(YCa)F3助烧AIN陶瓷的显微结构和热导率

采用（ＣａＹ）Ｆ３为助烧结剂,低温烧结（１６５０℃,６ｈ）制备出热导率为２０８Ｗ／ｍＫ的ＡＩＮ陶瓷,在烧结过程中,热导率随保温时间的变化服从方程,λ（ｔ）＝λ∞－△λ（．３＾－６／ｒ,用ＳＥＭ、ＳＴｈＭ、ＴＥＭ和ＨＲＥＭ对ＡＩＮ陶瓷的显微结构及其对热导率的影响进行了研究。结果表明,晶粒尺２对ＡＩＮ陶瓷热导率的影响可以忽略,而分隔在ＡＮＩ晶粒之间的昌界相会降低热导率。     

AIN和B对热压烧结Cf/SiC复合材料性能的影响

研究了烧结助剂ＡＩＮ 和Ｂ对Ｃｆ／ＳｉＣ复合材料力学性能的影响。结果表明：Ｂ含量较低时（小于０．５ｗ ｔ％ ）,Ｂ的增加能有效地提高复合材料的抗弯强度与断裂韧性,继续增加Ｂ的用量至１ｗ ｔ％ ,虽能大幅度提高复合材料的强度,但使复合材料的断裂韧性大大降低。ＡＩＮ 与ＳｉＣ高温反应形成固溶体,能起到强化和细化基体ＳｉＣ晶粒以及改善ＳｉＣ晶界结构的作用,但对复合材料内纤维与基体间界面的结合影响较小,因此与Ｂ的作用相比,ＡＩＮ 对复合材料密度和力学性能的影响较小。烧结助剂为５ｗ ｔ％ ＡＩＮ－０．５ｗ ｔ％ Ｂ,经１８５０℃和２５ＭＰａ 热压烧结后的Ｃｆ／ＳｉＣ复合材料具有较佳的综合力学性能,其抗弯强度与断裂韧性值分别为５２６．６ＭＰａ 和１７．１４ＭＰａ·ｍ １／２。     

SiC—AlN—Y2O3复相陶瓷的制备与性能

通过热压烧结技术，ＳｉＣ、ＡｌＮ和Ｙ２Ｏ３粉末混合体在１９２０￣２０５０℃、Ａｒ气氛下形成了致密的复相陶瓷。在室温下ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相材料的抗弯强度和断裂韧性分别达到６００ＭＰａ和７ＭＰａ·ｍ＾１／２以上。运用ＸＲＤ、ＳＥＭ和ＴＥＭ分析致密样品的断裂裂纹、形貌和组成。ＳｉＣ－ＡｌＮ－Ｙ２Ｏ３复相陶瓷在１３７０℃氧化试验３０ｈ，其氧化产物为莫来石。     

添加CaF_2－Y_2O_3的AlN陶瓷的显微结构及热导性质

本文探索了影响添加ＣａＦ２－Ｙ２Ｏ３的ＡｌＮ陶瓷热导率的显微结构因素．利用ＸＲＤ、ＸＰＳ研究了伴随烧结过程的晶格畸变规律，确定了氧及杂质碳在ＡｌＮ晶格中的扩散行为，从而导致了晶胞的收缩和膨胀．ＴＥＭ和ＨＲＥＭ观察到类似转相区的面缺陷和不同于ＡｌＮ结构的微区．结果表明，除了晶粒内部的缺陷，第二相强烈地影响烧结体的热导率，挥发性第二相有助于提高热导率．     

添加CaF2—Y2O3的AlN陶瓷的显微结构及热导性质

本文探讨了影响添加ＣａＦ２－Ｙ２Ｏ３的ＡｌＮ陶瓷热导率的显微结构因素，利用ＸＲＤ、ＸＰＳ研究了伴随烧结过程的晶格畸变规律，确定了氧及杂质碳在ＡｌＮ晶格中的扩散行为，从而导致了晶胞的收缩和膨胀，ＴＥＭ和ＨＲＥＭ观察到类似转相区的面缺陷和不同于ＡｌＮ结构的微区，结果表明，除了晶粒内部的缺陷，第二相强烈地影响烧结体的热导率，挥发性第二相有助于提高热导率。     

碳化硅和氧化铝陶瓷的热等静压氮化

通过对无压烧结、热压烧结和热等静压烧结ＳＩＣ陶瓷以及热压烧结的ＳｉＣ粒子补强Ａｌ２Ｏ３基复相陶瓷（ＳｉＣｐ－Ａｌ２Ｏ３）和ＳｉＣ粒子与ＳｉＣ晶须共同增强的Ａｌ２Ｏ３基复合材料（ＳｉＣｐ－ＳｉＣｗ－Ａｌ２Ｏ３）在氮气氛中进行高温氮化处理，成功地实现了这些材料的开口气孔表面裂纹的愈合。研究表明：热等静压氯化工艺可以显著提高ＳｉＣ和Ａｌ２Ｏ３陶瓷的抗弯强度，对断裂韧性也有较大的改善作用。对于热等静压烧结ＳｉＣ陶瓷，在１８５０℃和２００ＭＰａ氮气压力下氯化处理１小时后，其抗弯强度和断裂韧性分别由５８２ＭＰａ和５．７ＭＰａ·ｍ１／２提高到９０７ＭＰａ和８．４ＭＰａ·ｍ１／２；对于热压烧结的ＳｉＣｐ－Ａｌ２Ｏ３复相陶瓷和ＳｉＣｐ－ＳｉＣｗ－Ａｌ２Ｏ３复合材料，在１７００℃和１５０ＭＰａ氮气压力下氮化处理１小时后，其室温抗弯强度分别由４６０和７０５ＭＰａ提高到８９５和１０３３ＭＰａ。     

AlN-多型体陶瓷的研究 Ⅱ.AlN-多型体的力学性能和微观结构

在研究了 ＡｌＮ－型体 １５Ｒ, １２Ｈ和 ２１Ｒ的形成特性的基础上［１］;本工作测定了它们的力学性能,并利用ＳＥＭ观察了显微结构．结果表明,尽管ＡＩＮ－多型体的力学性能较差,但是具有适当烧结添加剂的ＡＩＮ－多型体的抗折强度在室温至１２５０℃的范围内能保持不变,甚至提高５０％;尤其是１５Ｒ和１２Ｈ．ＡＩＮ－多型体的硬度随其组份向ＡｌＮ方向靠近而增加,即２１Ｒ的硬度最高（１２．７～１４．４ＧＰａ）,１５Ｒ的硬度为最低（１．５～１２．８ＧＰａ）．ＡＩＮ－多型体的强度和断裂韧性与ＡｌＮ－多型体的类型之间没有这种明显的联系,它们的变化范围分别在３１３～３６６ＭＰａ和３．８～４．８ ＭＰａ·ｍ~（１／２）之间．本文依据 ＡＩＮ－多型体的结构特征及断裂形貌对它们的力学性能进行了讨论．     

添加Y2O3-Dy2O3的AlN陶瓷的烧结特性及显微结构

本文探索了以自蔓延高温（ＳＨＳ）法合成并经抗水化处理的ＡｌＮ粉为原料,以Ｙ２Ｏ３－Ｄｙ２Ｏ３作为助烧结剂的ＡｌＮ陶瓷的烧结特性及显微结构,结果表明,晶界处存在Ｄｙ４Ａｌ２Ｏ９、Ｙ３Ａｌ２Ｏ９、ＤｙＡｌＯ３、Ｄｙ２Ｏ３和ＤｙＮ等第二相物质,随烧结温度变化,第二相的种类、数量和分布不同,显微结构也随之变化,从而影响ＡｌＮ的热导率,在１８５０℃下,可获得热导率为１４８Ｗ／ｍ·Ｋ的ＡｌＮ陶瓷。     

AIN-多型体对形成长颗粒α-Sialon的影响

通过ＳＥＭ、ＥＤＳ等方法，研究了添加不同含量ＡＩＮ－多型体对（Ｙ＋Ｓm）－α－Ｓｉａｌｏｎ晶粒形貌的影响．结果表明，随ＡＩＮ－多型体添加量增多，材料中长颗粒α－Ｓｉａｌｏｎ的数量增加．本文对ａ’－ＡＩＮ－多型体两相区内长颗粒α－Ｓｉａｌｏｎ的形成机理进行了讨论．     

通过分子复合和增塑制备新型高分子固体电解质

利用（甲基丙烯酸甲酯－甲基丙烯酸）共聚物［Ｐ（ＭＭＡ－ＭＡＡ）］与聚氧化乙烯（ＰＥＯ）的分子间氢键复合抑制ＰＥＯ的结晶，分子复合形成的独特超分子结构赋予材料优良的力学性和成膜性，在此基础上通过增塑进一步提高ＰＥＯ链段的活动性和锂盐在体系中的溶解性，制备出室温电导率达８．３１×１０~（－５）Ｓ·ｃｍ~（－１）、成膜性优良、实用价值较高的高分子固体电解质Ｐ（ＭＭＡ－ＷＡＡ）／ＰＥＯ／Ａ_２Ｌ_１ＣｌＯ_４。     

Microstructure and thermal conductivity of spark plasma sintering AlN ceramics

Abstract

Dense aluminium nitride ceramics were prepared by spark plasma sintering at a lower sintering temperature of 1700°C with Y₂O₃, Sm₂O₃ and Dy₂O₃ as sintering additives respectively. The effects of three kinds of sintering additives on the phase composition, microstructure and thermal conductivity of AlN ceramics were investigated. The results showed that those sintering additives not only facilitated the densification via the liquid phase sintering mechanism, but also improved thermal conductivity by decreasing oxygen impurity. Sm₂O₃ could effectively improve thermal conductivity of AlN ceramics compared with Y₂O₃ and Dy₂O₃. Observation by scanning electron microscopy showed that AlN ceramics prepared by spark plasma sintering method manifested quite homogeneous microstructures, but AlN grain sizes and shapes and location of secondary phases varied with the sintering additives. The thermal conductivity of AlN ceramics was mainly affected by the additives through their effects on the growth of AlN grain and the location of secondary phases.     

原位裂解碳对氮化铝基微波衰减陶瓷性能的影响

碳材料具有优异的吸波性能, 但是难以在陶瓷基体中均匀分散。本研究通过酚醛树脂裂解的方法在氮化铝陶瓷基体中引入碳, 研究了酚醛树脂的添加量对氮化铝陶瓷烧结性能、微观形貌、导热性能和介电性能的影响。研究发现, 酚醛裂解形成的碳能够有效促进氮化铝陶瓷的致密化进程, 降低烧结温度。当酚醛树脂含量为3wt%, 1700℃烧结后陶瓷的致密度达到99.26%。此外, 裂解碳的引入能够显著提高材料的导热性能, 并在材料的气孔中和氮化铝的晶界处形成碳膜, 从而显著提高材料的介电性能。当酚醛树脂含量为6wt%时, 材料热导率达135.1W/(m·K), 在X波段的介电损耗为0.3, 表明材料具有良好的微波衰减能力, 有望应用于大功率的微波电真空器件中。     

温度对高压烧结氮化铝陶瓷热导率的影响

以直接氮化法合成的AlN微米粉为原料,添加3%(质量分数)的CaC2为烧结助剂,在5GPa的压力下烧结30min,考察不同烧结温度对AlN陶瓷热导率的影响。用阿基米德排水法、XRD、SEM等技术手段对AlN烧结体进行性能检测。研究表明,在1500～1800℃范围内,温度的升高能促使AlN陶瓷内部晶粒长大,晶型饱满,尺寸均一,晶界相减少,实现烧结致密化,利于热导率的提高。     

Microstructure and properties of spark plasma sintered AlN ceramics

Spark plasma sintering (SPS) is a newly developed technique that enables poorly sinterable aluminum nitride (AlN) powder to be fully densified. It is addressed that pure AlN sintered by SPS has relatively low thermal conductivity. In this work, SPS of AlN ceramic was carried out with Y₂O₃, Sm₂O₃ and Li₂O as sintering aids. Effects of additives on AlN densification, microstructure and properties were investigated. Addition of sintering aids accelerated the densification, lowered AlN sintering temperature and was advantageous to improve properties of AlN ceramic. Thermal conductivity and strength were found to be greatly improved with the present of Sm₂O₃ as sintering additive, with a thermal conductivity value about 131 Wm⁻¹K⁻¹ and bending strength about 330 MPa for the 2 wt% Sm₂O₃-doped AlN sample SPS at 1,780 °C for 5 min. XRD measurement revealed that additives had no obvious effect on the AlN lattice parameters. Observation by SEM showed that AlN ceramics prepared by SPS method manifested quite homogeneous microstructure. However, AlN grain sizes and shapes, location of secondary phases varied with the additives. The thermal conductivity of AlN ceramics was mainly affected by the additives through their effects on the growth of AlN grain and the location of liquid phases.     

Study on microstructure and thermal conductivity of Spark Plasma Sintering AlN ceramics

Dense aluminum nitride (AlN) ceramics were prepared by Spark Plasma Sintering with rare-earth oxide and CaF₂ as sintering additives. The effect of sintering additives on the density, phase composition, microstructure and thermal conductivity of AlN ceramics was investigated. The results showed that those sintering additives not only promoted densification through liquid-phase sintering but also improved thermal conductivity by decreasing oxygen impurities. Thermal conductivities of samples sintered with optimum proportion of rare-earth oxide and CaF₂ were higher than those of other samples. During the Spark Plasma Sintering process, the microstructures, especially the content and distribution of secondary phases, played important roles on the thermal conductivity of AlN ceramics.     

无压烧结制备高致密度AlN-BN复合陶瓷

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.     

电泳沉积制备氮化铝陶瓷的研究

采用电泳沉积法成功制备相对密度达到61.9%的均匀氮化铝素坯, 经无压烧结后可获得热导率为200W/(m·K)的氮化铝陶瓷. 研究表明, 以无水乙醇为溶剂、加入0.1wt%聚丙烯酸（PAA）做分散剂、pH值控制在9.7左右的悬浮液具有最佳分散性. 电泳沉积（EPD）成型比干压成型制备的预烧体孔容减小, 比湿法成型制得的预烧体大孔显著减少. 用扫描电子显微镜（SEM）对三种不同成型方法制得氮化铝陶瓷的显微结构进行了研究, 结果表明, EPD法所得氮化铝陶瓷的显微结构均匀, 晶粒尺寸5μm左右.     

晶界相和晶界对AlN陶瓷热导率的影响

本文研究了掺杂CaO Y2 O3热压烧结和常压烧结AlN陶瓷的晶界相及其产生过程和除氧机制 ;分析了两种烧结工艺烧制的AlN陶瓷的晶界成份 ;测定了不同晶界相含量和晶界成份对应的AlN陶瓷的热导率     

Effect of grain-boundary stabilization on the strength, thermal conductivity, and dielectric properties of aluminum nitride

The thermal conductivity, dielectric properties, and strength of A1N ceramics were studied. The ceramics were prepared by semidry pressing and sintering. Increasing the sintering time was found to increase the thermal conductivity of the ceramics up to 200 W/(m K). A nonequilibrium-phonon-propagation method was used to analyze the effect of grain boundaries and processing conditions on the thermal conductivity of the ceramics.     

一种低温共烧AlN陶瓷基片的排胶技术

介绍一种由高热导率AlN陶瓷和金属W共烧制备低温AlN陶瓷基片的排胶技术．研究了排胶过程中残余碳对AlN陶瓷基片相组成、烧结特性和微观结构的影响．结果表明：两步排胶法可以较好地解决W氧化及AlN陶瓷颗粒表面吸附残余碳的问题．