Gold And Tungsten Gold-plated "Rusty" Solution Measures
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- Category: Tungsten Information
- Published on Tuesday, 12 January 2016 16:06
Earlier we have discussed that if the gold and tungsten gold-plated products are cleaned improper, mixed dust or other impurities or contacted prolonged with light and air in the production process, will make the surface of gold and tungsten gold-plated discoloration even produce rust, but it does not mean that the reason of “rusty” is due to the inadequate purity of gold.
After a long storage time, the issues of gold and tungsten gold-plated products that most frequently occurring are including: "rusty" and fade. The so-called "rusty" in fact is the spots of the gold and tungsten gold-plated products’ surfaces, such spots are including white spot and red spot, these problems will reduce the beautiful and ornamental appearance of the gold and tungsten gold-plated products. So how should we properly remove these rust, in order to restore the original color of them?
Try not to touch the surface of the gold and tungsten gold-plated products when appreciating them in daily life, so as to avoid the perspiration of our hands or other dusts adhering to the collections’ surface. The white spot is mostly caused due to the cosmetics, laundry detergents or other things which are containing elemental mercury that would be combined with gold and tungsten gold-plated and form the mercury gold compound. For this problem, we can take it to the regular gold shops to have a high temperature treatment then the rust can be removed. The red spot is caused by the adhesion of dust impurity, and has no other treatment processes for a long time in the production process, this kind of rust can be remove by firing in the gold shop.
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Tungsten Alloy Radiation Shielding Door(2/2)
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- Category: Tungsten Information
- Published on Tuesday, 12 January 2016 16:04
Tungsten alloys, also known as wolfram heavy alloy or tungsten-nickel-iron alloy, due to its good thermal conductivity, oxidation and corrosion resistance, it has been widely used in many fields. In addition, it is also a non-toxic and environmentally friendly and high-density material, we all know that the greater the density of the material, whose radiation absorption capacity will be better, so the shielding made of tungsten alloy material, has an excellent rays radiation shielding performance.
For nuclear reactions institute, shielding the nuclear reactions room is one way to protect the health of workers. The walls of nuclear reaction room can be built with the thick concrete for radiation shielding, but for the entry and exit doors, it was impossible to use too heavy materials to manufacture. Therefore, we can use tungsten alloy material to make the shielding door, because the radiation absorption capacity of tungsten alloy is good, so we just need little heavy materials that can achieve the desired shielding effectiveness, thus can significantly prevent the escape of radiation from the nuclear reaction rooms.
In addition, the waiting rooms of hospitals, where are provided for the radiopharmaceuticals injected patients, also can use this method to shield the radiation, that is to use the tungsten alloy radiation shielding door to shield radiopharmaceuticals radiation, in order to protect the safety of both doctors and patients.
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Tungsten Alloy Radiation Shielding Door(1/2)
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- Category: Tungsten Information
- Published on Tuesday, 12 January 2016 16:01
Radiation is divided into many kinds, such as electromagnetic radiation, nuclear radiation and radioisotopes radiation and so on. Among them, nuclear radiation and radioisotopes radiation are the strongest, which is also do the largest harms to the human bodies, and therefore these two radiation need to be focused on. Currently the main types of nuclear radiation are α-ray radiation, β-ray radiation and γ-ray radiation, the latter two because of its combination of high-speed particles so their penetration power is stronger than α-rays, thus the radiation damage is greater. Due to the instability of atomic nucleus, radioisotopes will continuously emit α rays, β-rays, γ-rays and electron capture, and even decay into another kind of stable isotope.
We all know that β-rays and γ-rays, significantly have the radiation hazards like all ionizing radiation, so when using such kinds of rays to test or work, we must control the rays radiation around the operating area, especially for the nuclear reaction, which has a large number of radiation, the effective measures must be taken in order to shield these rays radiation. For example: to make the staff wear thick radiation suits, to install the tungsten alloy shielding in the nuclear reactor device or to install the tungsten alloy doors in the nuclear reaction rooms and so on.
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High Velocity Oxyfuel Spraying Producing Tungsten Carbide Based Coating Analysis
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- Category: Tungsten Information
- Published on Tuesday, 12 January 2016 14:28
HVOF (high velocity oxyfuel spraying, HVOF) method is the use of hydrogen, acetylene, propylene, kerosene and other fuel, oxygen for combustion, combustion in the combustion chamber or a special nozzle to produce 2100m / s or more over the speed supersonic burning flame. The powder was sent to a supersonic combustion flame to produce molten or semi-molten particles, high-speed impact deposition surface of the substrate to form a coating. Because tungsten carbide has good abrasion resistance, so the tungsten carbide based coatings prepared by HVOF method with good anti-wear, anti-corrosion properties.
Tungsten carbide coating on the resulting analysis found that the coating thickness of 300 microns, deposition efficiency of 55.15% and a porosity of 0.32%. Coating phase mainly composed of WC phase and also contains small amounts of W2C phase and amorphous phase or nanocrystalline phase, but W phase or η (Co6W6C, Co3W3C) does not appear, shows that very short residence time of the particles in the flame stream and the powder decarbonization to a small extent. The main reasons of small decarbonization degree of coating are as follw: (1) no η phase powder; (2) the experimental oxygen flow and kerosene flow design helps to get a relatively low flame temperature; (3) moving faster of spray gun and compressed air cooling during spraying, so that the coating heated degree is low. In addition, the coating powder stored in the WC hard phase, will help improve the wear resistance of the coating.
Testing tungsten carbide coating’s hardness, abrasion and corrosion resistance to salt spray found that the hardness of the coating nearly 1300HV, wear volume is quite small. Coating in neutral salt spray environment 360 hours and still maintain a smooth surface and has a metallic luster, corrosion does not occur, indicating strong corrosion resistance coating. After adding Cr easy since Cr2O3 ceramic layer formed on the surface of a thin coating, thereby improving the corrosion resistance of the coating.
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Using High Velocity Oxyfuel Spraying to Produce Tungsten Carbide Based Coating
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- Category: Tungsten Information
- Published on Tuesday, 12 January 2016 14:20
High velocity oxyfuel spraying (HVOF) rise in ordinary flame spraying of the early 1980s is a new type of thermal spray technology. HVOF flame spraying method because of its high speed, low temperature, high coating bond strength, compactness, high hardness, low porosity and low oxide content, is widely used in the aviation, metallurgy, textile machine, automobile, railways and other fields. With the latest statistics in 2015, in the thermal spray coating technology industry high velocity oxyfuel spraying occupies 25 percent of the market. In addition, HVOF technology has low flame temperature (about 2600 ~ 3000 ℃), high velocity flame, and during spraying process it can restrain and reduce tungsten carbide decomposition. Besides, tungsten carbide coating can be obtained and reservations tungsten carbide phase abrasion resistance, so the coating has good resistance to wear and corrosion resistance.
Using HVOF method to produce tungsten carbide based coating and the specific processes are as below: HVOF method is based on WC, Co, Cr and other raw materials, according to WC10Co4Cr ingredient preparation of raw materials. Prepared raw material by mixing milling, spray granulation and vacuum sintering to obtain a powder block, then by crushing and screening, control spray powder particle size to make the particle size reaches 15 ~ 45μm. After testing, 15 ~ 45μm spray powder has high spherical, good liquidity (~ 13 s / 50g), powder bulk density similar to (4.8 ~ 5.0 g / cm3), and single structure shows loose powder. Powder phase is WC and Co phase. The sample matrix material of coating is 45 # steel. Before spraying 45 # steel surface processed sand blasting by 50 to 70 mesh corundum blasting and using compressed air to purge the sample surface. Finally, use the robot fixed Praxair JP8000 supersonic flame spray gun to produce tungsten carbide based coating.
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Hydrothermal Synthesis Tungsten Trioxide
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- Category: Tungsten Information
- Published on Tuesday, 12 January 2016 10:26
Hydrothermal method was invented by the geologist simulating the natural mineralization in mid-19th century and later turned to study functional materials. Currently hydrothermal method has prepared hundreds of kinds of crystals. Hydrothermal method, also known as hydrothermal method, is the scope of liquid chemical method. It means in a sealed pressure vessel, carriing out at high temperature and pressure conditions of the chemical reaction. Hydrothermal reaction depends on the type of reaction and it can be divided into hydrothermal oxidation, water and heat reduction, hydrothermal precipitation, hydrothermal synthesis, water hot solution, hydrothermal crystallization.
The Main Steps:
1. Dissolving the 3.5gNa2WO4•2H20 in 20ml of distilled water, dubbed the solution;
2. Exchanging resin column to produce hydrated tungstate sol by the solution that was hydrated;
3. Stirring constantly the dropped sol with a volume of 70ml glass barrel;
4. Adding to the resulting sol, and mixing well under 4.84g of citric acid.
Conclusions:
Preparing quadrature phase WO3 nano-sized rectangular sheets by hydrothermal synthesis with citric acid as a controlling agent, which shows there is a great relationship between the structure of product and the reaction temperature. X-ray diffraction results show that the reaction product is a WO3 • H2O and a small amount of monoclinic WO3 (γ- WO3); with the reaction temperature, the product of the following occurs transition: WO3 • H2O → WO3. SEM results showed that the product obtained are rectangular sheet structure at the reaction temperature. They are less than the surface area, between 8 ~ 9 m2 • g-1. We can control the product's composition, morphology and specific surface area by adjusting the citric acid and the amount of substance ratio (nCit / nTA). When nCitn / TA = 0, the product of h-WO3 and WO3 • 1 / 3H2O is composition; when nCit / nTA = 0.5 and nCit / nTA = 1, the product is γ-WO3 morphology rectangular sheet. In the case of citric acid was added, than the surface area of the product decreases with an increase of nCit / nTA.
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Waste Tungsten-Nickel Catalyst Preparing Sodium Tungstate 2/2
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- Category: Tungsten Information
- Published on Monday, 11 January 2016 19:13
Nickel, is a kind of approximate silvery white, hard, malleable and ferromagnetic metal element. It can be highly polished and is of corrosion resistance. Tungsten is important strategic metal resource and is also one of China's traditional export minerals. With the continuously exploitation, tungsten resources are decreasing gradually and the waste is very serious. To make up for the original tungsten resource shortage, the recycling of waste tungsten becomes one of the important measures.
Sodium tungstate was prepared by roasting plus sodium-leaching-ion exrhange and with waste tungsten-nickel hydrogenation catalyst as the raw material. We can draw the following conclusions:
1. The influence of the waste catalyst grinding particle size: waste catalyst grinding particle size has a certain influence on leaching rate of tungsten. Tungsten leaching rate after grinding increases by 10%. Grinding to 0.15 mm is the best process condition of experiments.
2. The influence of the dosage of sodium carbonate: As the dosage of sodium carbonate increasing from 0.46 to 0.69, tungsten leaching rate increases by 30%. The effect is very obvious. However, when the dosage of sodium carbonate ratio increases continuously, it has no significant effect on the experimental results. So the most appropriate dosage ratio of sodium carbonate is 0.69.
3. The influence of water temperature and time: Leaching temperature from 80 ℃ to 90 ℃, the leaching rate of tungsten increases by 2%. Leaching time has a small influence on the leaching effect of tungsten. Leaching it in 1 h and 90 ℃, the leaching rate of tungsten can reach nearly 99%.
4. The influence of the adsorption process of ion exchange: String column adsorption method can make each resin to saturated exchange capacity, which greatly improves the production capacity of ion exchange column. Using 2 mol/L NaCl and NaOH 1 mol/L mixture liquid as desorption, tungsten desorption rate can reach 98.2%.
5. Mix and heat the desorbed liquid. By evaporation, crystallization and recrystallization white crystal can be got. The purity of sodium tungstate products can reach more than 99%.
In conclusion, the method of using waste tungsten - nickel hydrogenation catalyst as raw material, using roasting plus sodium-leaching-ion exrhange to prepare sodium tungstate has the advantages of simple steps, mild conditions, easy operation, high recovery rate and low production cost. It can meet the requirements of circular economy and environmental protection.
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Waste Tungsten-Nickel Catalyst Preparing Sodium Tungstate 1/2
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- Category: Tungsten Information
- Published on Monday, 11 January 2016 19:11
Tungsten is a kind of infusible and rare metal. China’s tungsten resources have significant superiority in the world. Although China's tungsten reserves, production and foreign trade exports are the first in the world at present, the situation of China's tungsten resources can’t be blindly optimistic. Tungsten resources which are available for exploiting in China are sharply reducing. Tungsten resources are facing a severe situation.
For this problem, many experts have studied the countermeasures. Recycling and efficiently using tungsten secondary resources is one of the important measures to make up for a lack of original tungsten resources. Waste tungsten - nickel hydrogenation catalyst is a kind of important marketable secondary resources. Realizing valuable metals recycling of waste tungsten - nickel hydrogenation catalyst, not only can reduce environmental pollution, increase the recycling of resources, but also can reduce the production cost of enterprises and improve the economic benefit.
This article introduces a kind of method of using waste tungsten - nickel catalyst to prepare sodium tungstate. Researchers using waste tungsten - nickel hydrogenation catalyst as raw materials, chemical metallurgy method, and according to the process principle of ion exchange method with leaching liquid, design the secondary resource recycling plan of tungsten to provide a reference for the industrial production practice. The process can be divided into the following steps:
1. Waste tungsten - nickel hydrogenation catalyst contains high sulfur and organic compounds, so it must be removed oil by oxidation to let the carbon and sulfur removal rate reach 99%.
2. Mix the waste catalyst with sodium carbonate. Leach with hot water after a period of time of sodium modifying and roasting. Most of the tungsten oxides go into solution after transforming sodium tungstate. Nickel, iron oxides remain in the residue.
3. After acid leaching, residue is removed nickel, iron and aluminum, then alkali leach by sodium carbonate. The filtrate merges into the main process and the silicon residue can be directly landfill at this time.
4. The leaching filtrate through ion exchange adsorption, desorption, the high concentration of sodium tungstate solution can be got. Sodium tungstate can be obtained by crystallization and recrystallization.
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Sodium Tungstate Spectrophotometry Determining Gingko Flavonoids
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- Category: Tungsten Information
- Published on Monday, 11 January 2016 19:07
Gingko Flavonoid is the Ginkgo biloba extract. It can increase CBF and improve the function of cerebral circulation. It also can protect brain cells, expand coronary artery, prevent angina and myocardial infarction, prevent thrombosis, and enhance the body's immune ability. It’s good for the patients with coronary heart disease, angina pectoris, cerebral arteriosclerosis, senile dementia and hypertension. The methods of determination are derivatives-gas chromatography, reversed-phase high performance liquid chromatography (HPLC), colorimetric method and so on.
This article mainly introduces a new method-spectrophotometry. Spectrophotometry is determining absorbance of light or luminous intensity of the material tested at a particular wavelength or within a certain wavelength range to make the qualitative and quantitative analysis of the material. The method is based on gingko flavonoids reacting with sodium tungstate to generate yellow tungsten acid ester. This method is highly sensitive, simple, fast, and reliable. If it can be used for the determination of actual samples, a satisfactory result will be got.
Experimental Methods:
1. Respectively add 0.08 mol/L sodium tungstate solution 2 ml in two 25 ml colorimetric tube. Add a certain volume of gingko flavonoids standard using liquid and shake well to dilute to scale.
2. Another is added to scale directly. Put the former in sample pool, the latter in reference pool and determine its absorbance at 304 nm.
Experimental results:
1. The reaction product of tungsten acid ester has maximum absorption at 304 nm, so the experiment selects the wavelength as measuring wavelength.
2. The acidity of the solution has a big influence on the production of tungsten acid ester, so the experiment selects neutral conditions to reaction.
3. The amount of sodium tungstate has a certain influence on the formation of tungsten acid ester. With the increase of the dosage of sodium tungstate solution, absorbance also increases accordingly.
4. At 20 ℃, absorbance value of solution is maximum. 40 minutes later the absorbance value decreases gradually.
5. The linear range of the method is 4 ~ 120 mu g/ml. Through determining of samples, the recovery is 100.0% ~ 100.6%.
In conclusion, the spectrophotometry of rapidly determining gingko flavonoids in pharmaceutical preparations has the advantages of convenience, rapidness, wide linear range, high sensitivity, high accuracy, less reagent dosage, less interference and good reproducibility. It can be easily used in determining gingko flavonoids in pharmaceutical preparations.
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Gold And Tungsten Gold-plated "Rusty" Reasons
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- Category: Tungsten Information
- Published on Monday, 11 January 2016 18:23
The glistening gold shops on the market everywhere sufficiently show the likability of a variety of people for gold products, but recent years, because of the problem of “rusty”, the quality of gold products was suspected by many people. They think the reason for affecting the quality of the gold products is the shorting purity of gold. But what is the real reason for the golden and brighten gold and gold-plated tungsten products were rusted? Is it the reason of gold purity that produces those rust?
It’s well known that the gold has weaken metal activity but high corrosion resistance, which makes its chemical properties steadily, and therefore it will not cause the problem of “rusty” when existed by the form of simple substance in nature. But the chemical affinity of gold and sulfide is strong, and therefore its stable chemical properties will be changed along with the adjunction of metals and the other problems produced in the production process when manufacturing the gold into a wide variety of shapes, handicrafts and jewelries. These problems include: the improper cleaning of gold in the production process, dust or other impurities intake during production process, prolonged exposure to air and light and so on. As for the tungsten gold-plated products, the reasons for being rusted dues to the improper store of gold plating solution in the gold-plating process and the adjunction content of other metals in the gold plating solution. These problems will make the gold-plated tungsten products’ surface rust, thereby greatly reducing the aesthetic and ornamental of the products. Thus, the "Rusty" surface of gold and tungsten gold-plated production does not prove the view of shorting purity of gold. It reminds us that should pay more attention to maintain the gold and tungsten gold-plated products, for avoiding the generation of rust.
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