S&Na Co-Assisted Synthesis Of Boride,Carbide And Nitride Micro/Nanocrystals

General and simple methods for the syntheses of borides, carbides and nitrides are highly desirable, since those materials have unique physical properties and promising applications. This thesis is focused on the design and applications of a new solid-state synthesis technology-Sodium&Sulfur Co-assisted Synthesis. The contents are related to the preparation of several boride, carbide and nitride micro/nanocrystals through this process. The reaction mechanisms, experimental details and crystalline developments of this process have been discussed in the thesis. We believe that these results may have some help to the research of chemical reaction dynamics, and offer some new ideas on low-temperature synthesis of boride, carbide and nitride micro/nanomaterials.(1) S&Na co-assisted synthesis of SiC nanowiresHere, SiC nanowires with the diameters of20-100nm and lengths up to tens of micrometers were prepared from related oxide and active carbon with the assistance of metallic Na and elemental S. The reaction mechanism is correlated with the intense temperature increase, based on the results from in-situ temperature monitoring and ex-situ XRD measurements. In-situ temperature monitoring showed that the reaction temperature could increase quickly to～850℃, once the autoclave was heated to100℃. Such a rapid temperature increase was attributed to the intense exothermic reaction between Na and S, which assisted the formation of SiC nanowires. Results in this report will greatly benefit the future extension of this approach to other compounds.(2) S&Na co-assisted synthesis of boride, carbide, and nitride micro/nanocrystalsIn this chapter, the sulphur-sodium co-assisted synthesis method is used to prepare a series of boride (TiB2, ZrB2, NbB2, CeB6, PrB6, SmB6, EuB6, LaB6), carbide (TiC, NbC, WC) and nitride (TiN, BN, AlN, MgSiN2, VN) micro/nanocrystals, using metal oxides and amorphous boron/active carbon/NaN3as raw materials. The as-obtained products are characterized by a series of techniques, such as XRD, SEM, TEM, and HRTEM techniques.