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Tungsten Carbide Die Status Quo

Details: Category: Tungsten Information; Published on Thursday, 16 June 2016 16:00; Written by xiaobin; Hits: 243

Currently, tungsten carbide material has become an indispensable role in the mold manufacturing. With the increasing complexity of the products and the higher requirement of the performance, the relevant researchers develop new carbide materials research as one of the directions. Several years ago, new carbide material mainly used Fe, Ni to replace Co, which usually used for cold heading die and cold extrusion die with high demand of toughness (such as YG15, YG20, YG25). Recent years, the hotpot turns to ultrafine grained and nano-crystalline carbide and gradient structure of cemented carbide. Fine-grained and ultrafine grain cemented carbide has been available, as YG8 fine grain carbide drawing dies in less than 1mm wire control, efficiency is three times the normal drawing die. Gradient cemented carbide is also divided into content gradient and structure gradient, they often fabricated by metal solution penetrated treatment. In addition, cast tungsten carbide heat die has a better performance in tube and wire rolling.

Based on the mechanism of tensile deformation of the metal mold uneven wear, Researchers have proposed the maximum and minimum drawing angle theory. They found that the gap between domestic and foreign mold die life lies in the angle of the design. Foreign mold at the bottom of the mold core and the mold housing bore center of the bottom-contact parts adopt double convex design, it is possible to force the center of the largest snug fit around the pore and for an interference fit. So some domestic manufactures have also been inspired, and correspondly make some improvements in the structure. Especially the improvements on the design of hexagonal carbide die, which changed into six casement combination so that it can save the consumption of tungsten carbide and convenient for assembling and changing. In terms of machining and assembling technologies, tungsten carbide usually uses hot or cold casement and vacuum brazing.

tungsten carbide die

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Tungsten Carbide Die Description

Details: Category: Tungsten Information; Published on Thursday, 16 June 2016 15:58; Written by xiaobin; Hits: 276

Compared with conventional steel die, WC-Co tungsten carbide die has many advantages, such as high density, high hardness, high strength, low coefficient of thermal expansion, excellent wear and corrosion resistance and so on, whose service life is several times longer than the steel die. Common used tungsten carbide die grades are YG3, YG6, YG6X, YG8, YG15, YG20, YG20C, YG25, etc, and some non-magnetic alloy die materials. According to the different applications, tungsten carbide dies can be divided into tungsten carbide drawing die, cold heading die, non-magnetic die, thermal die, etc.

Tungsten carbide drawing die takes the major part and it plays an important role in metal processing by the external force is a pressure force by the metal mold, the metal cross-section is compressed so as to obtain a desired cross-sectional shape and size. Due to plastic and steel die has bad performance in wear resistance and service life, and although diamond drawing die has high hardness and wear resistance, it cost a lot. In summary, tungsten carbide drawing die has excellent properties and medium cost, which is the major part of drawing die materials; Cold heading die and stamping die are mounted on the respective use of machinery by applying a deforming force, the blank pre-formed. Carbide material hardness and excellent wear resistance, life million times in 5000-6000, the size does not substantially change, so as to effectively guarantee the dimensional accuracy of the product; No-magnetic alloy die generally used for the production of magnetic materials. Before non-magnetic tungsten carbide non-magnetic appearing, people has been using non-magnetic steel, mold its poor performance, low hardness and short life, the inner wall of the mold used for a period of time after a serious nap and deformation phenomena, so that the dimensional accuracy and surface quality of the magnetic material has been greatly affected. Non-magnetic carbide prepared by strictly controlling the carbon content and adding trace elements (Cr, Mo, Ta, NiB, Al, VC), which can replace the steel and improve the efficiency.

tungsten carbide die

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Cesium Tungsten Bronze Ultrafine Powder Preparation

Details: Category: Tungsten Information; Published on Wednesday, 15 June 2016 18:05; Written by xinyi; Hits: 326

Tungsten(VI) oxide, also known as tungsten trioxide or tungstic anhydride, WO3, is a chemical compound containing oxygenand 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(VI) oxide occurs naturally in the form of hydrates, which include minerals: tungstite WO3•H2O, meymacite WO3•2H2O andhydrotungstite. These minerals are rare to very rare secondary tungsten minerals. Tungsten has a rich history dating back to its discovery during the 18th century.

WO3 has excellent performance in electrochromic, catalysis, gas sensing and other aspects, the composite oxides – tungsten bronze is a kind of metal oxides generally with deep metallic luster color, and usually a metal conductor or a metal semiconductor, the formula of tungsten bronze is AxWO3, but with the change of cation kind and the different number of moles （different value of a and x）, the structure and color depth of the compounds may vary. Currently, the researches are more about potassium cesium bronze tungsten and cesium tungsten bronze tungsten, because of the low resistance and excellent transmittance of visible and near-infrared shielding properties of cesium tungsten bronze tungsten, it’s widely used in the preparation of the conductive thin film used in a transparent glass partition thermal insulation coatings as agent.

The tungsten bronzes are a very interesting, but little appreciated, family of materials. They are not related to bronze, an alloy of copper and tin, except coloration. However, the structure of tungsten bronzes are similar to the high-temperature copper oxide superconductors. In fact, the tungsten bronzes were the first oxide superconductors and were the focus of extensive research 10-15 years ago. But by the early 1980s, most of this work had been set aside in favor of other pursuits.

The tungsten bronzes are a group of compounds made up of tungsten trioxide, WO3, and an alkali metal, such as sodium (Na) , potassium (K), rubidium (Rb) , or cesium (Cs). The general chemical form is MxW03, where M=Na, K, Rb, or Cs, and O<x<l. The color of these compounds varies with composition, at x=0.93 the color is a bronzelike golden-yellow, hence the name; at x =0.32 the color is a blue-violet. For this reason tungsten bronzes are use as pigments in dyes allld paints.

The variation in composition also affects the structure of the compound. Imagine a ¢ube with a tungsten atom at each comer, an oxygen atom in the middle of each edge and an atom of an alkali metal in the center of the cube. However, in a tungsten bronze there is not an atom at the center of every cube. When x< 1, only a certain fraction of the cubes will contain an alkali atom. If x is large, close to 1, the structure of the crystal lattice will be cubic. As x decreases, and fewer of the cubes are filled, the structure changes. At about x<0.3, or with less than 30% of the cubes full, the structure becomes hexagonal, with atoms arranged in hexagonal plates.

The cubic arrangement described above with an atom in the center of a cube is typical for perovskites, a group of ceramic materials with a variety of interesting electrical properties. The high--temperature superconductors are among these. In the cubic phase, tungsten bronzes are metallic and conduct electricity. However,in the hexagonal phase, they become superconductors. William Moulton, at Florida State University in Tallahassee, has done a lot of work with potassium, rubidium and cesium tungsten bronze superconductors. Dr. Moulton points out that these differences in properties depending on the direction of measurement in the crystal. The temperature at which a material becomes superconducting, of about 6K.

There was many methods to prepare cesium tungsten bronze, for example, a cesium tungsten bronze powder preparation method, the use of tungstate tungsten source, Cs / W molar ratio of 1: (2.857 100), at 180 ~ 200 ° C reaction conditions 1 ~ 3 days. The method for preparing a long reaction period, low efficiency, is not conducive to industrial production.

The present invention is directed to the above-mentioned deficiencies in the prior art, there is provided a method for preparing save raw materials, short reaction period cesium tungsten bronze ultrafine powders.

A method for preparing a cesium tungsten bronze ultrafine powder, comprising the steps of: (1) in accordance with Cs / W molar ratio of 1: (1.5 to 2.8) was weighed cesium salt, a tungsten salt, a chelating agent and an alcohol reagent, under conditions of 170 ° C reaction 3h; mixture (2) in the step (1) was charged into a pressure vessel bomb reacted at 260 ~ 270 ° C reaction conditions 5 ~ 8h; (3) the step (2) a reaction product obtained by ethanol washing, centrifugation, at 80 ° C and dried in vacuo to give crystals of the condition of complete crane cesium powder.

On the basis of the above method, the present invention also can do the following improvements.

Further, the tungsten salt of the step (1) is ammonium tungstate, ammonium paratungstate or ammonium metatungstate; the cesium salt is cesium nitrate or cesium hydroxide;

With the above further aspect, the beneficial effect is that the tungsten salts used contain NH4 +, not only to provide a tungsten source, and ammonia at high temperatures generated by the reaction can be used as a reducing atmosphere to protect its color stability, the resulting cesium tungsten bronze powder is obtained.

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CsxWO3 Type Peroxide Mimic Enzyme

Details: Category: Tungsten Information; Published on Thursday, 16 June 2016 15:48; Written by xinyi; Hits: 274

Diabetes has become a disease now affecting the normal human life. Generally, the concentration of glucose inside human bodies is 3-8mM, and the concentration of glucose in the body of patients with diabetes is 9-40mM. Glucose concentration is a key indicator of diagnosis of diabetes, there are already a lot of testing methods for detecting the concentration of dextrose, common are: high performance liquid chromatography, electrochemistry, colorimetry and the like. Wherein the colorimetric method in comparison with the other due to high sensitivity, easy operation and low cost by more people's attention. The glucose sensor is based on a large number of horseradish peroxidase assay set up, however, limited sources of natural enzymes, purification difficult, expensive, and in order to maintain its cleaning, the experimental conditions and operating environment requirements are more demanding , its application is extremely limited, so the development and application of enzyme mimics more and more people's attention.

Since the Fe₃O₄ nanoparticles are found to have catalytic properties similar to horseradish peroxidase, people have developed a series of functional classes peroxidase nanomaterials. Such enzyme having nanometer analog preparation process is simple, easy to storage conditions, low cost, high temperature and acid, etc., has become the object of focus on the people, and therefore continue to discover new catalytic activity contain nanomaterials, explore new nano analog enzyme is an important direction of current research.Through our preliminary investigation we found that many have photothermal effect nanomaterials such Fe₃CVCuS, Prussian blue, Au and so has the nature of nanometer analog enzyme. Cs_xWO₃ as photothermal material, according to the near-infrared at having before Chong shenGuo on Nanoscale et al reported a high absorption and a high conversion rate, and therefore can be used for cancer photothermal therapy. Based on these studies we believe Cs_xWO₃ nanorods may also have catalytic activity and enzyme applications like simulation, this idea was first proposed and validated.

The present invention thus provides in one kind Cs_xWO₃ class and mimetic peroxidase and its preparation method and application. Cs_xWO₃ nanomaterials can catalyze H₂O₂ to produce strong oxidizing hydroxyl radicals, highly efficient oxidation of 3,3 ', 5,5' - tetramethylbenzidine (TMB) produces color reaction. Short reaction time, color-fast, catalytic effect and applicability are higher than the natural peroxidase, and can be used in blood glucose levels in food testing.

The process according to Cs_xWO₃ class mimetic peroxidase is: will WCl₆ dissolved with stirring in absolute ethanol was added CsOH.H₂O, dispersed evenly, then add anhydrous acetic acid; the resulting mixed solution was transferred to Teflon autoclave, 235 ° C reaction 20h; centrifugal washing, washed with ethanol several times, and then at 60 ° C under vacuum to obtain dried 12h Cs_xWO₃ nanomaterials.

More specifically: slightly yellow 0.2976g WCl₆ WCl₆ ethanol solution under vigorous stirring until dissolved in 40mL anhydrous ethanol, and then 0.0636g CsOH-H2O was added to the dissolved; after uniformly dispersed in the mixed solution 10mL of anhydrous acetic acid was added to the above solution, the mixed solution was transferred to a Teflon 100mL autoclave, reacted at 235 ° C 20h, to give a dark blue product was washed with water by centrifugation, washed with ethanol several times, the resulting the product was vacuum dried at 60 ° C for 12h.

Cs_xWO₃ nanomaterials capable of catalyzing the oxidation of H₂O₂ substrate to produce color reaction: The Cs_xWO₃ nanomaterials, TMB and H₂O₂ was added to 25 mM, pH = PBS 4.0 buffer solution, the shake, the reaction 30 min, followed by UV spectrophotometry absorbance was measured by 652nm wavelength. Cs_xWO₃ + H₂O₂ + TMB experimental group to other group has a higher absorption values compared to explain Cs_xWO₃ nanomaterials indeed capable of catalyzing the oxidation of H₂O₂ to TMB oxTMB.

Aqueous solution of glucose and oxygen occurs in the catalytic reaction of the glucose oxidase produces H₂O₂can be quantified, and Cs_xWO₃ nanomaterials can catalyze H₂O₂ to produce strong oxidizing hydroxyl radical, then oxidized TMB oxTMB, measured by UV absorbance oxTMB, indirect detection of glucose content in the solution.

The present invention first found Cs_xWO₃ nanomaterials catalytically active class peroxidase, and measuring the glucose content of the solution applied. Cs_xWO₃ nanomaterials as a category for the determination of glucose peroxidase, short reaction time, color-fast, etc., the catalytic effect and applicability are higher than the natural peroxidase. And compared to horseradish peroxidase (HRP), it has a simple preparation process, low cost, stable chemical activity, etc., can be used as a substitute for natural peroxidase. And glucose oxidation enzyme-linked with, you can build a simple, fast, low-cost assay for the detection of glucose concentration, the detection limit is 0.1 μ Mo.

Compared with horse radish peroxidase (HRP), the Cs_xWO₃ nano material has the advantages of simple preparation process, low cost, stable chemical activity and the like; the catalytic effect and the applicability of the Cs_xWO₃ nano material are higher than those of natural peroxidase, and thus the Cs_xWO₃ nano material can be used as a substitute of natural peroxidase.

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Tungsten Oxide Thin Film Electrode Cyclic Voltammetry

Details: Category: Tungsten Information; Published on Wednesday, 15 June 2016 17:27; Written by Cristina; Hits: 432

To study the cyclic voltammetry of tungsten oxide thin film electrode, use three-electrode system, sulfuric acid solucion as electrolyte, the property is observed by measuring light current. Below is cyclic voltammograms of WO3 thin film electrode being heat treatment under 450℃ under dark and 500W xenon light source (light strength 100Mw/cm2). We can see that under darkness the polarization current of electrode is small within the scanning range, it is far smaller than anode polarization current under light. Photoelectrochemical reaction under light has good reversibility. Within electric potential 0.35~1.2V（vs.Ag/AgCl）, cathode Pt and anode WO3 thin film electrode reaction is as following:
Anode：2OH^-+ h⁺ → O₂ ↑+ 2H⁺
Cathode：2H⁺ + 2e^- → H₂↑
CV Curve

When exposed to light, if the applied bias is low, the Fermi level of WO3 is higher, electrolysis solution accepter is easier to trap photo electron near WO3 electrolyte interface of electrode, so the photo current of anode is weaker, even comes close to 0. With the increasing of bias, Fermi level of WO3 decreases as well, the accepter of electrolyte to trap the photo electron is getting harder which makes the photo electron largely spread to the electric substrate. When bias comes to a certain level, the extra electric filed enlarges the migration rate of photo electron, so photo current of anode strengthens with the shuffling of current.

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