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对在加压氮气中金属铝粉的直接氮化和氧化铝粉的碳热还原氮化法制备氮化铝粉末进行了研究。研究结果表明:铝粉在高温高氮压下快速氮化,生成氮化铝,其临界温度为700℃,氮气的临界压力为1MPa;在高氮压下,氧化铝可通过碳热还原氮化法生成氮化铝,其含氮量与保温温度,氮气压力和保温时间有关;在高氮压下,碳热还原氮化法制备氮化铝,可使用铝粉为晶种,能获得高质量的氮化铝(N〉33%,O〈1%,按质量计)粉末。 相似文献
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Effect of Ca-compound on low temperature synthesis of AIN ultrafine powders by carbothermal reduction nitride route from sol-gel precursor
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YANG Qinghua WANG Huanping ZHANG Wenjuan CHEN Shuwen HUA Youjie WANG Shifeng XU Shiqing 《化工学报》2012,63(6)
以硝酸铝、葡萄糖和硝酸钙为原料,通过溶胶-凝胶工艺获得了组分均匀的Al2 O3、C和CaO前驱体,进而利用碳热还原反应合成超细氮化铝粉体,探讨了钙助剂对氮化铝合成温度及粉体颗粒生长的影响规律.结果表明:钙助剂的添加,通过与前驱体中氧化铝在较低温度下发生反应,先后生成CaAl4 O7、Ca3 Al10O18、CaAl2 O4和Ca12Al14O33等铝酸钙相;上述铝酸钙相能在较低温度下形成液相,可有效促进氮化铝的合成和粉体颗粒的生长,从而在1400℃合成纯相氮化铝.当原料中钙铝摩尔比为0.0262时,在1350℃氮化得到了粒径60~80 nm的氮化铝粉体,仅有少量铝酸钙相存在;当氮化温度上升至1400℃时,铝酸钙相因挥发而消失,得到粒径100~180 nm的单相氮化铝粉体. 相似文献
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以硝酸铝、葡萄糖和硝酸钙为原料,通过溶胶-凝胶工艺获得了组分均匀的Al2O3、C和CaO前驱体,进而利用碳热还原反应合成超细氮化铝粉体,探讨了钙助剂对氮化铝合成温度及粉体颗粒生长的影响规律。结果表明:钙助剂的添加,通过与前驱体中氧化铝在较低温度下发生反应,先后生成CaAl4O7、Ca3Al10O18、CaAl2O4和Ca12Al14O33等铝酸钙相;上述铝酸钙相能在较低温度下形成液相,可有效促进氮化铝的合成和粉体颗粒的生长,从而在1400 ℃合成纯相氮化铝。当原料中钙铝摩尔比为0.0262时,在1350 ℃氮化得到了粒径60-80 nm的氮化铝粉体,仅有少量铝酸钙相存在;当氮化温度上升至1400 ℃时,铝酸钙相因挥发而消失,得到粒径100-180 nm的单相氮化铝粉体。 相似文献
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碳热还原法合成AIN粉末的径向反应器设计 总被引:1,自引:0,他引:1
本文将传质原理与化学反应动力学相结合,导出了氮气流量与碳热还原法合成AIN反应速率之间的关系。基于动量守恒定律分析了径向反应器内部气体压力及其分布的规律,提出了气体在反应器内均匀分布的条件和反应器选型准则。根据这些条件和准则设计了合成AIN粉末的径向反应器。实验结果显示AIN的转化率及颗粒度在径向反应器内均匀分布,且产率高于平底状反应器。这一结果证明反应器设计合理,径向反应器比平底状反应器有更好的传质效果。 相似文献
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Carbothermal Synthesis of Aluminum Nitride Using Sucrose 总被引:2,自引:0,他引:2
Youngmin Baik Kartik Shanker Joseph R. McDermid Robin A. L. Drew 《Journal of the American Ceramic Society》1994,77(8):2165-2172
Several aluminum oxides (α-Al2 O3 , θ-Al2 O3 , and AIOOH) were examined to study the differences in reaction behavior and powder characteristics during carbothermal nitrida-tion to AIN using sucrose and carbon black. The reaction conditions investigated were carbon-to-alumina ratio, reaction temperature, and time. Carburized sucrose resulted in Full conversion to AIN and produced a uniform powder morphology using a near-istoichiometric ratio of C:Al2 O3 while carbon black required higher C:Al2 O3 ratios (i.e., >4:1) for full conversion and led to agglomeration of the AIN powder. The most favorable reaction temperature was 1600°C, with the reaction time to full conversion being dependent on the type of Al2 O3 . The particle and agglomerate size of the AIN powders did not change significantly with reaction time. However, the particle size and morphology were strongly dependent on that of the initial AI2 O3 with sucrose, whereas agglomeration of the AIN occurs when using carbon black. A solid–solid reaction mechanism is proposed. 相似文献
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Joydeb Mukerji 《Journal of the American Ceramic Society》1989,72(8):1567-1568
Cubic ZrO2 is stabilized at room temperature by the addition of AIN. The percentage of c-ZrO2 in the mixture of c-ZrO2 and m-ZrO2 increases linearly with the addition of up to 20 mol% AIN and decreases thereafter. Stabilization becomes complete at 50 mol% AIN. The lattice spacing of the cubic phase gradually expands up to 20 mol% AIN. A displacement reaction ZrO2 + AIN → ZrN+Al2 O3 occurs above 20 mol% AIN and is completed at 50 mol% AIN. 相似文献
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试样以部分稳定氧化锆(PSZ)和金属Al粉为原料。在N5气氛下经1600℃×4h烧结可制备出以AIN为结合相的ZrO2-AlN复相材料(ZAN)。试验研究了金属Al的氮化反应过程。以及金属Al的加入量对复相材料性能的影响。结果显示:Al粉反应生成AIN的全过程,主要由界面反应和内扩散反应交替完成.且整个反应过程应为扩散机制控制。随金属Al粉引入量的增加、ZAN试样的热膨胀系数减小,抗折强度增大,抗热震性及抗氧化性提高。ZAN-3试样的综合性能优良,其常温抗折强度为73.61MPa,热膨胀系数为6.06×10^-6/℃。室温~1100℃水冷残余抗折强度为4.64MPa。 相似文献
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采用非氧化物AlN和Re2O3作为复合烧结助剂(Re2O3-La2O3与Y2O3)进行碳化硅液相烧结得到了致密的烧结体.烧结助剂占原料粉体总质量的20%,其中:AIN与(La0.5Y0.5)2O3的摩尔比为2:1,在30MPa压力下,1850℃保温0.5h热压烧结的碳化硅陶瓷,抗弯强度>800MPa,断裂韧性>8MPa·m1/2,明显高于同组分1 950℃无压烧结0.5h的碳化硅陶瓷的抗弯强度(433.7MPa)和断裂韧性(4.8MPam·m1/2.热压烧结的陶瓷晶粒呈单向生长,断裂模式为沿晶断裂.同组分无压烧结碳化硅陶瓷的显微结构可以观察到核壳结构. 相似文献
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Kinetics of the Reduction of Carbon/Alumina Powder Mixture in a Flowing Nitrogen Stream 总被引:1,自引:0,他引:1
The reduction of carbon/alumina powder mixture in a flowing nitrogen stream was investigated by weight loss measurement and X-ray diffraction. Experimental results indicated that the reaction rate could be increased by increasing the nitrogen flow rate, weight ratio of C/Al2 O3 , or reaction temperature. The rate was also found to be increased by decreasing the sample size, the grain sizes of carbon or aluminum oxide, or initial bulk density. Empirical expressions of consumption rates of Al2 O3 and C as well as production rate of AIN have been determined. 相似文献
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SiC/AIN composites with controlled interfacial solid solution were employed in the present work for investigating the effects of interfacial bonding and A1N polytypes on the mechanical properties. Platelike A1N polytypes and interfacial bonding were found to have substantial effects on the flexural strength, hardness, and fracture toughness. 相似文献
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Paul Bowen James G. Highfield Alain Mocellin Terry A. Ring 《Journal of the American Ceramic Society》1990,73(3):724-728
The degradation of A1N powder in excess H2 O at room temperature for up to 24 h was investigated. Samples were characterized by various techniques (IR; XRD; SEM; XPS; C, H, N analysis; surface area, particle size, and weight change measurements). The reaction rate was found to be significant, with 80% of the A1N being consumed in 24 h. The initial reaction product was found to be a porous, amorphous, hydrated alumina with stoichiometry near AlOOH. After ∽16 h a crystalline phase, bayerite Al(OH)3 , was detected which became the predominant phase after 24-h contact. The kinetics of the A1N consumption were found to be first order and the reaction rate linear. The kinetic data fitted an unreacted core model with a porous product layer where the surface chemical reaction controlled the overall kinetics. 相似文献
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The oxidation mechanisms in SiC-AlN solid solutions, exposed at 1370°C for 200 h in air, have been investigated by scanning electron microscopy (SEM), analytical and high-resolution electron microscopy (HREM), and X-ray diffraction techniques. Five hot-pressed compositions, including pure SiC and pure AIN, were examined. Assuming parabolic rate behavior, the values of the parabolic rate constants based on oxide layer thickness increased by over 2 orders of magnitude by increasing AIN contents from 0% to 62%. A continuous amorphous phase containing cristobalite and mullite crystallites was present at the oxide layer in 13% AIN and 27% AIN samples. Two reaction layers were found in the oxidized SiC–62% AIN solid solution. The inner layer consisted of a mixture of β-SiAION and graphite phases, while the outer layer consisted of mullite as a major phase and cristobalite as a minor phase. The oxidation proceeded in two stages: a partial oxidation of SiC–AIN to β-SiAION and carbon (graphite), and a final oxidation of β-SiAION to mullite + SiO2 . 相似文献