Researchers at the German Electronic Synchrotron Research Center
(DESY) have developed the world's second largest transparent ceramic
material, cubic silicon nitride (c-Si3N4), following diamonds. C-Si3N4
is also the second diamond and cubic boron nitride, the world's third
highest hardness of the ceramic material, but boron nitride does not
have a transparent nature, and the diamond can withstand the maximum
temperature of 750 ℃, and Germany developed c -Si3N4 transparent ceramic
material can withstand the maximum temperature of 1400 ℃, showing
excellent high temperature performance, not only that, because Si and N
elements of the chemical bond is very strong, c-Si3N4 chemical
properties are extremely stable, with good environmental stability Sex.
So the future can be used in extreme parts of the structure, such as
engines, ball bearing parts and cutting tools.
Under atmospheric conditions, the silicon nitride crystal structure is a hexagonal structure, after sintering is opaque. Under the condition of 130,000 times the atmospheric pressure, the hexagonal structure of silicon nitride is transformed into cubic symmetrical structure, also known as "spinel structure", and has the same structure as MgAl2O4 transparent ceramic.
DESY scientists in the large-capacity compression device (LVP) on the hexagonal silicon nitride after applying high temperature and pressure, in the pressure of 15.6Gpa (15.6 million times the atmospheric pressure) and 1800 ℃ under the conditions of the preparation of a diameter of 2 mm c-Si3N4 transparent ceramic round Film, is the first transparent sample of silicon nitride ceramics.
The results of XRD crystal structure analysis of c-Si3N4 show that the prepared c-Si3N4 material is completely transformed into cubic phase. DESY scientists said that the hexagonal structure of silicon nitride material to the cubic structure of the transition and carbon material conversion is similar to the carbon material at room temperature and pressure for the hexagonal structure, the application of high temperature and pressure into transparent diamond, but also for the cubic structure.
The transparency of silicon nitride is related to its internal grain boundaries, and the voids in the grain boundaries will decrease their transparency. But experts at the University of Tokyo, Japan, said that for the formation of high-pressure materials, the grain boundary is generally very thin, some vacancies such as oxygen vacancies will not gather around the grain boundary, but distributed throughout the material range, so the Its transparency has little effect.
C-Si3N4 material is the hardest and most intense transparent spinel ceramic material, which will play an important role in the future superhard, high strength and high temperature resistant structure. C-Si3N4 materials with diameters of 1 to 5 mm are relatively easy to produce c-Si3N4 materials with diameters of more than 1 cm, although they are easy to obtain and cost are low, but the production of large area c-Si3N4 materials requires greater pressure. Materials will face greater challenges.
Under atmospheric conditions, the silicon nitride crystal structure is a hexagonal structure, after sintering is opaque. Under the condition of 130,000 times the atmospheric pressure, the hexagonal structure of silicon nitride is transformed into cubic symmetrical structure, also known as "spinel structure", and has the same structure as MgAl2O4 transparent ceramic.
DESY scientists in the large-capacity compression device (LVP) on the hexagonal silicon nitride after applying high temperature and pressure, in the pressure of 15.6Gpa (15.6 million times the atmospheric pressure) and 1800 ℃ under the conditions of the preparation of a diameter of 2 mm c-Si3N4 transparent ceramic round Film, is the first transparent sample of silicon nitride ceramics.
The results of XRD crystal structure analysis of c-Si3N4 show that the prepared c-Si3N4 material is completely transformed into cubic phase. DESY scientists said that the hexagonal structure of silicon nitride material to the cubic structure of the transition and carbon material conversion is similar to the carbon material at room temperature and pressure for the hexagonal structure, the application of high temperature and pressure into transparent diamond, but also for the cubic structure.
The transparency of silicon nitride is related to its internal grain boundaries, and the voids in the grain boundaries will decrease their transparency. But experts at the University of Tokyo, Japan, said that for the formation of high-pressure materials, the grain boundary is generally very thin, some vacancies such as oxygen vacancies will not gather around the grain boundary, but distributed throughout the material range, so the Its transparency has little effect.
C-Si3N4 material is the hardest and most intense transparent spinel ceramic material, which will play an important role in the future superhard, high strength and high temperature resistant structure. C-Si3N4 materials with diameters of 1 to 5 mm are relatively easy to produce c-Si3N4 materials with diameters of more than 1 cm, although they are easy to obtain and cost are low, but the production of large area c-Si3N4 materials requires greater pressure. Materials will face greater challenges.
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