2016年12月23日星期五

Trace H2O2-Assisted High-Capacity Tungsten Oxide Electrochromic Batteries with Ultrafast Charging in Seconds

As common energy storage devices, batteries play a key role in our daily life. Modern batteries are no longer characterized by the simple purpose of energy storage, but with designed multi-functionality as one of the hot topics and development directions of the battery research. A new-style electrochromic battery has been conceived which enables the highly desired convenient user-device interface based on a friendly human-readable output. However, the field of combination between the technology of battery and electrochromism is still rather young with many unsolved problems. For example, the specific capacity that the electrochromic battery delivers is rather low and the battery device needs a very long time for self-charging (12 hours). Therefore, exploring smart electrochromic battery with high performances is undoubtedly a worthwhile field of inquiry, and various solutions for building electrochromic batteries with new device configurations are eagerly needed.

Tungsten Oxide Electrochromic Batteries Photo







The scientists have successfully developed a high-capacity electrochromic batteries with ultrafast charging in seconds.
The aluminum (Al)/tungsten oxide material system was selected to build new electrochromic batteries, and they show the extraordinary advantages. First, the new born battery established an interactive interface between user and devices. Second, ultrafast charging could be realized by the small addition of hydrogen peroxide (8s). Third, the capacity of this electrochromic battery was 6 times higher than those of congeneric devices. This study opens the door for the future electrochromic batteries development.

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Carbon Doped Tungsten Oxide Nanorods NO2 Sensor Prepared by Glancing Angle RF Sputtering

Nanostructures such as nanowires, nanorods, nanotubes of metal oxide semiconductor (MOS) materials have recently attracted monumental interest in gas-sensing applications because of their excellent performances owing to their large surface to vol-ume ratio, lower electron recombination rate and high stability. Among various MOS materials, tungsten oxide (WO3) is a highly promising candidate due to its fast response with high sensitivity toward NOx.
Resistance response of the carbon-doped and undoped tungsten oxide sensor towards NO2

Glancing angle depositio (GLAD) technique is a relatively new method for fabrication of well-ordered and sophisticated nanostructures i.e. nanorods, nanoblade and zigzag nanocolumns. It is a modified physical vapor deposition process, in which substrate surface is rotated and tilted to an angle greater than 80° with respect to the normal of substrate surface or less than 10°with respect to the direction of vapor flux. The vapor molecules directed to the substrate will experience shadowing and limited surface diffusion condition leading to the formation of isolated nanostructures. With this technique, the shape, size and density of nanostructures can be well controlled by deposition parameters such as deposition angle, operating pressure, substrate temperature, deposition power, and so on. In this report, carbon-doped WO3 nanorods is fabricated by GLAD technique using RF magnetron sputtering and investigated for NO2 gas sensor application. In addition, its performances are comparatively studied with that of the undoped ones.

Carbon-doped and undoped WO3 nanorods gas sensors have successfully been fabricated by the GLAD technique with RF magnetron sputtering.  By this technique, the vertically well-aligned homogeneous tungsten oxide nanorods with very low defect were achieved over a large area. It was found that carbon doping does not change any crystalline structure but increases the grain size and accelerates the nanorods growth leading to relatively high aspect ratios as compared to the undope one. The fabricated carbon-doped WO3 nanorods sensor exhibits high response and selectivity to NO2 at the concentration range of 0.5–5 ppm at an optimum operating temperature of 250℃. In addition, the carbon-doped sensor still works well for NO2 detection at lower operating temperature of 150℃ due to the decrease of activation energy and alteration of the depletion layer. Therefore, carbon-doped well-ordered WO3 nanorods with improved NO2 gas-sensing performances in terms of response, response  time, selectivity and operating temperature has been realized. Moreover, this technique offers distinct advantages over other methods such as high productivity, simplicity and low cost for well-ordered nanostructure construction.

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Tungsten Oxide Nanoparticle as Catalyst for Malonic Acid Ester Synthesis via Ozonolysis

Ozonolysis is of great interest to synthetic organic chemistry because it is one of the most efficient tools for oxidatively cleaving carbon-carbon double bonds. Ozonolysis is generally used to prepare biologically active molecules. Therefore, the reactions between ozone and organic compounds continue to be a subject of significant interest from mechanistic, synthetic, and environmental perspectives. The importance of O3 reactions with alkenes in the troposphere and solution has led to many experimental and theoretical studies of their kinetics and mechanism.

Scientists addresses tungsten oxide nanoparticle syntheses for use as a catalyst in the novel one-step synthesis of malonic acid ester. Malonic acid ester is directly synthesized and esterified via the ozonolysis of palm olein (palm oil fraction), which comprises 10% linoleic acid as an unsaturated fatty acid. The main advantages of using tungsten oxide nanoparticles as the catalyst for this esterification are to shorten the reaction time. Using tungsten oxide nanoparticles also has minor advantages such as simple synthetic operation, excellent yields, and recyclability. The structure and size of the tungsten oxide nanoparticles were investigated via field emission scanning electron microscopy (FE-SEM) and X-ray powder diffraction (XRD). The malonic acid ester was spectroscopically characterized via gas chromatography mass spectroscopy (GC-MS).

tungsten oxide photo

The study used a new approach to synthesize malonic acid ester via the direct ozonolysis of palm olein, where the fine bubbles of ozone played an active role to cleave the double bonds. This method was used for the first time with a tungsten trioxide catalyst for the esterification of malonic acid and had the advantages of synthetic simplicity, an excellent 10% yield, short 2 h reaction time, and recyclability. Malonic acid ester was characterized using mass spectroscopy. The prepared nanoparticles have a spherical shape and diameter of 24 nm have been investigated by the FESEM & XRD, respectively.

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Porous Orthorhombic Tungsten Oxide Thin Films Applied in Electrochromic Device and Photochromic Device

Tungsten oxide was used in the production of electrochromic devices and photochromic devices


Tungsten oxide, also known as tungsten trioxide or tungstic anhydride, WO3, is a chemical compound containing oxygen and the transition metal tungsten. It is obtained as an intermediate in the recovery of tungsten from its minerals. The tungsten oxide nanoparticles can be applied in many areas. They can be used in colorant and analysis reagent of chinaware,  used in producing metal tungsten material, gas sensors,  fire-proofing fabrics, imaging; large-area displays, catalysts; ceramic pigments; humidity sensors, infrared switching devices; high-density memory devices and so on.

Orthorhombic tungsten oxide (o-WO3) thin films, stabilized by nanocrystalline anatase TiO2, are obtained by a sol–gel based two stage dip coating method and subsequent annealing at 600℃. An Organically Modified Silicate (ORMOSIL) based templating strategy is adopted to achieve porosity. An asymmetric electrochromic device is constructed based on this porous o-WOlayer. The intercalation/deintercalation of lithium ions into/from the o-WO3 layer of the device as a function of applied coloration/bleaching voltages have been studied. XRD measurements show systematic changes in the lattice parameters associated with structural phase transitions from o-WO3 to tetragonal LixWO3 (t-LixWO3) and a tendency to form cubic LixWO3 (c-LixWO3). 

These phase transitions, induced by the Li ions, are reversible, and the specific phase obtained depends on the quantity of intercalated/deintercalated Li. Raman spectroscopy data shows the formation of t-LixWO3 for an applied potential of 1.0 V and the tendency of the system to transform to c-LixWO3 for higher coloration potentials. Optical measurements show excellent contrasts between colored and bleached states. An alternate photochromic device was constructed by sensitizing the o-WO3 layer with a ruthenium baseddye. The nanocrystalline anatase TiO2 in the o-WO3 layer has led to an enhanced photochromic optical transmittance contrast of ∼51% in the near IR region. The combination of the photochromic and electrochromic properties of the synthesised o-WO3 layer stabilized by nanocrystalline anatase TiO2 opens up new vista for its application in energy saving smart windows.

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Nanocrystalline Tungsten Oxide Thick Film Sensor for the Detection of H2S Gas

Resistance variation on the introduction of different concentration of test gas


Metal oxide semiconductors (MOS) have been utilized as gas sensing active materials for half a century. One of the most promising solid-state MOS chemo sensors is n-type semiconducting tungsten oxide-based  gas  sensor.  They  have  demonstrated  novel sensing  properties  such  as  high  sensitivity,  fast response  time  and  low  operation  temperature.  In particular,  pure  or  doped  tungsten  oxide  is  a  promising material for the detection of various substances, e.g., H2,H2S,NOx, NH3 and ethanol.

Scientists have investigated  the sensing characteristics  of  WOnanoparticles  to H2S  in  the 7 to 200 ppm range at working temperatures of the range of 100–225 ℃.  Semiconductor  gas  sensors  based  on nanocrystalline  WO3  powders  were  prepared  by  acid precipitation method. The thick films of the powder were coated on to glass  substrate, annealed at 600 ℃ and its response  to  different  concentration  of  H2S  gas  was studied.  Sensor behavior is presented in detail for representative concentration of 18ppm. The result showed that WOnanoparticles are good candidates for sensing H2S at a temperature of 200 ℃.

Sensitive  layers  of  tungsten  oxide  were  prepared  by dispersing  the  prepared  tungsten  oxide  powder  in methanol and drop casting on glass  substrates followed by  overnight  annealing  at  600 ℃.  The obtained crystalline phase of WO3 nanoparticles was triclinic in nature. The structure of sensor was characterized using XRD.  The surface morphology and elemental composition were characterized by scanning electron microscopy and energy dispersive X-ray analysis. It was found that the WO3 samples consisted of crystalline aggregates.  This was confirmed in TEM results.  The particles were spherical in nature.  Gas  sensing properties  of  samples  were  studied  for  the  detection  of H2S  gas.   Resistance  of  the  films  decrease  upon exposure  to  gases  and  attained  a  saturation  value.

Sensor regains its original value after test gas is removed. Sensor exhibit good sensing characteristics to H2S in the concentration range studied, 7 to 200 ppm over the temperature range 100-125 0C. The best results were obtained at operating temperature of 200 ℃ with a sensitivity of 1.3. Response and recovery time of sensor at this optimum temperature was 22 seconds and 4.1 minutes respectively. Lowest measurable concentration is found to be 7ppm. Resistance  always  returned  to  its initial  value  after  the  test  gas  is  shut  off  for  all concentration  studied. Results indicate that response of sensor is reproducible during this test. 

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Tungsten Carbide Powder Preparation Using Violet Tungsten oxide

Tungsten carbide is a chemical compound containing equal parts of tungsten and carbon atoms. In the tungsten carbide powder, carbon atoms will embed in the interstice of tungsten metal lattice, which will not destroy the lattice of original metal and will form interstitial solid solution. Therefore, it can be also called interstitial compound or insertion compound, which is mainly used in producing cemented carbide due to its high hardness. As tungsten carbide powder has large application range, it has given rise to the waves of researching the preparation of tungsten carbide powder. Violet tungsten oxide can be used in producing tungsten carbide powder, this is because it has single-crystal structure, abundant crack as well as its interior is composed by loose needle-like or rod like particles, which will be beneficial for making tungsten carbide powder that has superior quality. In the preparation of tungsten carbide powder by violet tungsten oxide, violet tungsten oxide is used as the raw material, which will be reduced by hydrogen in the four tube furnace according to the traditional technology, in which the raw material load will be 600g, the pushing speed will be 20min/load and the hydrogen flow will be 30.0m3/h. Under fully unified technology, the reduction process of various oxides will be carried out in the same furnace.

The tungsten powders that have been generated in the furnace will be respectively fit with carbon under same carbon content, which will be mixed evenly and will be carbonized in the same carbide furnace under the carbonization temperature of 1100 degrees Celsius to 1400 degrees Celsius, thus the tungsten carbide powder can be obtained. Tungsten carbide powder that is produced by violet tungsten oxide will have small and even particle size as well as narrow particle distribution, besides, it has no structural agglomerate, which can be made into superfine cemented carbide that has high strength and high hardness.

tungsten carbide powder photo

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