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The properties, preparation and common applications of bismuth trioxide

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Update time : 2020-05-20 14:40:34
Bismuth trioxide Bi2O3 is an important functional material, and it mainly exists in the four crystal types, i.e., roof, net and. Different crystal types can be applied in different ways. Leume type is a yellow monoclinic crystal with a relative density of 8.9 and a melting point of 825 ℃. It is soluble in acids but insoluble in water and alkali. The type is bright yellow to orange, cubic crystal, relative density 8.55, melting point 860 ℃, soluble in acid, insoluble in water. It is easily reduced to metal bismuth by hydrogen and hydrocarbon. -bi2o3 is a special material with a cubic fluorite structure, in which a quarter of the oxygen ions in the lattice are vacant, so it has a very high conductivity of oxygen ions. Bismuth oxide is mainly applied to electronic ceramic powder material, electrolyte material, photoelectric material, high temperature superconducting material and catalyst. Bismuth oxide as an important additive in electronic ceramic powder materials, the purity is generally required to be more than 99.15%, the main application objects are zinc oxide varistors, ceramic capacitors, ferrite magnetic materials three categories. Bismuth oxide is widely used, it is not only a good organic synthesis catalyst, ceramic colorant, plastic flame retardant, medicinal astringent, glass additive, high-refractive glass and nuclear engineering glass manufacturing and nuclear reactor fuel, but also an important doped powder material in the electronics industry.
                                                                
The synthetic methods
 
  1. The bismuth nitrate solution (80 ~ 90 ℃) was mixed with sodium hydroxide water solution without carbon dioxide. The solution remained alkaline in the precipitation process, resulting in Bi(OH)3 precipitation of white and expanded bismuth oxide hydrate. The solution was heated, stirred for a short time, and then dehydrated into yellow bismuth trioxide. The bismuth oxide was washed, filtered and dried by water decanting.
 
  1. In nitrogen atmosphere, drop 1.5mol/L sodium hydroxide solution without carbon dioxide into 0.1mol/L bismuth nitrate solution dissolved in 1mol/L nitric acid (at 80 ~ 90℃) and mix them. The solution remains basic during precipitation. Although a white, expanded Bi(OH)3 deposit was formed, it was dehydrated and changed into a pale yellow bismuth trioxide after being stirred in a hot solution for a while. Wash it 15 times with decanting water without air and carbon dioxide, and dry it after filtration.
 
  1. After the metal bismuth was put into a graphite crucible and melted, an arc was formed between the graphite electrode and the metal liquid surface under the flow of oxygen and then heated for oxidation. To ensure an adequate supply of oxygen, the crucible is placed in a large container and continuously fed with oxygen. The reaction temperature was 750 ~ 800℃, and the purity was 99.8% or more. The products are then quenched in water or on a cold sheet of metal.
 
  1. Slowly add Bi(NO3)3·5H2O acidic solution (20g dissolved in 2mol/L HNO3) to the excess sodium carbonate solution and stir vigorously. Bi2O3CO3 was precipitated, filtered, washed and dried. Put it in an aluminum boat, in the air, and heat it at 650K for about 1.5h, to get tany-bi2o3
 
5. Burn the basic bismuth nitrate at 400 ~ 500℃ to remove NO3- ions (3 ~ 4h) :
2 biono3 = Bi2O3 + NO + NO2 + O2
At the end of the burning, all of them turn to lemon yellow after cooling, which is the finished product.
 
6. Wash the industrial bismuth surface of 16kg99.9% with a small amount of dilute nitrate acid, and then wash the surface with conductive water to remove the nitric acid. Then add the 1:1 high purity nitric acid (35 kg nitrate and 20 of the relative density of 1.42 l water conductivity), 10 min to continue after the reaction. The filtrate was heated to 65 ~ 70℃, evaporated and concentrated to a relative density of 1.9. Then, the filtrate was cooled, crystallized, and dried to obtain bismuth nitrate. Use the bismuth nitrate obtained conductance water to dissolve a dilute solution, hydrolysis under stirring, let stand to make alkali type bismuth nitrate precipitation, precipitation with centrifuge dry or suction filter, and then use thermal conductivity water washing several times, the suction filter after drying, crushing, 7 ~ 8 h at 500 ℃ calcination, a bit cold after pulverization, burning 4 ~ 5 h again, after cooling for a quick high purity bismuth oxide by 99.99%
 
Application field
 
1. Electronic functional material
 
Bismuth oxide powder, as an electronic functional powder doping material, is widely used in the production of sensitive components, dielectric ceramics and other electronic components. It has the characteristics of high quality requirements, low quantity and wide surface. Generally, alpha Bi2O3 in monocline structure is the most stable, and its crystal structure contains a large number of oxygen vacancy, and oxygen ion has good conductivity, which can be used to make various solid oxide fuel cells and oxygen sensors. Bismuth oxide is also a commonly used active substance in chemical power supply, such as excellent corrosion inhibitor for mercury-free zinc battery, electrode material for lithium battery and additive to improve the rechargeable performance of alkaline Zn/MnO2 battery. It was found that the rechargeable performance of bismuth oxide was better than that of conventional bismuth oxide powder, and as an additive of EMD, the active material of positive electrode of primary battery, it showed excellent performance under deep discharge.
 
2. Combustion catalyst
 
Lead oxide is important in the department of double-base solid propellant burning rate catalyst, it can improve the burning rate, reduce the pressure exponent of propellant, but the lead toxicity is bigger, have a direct or potential harm to people or the environment. Bismuth compound is a kind of low toxicity, smoke less, burning rate catalyst of ecology is very safe. Experiments proved that [6], nano Bi2O3 in low pressure section of propellant burning rate of increase than nano PbO, and have the function of the lower propellant pressure index, thus lead oxide nanometer bismuth oxide has replaced the bright future.
 
3. Photocatalytic degradation of materials
 
Bi2O3 is reported to be photocatalyzed to treat nitrite containing wastewater. The results show that Bi2O3 has good photocatalytic activity. Due to the large specific surface area, many surface active points and high photocatalytic activity, nanomaterials have better photocatalytic properties.
 
4. It has been reported in the literature that the nanoparticles coated with bismuth oxide of sodium dodecylbenzenesulfonate have a large trivalent nonlinear optical coefficient, which is significant for the development of nonlinear optical devices even under weak light.
 
5. Urethane-heparin graft copolymer is a medical material with antithrombotic function, which can be used to prepare interventional catheters. The thin wall of the catheter must be filled with nano-bismuth oxide ultrafine powder that is not permeable to X-ray.
 
6. Radiation-proof material.
 
Current radiation protection materials are generally lead products, and lead is harmful to both the human body and the environment. Bismuth is a kind of "green metal", and the attenuation coefficient of bismuth is larger than that of lead. If combining the strong radiation resistance of bismuth oxide with the quantum effect of nanomaterials, it is of high performance for the development
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