Tungsten carbide is WC, TiC, TaC, NbC, VC and other refractory metal tungsten carbides and prepared by powder metallurgy from iron group metals as a binder. The tungsten carbide cutting tools are mainly TiN coating, ZrN coating, TiCN coatings, tungsten carbide cutting tools and wear resistance of the coating with many factors.

1. At low load, tungsten carbide substrate, TiN coating, ZrN coating close to the coefficient of friction, coefficient of friction when the TiCN coating at a certain range of values, TiCN coating surface to generate a more complex compound when the friction acts as a lubricant, so that friction coefficient decreases. With friction continues, the surface of the material occurs micro peeling, friction coefficient return to a normal state.

2. Tungsten carbide cutting tools coating at high speed and high load, low coefficient of friction than the load at low speed. This is because at low speed low load, the friction balls and the sample mainly localized mainly microparticles intermittent mechanical shock, will result in the coating peeling off, wear debris of these fine grains, high hardness, hindered and sliding friction of the sample, causing friction coefficient; and under high pressure, the contact surface friction increase participation and improve the wear surface was in contact stiffness, friction is converted to mechanical friction, the friction coefficient is relatively lower.

3. Wear Mechanism tungsten carbide cutting tools coated abrasive wear, friction under high load high speed state, the lowest friction coefficient ZrN coatings, friction best performance. Because the tool is often used for high-speed cutting tool material for this performance has very important significance.

4. Tungsten carbide coated with the coating hardness wear Obviously, microstructure has a close relationship, the higher the hardness, the more uniform coating of dense tissue microstructure, wear the better.

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With the acceleration of industrialization and urbanization in China, the major non-ferrous metal production and consumption of the rapid growth of non-ferrous metal resources gap is growing. Currently external dependence of copper, aluminum, lead and zinc mineral raw materials were 60%, 50%, 40% and 15%. Non-ferrous metal industry has become the bottleneck of resources and the environment to break an important industry, non-ferrous metals in effectively alleviate the tension between supply and demand, improve resource utilization efficiency, and promote the sustainable development of society has an important role. Meanwhile, non-ferrous metal products industry wide relevance, absorptive capacity and strong employment, capital and technology-intensive industries has broad prospects for development.

Promising sunrise industry

Non-ferrous metal industry has an important trend in the development of non-ferrous metal loop recycling good performance, non-ferrous metal recycling significant energy saving effect is.

Non-ferrous metals is an important basic raw material industry in the national economy. It has a good loop recycling performance. In 2010, China's imports of major physical volume of ferrous scrap is 7.21 million tons, of which 4.36 million tons of copper scrap, aluminum-containing waste 2.85 million tons, copper, aluminum, lead metal content of domestic recycling 405 tons, of which copper 1.1 million tons, 1.6 million tons of scrap, lead scrap 1.35 million tons, greatly ease the contradiction between supply and demand of China's non-ferrous metal resources, and reducing the exploitation of native minerals.

At the same time, in 2010, China's non-ferrous metal production reached 7.75 million tons major regeneration. Of which 2.4 million tons recycled copper, recycled aluminum 4 million tons, 1.35 million tons of secondary lead. And exploitation of native non-ferrous mineral resources compared to 2010 China Nonferrous Metals Industry renewable energy savings equivalent to 17.19 million tons of standard coal, water and 1.32 billion cubic meters, reducing solid waste emissions 1.16 billion tons, 370,000 tons of sulfur dioxide emissions reduction.




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The past couple of decades have witnessed an exponential growth of activities in this field worldwide, driven both by the excitement of understanding new science and by the potential hope for applications and economic impacts. The largest activity in this field at this time has been in the synthesis of new nanoparticles of different sizes and new shapes. Besides giving us new properties, creating novel nanostructures requires new understanding of the properties of their surfaces, which has been in the center of attentions from many scientific researchers. As one kind of well-known semiconductor materials, tungsten oxide and its hydrates (WO3•nH2O, n=0~2) have been extensively researched and employed in various application fields. Because many of their nanostructures and morphologies are inextricably bound to properties in several fields, scientists have been concentrating on the research of the preparation of micro/nanostructures of these materials. However, there still remains further investigations on the exploration of developing facile, green and economical techniques when controlling these interesting promising structures, which are believed to be very necessary for expanding the application fields of tungsten oxide hydrates materials. In this dissertation, a facile hydrothermal technique has been developed to prepare micro/nanostructured tungsten oxide hydrates materials (particles and films) with/without the assistant of templates and microwave heating. The following are the main results and conclusions:

Tungsten oxide hydrates crystallites with a diversity of phases and morphologies were successfully controlled by using tungsten powders as starting materials via a facile and additive-free hydrothermal process. Various micro/nanostructures of products, including cubic blocks, “snowflakes”, round angular blocks, hexagonal “gears”, cuboid rods, hexagonal plates and nanoflakes,were obtained by simply changing the reaction conditions. Results show that the nucleation, crystallization and diffusion of the growth units were found to play key roles in different conditions to vary the products phases and morphologies.

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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.Tungsten ores are treated with alkalis to produce WO3. Further reaction with carbon or hydrogen gas reduces tungsten trioxide to the pure metal.

Tungsten oxides inorganic semiconductor materials have received considerable attention in recent years because of their unique physico-chemical properties and widespread applications in various areas，such as electrochromic ( EC ) devices，gas sensors，photocatalytic systems，photoelectrochemical devices，and so on．Recently hydrothermal method has been exploited for the preparation of tungsten oxide micro / nanostructures with different sizes and shapes． Combining with our group' s work on the preparation of tungsten oxide micro /nanomaterials，the progress of preparation of tungsten oxide micro / nanomaterials by hydrothermal method is presented． The key influencing factors，such as the choice of reagents，the reaction time and temperature，are discussed in detail． The development trends of the tungsten oxide micro / nanomaterials fabricated by hydrothermal method are also proposed．

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WO3–CeO2–TiO2 catalysts for NO (nitrogen monoxide) reduction by ammonia were prepared by a sol–gel method. The catalysts were characterized by BET, XRD, Raman, NH3/NO adsorption and H2-TPR to investigate the relationships among the catalyst composition, structure, redox property, acidity and deNOx activity. WO3–CeO2–TiO2 catalysts show a high activity in a broad temperature range of 200–480 1C. The low-temperature activity of catalysts is sensitive to the catalyst composition especially under low-O2-content atmospheres. It may be related to the synergistic effect between CeOx and WOx in the catalysts. On one hand, the interaction betweenceria and tungsten oxide promotes the activation of gaseous oxygen to compensate the lattice oxygen consumed in NH3-SCR (selective catalytic reduction) reaction at low temperatures. Meanwhile, the Br nsted acid sites mainly arise from tungsten oxides, Lewis acid sites mainly arise from ceria. Both of the Br nsted and Lewis acid sites facilitate the adsorption of NH3 on catalysts and improve the stability of the adsorbed ammonia species, which are beneficial to the NH3-SCR reaction.

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In the past few years, an increasing interest has been put on the tungsten oxide films due to their potential applications in smart windows, gas sensors, photocatalytic reactions, and optoelectronic devices etc. The unique properties of the tungsten oxide films were usually determined by the oxygen defects and the valence states of tungsten ions. Besides, it is very important to improve the properties of tungsten oxide films and other oxide films by controlling their morphologies and crystalline phases, which mainly depend on the preparation technologies and thermal treating temperatures and atmospheres.

Tungsten oxide thin films were deposited on glass substrates by the magnetron sputtering of WO3 bulk at room temperature. The deposited films were annealed at different temperatures in air. The structural measurements indicate that the films annealed below 300 C were amorphous, while the films annealed at 400 C were mixed crystalline with hexagonal and triclinic phases of WO3. It was observed that the crystallization of the annealed films becomes more and more distinct with an increase in the annealing temperature. At 400C, nanorod-like structures were observed on the film surface when the annealing time was increased from 60 min to 180 min. The presence of W=O stretching, W–O–W stretching, W–O–W bending and various lattice vibration modes were observed in Raman measurements. The optical absorption behaviors of the films in the range of 450–800 nm are very different with changing annealing temperatures from the room temperature to 400C. After annealing at 400C, the film becomes almost transparent. Increasing annealing time at 400C can lead to a small blue shift of the optical gap of the film.

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Vacuum electronic devices have a wide application in civil and military fields such as communication, radar and industrial heating. Cathode is an important component in the device since it provides the required electronic beam for the device. Among all the electron emitters, scandate cathodes have aroused great attention among all the cathodes due to their copious emission property.

Scandia doped tungsten powders were prepared by spray drying combined with two-step hydrogen reduction. The particle size of doped tungsten powder, powder morphology and doped tungsten matrix were characterized by scanning electron microscope, X-ray diffraction and laser diffraction particle size analyzer, respectively. The reduction behavior of Sc2O3 doped tungsten oxide and the effect of Sc2O3 on the property of tungsten powder were studied by the temperature programmed reduction. The experimental results showed that the precursor powders prepared by spray drying had spherical shape. The addition of Sc2O3 could decrease the reduction temperature of tungsten oxide. The scandia doped tungsten powder had sub-micrometer size in the range of 0.1 to1 μm and scandium distributed evenly in the powder. By using this kind powder, sub-microstructure cathode matrices with semispherical grains and homogenous distribution of scandium were obtained.

The addition of Sc2O3 shifted the hydrogen consumption peak to the lower temperature side. Namely, the reduction temperature of tungsten oxide decreased with Sc2O3 addition. Adding scandia could decrease the particle size of tungsten. The scandia doped tungsten powder prepared by spray drying method had sub-micrometer size in the range of 0.1μm to1μm in semispherical shape and scandium distributed evenly in the powder. Using scandia doped tungsten powder, sub-microstructure cathode matrices with semispherical grains and homogenous distribution of scandium was obtained.

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Compared with other transition metal oxides, ungsten oxides have attracted great attention and have been investigated extensively due to their outstanding electrochromic, optochromic, and gas-chromic properties. ith those distinctive prop-erties, tungsten oxides have been used to makeflat panel displays, photoelectrochromic smart win-dows and gas sensors. Non-fully oxidized tungsten oxides (WO3x), such as W20O58, W18O49andWO2, are of particular interest because of their unique electronic characteristics, e.g. tungsten oxide has been found to be a semiconductor, a conductor or a superconductor in different oxidization states. Since one-dimensional tungsten oxide nano-materials exhibit superior properties in some promising applications compared with bulk materials, much effort has been made to synthesize tungsten oxide nanowires by using different methods, including a soft-chemistry approach, the chemical vapour deposition (CVD) method, hot-filament-assisted synthesis, flame synthesis and multistage field enhancement of tungsten oxide nanowires.

Tungsten oxide nanowires of diameters ranging from 7 to 200 nm are prepared on a tungsten rod substrate by using the chemical vapour deposition (CVD) method with vapour–solid (VS) mechanism. Tin powders are used to control oxygen concentration in the furnace, thereby assisting the growth of the tungsten oxide nanowires. The grown tungsten oxide nanowires are determined to be of crystalline W18O49. I–V curves are measured by an in situ transmission electron microscope (TEM) to investigate the electrical properties of the nanowires. All of the I–V curves observed are symmetric, which reveals that the tungsten oxide nanowires are semiconducting. Quantitative analyses of the experimental I–V curves by using a metal–semiconductor–metal (MSM) model give some intrinsic parameters of the tungsten oxide nanowires, such as the carrier concentration, the carrier mobility and the conductivity.

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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.Tungsten ores are treated with alkalis to produce WO3. Further reaction with carbon or hydrogen gas reduces tungsten trioxide to the pure metal.

The phase structure, morphology and particle size evolution of tungsten oxide reduced by hydrogen were studied by X-ray diffractometer ,scanning election is WO3-WO2.90-WO2.72-WO2-W. The surface morphology of powder changes from a smooth ro a rough particle and eventually the bigger secondary particles turn to sevetal smaller particles . The specific surface area of the powder increases during WO3 reducing to WO2.90-WO2.72 , reducing to W.

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Tungsten carbide cutting tool coating performance largely depends on the quality of the coating process and the coating, the coating quality preparation include: coating density, texture, microstructure, structural defects, residual stress. Coating process parameters include a deposition temperature, arc current, N2 partial pressure, a negative bias, coating time, the degree of vacuum and the like.

3. Nitrogen partial pressure
Nitrogen gas as the reaction gas, the size of the partial pressure of a serious impact on the phase composition of the coating. During deposition, the nitrogen also plays a role in the arc dimension, when the gas pressure in the cavity is too low, it is difficult to maintain a stable cathodic arc, can lead to the phenomenon of breaking arc, while the film will be such that the ratio of tungsten carbide cutting tool decrease in N, reach preferably TiN, TiCN, ZrN atomic ratio.

4.The negative bias
Bias is high, the ion bombardment enhanced dense. Pulse bias to some extent reduce the residual stress dawdle, and the bonding strength increases, the friction coefficient decreases. But the bias is too high, the base overheating, mechanical properties of  tungsten carbide cutting tool the coating hardness and bonding strength will decline.


 

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