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以比表面积分别为4.26和17.4 m2/g两种AlN粉末为原料,添加5%Y2O3作为烧结助剂制备AlN-15BN陶瓷(质量分数,%),研究了AlN粉末特性对复合陶瓷致密化过程的影响。结果表明,AlN粉末比表面积对复合陶瓷致密化有重要影响,比表面积高的AlN粉末所制备的复合陶瓷致密化过程主要发生在1500~1650℃,1650℃烧结3 h后,复合材料的相对密度达95.6%,继续升高温度,对材料的密度影响不大;而低比表面积的AlN粉末所制备的复合陶瓷的致密化过程主要发生在1650~1850℃,1850℃烧结3 h,复合陶瓷的相对密度为86.4%。即高比表面积的AlN粉末有利于获得相对密度高的AlN-BN复合材料。 相似文献
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无压烧结制备高致密度AlN-BN复合陶瓷 总被引:6,自引:0,他引:6
以低温燃烧合成前驱物制备的比表面积为17.4m2/g的AlN粉末和市售BN粉末为原料, 利用无压烧结工艺制备AlN-15BN复合陶瓷, 研究了复合陶瓷的烧结行为以及制备材料的性能, 结果表明: 由于AlN粉末的烧结活性好, 复合材料的烧结致密化温度主要集中在1500~1650℃之间, 在1650℃烧结后, AlN-15BN复合陶瓷的相对密度可达95.6%. 继续升高烧结温度, 材料的致密度变化不大, 热导率继续增加. 在1850℃烧结3h后, 可以制备出相对密度为96.1%, 热导率为132.6W·m-1·K-1, 硬度为HRA64.2的AlN-15BN复合陶瓷. 提出了高比表面积的AlN粉末促进复合陶瓷烧结的机理, 利用XRD, SEM等手段对烧结体进行了表征. 相似文献
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约束弧等离子体电弧法用等离子体高温热源激发高能粒子的化学反应,并与骤冷技术结合构成一个制备金属纳米粉体或化合物纳米粉末材料的等离子体过程,能极好地制备高溶点(例:Ni,Fe,C等)或低溶点(例:Al,Zn等)的纳米粉末,是当前极具工业化生产应用前景的方法之一。用约束弧等离子体电弧法制备了纳米Zn粉末,用XRD,TEM,TG,DTA技术研究了纳米Zn粉末的结构、晶粒大小、晶粒形貌和热稳定性。结果表明,该粉体平均粒径小于42 nm,晶粒形貌为带状,热稳定性好。此外该粉体具有高比表面积,可用作化学反应的催化剂。 相似文献
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Anodization is an effective surface treatment for improving the corrosion resistance of aluminium-matrix composites. For SiC particle-filled aluminium, anodization was performed successfully in an acid electrolyte, as usual. However, for AlN particle-filled aluminium, anodization needed to be performed in an akaline (0.7 N NaOH) electrolyte instead of an acid electrolyte, because NaOH reduced the reaction between AlN and water, whereas an acid enhanced this reaction. The concentration of NaOH in the electrolyte was critical; too high a concentration of NaOH caused the dissolution of the anodizing product (Al2O3) by the NaOH, whereas too low a concentration of NaOH did not provide sufficient ions for the electrochemical process. The corrosion properties and anodization characteristic of pure aluminium, Al/AlN and Al/SiC were compared. Without anodization, pure aluminium had better corrosion resistance than the composites and Al/SiC had better corrosion resistance than Al/AlN. After anodization, the corrosion resistance of Al/AlN was better than Al/SiC and both composites were better than pure aluminium without anodization, but still not as good as the anodized pure aluminium. 相似文献
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The isothermal nitridation of magnesium- and silicon-doped aluminium melt at 1273 K was investigated. With increasing Mg/Si ratio and decreasing oxygen content in the nitriding atmosphere, four major reaction mechanisms may be separated: (i) a passivating surface nitridation, (ii) a volume nitridation with precipitation of isolated AlN in the aluminium matrix, (iii) a volume nitridation resulting in a three-dimensionally interconnected AlN/Al composite microstructure, and (iv) a break-away nitridation with complete conversion of aluminium to AlN. The behavioural transition of the nitridation mechanism is reflected by the growth direction and the crystal morphology of AlN which change from inward (mechanisms i, ii) to outward (mechanisms iii, iv) growth of the reaction product with [0 0 0 1] as the dominating growth direction. Attempts are made to define the critical magnesium and silicon contents for the regime of controlled AlN/Al composite growth (mechanism iii) at 1273 K, in order to develop novel AlN/Al composite materials. 相似文献
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The infiltration of solid powder mixtures with molten aluminium has been investigated as a potential route for the synthesis
of ceramic/metal composites. Either titanium or tantalum powder was mixed with boron nitride flakes for the reaction powder
mixture. The infiltration occurred spontaneously at 1473K for both [Ti+BN] and [Ta+BN] powder mixtures. Owing to reactions
between the starting materials, both boride and nitride ceramics were produced in molten aluminium. TiB2 and AlN were produced
from the [Ti+BN] powder mixture, and TaB2 and AlN were produced from the [Ta+BN] powder mixture. When the [Ti+BN] powder mixture
was used, a reaction producing Al3Ti took place immediately after the infiltration of the molten aluminium, and a subsequent
reaction producing TiB2 and AlN proceeded gradually. The time required to convert BN flakes to TiB2 and AlN particles at 1473K
was in the range of 1800–3600 s. On the other hand, when the [Ta+BN] powder mixture was used, there was an initial incubation
period to allow the tantalum and molten aluminium to react with each other. The reaction between tantalum, BN and aluminium
took place after this incubation period.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
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本文介绍了氮化铝(AlN)陶瓷的特性,并以金属铝直接氮化法和氧化物高温碳还原氮化法为重点,阐述了AlN粉末的各种制备工艺及反应机理、主要工艺参数的影响,对各种方法的优缺点进行了评述。提出:还原法和直接氮化法是目前较成熟的方法,而气相反应法具有较好的推广应用前景。 相似文献
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Aluminium-matrix composites containing AlN, SiC or Al2O3 particles were fabricated by vacuum infiltration of liquid aluminium into a porous particulate preform under an argon pressure of up to 41 MPa. Al/AlN had similar tensile strengths and higher ductility compared to Al/SiC of similar reinforcement volume fractions at room temperature, but exhibited higher tensile strength arid higher ductility at 300–400 °C and at room temperature after heating at 600 °C for 10–20 days. The ductility of Al/AIN increased with increasing temperature from 22–400 °C, while that of Al/SiC did not change with temperature. At 400 °C, Al/AlN exhibited mainly ductile fracture, whereas Al/SiC exhibited brittle fracture due to particle decohesion. Moreover, Al/AlN exhibited greater resistance to compressive deformation at 525 °C than Al/SiC. The superior high-temperature resistance of Al/AlN is attributed to the lack of a reaction between aluminium and AlN, in contrast to the reaction between aluminium and SiC in Al/SiC. By using Al-20Si-5Mg rather than aluminium as the matrix, the reaction between aluminium and SiC was arrested, resulting in no change in the tensile properties after heating at 500 °C for 20 days. However, the use of Al-20Si-5Mg instead of aluminium as the matrix caused the strength and ductility to decrease by 30% and 70%, respectively, due to the brittleness of Al-20Si-5Mg. Therefore, the use of AIN instead of SiC as the reinforcement is a better way to avoid the filler-matrix reaction. Al/Al2O3 had lower room-temperature tensile strength and ductility compared to both Al/AlN and Al/SiC of similar reinforcement volume fractions, both before and after heating at 600 °C for 10–20 days. Al/Al2O3 exhibited brittle fracture even at room temperature, due to incomplete infiltration resulting from Al2O3 particle clustering. 相似文献
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Wetting and spreading of molten aluminium against AlN substrates were investigated between 1100 and 1290°C. The contact angles decreased linearly with time under isothermal conditions between 1100 and 1200°C. The isothermal rate of spreading of molten aluminium against AlN substrates was constant between 1220 and 1290°C and the rate increased exponentially with increasing temperature. Crystals of Al4C3 nucleated and grew on the substrate surface beneath the liquid. However, the formation of Al4C3 may not be solely responsible for the changes in contact angle and spreading. It is postulated that carbon contamination from the substrate and/or experimental equipment coupled with the low oxygen partial pressure of the chamber in the presence of graphite, were primarily responsible for the observed contact angle and spreading phenomena. The activation energy for the spreading process was 448 kJ mol-1, suggesting the presence of some chemical reaction at the interface. Carbon-rich aluminium may be initiating a continuous surface reaction with the AlN substrates by reducing the native oxide layer on the substrate surface. 相似文献
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TiN、AlN弥散相强韧化Al2O3基复合材料的工艺研究 总被引:3,自引:0,他引:3
在N2保护下,采用反应烧结制得TiN、AlN弥散相强韧化A12O3基复合材料。用SEM和X射线衍射法分析了试样的成分分布和显微结构,发现用该技术制备的复合陶瓷材料中,含有纳微米混合分布的AlN晶粒。通过测试试样的密度和各项力学性能,可以看出TiN、AlN弥散相强韧化Al2O3基复合材料有较为明显的效果。本文重点分析了制备工艺和成分配比对复合材料性能的影响。 相似文献
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Mechanical strength of ultra-fine Al-AlN composites produced by a combined method of plasma-alloy reaction,spray deposition and hot pressing 总被引:2,自引:0,他引:2
A. Inoue K. Nosaki B. G. Kim T. Yamaguchi T. Masumoto 《Journal of Materials Science》1993,28(16):4398-4404
Ultra-fine Al-AlN composites with high packing density were produced by the simple sequential process consisting of nitrogen plasma-alloy reaction, spray deposition and hot-pressing. The AlN content,V
f, was controlled in the range below about 40 vol % by changing the nitrogen partial pressure in the plasma-alloy reaction. The density of the Al-AlN composite withV
f=36% after hot-pressing for 7.2 ks at 673 K was 2.96 Mg m–3 which is nearly the same as the theoretical density. The constituent phases were f c c aluminium and hexagonal AlN and their lattice parameters are nearly the same as those of pure aluminium and AlN phases. The grain size and interparticle spacing of the AlN particles were as small as about 90 and 50 nm, respectively. The Vickers hardness number, Young's modulus and compressive strength of the dense Al-AlN composite were 193, 112 GPa and 628 MPa, and the high hardness above 100 was maintained in the temperature range below 673 K. It was therefore concluded that the sequential process is a useful technique to produce ultra-fine metal-ceramic composites with high mechanical strengths. 相似文献
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AIN粉末有机物表面处理及水解动力学 总被引:1,自引:0,他引:1
在AIN粉末表面涂覆油酸和8-羟基喹啉,有效地提高了AIN的耐水性.该粉末在40℃温水中至少稳定70h;但随水温升高稳定性变差,在60~80℃的水中发生水解反应.反应动力学呈扩散控制和固相表面化学反应控制两个阶段,均为一级反应,活化能分别为125kJ/mol和114kJ/moL产生上述现象的原因归于有机膜吸附在AIN表面,增加了水分子向AIN表面扩散的阻力,从而提高了AIN的耐水性.但这种吸附是物理吸附,水温升高时,在高动能水分子作用下解吸,导致AIN迅速与水反应.上述观点由TG-DTA、XRD和IR分析所证实. 相似文献