炉渣α-sialon粉的高温自蔓延燃烧合成及炉陶瓷性能的研究渣α-sialon

以高炉炉渣为原料，用高温自蔓延燃烧工艺合成了较为纯净的单相(Ca，Mg)α-sialon粉料(简称炉渣α-sialon粉)，并用无压和热压烧结工艺将炉渣α-sialon粉烧结成了炉渣α-sialon陶瓷，对炉渣α-sialon陶瓷的力学性能进行了检测，结果表明，炉渣α-sialon陶瓷有较好的力学性能，优良的抗冲刷性能和抗酸腐蚀性能。     

升温速率对Y-α-sialon陶瓷致密化及微观结构的影响

根据Y-Si-Al-O-N相图设计Y2O3掺杂α-sialon陶瓷的组成,采用热压烧结方法在1900℃保温30min制备了设计成分为Y0.4Si9.8Al2.2O1.0N15的sia-lon陶瓷,研究了升温速率对陶瓷致密化过程、物相组成以及微观结构的影响规律。结果表明,所制备的陶瓷相组成均为α-sialon;不同升温速率陶瓷的致密化过程曲线变化趋势相同,但随升温速率增大向高温区平移,收缩的起止温度和峰值收缩速率均随升温速率增大而增大;快速升温有利于提高晶核密度,抑制柱状晶发育,柱状晶的尺寸和长径比随升温速率增大而减小。     

Y-α/β-sialon的气压烧结

研究了Ｓｉ３Ｎ４粉末粒度分析发现相组成,ＡｌＮ粉末的粒度及分阶段烧工艺对气压烧结α／βｓｉａｌｏｎ的致密化,产物相组成和力学性能的影响,采用三阶段保温烧结（１７００℃,１ｈ,１８００℃,１ｈ及１９５０℃,１５ｈ）减少了Ｓｉ３Ｎ４与液相在高温反应促进了材料致密,适当的烧结工艺下及用适当的埋粉,细ＡｌＮ原料有利于材料致密。细Ｓｉ３Ｎ４原料（０．３μｍ）中氧杂质增加导致复合材料中α－ｓｉａｌｏｎｓ相减少     

不同稀土掺杂α-sialon陶瓷的透光性

利用放电等离子烧结(SPS)及1700℃高温热处理7和17h，研究了组份为‰133Si9．3Al2．7O1．7N14．3(R=Gd，Y和Er)的α-sialon在4000～1500cm^-1(2．5～6．6μm)范围的光学透过率．结果表明，经SPS烧结的样品不但达到致密化，且样品中α-simon晶粒的尺寸分布均匀．在SPS样品中，以Y203掺杂α-sialon的透光性最好,样品厚度为0．5mm时最高透过率达到56％．热处理7h由于第二相的形成导致透过率下降，但合适的热处理条件能提高样品的透过率，例如Gd117的红外最高透过率从SPS后的47％提高到56％。     

Microstructure and Mechanical Properties of Dy-α-sialon/Nano-size SiC Composites

The composite of Dy-α-sialon/10 wt pct nano-size SiC particles has been prepared from precursor powders of Si3N4, AIN, Al2O3, Dy2O3 and nano-size β-SiC. The hardness, toughness and bending strength of the composite at ambient temperature are a little higher than those of Dy-α-sialon.while the bending strength is maintained up to 1000℃ and about 2 times more than that of Dy-α-sialon at the same temperature. The fracture surfaces show that the grain size of the composite is smaller than that of Dy-α-sialon, and both Of them have predominately transgranular mode of fracture. It is believed that the decrease of the bending strength of Dy-α-sialon at elevated temperature is caused by the viscous flow of the grain boundary phase, while the addition of nanosize SiC particles effectively increases the viscosity of the grain boundary phase and therefore prevents the strength loss of Dy-α-sialon/nano-size SiC composites at elevated temperature     

TiN／O′-sialon复相陶瓷的常温导电性能研究

对原位TiN／O′-sialon纳米复相陶瓷（NTS）和采用“二步法”制备的TiN／O′-sialon复相陶瓷（TS）的常温导电性能进行了对比研究，并对材料TS进行了放电加工。研究结果表明，初始原料中20％（质量分数）和25％（质量分数）左右的TiO2加入量是决定材料NTS和TS中TiN能否形成导电网络的最低TiO2加入量，该导电临界值同基相O′-sialon与导电相TiN的颗粒尺寸比有关，此时相应材料的电阻率为1.6×10^-2和1.8×10^-2Ω·cm，满足放电加工的需要。烧结温度升高，两种材料的电阻率略有降低。随放电加工速度的增加，材料TS加工表面粗糙度明显增加。     

不同α—SiC粉料液相烧结特性的研究

比较α－ＳｉＣ进口粉料和国产粉料的粉料成分、粒度、显微结构,以及以Ａｌ２Ｏ３－Ｙ２Ｏ３烧结助剂液相烧结ＳｉＣ的力学性能,分析两者之间的差异。结果表明,进口粉在纯度、粒度和显微结构方面均优于国产粉,从而使其在烧结性能、力学性能的方面明显好于国产粉料,通过讨论其中的主要区别,提出了改善国产ＳｉＣ粉料的性能的一些措施。     

以Al-B-C为烧结助剂的SiC陶瓷热压烧结工艺

以SiC超细粉末为原料,Al粉、B粉和碳黑为烧结助剂,采用热压烧结工艺制备了SiC陶瓷,重点研究了烧结助剂含量(4～13 wt％)对SiC陶瓷物相组成、致密度、断面结构及力学性能的影响.除SiC主晶相外,X射线衍射图还显示了Al8B4C7相的存在;当烧结助剂的含量从4 wt％增至13 wt％时,扫描电镜照片显示陶瓷断面形貌从疏松结构变成致密结构,存在晶粒拔出现象;陶瓷力学性能随着烧结助剂含量的增加先升高后降低.当烧结助剂含量为10 wt％时,SiC陶瓷的力学性能达到最高,抗弯强度为518.1 MPa,断裂韧性为4.98 MPa·m1/2.Al、B和C烧结助剂在1850℃烧结温度下形成的Al8B4C7液相促进晶粒间的重排和传质,并填充晶粒间的气孔,提高了陶瓷致密度.     

反应烧结Si3N4透波陶瓷的制备与能研究

以国产Si粉和Si3N4粉为原料,添加适量的Y2O3和Al2O3烧结助剂,经凝胶注模成型后,在流动的高纯氮气氛中,采用反应烧结工艺制备出结构均匀、性能良好的Si3N4透波陶瓷,并深入研究了组分配方和烧结工艺对硅粉氮化率及材料的力学性能与介电性能的影响.研究结果表明:提高烧结温度能明显改善硅粉的氮化程度,当烧结温度超过1450℃、保温4h以上时,硅粉可完全氮化;起始原料中Si3N4含量为65％时,样品的介电性能最好,其介电常数为4.8,损耗角正切值为0.78×10-2;起始原料中Si3N4含量为35％时,样品的力学性能最好,其抗弯强度为129.5MPa.     

复相烧结助剂中MnO2对α-Al2O3陶瓷支撑体性能的影响

采用挤压成型法和固态粒子烧结法制备α-Al2O3陶瓷支撑体,主要研究复相烧结助剂MgO-MnO2-TiO2中MnO2添加量(质量分数)对陶瓷支撑体性能的影响。通过压汞法、内外加压法、三点弯曲法、质量损失法、扫描电镜和X射线衍射等方法对α-Al2O3陶瓷支撑体的孔隙率、纯水通量、抗折强度、酸碱腐蚀、微观结构及晶体类型和晶相成分进行分析表征。研究结果表明:MnO2能够和Al2O3形成固溶体Mn2AlO4,使晶格畸化,增加晶体的结构缺陷,从而降低烧结温度,促进α-Al2O3陶瓷支撑体的烧结。当MnO2添加量少于0. 5%时,烧结不完全;MnO2添加量大于2%时,晶粒出现异常生长;MnO2的添加量为1. 5%时,制备的α-Al2O3陶瓷支撑体样品性能最佳,孔隙率为38. 25%,抗折强度为80. 3 MPa,纯水通量达6579. 52 L/(m2·h·MPa),酸/碱腐蚀重量损失率为1. 22%/0. 90%。     

Absorption spectra of rare-earth-doped α-sialon ceramics

Abstracts are not published in this journal This revised version was published online in November 2006 with corrections to the Cover Date.     

Preparation and properties of stable dysprosium-doped α-sialon ceramics

Dense ceramics with overall compositions DyxSi12-4.5xAl4.5xO1.5xN16-1.5x, where 0.2≤x≤1.0, along the Si3N4–Dy2O3·9AlN tie line were prepared by hot-pressing at 1800°C. The dysprosium-doped α-sialon phase formed in the composition range 0.3≤x≤0.7. Sintered materials of different compositions were post-heat-treated at temperatures in the range 1300–1750° C for different times and it was shown that the Dy-α-sialon phase is stable over a large temperature interval and during heat treatment times up to 30 days. Unlike corresponding neodymium- and samarium-doped α-sialons, dysprosium-doped α-sialon does not decompose into β-sialon and rare-earth-rich grain-boundary phase(s) at temperatures below 1550°C. The α-phase can coexist with a liquid phase at temperatures ≥1550°C and with the Dy-M′-phase (Dy2Si3-xAlxO3+xN4-x) at lower temperatures. When heat treated at 1450°C, any residual liquid grain-boundary phase reacted with minor amounts of the α-sialon phase and devitrified to Dy-M′-phase, yielding a glassy phase-free material. The Dy-M′-phase formed had the maximum aluminium substitution, i.e. x≈0.7. Dysprosium-doped α-sialon exhibited very high hardness (Hv10=22 GPa) and a fracture toughness of 4.5 MPa m1/2, and the hardness and toughness decreased only slightly after devitrification of the glassy phase. Some elongated α-sialon grains were formed at high x values in glassy phase-containing materials, but their presence did not affect the toughness significantly. This revised version was published online in November 2006 with corrections to the Cover Date.     

Eu stabilized α-sialon ceramics derived from SHS-synthesized powders

The characteristics of Eu-stabilized α-sialon ceramics derived from self-propagating high-temperature synthesis (SHS) Eu α-sialon powders without and with the addition of Y₂O₃ are investigated. The results showed that the amount of α-sialon phase formed in sintered Eu α-sialon composition was much less than that in SHS-ed powder when the composition was hot-pressed at 1800 °C for 1 h, while the transformation of α-sialon to β-sialon phase did occur at the same time, which could be attributed to the metastability of SHS-ed powder because of the high heating and cooling rate during the SHS process and the reduction of Eu³⁺ to Eu²⁺ under the reduction conditions during hot pressing. By addition of Y₂O₃ into SHS-ed Eu α-sialon powder, thus to form (Y,Eu) α-sialon phase in the sintered sample, the stability of α-sialon phase was improved, as the ratio of α-sialon to α-sialon was increased from 70 wt.% in SHS-ed powder to 83 wt.% in the sintered product by 50 mol% of Y₂O₃ added into SHS-ed powder.