AlN陶瓷低温烧结制备与性能研究

采用两组复合烧结助剂Y2O3-CaF2,Y2O3-CaF2-Li2CO3在1600℃烧结AlN陶瓷,对AlN陶瓷烧结密度,热性能和电性能进行了测试,并分析了AlN陶瓷物相变化和微观结构。结果表明,复合烧结助剂在低温下能明显促进AlN陶瓷致密化及晶粒生长发育,尤其是添加3wt%Y2O3-2wt%CaF2作烧结助剂,1600℃常压烧结4h制备了结晶良好,相对密度为98.4%,热导率为133.62W/m.K,同时具有较低相对介电常数的AlN陶瓷。在低温常压条件下制备出性能较高的AlN陶瓷。     

AlN陶瓷粉末的主要制备方法及展望

论述了国内外氮化铝陶瓷粉末的主要制备方法：铝粉直接氮化法、Al2O3碳热还原法、化学气相沉积法、溶胶-凝胶法、自蔓延高温合成法和等离子化学合成法,分析了这几种制备方法的特点和研究进展,为氮化铝粉末的制备指明了方向。     

无压烧结高导热AlN陶瓷的研究进展

AlN以其优异的高热导率、与Si相匹配的热膨胀系数及其它优良的物理化学性能受到了国内外学术界的广泛关注,被誉为新一代高密度封装的首选基板材料.本文详细综述了AlN陶瓷的导热机理和无压烧结工艺等方面的研究进展,并介绍了烧结助剂的选取原则和AlN陶瓷热导率与温度的关系,以及展望了AlN基板的发展趋势和前景.     

电子封装用高导热AlN陶瓷基板研究进展

高导热AlN陶瓷是新型功率电子器件重要的基板材料,在5G通讯、微波TR组件、IGBT模块等高端电子器件领域具有广泛的应用。综述了国内外电子封装用高导热AlN陶瓷基板及其制备技术的研究进展。探讨了晶格氧、非晶层、AlN晶粒尺寸、晶界相及气孔等微结构因素对AlN陶瓷热导率的影响。提出选用高纯超细AlN粉体原料,合理选取烧结助剂的类型与添加量,优化排胶、高温烧结与热处理工艺是改善AlN陶瓷结构,实现AlN陶瓷热导率提升的有效途径。     

烧成制度对AlN陶瓷性能及显微结构的影响

为了制备结构致密的Al N陶瓷,在Al N粉末中加入2%(w)的Y2O3,经细磨、造粒、成型烘干后,在热压炉内于氮气气氛中1 800~1 950℃分别保温1~4 h无压烧结制得Al N陶瓷,并研究了烧成温度和保温时间对Al N陶瓷致密度、导热性及显微结构的影响。结果表明:随着烧成温度的提高和保温时间的延长,添加Y2O3的Al N陶瓷的晶粒趋于均匀,显气孔率下降,致密化程度提高;当烧成温度为1 850℃,保温时间达到2 h时,Al N陶瓷的相对密度达到99.8%,热导率达到94.8 W·(m·K)-1。     

AlN陶瓷粉末的主要制备方法及展望

论述了国内外AlN陶瓷粉末的主要制备方法:铝粉直接氮化法、Al2O3碳热还原法、化学气相沉积法、溶胶—凝胶法、自蔓延高温合成法和等离子化学合成法,分析了这几种制备方法的特点和研究进展,为AlN粉末的制备指明了方向。     

微波烧结AlN陶瓷的初步研究

采用微波高温烧结工艺,制备了致密的AlN陶瓷,并初步探讨了微波烧成环境对烧结体性能的影响.结果表明:利用微波烧结AlN陶瓷,虽然在节能省时方面效果显著,但是微波烧成环境对AlN陶瓷的烧成影响比较复杂,本文着重指出烧成环境中的碳热还原气氛能极大地加快AlN陶瓷的致密化速率,但容易在AlN陶瓷晶界相内部产生气孔,使AlN陶瓷的热导率降低.     

臭氧发生器用AlN陶瓷基板材料的研究

为了提高臭氧发生器的臭氧产量,要求臭氧发生器用的陶瓷基板材料具有较高的介电性能和热导率.本文研究了掺杂成分CaO、Y2O3、YF3、(Y,Ca)F3对臭氧发生器用AlN陶瓷基板材料的相对密度、热导率、介电常数、介质损耗等性能的影响.采用XRD分析其物相和SEM观察其显微结构,结果表明,掺杂成分对改善陶瓷基板材料性能的作用大小依次排列为(Y,Ca)F3>YF3>Y2O3>CaO,最适合的掺杂配方是(Y,Ca)F33.0wt%,YF32.0wt%,Y2O31.0wt%,CaO1.0wt%.     

Al/AlN复相陶瓷的高压烧结研究

利用六面顶高压烧结(压力为5.0 GPa)手段实现了Al/AlN复相陶瓷的高压烧结,得到了高致密的Al/AlN复相陶瓷.结果显示,在压力为5.0GPa、温度为1600℃,烧结时间仅为20min就可以使烧结体的相对密度达到99.3%,热导率达到70W/mK,随着烧结时间的延长,相对密度和热导率都有所增加;并且经50min烧结的烧结体相分布均匀,晶界清晰,晶粒多为六角晶型,断裂多为穿晶断裂.     

磷酸对AlN陶瓷烧结的影响

为了研究磷酸对AlN陶瓷烧结的影响,利用磷酸对AlN粉末进行酸洗处理制备了具有较高抗水解能力的AlN粉末,在碳管炉氮气气氛下进行陶瓷烧结;利用XRD和SEM对AlN陶瓷进行了表征,并进行了密度的测定。结果表明磷酸酸洗降低了AlN的含氧量,优化了粉末烧结性能,有利于AlN陶瓷的致密化。经过磷酸酸洗的粉末在1800℃下烧结,陶瓷样品微观结构良好,相对密度为98.8%,且没有新杂质相形成。     

关于氮化铝陶瓷导热性的讨论

本从声子机理出发，探讨了影响氮化铝陶瓷导热性的主要因素；提出了提高导热率的努力方向，即结构上努力减少晶格缺陷（主要是杂质固溶）和晶界缺陷（包括第二相析出，晶界玻璃相，气孔），并使相的分布尽量合理；指出了提高A1N陶瓷导热率的可能途径，即严格控制A1N粉末质量，选择合理的烧结助剂，采用还原气氛烧成等。     

Effects of doping Al-metal powder on thermal,mechanical and dielectric properties of AlN ceramics

In this work, the influence of Al-metal powder addition upon that thermal, mechanical and dielectric properties of aluminium nitride (AlN) ceramic was studied. The findings show that adding Al-metal powder improves not only the mechanical and thermal properties of the AlN ceramic but also has no negative impact on its dielectric properties. Based on Y₂O₃ as sintering aid, the AlN ceramic with 1.0 wt% Al doping were 14.35% higher thermal conductivity, 11.73% higher flexural strength and 59.50% higher fracture toughness than those doped without Al, respectively. This study showed that the addition of Al-metal powder may favor the purifying of the AlN lattice and the formation of homogenous and isolated second phase, which would increase the AlN–AlN interfaces and improve the thermal conductivity. Furthermore, the grain boundaries of AlN ceramics might be strengthened by the isolated second phases due to the thermal mismatch between the second phases and AlN grains, thus strengthening and toughening the AlN ceramic doped with Al. However, the large additive amount of Al powder (>1.0 wt%) was not help the isolation and homogenization of the second phase, giving a deterioration in an AlN ceramic's mechanical and thermal properties. These results suggest that the introduction of an appropriate dose of aluminium metal powder is a simple method that can be used to improve the AlN ceramic's mechanical and thermal properties simultaneously.     

AlN瓷的制备方法

本实验直接采用Ａｌ２Ｏ３粉还原氮化制备ＡｌＮ瓷，以简化ＡｌＮ瓷的制备工艺，提高ＡｌＮ瓷性能，降低成本。结果表明烧结体的主晶相确定为ＡｌＮ，且瓷导热率最高可达１０４Ｗ／ｍ．Ｋ。     

不同烧结气氛下制备的AlN陶瓷结构和电性能的差异

以AlN粉末为原料、Y2O3粉末为烧结助剂,分别在氮气气氛下和真空气氛下,采用放电等离子烧结方法在1700℃、25MPa条件下保温10min制备AIN陶瓷。X-射线衍射、扫描电镜和X-射线光电子能谱分析表明：不同烧结气氛下制备的AlN陶瓷的结构和体积电阻率各有不同。真空气氛AlN陶瓷与氮气气氛AlN陶瓷相比较,除舍有主晶相AlN和第二相Y3Al5O12外,还含有微量Al2Y相。正是由于微量Al2Y相的存在,使得真空气氛下得到的AlN陶瓷比氮气气氛下得到的A1N陶瓷的体积电阻率低约2个数量级。     

Densification and properties of AlN ceramic bonded carbon

To obtain light and tough materials with high thermal conductivity, AlN ceramic bonded carbon (AlN/CBC) composites were fabricated at temperatures from 1600 to 1900 °C in a short period of 5 min by the spark plasma sintering technique. All AlN/CBCs (20 vol% AlN) have unique microstructures containing carbon particles of 15 μm in average size and continuous AlN boundary layers of 0.5-3 μm in thickness. With an increase in sintering temperature, AlN grains grow and anchor into carbon particles, resulting in the formation of a tight bonding layer. The AlN/CBC sintered at 1900 °C exhibited a light weight (2.34 g/cm³), high bending strength (100 MPa), and high thermal conductivity (170 W/mK).     

纳米陶瓷材料及其制备与应用

由于硬度高、耐高温、耐磨损、质量轻和导热性好，陶瓷材料是现代工业三大基本材料之一，但其脆性大、韧性小而限制了在一些特殊领域的应用。纳米材料及技术运用到陶瓷材料中极大地改善了它的应用性能。本文比较了传统陶瓷与纳米陶瓷的优缺点，介绍了纳米陶瓷材料材料的特性和种类，以及制备方法、应用和国内研究现状。     

Phase and microstructure optimization of grain boundary oxides and its effect on the thermal conductivity of Y2O3-doped AlN ceramics

AlN green bodies with variable O and C contents were employed to fabricate Y₂O₃-doped AlN ceramics of different grain-boundary phase compositions and microstructures via debinding in air and N₂, respectively. The microstructural evolution and grain-boundary oxide migration and their effects on the properties of the ceramics were explained. Finally, modified models were built to predict the thermal conductivity of these AlN ceramics with complex microstructures. During sintering, the oxide melt migrates to the ceramic surface driven by the differences between the surface energy and solid/liquid interface energy of the melt. The phase compositions and distributions of the grain-boundary oxides vary with sintering temperature. In addition, the amorphous layers were detected experimentally. All of these factors have great effects on ceramics properties. AlN ceramics were shown to have a thermal conductivity as high as 221.64 W/(m·K), which agrees with the value predicted via modified models.     

Grain boundary blocking effects in Sm/Yb-doped AlN ceramics

The effect of microstructural changes on the electrical and thermal properties of AlN ceramics is studied in terms of cation size and nature of sintering aids (i.e. Sm₂O₃ and Yb₂O₃) in AlN ceramics. It is revealed that the addition of Yb₂O₃ to Sm-bearing AlN ceramics results in 80 % reduction of thermal conductivity with an increase of the grain boundary resistivity that is one order of magnitude larger than for the sample without Yb₂O₃. Additionally, the grain boundary/grain resistivity ratio is significantly increased, when the Sm₂O₃ sintering aid is employed instead of Yb₂O₃, for which the secondary phases at the grain boundaries and the triple junctions are responsible for the increase in the electrical resistivity. The microstructural investigations confirm the tendency of the secondary phase to segregate at the triple junctions in Sm-containing AlN ceramics while it is grain boundaries that are favored as segregation site in the case of Yb.     

Secondary phases,microstructures and properties of AlN ceramics sintered by adding nitrate sintering additives

AlN ceramics were sintered at a temperature range from 1650 to 1800°C through adding the Ca and Y nitrate sintering additives. Secondary phases, microstructures and properties of the AlN ceramics were studied. When the AlN ceramics are sintered at 1650 or 1675°C, CaO and Y₂O₃ from the sintering additives react with Al₂O₃ in the AlN powder to generate CaAl₄O₇ and Y₃Al₅O₁₂. Part of Y₃Al₅O₁₂ reacts with CaO and Al₂O₃ to form CaYAl₃O₇ at 1700°C. At 1800°C, CaYAl₃O₇ decomposes into CaAl₄O₇ and Y₃Al₅O₁₂. Finally, CaAl₄O₇ volatilises and only Y₃Al₅O₁₂ remains. As the sintering temperature increases, the AlN grains grow continuously and the bending strength and thermal conductivity of the AlN ceramics increase first and then decrease. The AlN ceramics sintered at 1700°C are fully dense and have the highest bending strength and thermal conductivity of 373·7 MPa and 136·7 W m^?1 K^?1 in this work.