2021年5月19日星期三

Nano Tungsten Oxide for Semiconductor Memory

The reason why semiconductor memory chooses nano tungsten oxide material to produce storage media is that it is a very important semiconductor material with good electrochemical performance, and its resistance value can undergo reversible transformation under the action of an electric field. Next, let's take a look at the manufacturing method of a storage device based on a tungsten oxide storage element.

Manufacturing method (1)

The storage device includes a plug that extends upward from the top surface of the substrate through a dielectric layer. A bottom electrode, the outer surface of the bottom electrode has tungsten, the bottom electrode extends upward from the top surface of the plug. An insulating material, the insulating material surrounds the bottom electrode is in contact with tungsten on the outer surface of the bottom electrode. The storage element is located on the upper surface of the bottom electrode, the storage element includes a tungsten oxide compound, and the storage element can be programmed to at least two resistance states. And the top electrode, the top electrode overlay and contact the storage element. In addition, the plug has a first lateral dimension, the bottom electrode has a lateral dimension, the lateral dimension is parallel to the first lateral dimension of the plug, and the lateral dimension is smaller than the first lateral dimension of the plug.

Manufacturing method (2)

The tungsten oxide storage part is formed using a non-critical mask tungsten oxide material, or in some embodiments, it may be formed without any mask. The memory device disclosed herein includes a bottom electrode and a memory element, and the memory element is located on the bottom electrode. The memory element includes a tungsten oxide compound and has more than two resistance states; the upper electrode includes a barrier material located on the memory element, and the purpose of the barrier material is to prevent metal ions from moving from the upper electrode into the memory.

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Compared with traditional semiconductor storage devices, tungsten oxide storage devices have better response performance.

Preparation Method of White Tungsten Oxide

 Tungsten oxide is a very classic low-dimensional transition metal oxide material, which is attracted by its special physical and chemical properties (such as electrochromism, photochromism, catalytic activity, superconductivity and large load capacity, etc.) A large number of materials, semiconductor devices, and physics and chemistry researchers are paying attention. However, there is no report on white tungsten oxide and its preparation method.

The chemical formula of white tungsten oxide is the same as that of purple tungsten oxide, which is W18O49. It can be excited to become blue under the irradiation of ultraviolet light, and it can be restored to white after removing the ultraviolet light. It is widely used in construction, automobiles and other fields.

A method of producing white W18O49, there are the following steps:

Disperse the tungsten hexachloride ultrasonically in anhydrous n-butanol, of which 150ml anhydrous n-butanol is used per gram of tungsten hexachloride. When the system turns from yellow to blue during the ultrasonic process, stop the ultrasound, and then add it to the system Sodium nitrate, the amount of sodium nitrate is 1.5-3 times the mass of tungsten hexachloride, put the mixed system into the reaction kettle, control the reaction temperature at 180-220°C, and control the reaction time at 6-12 hours; wait for the end of the reaction After cooling to room temperature, the obtained product was washed with water and ethanol, centrifuged, and dried to obtain powdery white W18O49.

This method uses tungsten hexachloride and n-butanol as reactants. The color of the reaction product W18O49 can be adjusted by controlling the amount of sodium nitrate added. When the mass ratio of sodium nitrate and tungsten hexachloride is more than 3:2, white 118049 can be obtained. . The advantage is that by adding sodium nitrate to the system to modify the surface of the tungsten oxide, white tungsten oxide is obtained, which is obviously different from the W18O49 obtained by the general solvothermal method in appearance and color; and the production is simple and easy.

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Tungsten Trioxide for Mulch

 In addition to the production of tungsten trioxide (WO3) ultrafine particles, they can be used to produce tungsten powder, tungsten carbide powder, yellow ceramics, electrode materials for energy storage batteries, anti-corrosion paints and coatings, and can also be used to make multifunctional mulch films. Compared with ordinary agricultural film, the agricultural film containing tungsten oxide additives has higher comprehensive performance, which is mainly manifested in better heat insulation effect and better light transmission performance.

In areas with strong sunlight, when the temperature is too high, it is easy to produce drought and cell dehydration, which affects the physiological and metabolic activities of plants, such as photosynthesis, water metabolism, endogenous hormones, and thermal stability of cell membranes, which in turn leads to the appearance and growth of plants abnormal. Therefore, it is of practical significance to produce agricultural film with good heat insulation effect. However, a film with excellent heat insulation effect means that it has better near-infrared absorption performance.

In addition to good heat release effect, the new thermal insulation film also needs to have excellent light transmittance, so that it is convenient for managers to observe the production of crops at any time, without lifting the film, which improves the work efficiency of managers. At the same time, it can also reduce the rate of film breakage. The agricultural film with excellent light transmittance means that it has a higher transmittance to visible light.

WO3 is a classic transition metal n-type semiconductor material. It has excellent optical properties, that is, it has a significant absorption effect on near-infrared light in the 1400~1600nm and 1900~2200nm bands, and it also has high permeability to visible light. Therefore, it is favored by materials researchers at home and abroad. It is often used as a key modifier for commercial mulch films, which can significantly increase the near-infrared absorption capacity and light transmittance of the product, which is more conducive to the growth of crops.

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New Production Process of Tungstic Acid

Tungstic acid is made of artificial white tungsten (CaWO4) and concentrated acid under heating and cooking conditions. Artificial white tungsten is prepared by removing molybdenum (Mo) from industrial sodium tungstate solution by sodium sulfide method and adding calcium chloride. If the process is not treated by the sodium sulfide method, there will be no molybdenum removal effect, and the sodium sulfide method for removing molybdenum is more troublesome. Because the process needs to be produced under high temperature and high acidity conditions, it has high energy consumption and high acid consumption. The corrosiveness is strong, and the yield is not high. Therefore, the following will introduce a new production process of tungstic acid. The specific steps are as follows:

Add hydrogen peroxide (H2O2) complexing agent to industrial sodium tungstate (concentration between 0.2N and 1N). The amount of complexing agent is the molar ratio of tungsten: hydrogen peroxide of 2:1 to 2:2, add hydrochloric acid in the room temperature range of 10℃ to 28℃ to make the solution acidity between 0.5N and 2N (if the content of chromium and molybdenum impurities in sodium tungstate is high, the acidity of the solution should be adjusted to 2N), and then pass sulfur dioxide or add sulfite or bisulfite to directly prepare tungstic acid. The prepared tungstic acid is washed sequentially with 1N HCl, 0.5N HCl and absolute ethanol to obtain a pure product. Note: The amount of sulfur dioxide or sulfite or bisulfite is that the molar ratio of sulfur dioxide or sulfite or bisulfite: hydrogen peroxide is between 1:0.7 and 1:1.3.

Compared with the existing production method, the advantages of this technology are that in addition to the classic sodium sulfide removal of molybdenum process and the process of preparing artificial white tungsten with calcium chloride; since concentrated acid is no longer needed, it consumes less acid and consumes less energy and wastes; the production efficiency can be 98%, which is 10% higher than the existing process, and the molybdenum removal effect can reach 70% to 80%.

In general, the new technology has the advantages of simple operation, high yield, weak corrosiveness, less three wastes, high purity and high activity.

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2021年4月25日星期日

Ammonium Paratungstate

Ammonium Paratungstate(APT) is an important raw material product in tungsten smelting process, the appearance is white crystalline.

It is mainly used for the reduction of tungsten oxide or ammonium metatungstate, and also used as catalysts or additives in chemical industry.


The tungsten concentrate is screened and pressed, ammonium tungstate solution was prepared by ion exchange or extraction process, after the crystallization process, ammonium paratungstate was obtained.

In the process of smelting, ammonium paratungstate solution (Na2WO4) was obtained from tungsten concentrate by ion exchange or extraction, in order to truly use ammonium paratungstate, an important process is needed: crystallization process.

The crystallization process of ammonium paratungstate is one of the important processes in the tungsten smelting process, the crystallization methods of APT in industry mainly include evaporation crystallization method, neutralization crystallization method and freezing crystallization method. Evaporation crystallization is the most widely used method in China. The process and equipment are simple and easy to be large-scale. At the same time, it has the function of purification of tungsten, and the efficiency is the best.

Ammonium paratungstate is one of the main products of tungsten export in China. However, the added value of raw materials such as ammonium paratungstate is low, it has low profit, therefore, the export amount of ammonium paratungstate is also decreasing year by year in China.

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Nanometer Tungsten Sulfide Will Treat Cancer Cells In The Future

Photothermal therapy utilizes with high light heat conversion efficiency, inject it into the human body, target recognition technique is used to aggregate near the tumor tissue.

The method of converting light energy into heat energy to kill cancer cells under the irradiation of external light source is a kind of cancer treatment method with great expectation by human beings.

In the process of photothermal therapy, the selection of photothermal agents is a key link. These therapeutic agents can effectively convert laser energy into heat energy, thus enhancing the heating efficiency of laser. In order to achieve effective and selective photothermal therapy, photothermal agents must meet several conditions: It can absorb and transform laser energy effectively; A solvent that can be dissolved in a biologically friendly solvent, ensure that the treatment agent enters the tumor tissue smoothly; The surface of particles is easy to be functionalized, which is conducive to the cooperation with other methods such as targeted therapy; Low toxicity of the material itself.


Graphene has excellent biocompatibility, stability, low cytotoxicity and other advantages, the band gap of graphene is zero, the fluorescence intensity of quantum dots is weak, the quantum yield is low, and it is not a perfect photothermal agent. When graphene is abandoned, transition metal two dimensional sulfides have attracted much interest, nano tungsten sulfide (molybdenum) is a sandwich structure consisting of hexagonal metal atoms sandwiched between two layers of sulfur elements, the band gap of the two-dimensional structure is 2.0eV (1.9eV), it has better light conversion and absorption capacity, tungsten itself is an excellent X- ray absorbing material, it has a wide range of applications in the field of hospital testing imaging equipment, therefore, in the process of photothermal therapy, tungsten sulfide can be used for contrast imaging, and can be used for the treatment of operation, can achieve dynamic tracking, diagnosis and treatment integration.

Uniform size tungsten disulfide nanosheets were obtained by intercalation of lithium ions, the surface modification of poly (ethylene glycol) polymer makes it have better water solubility and biocompatibility, tungsten sulfide nanomaterials have good optical absorption properties in the near infrared region. The sulfur nanoparticles were injected into the mice through the caudal vein, and the tumor was enriched by the high permeability and retention effect (EPR effect) of the tumor. Because tungsten can absorb X- rays, it is the first time to achieve very good tumor CT imaging in animal models. At the same time, based on the near-infrared absorption property of tungsten sulfide nanomaterials, it can be used for photoacoustic imaging of tumors. Under the near-infrared laser irradiation, all the tumors were completely killed and reached the goal of complete cure.

Research shows that nano tungsten sulfide treatment agent in the future will likely be large-scale clinical application in cancer therapy, as a tool for human tumor sniper, which is mainly due to nano material not only has good absorption of tungsten sulfide and light conversion properties, but also has low toxicity, and can be modified through molecular and simple cells compatible.

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Tungsten Disulfide Lubricant

The industrial production department has put forward more and more strict requirements on the performance of lubricating oil (grease).

Ordinary equipment is often replaced by low-performance lubricants (grease) instead of high-performance products, causing equipment damage or lubricating oil (grease) consumption, therefore, it is of great significance to accelerate the research and development of high temperature lubricating oil (grease) to meet the needs of the domestic market.

Tungsten sulfide is a compound of tungsten and sulfur, and it is a new kind of solid lubricant with excellent performance, not only suitable for general lubrication conditions, but also for high temperature, high pressure, high vacuum, high load, radiation and corrosive medium working environment, the magnetic properties of WS2 clusters are not only lubricated but also adsorbed on the metal surface during lubrication. A layer of nano protective lubricating membrane is formed on the metal surface.

Tungsten sulfide has a very small coefficient of friction (about 0.03), it can be used as additive in metal powder to improve the adhesion of metal powder under high speed friction condition and to obtain stable friction coefficient. Nanometer WS2 has excellent oxidation resistance, can be used as additive in lubricating oil (grease), it can effectively improve the lubricating oil (grease) properties of extreme pressure and anti-wear performance, it is not only good lubricating performance, and long service life.

The purity of tungsten sulfide is still very expensive, especially nano tungsten sulfide. In China, in addition to aerospace, tungsten sulfide has been widely applied in various industrial machinery operation in high temperature, the most mainstream collocation is that use tungsten sulfide ultrafine powder as additives in lithium complex greases, both can control costs, and to effect.

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Nano Tungsten Oxide for Semiconductor Memory

The reason why semiconductor memory chooses nano tungsten oxide material to produce storage media is that it is a very important semiconduc...