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.


If you have any other question or inquiry of tungsten oxide, please feel free to contact us through the following methods:
Tel.: +86 592 5129696/86 592 5129595

Fax: +86 592 5129797


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.

If you have any other question or inquiry of tungsten oxide, please feel free to contact us through the following methods:
Tel.: +86 592 5129696/86 592 5129595

Fax: +86 592 5129797

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.

If you have any other question or inquiry of tungsten oxide, please feel free to contact us through the following methods:
Tel.: +86 592 5129696/86 592 5129595
Fax: +86 592 5129797

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.

If you have any other question or inquiry of tungsten oxide, please feel free to contact us through the following methods:
Tel.: +86 592 5129696/86 592 5129595
Fax: +86 592 5129797

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.

If you have any other question or inquiry of tungsten oxide, please feel free to contact us through the following methods:
Tel.: +86 592 5129696/86 592 5129595
Fax: +86 592 5129797

Defect State Nano Structure Tungsten Oxide Catalyst Is Invented

USTC(University of Science and Technology of China) recently announced that professor Xiong Yujie research group designed a kind of tungsten oxide nano structure in defect state based on inorganic solid accurate preparation of chemical and use crystalline defect project. Under broad spectrum illumination, it shows fine oxidation coupling catalytic property which is expected to realize low cost and low-energy organic chemical technology. Tungsten oxide has good photocatalytic property due to its special structure, it has already been used as varies of catalyst and also other industrial fields. 

Most of catalytic reaction is based on the application of precious metal oxide and motivated by burning of petroleum and coal. It has disadvantages of high cost and high energy consuming. Compared to precious metal catalyst, metal oxide has benefits of low cost. However, it shows shortcomings in oxygen molecular system which can not capture solar energy and pass it into oxygen molecular.
Defect Rich WO3 Nanosheet
In order to solve the problem, Xiong Yujie research group designed a kind of nano structure tungsten oxide. Usually metal atom of metal oxides has coordination saturation property, it can not active oxygen molecular by chemical absorption. During the research, construct of oxygen vacancy defect overcomes the shortcomings and accelerate photo electron transact from metal oxides catalyst to oxygen molecular. Defect state also broadens light absorption range of photocatalyst which enables it to capture solar energy in visible light and near infrared area. The two big steps realize the valid capture of solar energy and energy transaction, solves the bottleneck problems of oxides catalyst in the organic synthesis of photocatalytic activity.

Based on this acknowledgement, researchers are able to adjust solar energy to drive organic oxygen coupling reaction based on crystalline defect project. It provides possibility to use solar energy take place of heat source organic synthesis, and make an improvement for design of photocatalyst material.

If you have any other question or inquiry of tungsten oxide, please feel free to contact us through the following methods:
Tel.: +86 592 5129696/86 592 5129595
Fax: +86 592 5129797