Synthesis And The Nature Of Hexagonal Nano-Aluminum Nitride Powder At Low-temperature

The rapid development of modern technology is demanding materials with higher qualities. AlN ceramics will be widely used in many high-tech areas because of its remarkable properties, such as high thermal conductivity, high electrical resistivity, low dielectric constant and dielectric loss, no toxicity, as well as low thermal expansion coefficient close to that of silicon. While commercial degree of AlN is not high today. The main factors that delay the further development of AlN are its high production cost and the difficulties to produce complex shape AlN parts. These problems, including improving reaction conditions, decreasing sythesis temperature and are discussed in this paper in order to improve the application and development of AlN ceramics.Many work indicated that optimization of the starting materials is an effective way to accelerate the reaction rate. In this paper , a new complex decomposition reaction is given, AlCl₃ and NaN₃ were used to synthesize AlN powder. The XRD shows that the obtained samples at 380℃ are pure hexagonal AlN and the impurity in the samples is lower than the resolution limit of the spectrometers. The peak lies where 2θ =33.3°. At this temperature AlN nanocrystals begin to produce,but is not very well. The TEM shows that the reticular is about 100nm,and the reticular gets united without regular shape. The XRD and TEM show that AlN synthesized at 450℃ with the same starting materials is pure hexagonal AlN and the peak lies where 20=33.3°too. There is no obvious impurity on XRD. The nanocrystals synthesized at this temperature is about 75nm with regular shape and clear sketch. XPS show that there are C O N Al in the surface of the two samples. Of these, C and O are impurity.Oxygen is introduced because the AlN reticular is in nano range, so the activity on its surface is very big. So it is very easy to absord oxygen in the air.Except this, the influence of the time of heat preservation and heating to AlN structure is given. The result shows that the influence of heating time to AlN structure is not very obvious. The time of heatingpreservation only has little influence to crystallization degree, as the time prolongs, crystallization degreebecomes better.