Low-temperature hot-press sintering of AlN ceramics with MgO–CaO–Al2O3–SiO2 glass additives for ceramic heater applications

Aluminum nitride (AlN) is used a ceramic heater material for the semiconductor industry. Because extremely high temperatures are required to achieve dense AlN components, sintering aids such as Y₂O₃ are typically added to reduce the sintering temperature and time. To further reduce the sintering temperature, in this study, a low-melting-temperature glass (MgO–CaO–Al₂O₃–SiO₂; MCAS) was used as a sintering additive for AlN. With MCAS addition, fully dense AlN was obtained by hot-press sintering at 1500 °C for 3 h at 30 MPa. The mechanical properties, thermal conductivity, and volume resistance of the sintered AlN–MCAS sample were evaluated and compared with those of a reference sample (AlN prepared with 5 wt% Y2O3 sintering aid sintered at 1750 °C for 8 h at 10 MPa). The thermal conductivity of AlN prepared with 0.5 wt% MCAS was 91.2 W/m?K, which was 84.8 W/m?K lower than that of the reference sample at 25 °C; however, the difference in thermal conductivity between the samples was only 14.2 W/m?K at the ceramic-heater operating temperature of 500 °C. The flexural strength of AlN–MCAS was 550 MPa, which was higher than that of the reference sample (425 MPa); this was attributed to the smaller grain size achieved by low-temperature sintering. The volume resistance of AlN–MCAS was lower than that of the reference sample in the range of 200–400 °C. However, the resistivity of the proposed AlN–MCAS sample was higher than that of the reference sample (500 °C) owing to grain-boundary scattering of phonons. In summary, the proposed sintering strategy produces AlN materials for heater applications with low production cost, while achieving the properties required by the semiconductor industry.     

Ti/AlN陶瓷界面反应的热力学研究

对AlN陶瓷在室温和超高真空条件下蒸镀金属钛过程的界面反应进行了热力学研究，并用X光电子能谱（XPS）进行了验证，表明在金属钛沉积以前AlN陶瓷在空气中表面部分被氧化，当样品沉积了金属钛后，刚沉积上的钛是氧化状态，随着钛沉积厚度的增加，表面TiN和Al2O3的成分都增加。     

复合助剂对低温常压烧结AIN性能的影响

研究了Y2O3,LiO2,CaO烧结助剂对AlN陶瓷常压烧结致密度和性能的影响。结果发现,同时添加Y2O3,LiO2,CaO作为助剂,在1600℃低温烧结就能获得具有高致密度、较小的晶粒尺寸(1μm~4μm)、较高的抗弯强度(331MPa)、断裂韧性(3.8MPa·m1/2)及导热率(118W·m-1·K-1)的AlN陶瓷。     

填料并用对双组分室温硫化导热硅橡胶性能的影响

以α,ω-二羟基聚二甲基硅氧烷为基胶,Si3N4、AlN、Al2O3为导热填料,制备了填充型双组分室温硫化（RTV-2）导热硅橡胶.研究了填料Si3N4/Al2O3或AlN/Al2O3并用对RTV-2硅橡胶导热性能、工艺性能及力学性能的影响.结果表明,当填料的总体积分数为0.45时,对于Si3N4/Al2O3填充体系,随着体系中Al2O3体积分数的增加,RTV-2导热硅橡胶的热导率先升后降、拉伸强度先增后减,而扯断伸长率则呈逐渐升高的趋势,基料的粘度先减后增;当Al2O3的体积分数为0.14时,RTV-2导热硅橡胶的热导率最高、拉伸强度最大,基料的粘度最小,综合性能最佳.对于AlN/Al2O3填充体系,随着体系中Al2O3的体积分数的增加,RTV-2导热硅橡胶的热导率先升后降、拉伸强度及扯断伸长率先减后增,基料的粘度呈上升趋势;当Al2O3的体积分数为0.07时,RTV-2导热硅橡胶具有较好的导热性能和工艺性能,但力学性能偏低.     

AlN-BN复合陶瓷制备工艺研究进展

本文详细介绍了AlN-BN复合陶瓷材料制备工艺的研究状况,包括AlN、BN粉末的合成制备和AlN-BN复合材料的制备工艺,评述了各种方法和工艺的优缺点。最后指出了粉末制备工艺中的自蔓延高温合成法、电弧等离子体法和烧结工艺中的反应烧结、放电等离子烧结是很有价值的研究方向。     

Cu掺杂AlN的铁磁稳定性的第一性原理计算

文章采用基于密度泛函理论的平面波超软赝势法,结合广义梯度近似计算了Cu掺杂AlN的晶格常数、能带结构、电子态密度、铁磁态和反铁磁态的总能量,并通过平均场近似的海森堡模型估算了居里温度Tc。结果表明,Cu掺杂体系的能带结构呈现半金属性,半金属能隙为0.442eV。铁磁性是Cu原子的3d态与其最近邻的N原子的2p态通过p-d杂化作用而稳定的。当两个Cu原子相距最远且自旋平行排列时,体系具有最低的能量,估算出此时的居里温度高于室温,因此Cu掺杂AlN有望作为稀磁半导体材料。     

反应烧结制备Ti_2AlN-TiN复合材料

采用2Ti/2Al/3TiN粉体为原料,通过反应热压烧结,以制备Ti2AlN-TiN复合材料。采用X射线衍射（XRD）、场发射扫描电镜（FE-SEM）结合能谱仪（EDS）分析试样。研究结果表明,在1350℃保温2h,压力为30MPa,可烧结得到组织细小、致密的Ti2AlN-TiN复合材料。材料中层片状Ti2AlN晶粒长约5m,TiN晶粒大小为1~2m。复合材料具有良好的机械性能,其显微硬度与弯曲强度分别达8.57GPa和450MPa。     

Effect of AlN addition on the electrical resistivity of pressureless sintered SiC ceramics with B4C and C

The effect of 0–12 wt% AlN addition on the electrical resistivity of SiC ceramics pressureless sintered with 0.7 wt% B₄C and 2.5 wt% C additives was investigated. The elemental analysis of SiC grains revealed a codoping of Al and N in the SiC lattice with a higher N concentration with 1 wt% AlN addition and a higher Al concentration with 12 wt% AlN addition. The electrical resistivity decreased by four orders of magnitude (1.7 × 10⁵ → 8.3 × 10¹ Ω cm) with 1 wt% AlN addition due to the increased carrier density (1.7 × 10¹⁰ → 2.3 × 10¹⁵ cm⁻³) caused by excess N-derived donors. However, subsequent AlN addition (4 → 12 wt%) led to an increase (2.9 × 10³ → 1.2 × 10⁴ Ω‧cm) in electrical resistivity due to (1) increased Al dopants which act as deep acceptors for trapping N-derived carriers causing a decrease in carrier density (2.3 × 10¹⁵ → 5.9 × 10¹³ cm⁻³), (2) the formation of electrically insulating SiC-AlN solid solution, and (3) the presence of electrically insulating AlN grains at the grain boundaries.     

TEM Study on the Internal Oxidation and Nitriding of Dual Phase Fe–Mn–Al–C Alloy AfterNaCl-Induced Corrosion

A dual-phase Fe–Mn–Al–C alloy was oxidized at 750°C in air with 2 initial mg/cm² NaCl deposits. After 9 hr of exposure a fine-void zone was observed in the middle subscale and a coarse-void layer in the inner subscale. The fine-void zone formed due mainly to the interaction between selective oxidation of manganese and the oxidation of metal chlorides, while the formation of the coarse-void layer was caused by chlorination. The product remaining in the fine-void zone was mostly Al₂O₃, and the structure of the substrate in this zone is oxidation-induced ferrite, where nitriding of aluminum occurs forming AlN. Fine Fe₃O₄ particles fill in the coarse voids and the structure of the substrate in this layer is secondary austenite. The mechanism of the formation and growth of the internal oxidation and nitriding in the void zones of the subscale are discussed.