碳化硅纳米晶须的制备及热稳定性研究

Synthesis and Thermal Stability of Silicon Carbide Nanowhiskers

以石墨粉和硅粉为原料,在1 550℃下,采用碳热还原法制得碳化硅纳米晶须。X射线衍射（XRD）和场发射扫描电镜（FE-SEM）表明,产物主要由3C-SiC纳米晶须和颗粒组成,晶须直径为100~150 nm,长度为5~15μm。在空气气氛中的热重分析（TGA）实验显示,温度高于400℃时,产物质量逐渐增加,温度至800℃时质量增加了约1%,增重现象为SiC纳米晶须的氧化所致。产物经1 100℃氧化后的XRD表明,SiC被部分氧化生成了无定形二氧化硅。空气气氛中,产物在700、9001、100℃的热稳定性实验表明,在1 100℃时,SiC纳米晶须形貌发生了较大变化,其表面出现熔融并粘连在一起。高温下的氧化反应是导致晶须形貌变化的主要原因。

SiC nanowhiskers are fabricated at 1550℃ via a carbothermal reduction method using silicon powders and graphite powders as raw materials.The XRD pattern and the field-emission scanning electron microscopy images show that the products are composed of 3C-SiC nanowhiskers and particles,and the nanowhiskers have lengths of 5~15 μm and diameters of 100~150 nm.Thermal gravimetric analysis shows that a gradual weight gain is observed above 400℃ and about 1% weight gain can be obtained at 800℃,suggesting that SiC is oxidized in air.The XRD of the products after oxidation at 1100℃ shows that SiC nanowhiskers are oxidized partly to form amorphous silica.The as-synthesized products are exposed at temperatures of 700℃,900℃ and 1100℃ in air,and a pronounced morphology change occurs at 1100℃,the surface of SiC nanowhiskers melts and sticks together.High-temperature oxidation is the dominating reason for the morphology change.