2017年5月17日星期三

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 bronze, 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 Structure

Preparing method of  cesium tungsten oxide ultra fine 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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Tungsten Oxide Four-in-one Catalyst Developed

Brown University researchers have developed a new tungsten oxide four-in-one catalyst that can perform four separate chemical reactions in sequential order and in one container to produce compounds useful in making a wide range of pharmaceutical products.

"It normally takes multiple catalysts to carry out all of the steps of this reaction," said Chao Yu, a post-doctoral researcher at Brown who co-led the work with graduate student Xuefeng Guo. "But we found a single nanocatalyst that can perform this multistep reaction by itself."

The research, described in the Journal of the American Chemical Society, was a collaboration between the labs of Brown professors Christopher Seto and Shouheng Sun, who are coauthors of the paper.

The work was done, the researchers said, with an eye toward finding ways of making the chemical industry more environmentally sustainable. Multi-reaction catalysts like this one are a step toward that goal.

"If you're running four different reactions separately, then you've got four different steps that require solvents and starting materials, and they each leave behind waste contaminated with byproducts from the reaction," Seto said. "But if you can do it all in one pot, you can use less solvent and reduce waste."

The team made their new catalyst by growing silver-palladium nanoparticles on the surface of nanorods made of oxygen-deficient tungsten-oxide (tungsten-oxide with a few of its oxygen atoms missing). The researchers showed that it could catalyze the series of reactions needed to convert common starting materials formic acid, nitrobenzene and an aldehyde into a benzoxazole, which can be used to make antibacterials, antifungals and NSAID painkillers. The researchers showed that the catalyst could also be used to create another compound, quinazoline, which is used in a variety of anti-cancer drugs.

VTO photocatalyst structure

Experiments showed that the catalyst could perform the four reactions with a nearly quantitative yield -- meaning it produces the maximum possible amount of product for a given amount of starting materials. The reactions were performed at a lower temperature, in a shorter amount of time, and using solvents that are more environmentally friendly than those normally used for these reactions.

"The temperature we used to synthesize this product is around 80 degrees Celsius," Guo said. "Normally the reaction happens around 130 degrees and you need to run the reaction for one or two days. But we can get a similar yield at 80 degrees in eight hours."

The new catalyst also is able to make the benzoxazole compounds using starting materials that are more environmentally benign than those generally used. The reaction chain requires a hydrogen source for its initial step. That source could be pure hydrogen gas, which is difficult to store and transport, or it could be extracted from a chemical compound. A compound called ammonia borane is often used for this purpose, but the new catalyst enables formic acid to be used instead, which is "cheaper, greener and less toxic," Yu said.

And while many catalysts tested in these reactions cannot be used more than once without severely damaging their efficiency, the researchers were able to use the new catalyst up to five times with little drop-off in reaction yield.

Sun says that studies like this one represents an emerging line of research in greener chemistry.

"Normally in catalysis we're doing one reaction at a time, with a different catalyst for each reaction" said Shouheng Sun, a professor of chemistry at Brown. "But there's growing interest in coming up with catalysts that can perform multiple reactions in one pot, and that's what we've done here."



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Tungsten Oxide Is Safe for FCM Plastics

A European Food Safety Agency (Efsa) science panel has concluded that the use of tungsten oxide as a reheat agent in PET plastic food contact material (FCM plastics) is safe for consumers.

The question of safety was put to Efsa in 2014 by the Colormatrix Group through the UK competent authority, the Food Standards Authority. The agency asked its Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF) Panel to review it. The panel's dossier included studies on the identity of the substance, its migration into food simulants and potential toxicity in line with the EU food contact materials regulations.


Tungsten oxide is a mixture of oxides used as a reheat agent to increase the infrared heat absorption of plastics from heat lamps during blow-moulding processes. It has the advantage of having a minimal effect on the transparency of the packaging, when used at the proposed maximum use level of 75ppm.

The detailed reasoning behind the CEF panel's approval is explained in a Efsa Journal paper. The migration level observed in the applicant’s dossier, using tungsten oxide at double the proposed maximum level, and migration into a worst-case 95% alcohol food simulant, was only 1μg/kg – measured as tungsten.

The panel considered that this low migration rate of an insoluble compound would be typical for any foreseeable use as a reheat additive in PET.

Two in vitro genotoxicity studies – a bacterial gene mutation test and a micronucleus assay – were conducted by the company. Both showed results which, in the panel’s opinion, cleared tungsten oxide of gene mutation, chromosomal and numerical aberration hazard.

Tungsten oxide has also been evaluated by Echa, it noted, and assigned an oral derived no-effect level (Dnel) of 0.6mg/kg body weight per day.

Specifically, the CEF panel concluded that tungsten oxide was not a safety concern for the consumer if the additive is used as a reheat agent in PET. For other technical functions or for use in other polymers, it added that migration should not exceed 50μg/kg expressed as tungsten.


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A New Process Increases Speed and Color Options of Switchable Windows Without Tungsten Oxide

Electrochromic glass windows on the market are able to change color tints when an electric voltage is applied, but don't offer very many color options. But according to New Atlas writer Darren Quick, that's about to change.

Now researchers at the Fraunhofer Institute for Applied Polymer Research (IAP), working with Tilse Formglas GmbH have turned to a different technology that speeds up the switching process considerably and provides different color shades to tinted windows. Here's how the whole thing works:

Most electrochromic glass windows on the market are produced by coating two panes of glass in a thin film of translucent indium tin oxide or fluorine-doped tin oxide to make the glass electrically conductive. Then one of the panes is coated in electrochromic tungsten oxide and the two panes are brought together with the coatings facing each other and a gel-like electrolyte separating them. When a voltage is applied, the tungsten oxide coating darkens, and when the polarity of the voltage is reversed, the coating lightens. The lightening and darkening process doesn't happen instantly, with windows measuring around 2.5 square meters (27 sq ft) potentially taking up to 20 minutes for the process to complete.

YTO photo

The new process still starts with coating two panes with tin oxide, but the tungsten oxide coating is skipped. Instead, the two panes are again brought together, but with a specially developed resin containing electrochromic organic monomers sandwiched between them. Heat or UV radiation is then used to cure the resin before a direct current is applied to ensure that the monomers on an electrode bond to form an electrochromic polymer.

The end result is a pane that can be switched much faster and at a much lower voltage. According to Dr. Volker Eberhardt, a scientist at Fraunhofer IAP, a pane measuring 1.2 sq m (13 sq ft) in size will darken in 20 to 30 seconds, compared to over 10 minutes for standard tungsten-oxide-based panes. Additionally, the researchers say that using other monomers will allow the creation of panes with red or purple tints in the future.


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Tungsten Oxide in Eco-Friendly Fashion

Most consumers think luxuries and fast fashion are totally different concept. Designer clothes are expensive so we think it is totally in accordance with eco-friendly fashion. Not really. Just like carbon emission rate is the same in first class and economic class, fast fashion has been doing harm to environment.

Today, both luxury brands and minority brands attach great importance to environment, and hae taken measures to produce eco-friendly products. For example, New York designer Maria Cornejo uses special white fiber from regeneration wood paper pulp.

Cornejo called the new manmade fiber as Eco Drape. She said:’ Made eco-friendly fashion is a long way to go. Manmade fiber is the mostly favored material. By transforming it into eco-friendly material can greatly protect environment. It is free from illegal cutting trees and prohibited chemicals. What makes it more valuable is the incompatible weight and dropping style.

Eco-friendly principle is also pursued by Stella McCartney. She said:’ Clothes designer is my first job. The first thing I considered about is to make sure environmental friendly while have good design. She uses regeneration micro fiber which is dyed by tungsten oxide, which is non toxic and makes clothes quality better.

tungsten oxide photo

Tungsten oxide is widely used in coloring agent and has advantages of non-toxic, environmental friendly, anti-fading in color, economic, etc..

While developing fashion industry, moral ethnic and substantial development are also important. It is the director of fashion industry that fashion brands shouldn't ignore. Substantial development in fashion is the focus of customers. When facing economic recession, we overcome it. Consumers care about whether it is benefit for local economy development. They focus on environment problems. but are also fascinated about good looking fashion. Both inside and outside.


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Tungsten Oxide Ceramic Nonlinear Characteristics

A varistor is an electronic component with an electrical resistance that varies with the applied voltage. Also known as a voltage-dependent resistor (VDR), it has a nonlinear, non-ohmic current–voltage characteristic that is similar to that of a diode. In contrast to a diode however, it has the same characteristic for both directions of traversing current. At low voltage it has a high electrical resistance which decreases as the voltage is raised.

Varistors are used as control or compensation elements in circuits either to provide optimal operating conditions or to protect against excessive transient voltages. When used as protection devices, they shunt the current created by the excessive voltage away from sensitive components when triggered.

WO3 photo

In recent years, studies on low-voltage varistor materials have gotten widespread attention, such as TiO2, Sr TiO3 and WO3. In 1994, WO3 ceramics nonlinear behavior was first reported. The study shows that tungsten oxide ceramic material has low breakdown voltage and good dielectric properties, which makes it ideal for low voltage varistor material.

With the further study of nonlinearity WO3 ceramics, we found that non-linear characteristics and mechanism of WO3 are not significantly different from conventional ceramic varistor materials of ZnO and SnO2. WO3 ceramic normally sintered exhibits significant nonlinear characteristics. The high temperature quenching sample has no nonlinear behavior. quenched ceramic samples restored after heat treatment under oxygen-rich conditions. Impedance spectroscopy analysis showed that the ceramic samples with non-linear characteristic have high resistivity layer at grain boundaries,  while the sample without non-linear behavior not. It’s believed that a high-impedance grain boundary layer is a non-equilibrium grain defects occurred inside and outside and migration of ceramic during cooling, forming high-resistivity layer on the grain surface under the action of oxygen adsorbed. Because of internal and external features of this huge grain of resistance differences, the electronic barrier informs in the grain boundary. This is the origin of the nonlinear characteristics of WO3 ceramics.


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Functional Ceramics And Tungsten Oxide

Functional ceramics have many excellent properties in electricity, magnetism, sound, light, heat, etc. that make it difficult for other material to match, and some have more than one function. And these properties usually depends on the internal electronic state or structure of the atomic nucleus. It’s also known as electronic ceramics. It has been widely used in energy development, electronic technology, sensor technology, laser technology, photonics technology, infrared technology, biotechnology, environmental science and other aspects. In addition, the semiconductor ceramic, the insulating ceramic, the dielectric ceramic, luminescent ceramics, photosensitive ceramic, absorbing ceramics, ceramic laser, a ceramic nuclear fuel, propellants ceramics, ceramic converting solar light into energy storage and ceramics, ceramics solid battery, ceramic damping biotechnology ceramics, catalysis ceramics, film and other special functions, which also play important roles in automatic control, instrumentation, electronics, communications, energy, transportation, metallurgy, chemicals, precision machinery, aerospace, defense and other departments.

tungsten oxide photo


In recent years, nanotechnology has developed rapidly with many active researches. When entering the nanoscale, the particles has quantum size effect, surface effect and macroscopic quantum tunneling effect, making the material exhibit unusual physical and chemical properties. Tungsten oxide is an important functional material, widely applied in aspects of electrochromic, toxic gas detection and photocatalytic degradation. In 1994, Makarov and Trontelj found WO3 doped Na2CO3 and MnO2 has an obvious nonlinear I-V characteristic, which indicates WO3-based functional materials have the potential being applied to the varistor.

The electrical properties of WO3 functional ceramics and WO3-based ceramics doped low metal elements and rare earth elements have been studied that there is a certain non-linear characteristic no matter WO3 ceramics doped or not, and the doping process can change its non-linear coefficient. But most researches on tungsten trioxide functional ceramics use micron WO3 as raw material, common electronic ceramics preparation process, focusing on changing the doping elements and proportions, observing the effects on the electrical behaviors, and there are few reports about Effect of changing the sintering process on tungsten trioxide-based functional ceramic electrical behaviors.


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Tungsten Oxide Modified Titanium Dioxide Nanotube Preparation Method

TiO2 photocatalyst due to its excellent photocatalytic performance which has the advantages of light corrosion and chemical corrosion, non-toxic and of low cost has become a topic for many scholars. Titanium dioxide powder is frequently studied at present, however, powder photocatalyst used in water treatment usually require power to maintain the suspension. It was stirred with another catalyst separation and recovery of difficult practical application is limited. Anodic oxidation method for the manufacture of titanium substrate surface titania nanotube array films not only solve the problem of catalyst separation and recovery, and its special tubular structure can provide access to electronic transmission, reducing the composite photo-generated electrons and holes to a certain extent, help improve the efficiency of photocatalytic reaction.

tungsten oxide photo


A method for the preparation of the tungsten oxide modified titanium dioxide nanotube comprising the steps of:
(1)Wash the titanium sheet which has a thickness of 0.1mm, 99.9% purity titanium sheet is cut to size 20mm x 45mm, followed by surface degreasing. After oxide treatment, rinsed it with deionized water and clean air.
(2)After cleaning, anodic oxidation 1h in the electrolyte, rinse with deionized water, then air dried, and then a heating rate of 5 °C / min was raised to 450 °C. Calcining 1h to obtain a surface with titanium dioxide nanotube.
(3)The surface of the resulting titanium dioxide nanotube thin film of titanium sheet is immersed in an aqueous solution of sulfuric acid concentration of 0. 2-1.0M in 2-6h, remove dry and then immerse in a concentration of 0.3M aqueous solution of ammonium paratungstate for 2h, remove the air-dry after the muffle furnace. The temperature increasing rate of 5 °C/min was raised to 450 °C, calcined for 1h to obtain tungsten oxide modified titanium dioxide nanotube.


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