What is zinc oxide and in what cases is it used?
Zinc oxide is a mineral compound with the chemical formula ZnO, which is present in pure form as a white powder and its natural source is the mineral zensite. This compound is soluble in water and is synthesized and used in the commercial world. Given that zinc oxide is produced in the zinc production process, the price of zinc oxide is a function of the global price of zinc.
This chemical as an additive in the preparation of many materials and products such as food additives, ceramics, glass, rubber, plastics, cosmetics, paints, adhesives, oils and lubricants, commercial pigments, batteries, ferrite magnets, inhibitors And fire. Are used.
Interesting and valuable features of this combination such as high transparency, wide energy gap range, high mobility of electrons and high light emission when electrons are excited have caused this combination to be used in the manufacture of electrodes for displays, transistors and LED lights. Be.
History of use and production of zinc oxide
Zinc oxide was first made by the Romans in 2,000 BC. It was then synthesized by the Indians in the 16th century, in China in the 17th century, and in Europe in 1850. Initially used as a watercolor and diluent in paints and in 1890 in the preparation of oil paints. In 1970, it was used to make photocopy paper and to improve paper quality.
Most recent scientific research has focused on ZnO as a semiconductor material. Attention to the properties of ZnO began in 1912, when semiconductors began to grow, after the invention of the transistor. In 1960, very interesting piezoelectric properties of ZnO were discovered, which led to the first application of electronics as a thin layer in surface sound wave components.
Since 1990, research on ZnO has increased dramatically. At 1974, Celsius decomposes into oxygen and zinc vapor, indicating its relatively high stability. It is an amphoteric oxide and can act as both an open and an acid. It is almost insoluble in water and alcohol.
The purity of white was so great that some artists in the late nineteenth century used white as a background for painting, but after a hundred years, these paintings were abandoned. Also in the second half of the twentieth century, zinc oxide was used in the rubber industry. In the 1970s, the second major use of zinc oxide was paper copy additives, but in the 21st century, the zinc oxide approach as a paper copy additive was eliminated.
Familiarity with zinc oxide preparation processes
Every year, thousands of tons of zinc oxide are produced in different ways and consumed in different fields. This combination is prepared in several general ways, which we will briefly describe each of these methods in the following.
Indirect method : In the indirect method, zinc metal is melted in graphite plants and converted to steam at temperatures above 907 ° C. Zinc vapor reacts with oxygen in the air to form a bright ZnO with a drop in temperature. The zinc oxide particles are then transferred to a cooling duct and collected in a chamber. Most of the zinc oxide produced in the world is produced indirectly.
Direct method : In the direct method, the zinc-containing rocks are melted and then the molten material is reduced to zinc vapors by heating by a carbon source such as anthracite (carbothermal reduction). The product produced at this stage continues the indirect method and is oxidized in the same way. The difference between this method and the previous method is in the degree of purity of the raw materials used . In the direct method, the final product has less purity and therefore lower quality .
Wet chemical process : In this method, the process of producing zinc oxide from aqueous solutions of zinc salt begins. From these solutions, zinc carbonate or zinc hydroxide precipitate can be obtained and then these solid precipitates are calcined at 800 ° C.
It is interesting to know that in the fourth method, which is laboratory synthesis , the color of zinc oxide can be changed to green or red by changing the amount of oxygen concentration used in the preparation of the final composition.
Applications of zinc oxide
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Industrial uses
This compound is used in the manufacture of many materials in industry such as plastics, ceramics, glass, cement, rubber (car tires), softeners, paints, waxes, adhesives, foods, batteries and.. Zinc oxide powder has many uses. Its main applications are summarized. Most applications use the reaction of zinc oxide as the constituent of other zinc components
Its applications in materials science include high refractive index, high thermal conductivity, antibiotics and UV protection materials . It is used in a similar way to materials such as plastics, ceramics, glass, wood, cement, paints, greases, ointments, adhesives, seals, pigments, batteries, fire extinguishing circuits and many more
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Making tires
Between 50 and 60% of ZnO use is in the rubber industry. The industry uses zinc oxide and stearic acid to boil rubber. The addition of zinc oxide makes the rubber resistant to destructive factors such as fungi as well as ultraviolet light.
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Ceramic industry
Zinc oxide is widely used in the ceramic industry in the production of glazes. Relatively high heat capacity, good thermal conductivity and low coefficient of expansion of this material has led craftsmen to use it in the production of ceramics, glazes and enamels.
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Food additive
In the food industry, zinc oxide is added to products such as breakfast cereals, cornflakes and dietary supplements as a source of essential zinc. Of course, it is also worth noting that in order to enrich food products with zinc, zinc sulfate is also used.
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Production of commercial pigments
Zinc oxide is one of the raw materials in the production of pigments necessary for paper coatings and white paint of porcelain, and in general, along with titanium, is one of the main bases of white paint. Paints containing this compound are used for painting interior walls, exteriors of buildings and even cars due to the benefit of UV resistance, moisture, corrosion, destructive effects of microorganisms and even fire.
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Cosmetics industry
ZnO is also used in the production of cosmetics, and manufacturers active in this field use this combination to produce products such as nail polish, baby body lotions, soaps, facial ointments, as well as cosmetics. Due to its ability to absorb the sun’s ultraviolet rays, zinc oxide is also used in the manufacture of sunscreens, thus protecting the skin from sunburn.
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Methane improvement
In the methane pretreatment step, ZnO is used to remove hydrogen sulfide from natural gas. This compound reacts with hydrogen sulfide to produce water and zinc sulfide.
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medical
Another application of zinc oxide is in medicine; Because this compound has antiseptic properties and is a very good absorber for ultraviolet rays. In the medical world, this compound is used to treat a variety of skin diseases such as dermatitis, itching caused by eczema, burns, cuts and even acne.
Apart from these, zinc oxide is also used to make anti-dandruff shampoos as well as ointments and creams that protect the skin from the sun.
The method is based on zinc oxide
Zinc nanoparticles have been widely used in various industries including food, pharmaceutical, rubber, electronics and the like. This material is being made using various and new methods, in other words, with new initiatives in the world, and the annual written works of researchers show this. In this regard, a number of researchers have studied the production of nanoparticles of zinc oxide and its bonding properties
They obtained zinc nanoparticles through homogeneity. Polymethyl methacrylate bonding method was used to prevent the accumulation and agglomeration of zinc particles and to improve the effective surface
In this way, the surface of zinc oxide particles was first treated with a pairing agent, which created double bonds on the surface of zinc oxide particles and prevented agglomeration. They found that increasing the concentration of the monomer could increase the particle bonding, and that the addition of some surfactants was effective in dispersing the particles
In another study, a number of researchers obtained zinc oxide particles by precipitation in an iatonic organic medium. Zinc nanoparticles are subsequently obtained by agar gel containing zinc sulfate under the influence of -OH ions, The band structure of nano-zinc oxide produced in stellar, elliptical and spherical shapes is produced by the deposition of cycles consistent with the effect and diffusion -OH.
Particles with star and ellipse shapes are formed by the process of dissolving a substance obtained by pre-precipitating 3Zn (OH) ZnSO. The obtained dimensions are between 100 and 500 nm.
In the research on the preparation of zinc nano oxide from zinc oxide minerals, first zinc oxide concentrate was separated in two stages of cold and hot purification and its impure elements were separated and the resulting zinc sulfate solution was used to produce zinc nano oxide powder. Then the effective parameters in the production of ZnO nanopowder powder were investigated.
For this purpose, six temperature parameters, concentrations of Na2Co3, NaoH and ZnSo4, reaction time and stirring speed were designed at 4 levels, in which case the optimal condition was obtained when the concentration of zinc sulfate, sodium carbonate and sodium hydroxide was 1 mol/l and The reaction temperature should be 90 ° C. Also, stirrer time and speed factors had little effect on the target response.
That is, the effect of factors such as reaction time and stirring speed on their selected levels is not apparent when other parameters are at their optimum level. Finally, by performing an experiment with optimal conditions, it was found that the obtained powder shows only ZnO peaks and the obtained powder has dimensions of 70 to 150 nm.
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