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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2016年11月28日星期一

Tungsten Oxide Used to Increase the Heat-input Amount of Near Infrared Radiation

The invention relates to the use of tungsten oxide or tungstate to increase the heat-input amount of near infrared radiation. It was found that these materials exhibit a distinct higher effect than other known Infrared Radiation(IR) absorbers although absorbing the same amount of energy. This is very surprising and cannot be explained so far. Tungsten bronzes incorporated in coatings led to a much higher temperature increase upon irradiation with IR than expected according to its spectral absorption capacity. The temperature increasing measured was distinctly higher than found with other known IR absorbers and reached almost the temperature observed with carbon black.

Tungsten Oxide Photo

Many technical processes (like laser welding and marking of plastics, Near Infrared Radiation(NIR) curing and drying of coatings, drying of printings, laser marking of paper, curing and drying of adhesives, fixing of ink toners to a substrate, heating of plastic pre-forms etc.) require an efficient, quick and focused local heat-input through IR radiation. The conversion of IR radiation into heat is realized by placing appropriate IR absorbers at the place where the heat is required. Carbon black is a well known efficient IR absorber for such processes. But carbon black has one big draw back: that's its strong black colour. Thus carbon black cannot be applied for coloured (other than black or grey), uncoloured, white or transparent systems. For such systems a "white or colourless carbon black" is a great technical need.

Very surprisingly the tungsten oxide material of the present invention comes quite near to this target profile, although it is slightly bluish to grayish. But due to its surprisingly high efficiency of conversion of IR radiation into heat, this tungsten oxide material can be applied at such a low concentrations that its own colour is acceptable for most applications. The same is true for transparency: the material (plastics, coatings) containing this tungsten oxide remains also highly transparent.

The NIR curing of coatings can be used for all type of coatings including both pigmented and unpigmented coating materials. Depending upon the nature of the organic binder, coatings may comprise solvent or may be solventless or water-free. They may also comprise fillers and other additives in addition to the pigments. Any kind of coating is suitable in the method according to the invention, for example, powder coatings, clearcoats, high-solids coatings, effect coatings, high-gloss coatings, silk-finish coatings, matt-finish coatings, spray coatings, dip-coatings, pour-coatings etc.


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Tungsten Oxide Metallic Smart Windows Could Function in the Future as Electronics

Tungsten oxide is one of the mostly studied cathodic coloring electrochromic material. Electrochromic property of WO3 has been made into different electrochromic device and is applied in real life. There are many advantages of electrochromic device, transmittance can change continuously in a wide range and can be adjusted manually.

A B.C. engineering lab has created metal-coated glass that transmits up to 10 per cent more light than conventional glass and opens the door to windows that function as electronics. The most immediate use of the technology is to create smart window that can be programmed to absorb or reflect heat, depending on the needs of a building’s occupants, said lead investigator Kenneth Chau, a professor at the University of British Columbia Okanagan. “What’s interesting about this discovery is that it’s counterintuitive, because we always think of metals as being opaque, so it runs against our expectations,” he said. “I think one of the most important implications of this research is the potential to integrate electronic capabilities into windows and make them smart.”

Tungsten Oxide Metallic Smart Window Photo

But weren’t we all expecting glass to get a lot smarter?
“That’s true. When you watch Iron Man movies, they have displays on glass, they do computations on glass. This is a tiny step in that direction,” he said. Films like Iron Man and Star Trek provide scientists with inspiration for scientific progress, he said. “There is a dream that we can make glass smarter. These films give us concepts to strive for; the hard work is uncovering the science to make it happen.”

Glass is a crystalline structure that is fairly transparent, but not completely, you can still see it. Thin layers of metal actually boost the amount of light that goes through. While conventional glass does not conduct electricity, the metal layer creates an object with very different properties and the possibility of adding a variety of advanced technologies to a brilliantly transparent surface. Adding electronic control to windows will allow you to change the amount of light and heat passing through to more effectively use the energy provided by the sun naturally.

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Tungsten Oxide Industry Analysis and Outlook 2016-2023

Tungsten Oxide Market: Emerging Applications and Drivers
Tungsten oxide has several everyday uses. It is used in the manufacture of tungstates for fireproofing fabrics, for x-ray screen phosphors, and in gas sensors. Tungsten trioxide is also used as a pigment in coatings, paints, and ceramics due to its rich yellow color. In addition, tungsten trioxide has also proven useful in the production of smart windows or electro chromic windows. Smart windows are essentially electrically switchable glass that can alter its light transmission properties when a certain voltage is applied. This allows the user to obtain the desired level of tint on their windows by deciding how much light they want passing through.

The growth in end user industries is expected to increase consumption of tungsten oxide. The growth in medical and firefighting industry is set to drive the tungsten oxide market. In addition, rising consumption of semi-conducting compounds in emerging economies of Asia Pacific and Latin America is expected to boost demand for tungsten oxide. However, availability of substitutes and fluctuating raw material prices could hamper the growth of the market.

Tungsten Oxide Photo

Tungsten Oxide Market: Regional Dynamics
Growth in tungsten oxide demand is expected to be led by the Asia Pacific market, particularly China which accounted for majority of consumption in 2013. Major manufacturers of tungsten compounds are relocating their production facilities to China due to availability of cheap labor, infrastructure and attractive government policies. Republic of Korea, India, Vietnam, Malaysia, Cambodia, Australia, New Zealand and Sri Lanka are other major consumers of tungsten oxide in Asia Pacific. North America and Europe are mature markets and expected to experience moderate growth.

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Tungsten Oxide As New Material Can Boost Waste Heat Harvesting

A new material that emits short-wavelength thermal radiation when heated could be used in systems that convert waste heat into electrical energy thus boost waste heat harvesting. Created by an international team co-led by researchers at Purdue University, the University of Alberta and Hamburg University of Technology, the material comprises alternating layers of 20 nm of tungsten oxide and 100 nm of hafnium oxide.

Tungsten oxide 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. Tungsten ores are treated with alkalis to produce WO3. It is insoluble in H2O and acids, but soluble in hot alkalis. It is n type semiconductor material, the special physical and chemical property make it used in various filed and become the important functional material in modern scientific research.

tungsten oxide photo

The structure was chosen so that the emission of long-wavelength infrared photons from the material is suppressed while the emission of shorter wavelength photons is enhanced. These shorter wavelength photons have enough energy to drive a photovoltaic cell, while the longer wavelength photons do not. The research team tested the material by heating it to 1000˚C and using it to power a photovoltaic cell. They found that the new material produced 90% more electrical energy than a conventional black-body infrared emitter. It could someday be used to generate electricity from the waste heat produced by industrial processes and even automobile engines.


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N-doped Nanoporous Tungsten Oxide Electrode

Doping is commonly used to improve visible light responsive of transition metal oxide. A lot of researches show that metal ion like rare earth can promote the photocatalytic property of semiconductor material, however, metal doping may cause thermal stability of catalyst decreasing, it will introduce photo electron and recombination center of valance to lower its photoelectric property. Doping N can greatly improve the visible light absorption rate of semiconductor material.
Preparing of nanoporous tungsten oxide electrode:

1) Treating method for tungsten foil: Firstly cut it into 10mm x 15mm pieces, using waterproof abrasive to polish it, then clean it with acetone, isopropanol, methyl alcohol and deionized water ultrasound cleaning for 15min, blow it with nitrogen gas.

2) Use tungsten foil as anode, Pt foil of 10 x 15mm as counter electrode, put them into electrobath, the distance between two electrodes is 25mm. Then put electrobath in water bath of constant temperature, adjust the bath temperature to control the reaction temperature. The reacting area is 0.88cm2. Adding a certain amount of ready-prepared 1mol/L(NH42SOsolution electrolyte with different concentration of NH4F.

Photoaction Spectra
(Photoaction spectra of nanoporous WO3 photoelectrodes annealed at different temperature)

N-doping method:
Put the prepared nanoporous WOin tube furnace, inject NH3/N2(1:2), heat to certain temperature by heat up rate 5℃/min, keep it for a while, then cool it down to room temperature. Purity of NH3 and N2 is 99.999%, flow rate is 120ml/min.


Schematic Diagram
(Schematic diagram of energy band for undoped and N-doped nanoporous WO3 photoelectrodes)

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Cesium Tungsten Oxide Ultra Fine Powder Preparing Method

Tungsten oxide has excellent performance in electrochromic, catalysis, gas and other aspects. The composite oxides - tungsten bronze metal oxides generally refer darker colored metallic luster, and usually a metal conductor or metal semiconductor. Currently, cesium tungsten oxide, due to its low resistance and excellent visible light transmittance and near-infrared shielding properties, is widely used in the preparation of the conductive film used in glass septum thermal insulation coating.

The traditional preparation method of cesium tungsten oxide uses tungsten, tungsten acid source, Cs/W molar ratio of 1: (2.857~100), at 180~200°C reaction conditions for 1~3 days. The preparation takes a long reaction period, is of low efficiency, which is not conducive to industrial production.

Cesium Tungstate Molecular Photo

A process for preparing cesium tungsten oxide ultrafine powder, comprising the steps of:
(1) In accordance with Cs / W molar ratio of 1: (1.5 to 2.8), weigh cesium salt and tungsten salt. A chelating agent and alcohol reagent are added and reacting under 170 °C condition for 3h. Then mix them up.
(2) The step (1) was charged into a pressure vessel bomb reaction under 260 ~ 270°C reaction condition for 5 ~ 8h;
(3) The Step (2) was obtained by reaction of an alcohol wash, centrifugation, at 80°C under conditions of complete crystallinity dried in vacuum to obtain cesium tungsten oxide powder.


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2016年10月26日星期三

Preparing Ammonium Paratungstate from Worn-Out Tungsten Oxide

Warn-out tungsten oxide including tungsten trioxide and blue tungsten oxide ect. which have been scrapped, and substandard thus must be reworked. This warn-out tungsten oxide which can not directly be used in tungsten smelting or other industries can be recycling. In this paper we will present a method for recovering ammonium paratungstate from warn-out tungsten oxide.

tungsten oxide


1. Handling the raw material
Screen the warn-out tungsten oxide by a 60~80 mesh sieve to remove caking tungsten oxide and mechanical inclusions; then the grinding caking tungsten oxide and also screen it;

2. Autoclaving with ammonia for preparing ammonium tungstate solution
1) Dilute the concentrated ammonia in deionized water or use water to absorb liquid ammonia, get ammonia with concentrate of 8~20%; and then formulating the slurry with stirring at the ratio that weight of tungsten oxide: volume of ammonia is 150~350g/L;
2) Add hydrogen peroxide when the material contains blue tungsten oxide, compress the kettle cover, heating to the
pressure in the kettle is in the range of 4~l0kg/cm
2 with stirring; the reaction time supposed to be 60~180 minutes;
3) Stop heating and cooling down to room temperature (20~40℃) after finishing the reaction; check if the color of solution is blue or not, if so, supplemented with hydrogen peroxide until it disappear; adjust the concentration of ammonia in ammonium tungstate solution among 3~5% with ammonia or water, and the concentration of WO3 is controlled among 120~350g/L.


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Ammonium Paratungstate Preparing Ultrafine Cesium-tungsten Oxide Powder

Cesium is a golden yellow metal, low melting point active metal, easily oxidized in air and can react violently with water to produce hydrogen and even explode. There is no elemental form of cesium in nature, cesium minimal distribution in the ocean in the form of cesium salt. Cesium tungsten bronze is widely used because of its low resistance, excellent visible light transmittance, near-infrared shielding properties. Also it is widely used in preparing conductive thin film, since being the glass transparent insulation coating as insulating agent, it has excellent properties like low resistance, excellent visible light transmittance and near-infrared shielding performance. The article provides a method that using ammonium paratungstate and cesium nitrate as raw materials to produce Cesium-tungsten oxide ultrafine powder, the specific steps are as follows:

cesium

1. Weighing the cesium nitrate, ammonium paratungstate by the molar ratio of Cs/W being 1: (1.5 to 2.8), and adding chelating agent and alcohol reagent, reacting at 170°C for 3 hours;
2. Loading the mixture obtained in step 1 in a pressure vessel shells, raising the temperature to 260~270°C for reacting for 5 to 8 hours;
3. The reaction obtained in step 2 is carried out alcohol washing, centrifugation; then dried in the conditions of 80°C in vacuum, thus to generate complete crystalline cesium-tungsten powder.

Using this method to prepare cesium-tungsten oxide ultrafine powder has many advantages, such as: saving the materials, thus to save costs; shorten the preparation period, make it advantaged for industrial production; products prepared are ultrafine powders with a very low resistance.

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Tungsten Oxide Thin Film Electrode Cyclic Voltammetry

Nano semiconductor material used as photocatalyst to photolysis water has gained well efficiency. TiO2 has high catalytic activity and stability is widely used as a kind of photocatalytic material. But its band gap is big (~3.2 eV), it can only be motivated by ultraviolet with short wave length, its light transaction efficiency is low (~4%). Tungsten oxide is an indirect band series transition semiconductor material. Compared to TiO2, it has narrow band gap (2.5~3.0 eV), the relevant absorbing wave length is 410~500nm and well photoelectric responsive property in visible light area.

WO3 Thin Film Electrode

Tungsten oxide thin film electrode preparation method:
Raw material: FTO glass; tungstic acid; hydrogen peroxide; acetone.

(1) Be ready with clean FTO glass as the substrate of depositing WO3. Cut FTO glass into 1.2cm*2.5cm pieces and clean it by ultrasound and ultraviolet. The clean and flatness of FTO substrate has big effect on adhesive force and uniformity of thin film electrode. So before depositing thin film electrode, the FTO glass should be well cleaned. Firstly, clean the dirties on the surface by ethyl alcohol. Then put the substrate in acetone and ultrasound for 30min to eliminate the ethyl alcohol and oil contamination on the surface. After that, ultrasound it in water for 20 min to eliminate the residual acetone. Finally dry it by nitrogen gas. Then put it into ultraviolet disinfectant tank to sterilize.

(2) Weigh 0.02g tungstic acid and dissolve it by 20ml 30% hydrogen peroxide. Stay it for 12 hours to obtain transparent tungstic acid solution, it will be used as electrolyte solution to deposit WO3.

(3) Use substrate obtained from step (1) as working electrode, measure 30 micro liter tungstic acid solution, dispensing it evenly on the surface of FTO conductive glass. Dry it under room temperature, colorless thin film is obtained.

(4) Put the deposited thin film from step (3) into tube furnace, calcinating it for 2 hours under 500℃, colorless WO3 electrode is obtained.

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Tungsten Oxide in Inverted Polymer Solar Cell

Interest in solar cells to capture sunlight and generate electricity is increasing due to oil energy crisis and rising concerns over global climate change. Inorganic solar cells can yield high power conversion efficiency but the expensive fabrication process makes them infeasible in common use. Instead, polymer solar cells PSCs are a good candidate because semiconducting polymers can be dissolved in common solvents and printed like inks so that economical roll-in-roll fabrication process can be realized. The photoactive layer composed of electron donating and accepting materials absorbs light and generates excitons. Then electrons and holes can be efficiently separated from each other due to the nanometer-scale interpenetrating network of electron donor and acceptor within the whole photoactive layer.3 However, a simple structure that sandwiched the photoactive layer between two electrodes anode and cathode is not perfect enough. The low efficiency of charge collection at the interface between the photoactive layer and electrodes results in poor performance of PSCs.4 In order to solve this problem, interfacial layers, such as a combination of poly-ethylenedioxythiophene: polystyrenesulfonate and lithium fluoride LiF, are commonly introduced between the active layer and electrodes to improve charge carrier collection and to enhance the open-circuit voltage.
WO3 Solar Cell Structure
Nevertheless, PEDOT: PSS has been demonstrated to have a side effect on the performance of PSCs due to its corrosion to indium tin oxide ITO and electrical inhomogeneities. In order to overcome this problem, one might simply introduce interfacial layer materials to improve the performance of PSCs. Recently, molybdenum oxide MoO3, vanadium oxide V2O5, and nickel oxide NiO have been demonstrated to effectively substitute PEDOT:PSS as the anodic buffer layer in PSCs. An alternative approach is to reverse the device architecture and hence to form inverted PSCs, in which MoO3 and V2O5 were usually inserted between the active layer and top electrode.

In this letter, we introduce a low-cost, nontoxitoxic, and easily evaporable tungsten oxide WO3 as a hole extraction layer in inverted PSCs with nano crystalline titanium dioxide nc-TiO2 as an electron selective layer. The device architecture is shown schematically in Fig. 1 a. and the energy level diagrams of different materials used in the device fabrication are shown in Fig. 1b. Meanwhile, transparent inverted PSCs are fabricated with thermally evaporable Ag13 nm/WO340 nm as a transparent anode when introducing a 10 nm WO3 buffer layer. After a cleaning step, TiO2-sol was spin coated on ITO-coated glass substrates at 3000 rpm. Then the samples were moved to a muffle furnace and annealed at 450 °C for 2 h. After annealing treatment, nc-TiO2 was formed. In this letter, poly3-hexylthiophene P3HT Rieke Metals was used as electron donor material, and -phenyl C61 butyric acid methyl ester PCBM Solenne BV was used as electron acceptor material. The mixed chlorobenzene solution composing of P3HT 10 mg/ml and PCBM 8 mg/ml was then spin coated on top of the nc-TiO2 layer at 700 rpm in ambient air. Then the samples were heated in low vacuum oven at approximately 150 °C for 10 min. Subsequently, the samples were pumped down in vacuum 10−3 Pa. Finally WO3 and 60 nm top electrode Ag, Au, and Al were thermally evaporated in sequence. The active area of the device was about 0.064 cm2 .
WO3 Solar Cell Curve
In summary, we have explored the use of WO3 in inverted polymer solar cells. Due to the high work function 4.8 eV, WO3 efficiently extracts holes and suppresses electrons from the active layer. The thicknesses of WO3 and different top metal electrodes on device performances are also investigated. Transparent inverted PSCs are fabricated with Ag13 nm/WO3 40 nm as a transparent top electrode when introducing a 10 nm WO3 buffer layer, which have the potential to realize a multiple device structure to absorb more solar photons by the multiple photoactive layers to achieve high device performance.

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Tungsten Oxide as Alternative Energy Source

While the global climate heats up, so does the conversation on sustainability and the need for alternative energy and fuel resources. Dr. Robert Mayanovic, assistant department head of physics, astronomy, and materials science at Missouri State University, brings new hope to the topic as he has helped to discover a porous metal-oxide that could potentially be used as an alternative to traditional energy and fuel resources.

“Basically, we are looking for ways to develop materials that can be used in the future to harness conventional or alternate energy sources in a more sustainable fashion than what materials offer today,” said Mayanovic. “The first phase of the project is to test the stability of the materials in extreme environments.”

Tungsten Oxide Catalyst

Using a large x-ray machine called a synchrotron, which allows the materials to be probed down to the atomic level, Mayanovic and colleagues Dr. Sonal Dey of Colleges of Nanoscale Science and Engineering, and Dr. Ridwan Sakidja, associate professor of physics, astronomy, and materials science at Missouri State, found the porous metal-oxide (tungsten oxide) to be very stable under high temperatures and nominal pressures in water.

“Once this particular metal-oxide porous material is further modified to have excellent catalytic properties, it may potentially be used to break down bio-matter waste to liberate hydrogen and methane so that these gasses could be used as energy sources,” Mayanovic adds.

Initially collaborating with other scientists from the Energy Frontier Research in Extreme Environments Center (EFree), Mayanovic now continues to develop his research on tungsten oxide, hoping to provide the world with a new means to sustain the planet. Most recently, Mayanovic had the opportunity to be published in “Nanoscale”, a peer reviewed scientific journal that covers experimental and theoretical research in all areas of nanotechnology and nanoscience.

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