–Mn anode presented a maximum power density of 91 mW cm−2 at room temperature. Scanning electron microscopy and electrochemical impedance studies indicated that the alloying element Mn prevented the formation of dense oxide film on the alloy surface and facilitated peeling off of the oxidation products.  相似文献   

7.
Mg1?xPdxNi (x = 0.03, 0.05, 0.06, 0.07, 0.08, 0.10, 0.20) type alloys were synthesized by mechanical alloying and their electrochemical hydrogen storage characteristics were investigated. The XRD studies showed that Mg6Pd and Mg–Pd phases form in the high-Pd-containing alloys. The discharge capacities of the alloys increased sharply up to 15 h milling. Further increase up to 25 h did not cause change in the discharge capacities considerably. Among the Mg1?xPdxNi ternary alloys, Mg0.93Pd0.07Ni alloy was observed to exhibit the best charge/discharge cyclic performance. The hydrogen storage capacity of the high-Pd-containing alloys (Mg1?xPdxNi; x > 0.07) deteriorated as Pd content of the alloy increased. This observation was attributed to the Mg–Pd phase formations. According to the EIS experiments as Pd atomic ratio increased up to 0.07 the charge transfer resistances of the alloys decreased. Further increase in Pd atomic ratio, however, brought about the increase in the charge transfer resistances.  相似文献   

8.
Hydrogenated amorphous silicon solar cells have been realised in both a p–i–n configuration on a Corning glass substrate as well as in a n–i–p configuration on stainless-steel substrate. The performance degradation of the two kinds of cell under solar illumination has been examined for a 140 h period. During degradation, the two devices were kept under load in the maximum power condition that is normally used in a solar plant. The performance of the Corning glass deposited device exhibited a higher rate of degradation with respect to the other cell. A discussion on the possible reasons for this behaviour is given.  相似文献   

9.
The influence of varying relative humidity (RH55 and 75%) during thin film deposition from an oxalato-acetylated peroxotungstic acid sol by dip coating, on the microstructure and electrochromic properties of pristine tungsten oxide (WO3) films obtained upon annealing is presented. The films fabricated under a relative humidity of 55% are amorphous whereas the ones cast under a substantially humid atmosphere (RH75%) are characterized by interconnected nanocrystallites with a triclinic phase and a nanoporous surface morphology as well. Upon lithium insertion, larger integrated values of transmission modulation and coloration efficiency are observed over the photopic and solar regions, for the films prepared under a RH75% as compared to that observed for the films deposited under a RH of 55%. Functional improvements are due to the larger surface area of nanocrystallites and a porous microstructure, a consequence of a higher degree of hydration and hydroxylation in the former films in contrast to the non-porous and a rather featureless structure of the latter films. Faster switching kinetics between the clear and blue states, a greater current density for lithium intercalation, a higher diffusion coefficient for lithium and a superior cycling stability, again shown by the film fabricated under a 75% RH confirm that the WO3 film microstructure is most conducive for a more facile ion insertion–extraction process, which hints at its potential for electrochromic window applications.  相似文献   

10.
A new hydrogen generation material, Al-Ca alloy, is prepared by ball milling method. Results show the prepared Al-Ca alloy can react with to produce hydrogen, but its hydrogen yield is lower. NaCl addition can further greatly improve hydrogen generation of Al-Ca alloys. The amount of NaCl addition and ball milling time depends on the Ca contents of alloys. As the Ca contents of alloy increase, the amount of NaCl addition or ball milling time may be reduced accordingly. Increasing Ca contents, NaCl addition or ball milling time is beneficial to improve the hydrogen generation rate. Al-Ca alloys can react with water to produce hydrogen at the temperature ranging from 10 °C to 80 °C, and simultaneously a great amount of heat is released. With the increase of air exposure time, the dense Al2O3 and CaO layer formed on the surface of alloy particles will reduce the oxidation reaction rate. Chloride ions and sulfate ions can greatly decrease the induction period of hydrogen generation reaction and obviously improve hydrogen generation rate. Ca2+ ions and Mg2+ ions can affect the production of hydrogen due to their strong affinity to OH, especially Mg2+ ions which greatly decrease the hydrogen yield to 20%.  相似文献   

11.
Mixed CeO2–TiO2 coatings synthesized by sol–gel spin coating process using mixed organic–inorganic Ti(OC3H7)4 and CeCl3·7H2O precursors with different Ce/Ti mole ratios were investigated by a wide range of characterization techniques. The attempts were directed towards achieving coatings with high transparency in the visible region and good electrochemical properties. Elucidation of the structural and optical features of the films yielded information on the aspects relevant to their usage in transmissive electrochromic devices. The films have been found to exhibit properties for counter electrode in electrochromic smart windows in which they are able to retain their transparency under charge insertion, high enough for practical uses. The high optical modulation and fastest switching for WO3 film in the device configuration with the Ce/Ti (1:1) film is interpreted in terms of conducive microstructural changes induced by addition of TiO2 in an amount equivalent to CeO2.  相似文献   

12.
Hitherto unexplored irreversible changes during initial coloration/bleaching cycles for sol–gel-derived tungsten oxide (WO3) films have been investigated using cyclic voltammetric and spectrophotometric techniques. Non-ideal features appearing in the initial five anodic (deintercalation) cycles in the voltammogram with simultaneous decreased optical transmission of the bleached films have been explained in terms of possible stoichiometric variations affecting the coloration efficiency (CE) of the films and the associated mechanisms. Electrochromic stability attained thereafter manifests in retraceable voltammograms and almost invariant value of the CE.  相似文献   

13.
The technique of trace element doping to modify the solidification mechanism of faceted/non-faceted eutectics has been applied to the Mg–Mg2Ni alloy system. It is demonstrated that the micro- and nano-structure of cast hypoeutectic Mg–Mg2Ni alloys can be varied by trace additions of Na, Ca or Eu to the liquid prior to solidification. As a result, the reversible hydrogen absorption capability was in excess of 90% of the theoretical value of 6.8 wt.% under the absorption parameters of 350 °C and 1 MPa for 24 min and subsequent desorption at 0.2 MPa for 24 min after activation. The hydrogen absorption kinetics have been dramatically improved under realistic industrial conditions, and show no sign of reduced capacity over 200 cycles. This processing route results in a non-pyrophoric material that may be produced in large quantities at comparatively low cost.  相似文献   

14.
A new silicon solar cell structure is presented in which the p–n junction is formed by alloying aluminum with n-type silicon, and where this p–n junction is located at the back (unilluminated) side of the cell. With a phosphorus front diffusion, the resultant n+np+ structure has been implemented using dendritic web silicon substrates which are 100 μm thick and doped with antimony to 20 Ω cm. Such a structure eliminates shunting of the p–n junction, provides an effective front surface field, enables a high minority carrier lifetime in the base, and is immune to light-induced degradation. Using only production-worthy, high-throughput processes, aluminum alloy back junction dendritic web cells have been fabricated with efficiencies up to 14.2% and with corresponding minority carrier (hole) lifetime in the base of 115 μs.  相似文献   

15.
We report the successful application of reduced graphene oxide–titania (rGO–TiO2) nanocomposite as an efficient photoanode for dye‐sensitized solar cell (DSSC). The DSSC assembled with the rGO–TiO2‐modified photoanode demonstrated an enhanced solar to electrical energy conversion efficiency of 4.74% compared with the photoanode of DSSC composed with unmodified TiO2 (2.19%) under full sunlight illumination (100 mW/cm2, AM 1.5G) as a result of the better charge collection efficiency of rGO, which reduced the back electron transfer process. Influence of the rGO content on the overall efficiency was also investigated, and the optimal rGO content for TiO2 was 0.5 mg. Further, the modification of rGO–TiO2 on the compact layer TiO2 surface led to an increase in efficiency to 5.83%. The superior charge collection and enhanced solar energy conversion efficiency of the rGO–TiO2 nanocomposite makes it to be used as a promising alternative to conventional photoanode‐based DSSCs. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

16.
Electrochromic (EC) “smart” windows for buildings represent an effective way to modulate the intensity of incoming solar radiation. While it is accepted that WO3 films represent the best option for the working electrode, the choice of the best counter-electrode is still debatable. Optical properties of counter-electrodes such as Ce, Fe, V and Sn oxides are presented. Electrochromic windows were made with a sol–gel WO3 active colouring film (150°C), Ce, Fe, V oxide counter-electrodes and a sol–gel organic–inorganic hybrid (Li+ormolyte) ion conductor. The electrochromic responses of these devices predicted from the charge capacities, photopic transmittances and coloration efficiencies of individual films are compared with measured values.  相似文献   

17.
This study examined the material and electrochromic properties of vanadium–titanium oxides (V–Ti oxides) as a counter electrode material in electrochromic devices. These oxides were deposited on an ITO substrate using a co-sputtering method at different levels of RF power. Electrochemical experiments of these oxides were carried out using half-cell and semi full-cell tests which are good methods for measuring the potential applied to each electrode. The change in electrochromic properties after 1000 cycles of a semi full-cell test was examined. Reversibility and durability of an electrochromic device were improved by increasing the titanium content in V–Ti oxides.  相似文献   

18.
Up to now antireflective silica thin films deposited on glass do not have enough strength and display poor adhesion to the substrate. Three methods to obtain silica antireflective films on glass were surveyed to identify the best way to produce the antireflective effect on glass by introducing a certain degree of porosity. Porous silica layers, obtained from the polymeric and colloidal methods, permit a considerable reduction of these light reflections compared with uncoated glasses in all the cases studied, but the degree of reduction as well as the adhesive properties is different depending on the method used to achieve the precursor solution. The AM1.5 solar transmittance increased from 0.915 for the bare slide up to 0.970 for the best-made sample corresponding to the Triton-doped silica.  相似文献   

19.
Thin films of titanium dioxide and titanium–vanadium oxide were obtained by a sol–gel method. The coatings are uniform, smooth with very good optical properties. The solutions of both kinds are stable for more than a year. Structure and vibrational properties were studied with the help of X-ray diffraction (XRD) analysis and infrared spectroscopy (IR). The refractive indices and film thicknesses were measured by an ellipsometer at a wavelength of 638.2 nm, as a function of annealing temperature. The optical properties were investigated by ultraviolet–visible (UV–VIS) spectroscopy.  相似文献   

20.
CeO2–TiO2–ZrO2 thin films were prepared using the sol–gel process and deposited on glass and ITO-coated glass substrates via dip-coating technique. The samples were heat treated between 100 and 500 °C. The heat treatment effects on the electrochromic performances of the films were determined by means of cyclic voltammetry measurements. The structural behavior of the film was characterized by atomic force microscopy and X-ray diffraction. Refractive index, extinction coefficient, and thickness of the films were determined in the 350–1000 nm wavelength, using nkd spectrophotometry analysis.Heat treatment temperature affects the electrochromic, optical, and structural properties of the film. The charge density of the samples increased from 8.8 to 14.8 mC/cm2, with increasing heat-treatment temperatures from 100 to 500 °C. It was determined that the highest ratio between anodic and cathodic charge takes place with increase of temperature up to 500 °C.  相似文献   

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