Interstellar SiC Dust

In the vast universe,there is a class of important substances in addition to a variety of stars,planets and other objects,that is interstellar dust.The interstellar dust referred to here includes all the tiny solid particles scattered in interstellar gas.Interstellar dust particles mainly consist of C,O,Mg,Si,Fe and other elements.The combinations of these elements can form oxides(magnesia ? silicon oxide and iron oxide et al)? silicate(olivine and pyroxene)? and carbon(diamond,graphite,graphene,polycyclic aromatic hydrocarbons,amorphous carbon and silicon carbide).As the Si element in interstellar space only exists in solid dust grains,silicon carbide(SiC)particles are one of the important components of cosmic dust.This work first mainly collects the detailed information of SiC.In the first chapter,the physical,chemical and optical properties of SiC are introduced in detail.Silicon carbide exhibits an extensive range of well ordered structures.There are cubic,rhombohedral and hexagonal three basic structure.Ratyher arbitrarily,the rhombohedral and hexagonal classes of SiC polytypes are collectively called ?-SiC,and the cubic cless is called?-SiC.Small silicon carbide dust particles show a prominent lattice vibrational band at~11.3?m,the strength and peak are related to the grains shape,structure,size,and composition of the particles themselves.In the second chapter,this paper briefly describes the SiC characteristics observed in the environment including carbon stars,meteorites and Magellan cloud,and the information about the SiC dust particles reflected by these observations.Almost all of the carbon stars have observed 11.3?m SiC emission characteristics,and the study found that carbonite SiC consisted of SiC core and carbonaceous mantle.The existence of SiC in the interstellar medium(ISM)was established through the detection of presolar SiC grains in primitive meteorites based on the isotopic anomaly.According to the isotopic composition of C,N,Si and other elements,meteorite SiC can be divided into five categories.Similar to the galactic source,the carbon stars in the Magellan cloud also observed the emission characteristics of SiC.In this paper,the formation process and damage process of interstellar SiC dust particles are also studied.Dust particles may experience a lot of damage process after injected into the interstellar space,which will change the size and shape of the grains.In this paper,four kinds of interstellar dust damage mechanism are introduced.Based on the law of absorption of matter,the upper limit of abundance of SiC 5% inspace is discussed.The reason for this low abundance may be that the carbonaceous clouds is thick enough to leave some SiC in the clouds without entering interstellar space;or SiC has been destroyed after they are ejected into interstellar space.Finally,the problems in the study of SiC dust particles are listed,and the future development of SiC grains is also discussed.