Using different power laser radiation study tungsten oxide nanowires found that with increasing laser power (0.72mw ~ 20mw), the Raman spectra of tungsten oxide nanowire has significant changes, when the laser power Raman spectra of tungsten oxide nanowire is low the Raman signal also not strong. Peak shape and peak data will not change much. As the power increases, the Raman signal also increases. When the laser power is increase to certain strength, then tungsten oxide will react with oxygen become tungsten trioxide. At this time the tungsten trioxide is monoclinic phase.

When the laser power drops to 3mw the Raman peaks has been unable to return to the peak, indicating that the oxidation process is irreversible. With the laser power is increased again, tungsten trioxide nanowire phase transition from monoclinic phase to β phase, has studying by the changing of laser power found the monoclinic phase of tungsten oxide change to the β phase so the this process is reversible. Laser powde has an impact on tungsten oxide nanowires, Keywords: tungsten oxide nanowires, laser power

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Thermal evaporation method is a vapor deposition method, and it has a high efficiency character. Production tungsten oxide nanowires process is firstly setting base pressure to 10-1Pa, work forced to 10Pa, evaporation time is 15min.

Then put tungsten powder on the stove and silicon wafer near tungsten powder by horizontally. Then putting inert gas clean up argon gas and the inert gas flow is 70sccm. Finally heating tungsten powder and it will oxidize to tungsten oxide then grow deposited on a silicon wafer developed to nanowires. At the same time the evaporation temperature are set to 975 ℃, 1000 ℃, 1025 ℃, 1050 ℃, wafer silicon temperature was maintained at 550.

After study experts found that the growth of tungsten oxide nanowires exist certain rules, with the evaporation temperature, the vapor concentration in the silicon surface can also become large, over saturation increases, increasing the number of nucleation, tungsten oxide nanowires diameter increases, the height of increase first then to decrease, reduce the crystal orientation when the temperature is too high. The wafer silicon temperature increase, the active of tungsten oxide vapor molecules on silicon becomes large and the crystallization speed of tungsten oxide nanowires accelerate, height has increased. It is easy to found producing different morphologies tungsten oxide nanowires can through control evaporation source and the wafer temperature.

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Producing tungsten oxide electrochromic films has some methods such as vacuum thermal evaporation, electron beam evaporation, sputtering, vapor deposition, electro deposition and sol - gel method. Tungsten oxide electrochromic film deal with heat treatment with certain temperature can improve the adhesion and cycle life, but the high temperature heat treatment it will affect the response time and color film. Generally, physical production methods require high temperature heat treatment, such as electron beam evaporation required 500e heat treatment, thermal evaporation required 350e, the RF sputtering for an 200 ~ 300e. These methods often are limited because the equipment is expensive, technically complex and demanding of process conditions. Chemical production of the sol - gel method is simple equipment and it can produce large-scale uniformity film with low temperature, but usually need more than 100e heat treatment. Alkoxide method requires 250e heat treatment, the ion exchange method needs 150e, halogenated oxidation method needs 120e.

But using sodium tungsten as raw material and ethanol and polyvinyl alcohol (PVA) as an additive, obtained tungsten acid solution by ion exchange, and then using sol - gel method to producing superior performance tungsten oxide electrochromic films. This film simply need 75e heat treatment, the driving voltage of -1 ~ + 1V, fully shaded and faded time of only a few seconds, coloring in an aqueous solution - fade cycles up to 600 times, the color can be kept after coloring the number of days.

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Ultrasound chemical method is an effective method for produce specific nano materials. It is a convenience, effective and safe method which organic bond with physical method and chemical method, and it developed as an important method such as synthetic material and handling materials, so it has aroused great interest and attention.

And with the application of nano-tungsten oxide powder is increasingly widespread, it is recognized that tungsten oxide nano-particles agglomeration issues that affect the performance of the powder. Therefore, during tungsten oxide nano powder produce in addition to pay attention to fallow the influence which tungsten acid nano particle will affect tungsten oxide particle size and at the same time how to control the nano tungsten oxide particle increase is also a key issue.

So, while using ultrasound-assisted chemical adding surfactant can not only improve the chemical reaction of the micro-environment, but also can product micelles which it can as templates for formed synthesis nanomaterials in the solution.

at a temperature of 500 ℃,using ultrasound chemical method adding surfactant and calcine tungsten acid for 3hours which can get better nano-oxide powder material. And this method also has some advantages such as low cost, simple and easy handling and so on.

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Tungsten Carbide Rod with Holes

Tungsten carbide rod can be made into tungsten carbide rod with single straight hole, tungsten carbide rod with dual straight holes and tungsten carbide rod with double helix hole. Tungsten carbide rod with holes can be used to make all kinds of tungsten carbide tools, processing heat-resistant alloys and Ti alloy. Tungsten carbide rod with hole also plays a part in cooling process of machining.

Below is the common dimension of tungsten carbide rod with holes.

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Tungsten sputtering target is made of tungsten powder. Tungsten sputtering target owns three types: flat-target type, arc-target type and rotary target type. Tungsten sputtering target can be applied in tool and mould coating, glass coating, or high temperature resistance, wear resistance, corrosion-resistant in high-grade decorative items and other industries.

Tungsten sputtering target in tool and mould coating application:

With the development of aerospace and automotive industry and the advance of technology and the improvement of production efficiency, people are pursuing tungsten sputtering targets with high-performance in tools and moulds. Currently, European countries and Japan are in great need for the tool and mould. According to statistics, the proportion of demand in developed countries is more than 90%, while China's demand for coated tool is rising.

Tool and mould coating application is mainly used for tools and mould coating. After the mold coating, its surface will be strengthened, the use of life will improve, in short, all aspects of performance will be enhanced.

Commonly used decorative coating materials are: tungsten, titanium, aluminum, etc.

 

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Hydrothermal method is a commonly method used for producing nanocrystalline materials, it has the advantage of relatively inexpensive test, can achieve mass production. And hydrothermal method help to protect the environment, it will collect toxic substances in closed condition. Hydrothermal Method refers to in autoclave using aqueous solution as a reflection of the system, the system by heat and pressure to create a relatively high temperature, high pressure environment making poorly soluble or insoluble substance materials dissolved and crystalline. This is an effective way to inorganic synthesis and handling material. Synthetic methods:

(1) spin-coated with tungsten oxide on FTO glass seed.                                                                            

( 2) 3.29g NA2WO4 powder was dissolved in 76ml of deionized water and added hydrochloric acid (30mol / L) adjusting PH value to 2.0.

(3) 2.64g (NH4) 2SO4 was added to the reaction precursor to control morphology of tungsten oxide. Stirred with a magnetic stirrer one hour later, the clear solution was placed in a reaction vessel.

(4) FTO glass reactor placed in a vertical, heated at 180 ℃ Condition 4 hours.

(5) Finally FTO cleaned in a vacuum oven at 60 ℃ with dried for 12 hours.

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Tungsten Carbide Rod Powder Extrusion Molding Existing Problems

Although our country has already had the ability to produce tungsten carbide rod itself, the species and quality or property is far away from other foreign countries. The reason is because the immaturity not only in knowledge but also in technology. First of all, the research and exploration for the binder is far away from the standard. The study on the mix principle of powder and binder is insufficient. The binder production technology is still highly confidential technology. There is no formal report about practical binder-making process. The application for the introducing technology is not enough, it maintains the level which can only satisfy the present producing requirement. Manufactures do not cooperate with each other to search for the best technology and overcome problems. Also the study on the basic theory stays on the surface, especially rheology theory in the powder extrusion molding processing. 


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There are four stable tungsten oxides: yellow tungsten oxide (WO3), blue tungsten oxide (WO2.90), violet tungsten oxide (WO2.72) and tungsten oxide (WO2). Wherein the tungsten oxide formula is WO2, the molecular weight is 215.85. It is brown monoclinic crystal powder, density is 10.9 ~ 11.1g/cm3, a melting point of 1500 ~ 1600 ℃, boiling point 1730 ℃. Insoluble in water, alkali solution, hydrochloric acid and sulfuric acid, but it was dissolved in H2SO4, to form a red salt. It is can easily oxidized to high tungsten oxide by nitric acid. In an inert gas WO2 easy form metallic tungsten and tungsten trioxide. WO2 is raw material for produce tungsten dioxide and tungsten powder.

Tungsten dioxide in the air is rapidly oxidized to tungsten trioxide and heated at 500 ℃ will turn to blue tungsten oxide. At 1020 ℃, tungsten oxide can be reduced to metallic tungsten. At 250 ~ 300 ℃, using hydrogen or carbon monoxide restore tungsten trioxide, and in the vacuum heated tungsten trioxide to 200 ~ 250 ℃, can obtain violet tungsten oxide powder. the producing of tungsten oxide is mix tungsten powder and tungsten trioxide at the molar ratio of 1: 2 and under vacuum heated to 950 ℃, or at 900 ℃ can be produced WO3 by H2 with air steam reduction.

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Tungsten Carbide Rod Powder Extrusion Molding Development

Since the reform and opening-up policy, China has made a large progress in tungsten carbide rod powder extrusion molding, including import large extrusion machine from other companies. Through the introduction, the extrusion amount, quality and species also improve a lot. There are two methods of tungsten carbide rod powder extrusion molding. One is powder extrusion molding without binder which is being processing under heating. The other is powder extrusion molding with binder which can improve the quality of tungsten carbide rod. Although some manufactures also introduce technologies like binders, the raw materials and binder can not match to each other cause the difficulties in produce high quality tungsten carbide rod. Paraffin is the main binder we use in powder extrusion molding today, but the tungsten carbide rod made by this kind of binder is not strong enough, or the surface is rough if the product dimension is large. So find the perfect binder is the key problem. 


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