Papers by Keyword: AlN Powder

Abstract: Aluminum nitride (AlN) power was successfully synthesized by direct nitridization method heating for 4h at 950°C with magnesium (Mg) and ammonium chloride (NH₄Cl) as additives. The morphology and microstructure of nitride product were done by XRD and SEM. Result reveals that the nitride producs was pure hexagonal phase. In addiation, whiskers in the power which diameter is at the nanoscale and length ranging from a few microns were also observed, and EDS test displays the component of whiskers is AlN.

Abstract: In this article, the high-performance modified AlN powder was prepared, using Y(NO₃)₃·6H₂O as the modifying agent, and characterizing by pH meter, TG , XRD and SEM. The results show that the Y₂O₃ coating was formed on the AlN surface, the pH value of aluminum nitride of treatment suspension solution maintains 7.75 in water bath for 100 hours. Therefore the conclusion is that surface modification with rare earths can effectively inhibit the hydrolysis of the AlN powder.

Abstract: AlN single crystal can be grown by physical vapor transport (PVT) method. The purity and particle size of the source material are important factors for single crystal growth to obtain good quality of AlN single crystal. The aim of this study was purification of AlN powder and growth of its particle size through thermocyclic treatment. The initial particle size was about 1.0 μm and the purity was 98.4% containing 1.6% oxygen and metallic impurities such as Fe, Sn, Ca, Na and Mg etc. which were analyzed based on KSL1612. For purification of AlN powder, it was performed using a thermocycle process with various thermocyclic numbers. After the thermocycle treatment, it is able to obtain large particle size AlN powder as much as 30μm and purity was increased to 99.6% based on chemical analysis.

Abstract: Nano-sized aluminum nitride (AlN) powders were synthesized through a carbothermal reduction nitridation (CRN) route from a sol-gel low temperature combustion precursor. The precursor was precalcined at 600-1200 °C and then nitrided at 1400-1550 °C for different holding time to obtain AlN powders. During the whole preparation process, the amorphous alumina in the precursors first transformed to γ-Al₂O₃, then to α-Al₂O₃, and AlN was obtained through the nitridation of α-Al₂O₃ with the reduction of carbon. The results show that the appropriate precalcination benefits the activity of precursors and promotes the formation of AlN phase due to the transition of amorphous alumina to γ-Al₂O₃, and the optimum precalcination temperature is 1000 °C. The effects of different nitridation parameters on the microstructure of AlN powders were also investigated. By being nitrided at 1500-1550 °C for 2 h, the AlN powders present a good distribution and small particle size of 30-90 nm from the precursor precalcinated at 1000 °C.

Abstract: AlN powders were synthesized by carbothermal reduction method using a combustion synthesis precursor derived from aluminum nitrate (oxidizer), glucose (carbon source), and urea (fuel) mixed solution. Effects of carbon source content on the combustion temperature of solutions, the particle size and morphology of the precursors and the synthesized AlN were studied in detail. The results indicated that a regular variation in the particle size and morphology of precursors had been observed with the increasing molar ratio of glucose to aluminum nitrate (C/Al). The products prepared with (C/Al=8–12), calcined at 1500 oC for 2 h, could have completed the nitridation reaction, while the nitridation products prepared with (C/Al=4 and 16) are opposite. The nitridation products prepared with (C/Al=8–12), calcined at 1500 oC for 2 h, are comprised of well-distributed spherical particles of AlN with the average size ranging from 50 to 80 nm.

Abstract: The process of non-isothermal oxidation of AlN powder (d₅₀=15μm, 5μm and 0.5μm) were studied by TG-DTA and XRD in atmosphere of 80%N₂ and 20%O₂ mixture at flowrate of 55ml/min and heating rate of 10 /min. The experimental results reveal that the AlN powder obviously began to be oxidated and its weight increased at 900-1000°С . The process of dynamics of oxidation reaction between AlN and O₂ was controlled alternately by reaction and diffusion. Non-isothermal oxidation dynamic parameters (activation energy E, reaction orders n and pre-exponential factor A) of d₅₀=5μm AlN powder were obtained by the experimental data. E equals about 417.4kJ/mol, n about 2.9 and A about 3.47×10¹². Due to smaller activation energy E and larger pre-exponential factor A in dynamic parameters of AlN powder non-isothermal oxidation, powdery AlN is easily oxidated at high temperature and in air and has a larger oxidation reaction rate. If AlN material with high thermal conductivity characteristics is introduced to prepare composite with high thermal shock resistance, the AlN powder must be treated for oxidation resistance.