无压烧结Si3N4—MgAl2O4—Al2O3系复合材料

本文对Ｓｉ３Ｎ４－ＭｇＡｌ２Ｏ４－Ａｌ２Ｏ３系复合材料的无压烧结进行了研究，讨论了Ａｌ２Ｏ３含量对材料性能的影响及烧结工艺对材料性能和显微结构的相互关系。实验表明，两段法烧结可以得到性能良好的Ｓｉ３Ｎ４－ＭｇＡｌ２Ｏ４－Ａｌ２Ｏ３复合材料。     

氧化对添加Al_2O_3的Si_3N_4陶瓷材料强度的影响

实验表明,Si_3N_4陶瓷在1200℃的空气中氧化后,其室温强度随着氧化时间的增加呈现出先增加后下降的趋势,其中在1200℃的空气中氧化75小时后宣温强度提高了16%。当在1300℃的空气中氧化100小时后,高温强度提高了22%。     

纳米SiC粉中的氧含量对Al_2O_3陶瓷无压烧结的影响

讨论了纳米 SiC中的氧含量对 Al2O3/ SiC纳米复相陶瓷性能的影响 .发 现当氧含量偏高时,烧结体难以致密化,同时在组织中出现大尺寸气孔 .实验证明,氧含量 较低的纳米β SiC可以使烧结体密度和强度得到极大提高;而氧含量偏高的 Si/C/N非晶 复合粉,提高性能的作用甚微 .其根本原因就是,粉体中的氧与硅形成蒸气,从而使烧结体 中出现气孔 .     

烧结温度和成分对Al_2O_3-TiC复合材料力学性能影响

以α-Al2O3粉、TiC粉为原料,采用热压烧结工艺制备了Al2O3-TiC复合材料,系统研究了烧结温度以及成分对Al2O3-TiC复合材料的组织结构和力学性能的影响规律.结果表明:α-Al2O3与TiC间没有发生化学反应,两相间具有很好的化学相容性.TiC的引入有利于提高Al2O3-TiC复合材料的力学性能.1 600℃热压烧结的Al2O3-20%TiC复合材料具有最佳的力学性能,其抗弯强度和断裂韧性分别达到509.45 MPa和5.27 MPa·m1/2,复合材料的断裂方式主要是沿晶断裂,同时伴有穿晶断裂.     

Al_2O_3/Al合金复合材料的耐磨性的研究

以国产氧化铝短纤维作为增强体,制备了氧化铝短纤维增强铝合金复合材料。本文研究了这种材料的耐磨性能,研究结果表明,氧化铝短纤维具有增强作用,复合材料比基体有高得多的硬度;在润滑条件下,复合材料的磨损率比基体的低,在较大载荷作用下,复合材料表现了优良的抗粘着磨损的能力,在一般磨损情况下,纤维体积率小于15％,可保证复合材料有足够的耐磨性。     

碳化硅陶瓷的无压烧结技术

比较了无压烧结的几种工艺,并介绍其最新进展.液相烧结导入了液相使晶界结合减弱,在较低的温度下实现烧结,成为近期研究的焦点.     

无压烧结SiC/TiB2复合材料组织与性能的研究

以TiB₂为基体、SiC为主要添加相、B₄C和纳米炭黑为烧结助剂,采用无压烧结方法制备SiC/TiB₂复合材料,研究SiC添加量对SiC/TiB₂复合材料的显微组织、力学性能及体积电阻率的影响。结果表明：随着SiC含量的增加,复合材料的晶粒尺寸逐渐减小,开口气孔率逐渐降低,抗折强度、断裂韧性及维氏硬度均呈现上升趋势;当SiC的质量分数为20%时,复合材料的力学性能最佳,此时其抗折强度、断裂韧性和维氏硬度分别为189.5 MPa、4.19 MPa·m^1/2和15.8 GPa;随着SiC含量的增加,复合材料的体积电阻率增大,导电性能有所降低。     

SiC(N)/Si3N4吸波材料的制备与性能

通过掺杂纳米SiC(N)吸收剂，采用无压烧结工艺，制备了SiC(N)／Si3N4复合型吸波材料。对材料进行了XRD、SEM及强度分析，结果表明：随着纳米吸收剂SiC(N)加入量的增加，材料的烧结性能趋于下降，表现为α-Si3N4的含量增多，柱状β-Si3N4的尺寸变小，材料气孔增大，强度降低。     

Sialon陶瓷的无压烧结

以Si_3N_4、Al_2O_3和AlN为原料,Y_2O_3为烧结助剂,采用无压烧结制备Sialon陶瓷．对试样的体积收缩率、抗弯强度、洛氏硬度等力学性能进行测试,扫描电镜(SEM)观察表明,在无压烧结条件下,采用埋粉烧结并充N_2保护,烧结温度为1700℃,保温90min可得到Sialon陶瓷,其中成分为54%α-Si_3N_4 32%Al_2O_3 8%AlN 6%Y_2O_3的Sialon陶瓷,其抗弯强度为390．08MPa,硬度为92．5HRA,显微结构为明显的柱状晶．     

Al_2O_3-TiC复合材料放电等离子烧结(SPS)致密化研究

用燃烧合成及放电等离子烧结法制备出致密Al_2O_3-TiC复合材料;分析了烧结温度与材料致密度、显微结构及力学性能的关系;真空气氛、1650℃、保温5min烧结试样的相对密度达99.8％,断裂韧性为4.61 MPa·m~(1/2);更高温度下烧结,气相反应加剧,不利于致密度进一步提高,力学性能也有所下降。沿晶断裂是其主要断裂方式。     

TiC Particle Reinforced Silicon Nitride Composite Joined With Y_2O_3-Al_2O_3-SiO_2 Mixture

Silicon nitride composite is joined to itself by heating interlayer of Y2 O3 -AL2O3 -SiO2 mixtures above their liquidus temperatures in flowing nitrogen. The joined specimens are tested in four point flexure from room temperature to 1373 K. The interface microstruclure and fractured surfaces after testing are observed and analyzed by SEM, EPMA and XRD respectively. The results show that F2 O3 -A12 O3 -SiO2 glass reacts with Si3 N4 at interface, forming the Si3 N4/Si2 N2 O( Y-AlrSi-O-N glass/ Y-Al- Si-O glass gradient interface. With the increase of bonding temperature and holding time, the joint strength first increases, reaching a peak, and then decreases . According to interfacial analyses , the bonding strength depends on joint thickness .     

THE CHARACTERISTICS OF THE PRESSURELESS SINTERED Si_3N_4-MgO-Ce0_2 CERAMICS

An investigation of the pressureless sintering of Si3N4 with MgO-CeO2 revealed that MgO-CeO2 is a most effective sintering aid for silicon nitride. The amount of MgO-CeO2 and sintering conditions have a strong influence on the densification behaviour and mechanical properties of the sintered materials. The effect of the additive and sintering conditions are discussed. The silicon nitride pressureless sintered with MgO-CeO2 retained a relative density of 98. 5% and a bending strength of 950 MPa. The Si Mg-Ce-O-N system is of great value for application and theoretical study.     

THE AUTOMATIC CRYSTALLIZATION OF MgO DURING THE SINTERING Si_3N_4-MgO-CeO_2 CERAMICS

The automatic crystallization of MgO duringthe sintering of Si_3N_4-MgO-CeO_2 is first discovered.ForSi_3N_4-MgO-CeO_2,ceramics,the MgO-CeO_2 would reactwith SiO_2 to form liquid at 1450℃ and then transform intoglassy phase in the sintered bodies after cooling down.Above1550℃,MgO would crystallize automatically during sinter-ing.So the glassy phase which is harmful to the high temper-ature properties is then eliminated.The present work is ofgreat value for theoretical study and application.     

ZrO2对热压Si3N4陶瓷材料断裂韧性及显微结构的影响

研究了ＺｒＯ２对热压Ｓｉ３Ｎ４陶瓷材料的断裂韧性Ｋｉｃ、显微结构及结构组成的影响。结果表明，Ｚｒｏ２的含量对Ｓｉ３Ｎ４陶瓷的断裂韧性有显著影响，在１０ｗｔ％时出现峰值ＫＩＣ为７．８３ＭＰａ．ｍ＾１／２，提高约２１．４％，热压Ｓｉ３Ｎ４－ＺｒＯ２系统中能有效地撸制ＺｒＮ的生成。     

Design,preparation,and structure of particle preforms for Si_3N_(4(P))/Si_3N_4 radome composites prepared using chemical vapor infiltration process

A particle preform was designed and prepared by conglomerating and cold-pressed process,which was condensed by chemical vapor infiltration(CVI)process to fabricate silicon nitride particles reinforced silicon nitride composites.The conglomera- tions are of almost sphericity after conglomerated.There are large pores among the conglomerations and small pores within them- selves in the preform according to the design and the test of pore size distribution.The pore size of the preform is characterized by a double-peak distribution.The pore size distribution is influenced by conglomeration size.Large pores among the conglomerations still exist after infiltrated Si_3N_4 matrix.The conglomerations,however,are very compact.The CVI Si_3N_4 looks like cauliflower- shaped structure.     

Pressureless Sintered 3Y-TZP/20%Al2O3 Composite Ceramic

0　ＩｎｔｒｏｄｕｃｔｉｏｎＹ ＴＺＰ(Ｙ2 Ｏ3 ｓｔａｂｉｌｉｚｅｄＺｒＯ2 ｐｏｌｙｃｒｙｓｔａｌ)ｉｓａｋｉｎｄｏｆｃｅｒａｍｉｃｍａｔｅｒｉａｌｓｗｉｔｈｅｘｃｅｌｌｅｎｔｓｔｒｅｎｇｔｈａｎｄｆｒａｃｔｕｒｅｔｏｕｇｈｎｅｓｓａｔｒｏｏｍｔｅｍｐｅｒａｔｕｒｅｄｕｅｔｏｔｈｅｓｔｒｅｓｓ ｉｎｄｕｃｅｄｍａｒｔｅｎｓｉｔｉｃｔｒａｎｓｆｏｒｍａｔｉｏｎｏｆｔｈｅｍｅｔａｓｔａｂｌｅｔｅｔｒａｇｏｎａｌｐｈａｓｅｔｏｔｈｅｓｔａｂｌｅｍｏｎｏｃｌｉｎｉｃｐｈａｓｅ[1,2 ].Ｉｔｈａｓｂｅｅｎｒｅ ｐ…     

HIGH-TEMPERATURE CHARACTERIZATION OF SELF- REINFORCED Si_3N_4 WITH ADDITIVES Y_2O_3 AND La_2O_3

High-temperature strength and fracturetoughness,oxidation behavior,and thermal shock of the SRSi_3N_4 with Y_2O_3 and La_2O_3 as complex additives are inves-tigated.The research results show that the strength does notdecrease until 1400℃;the fracture toughness,while,in-creases with temperature rising and presents peak value at1350℃.The oxidation behavior obeys parabolic law,andthe oxidation procedure is mainly controlled by diffusion of additive ions.The high oxidation resistance of this mate-rial is primary due to the presence of refractory Y~(3 )andLa~(3 )at intergrnular glass phase.The thermal shock exper-iments show that the damage of strength is far larger thanthat of fracture toughness.     

IC制造中氮化硅薄膜的制备方法

氮化硅薄膜是芯片制造中广泛运用的一种绝缘薄膜,其可用作芯片表面的掩蔽膜及钝化膜。简要介绍IC制造中几种主要的氮化硅薄膜的制备技术,并探讨新型的制备技术。     

Si3N4-SiO2复合材料的制备及介电性能研究

以国产氮化硅、二氧化硅粉为原料，以氧化镁、氧化铝为烧结助荆，经干压成型后，在流动的高纯N2作为控制气氛的条件下，常压烧结出结构均匀，具有良好介电性能的Si3N4-SiO2复合材料。研究了原料、烧结温度、烧结助剂对材料介电性能的影响。结果表明：SiO2、MgO、Al2O3可促进坯体的烧结及致密，同时时材料的介电性能有较大的影响。当烧结温度低于1550℃时，随着烧结温度的升高，材料的介电常数趋于增大。当烧结温度高于1550℃时，随着温度的升高，材料中缺陷增加，相对密度降低，因此材料的介电常数趋于减小。