The investigation of production parameters of boron nitride nanotubes by mechanical alloying method

In this study, boron nitride nanotubes were successfully synthesized by high energy ball milling method. This process was completed in two steps. The first step was the milling process of starting powders (amorphous boron and hexagonal boron nitride). At the second step, the ball milled powders were transformed to boron nitride nanotube. In milling process was performed by using a different milling parameters in a planetary ball mill. Miling parameters were chosen agitator speed 450-850 rpm, ball to powder weight ratio 16/1-32/1-64/1, long milling time 4-5-6-7h and short milling time 15-30-45-60-120 min, milling atmosphere N2-NH3. The milled powders were analyzed using X-ray difraction.Thus, the quantity of amorphization and particle size which is formed in starting powders during milling were determined. The second step was isothermal annealing process at selected temperatures. With this aim, the milled powders were annealed by using different annealing parameters. Annealing parameters were chosen annealing atmospheres NH3+N2-NH3+Ar- NH3-N2-Ar, annealing temperatures 1100°C-1300°C-1500°C, annealing times 2-4-6h. Thus, the transformation to nanotube was achieved. Ideal conditions to achieve a high amount BNNT, milling for 850 rpm, 32/1 BPR, 2h under N2 atmosphere and annealing, 2h under NH3+N2( for a-B)- NH3+Ar (for h-BN ) atmosphere in 1300°C, respectively. After the annealing process, the obtained samples were analyzed by XRD, and HR-TEM,EDS techniques. With results of XRD and HR-TEM, it was determined whether the boron nitride nanotube was formed or not. Also, the lenght and diameter of boron nitride nanotubes were determined. The obtained results confirm that the production of the boron nitride nanotube can be performed by mechanical alloying method.