反应烧结制备Si3N4/SiC复相陶瓷及其力学性能研究

以两种不同配比Y₂O₃/Al₂O₃ (A, 2:3; B, 3:1, 总量15 wt%)为烧结助剂, 通过添加不同质量分数的SiC粉体,反应烧结制备了高强度的氮化硅/碳化硅复相陶瓷。并对材料的相组成、相对密度、显微结构和力学性能进行了分析。结果表明: 在1700℃保温2 h情况下, 烧结助剂A 与B对应的样品中α-Si₃N₄相全部转化为β-Si₃N₄; 添加5wt% SiC, 烧结助剂A对应样品的相对密度达到最大值94.8%, 且抗弯强度为521.8 MPa, 相对于不添加SiC样品的抗弯强度(338.7 MPa)提高了约54.1%。SiC能有效改善氮化硅基陶瓷力学性能, 且Si₃N₄/SiC复相陶瓷断裂以沿晶断裂方式为主。     

模板转化法制备苎麻纤维织物SiC陶瓷

以苎麻纤维织物为生物模板,通过浸渍含有硅粉的酚醛树脂溶液,后经压制成型、碳化和1500℃烧结等工艺,制备了具有生物纤维形态的SiC陶瓷。利用XRD、SEM等测试技术,研究了不同烧结助剂对样品的各项性能和微观形貌的影响。结果表明:烧结助剂对苎麻纤维织物SiC陶瓷的失重率、显气孔率、体积收缩率等性能均产生了影响;添加Al_2O_3-Y_2O_3-SiO_2三元烧结助剂的SiC陶瓷具有最大的显气孔率和最小的体积收缩率;陶瓷中的SiC主要以β-SiC的形式存在;微观形貌分析显示,样品很好地保留了苎麻织物的纤维状微观结构。     

High temperature strength and oxidation behaviour of hot-pressed silicon nitride-disilicate ceramics

Twelve different silicon nitride-disilicate ceramics have been fabricated by hot-pressing Si3N4 with the oxides of Y, Yb, Ho, Dy, Er, Sm, Ce, Lu, La, Pr, Gd, and Sc that are used as sintering additives. The high temperature strength and oxidation behaviour of the hot-pressed ceramics were investigated and correlated with the cationic radii of the oxide additives. The flexural strength at 1200°C increased, from 666 MPa for Si3N4-La2Si2O7 to 965 MPa for Si3N4-Sc2Si2O7 which is correlated with a decreasing cationic radius of the oxide additive. The weight gain during oxidation at 1400°C for 192 h in air decreased, from 0.8732 mg cm-2 for a Si3N4-Sm2Si2O7 ceramic to 0.1089 mg cm-2 for a Si3N4-Sc2Si2O7 ceramic, which is a function of the decreasing cationic radius of the oxide additive. This revised version was published online in November 2006 with corrections to the Cover Date.     

添加剂对热压钛酸铝陶瓷性能与结构的影响

ＭｇＯ－Ａｌ２Ｏ３－ＳｉＯ２、Ａｌ２Ｏ３－ＳｉＯ２、Ｓｉ３Ｎ４、ＳｉＣ四种添加剂对热压钛酸铝陶瓷力学与热学性能的影响。结果表明：引入添加剂后钛酸铝陶瓷的抗弯强度得到极大的改善，同时，由于陶瓷结构的变化，其热膨胀系数也明显增加。Ｘ射线衍射结果表明：添加剂在热压条件下与钛酸铝陶瓷发生了反应并形成固溶体。     

Effect of a new additive on mechanical properties of hot-pressed silicon carbide ceramics

The mechanical properties and microstructure of SiC ceramics, hot pressed by simultaneously adding nano-SiC and oxides (MgO+Al₂O₃+Y₂O₃) or nitrate salts (Mg(NO₃)₂+Al(NO₃)₃+Y(NO₃)₃) as additives, were evaluated. The oxide additives system slightly influenced the mechanical properties of the ceramics, while the addition of nano-SiC lead to finer microstructure, and 5 vol.% nano-SiC changed the fracture mode from intergranular type to transgranular type. The ceramics with nitrate salts had fine, equiaxed grains with an average grain size larger than that of the system added oxides, thus inducing lower Viker’s hardness and flexural strength, while the presence of crystalline YAG phase improved the fracture toughness by 54.7%. Also, an observed increase in grain growth—with decreasing weight fraction of liquid and the grounded grain morphology in this system—confirmed a diffusion-controlled growth mechanism. Although the sample with the least amount of additives has the lowest relative density and largest grain size, its flexural strength did not drastically decrease. The influence of nano-SiC on the fracture toughness in the nitrate additive system was negligible.     

碳源及添加比例对固相烧结碳化硅陶瓷微观结构及性能的影响

研究了碳的添加量为6wt%条件下, 添加碳源的种类及添加比例对制备的无压固相烧结碳化硅陶瓷的微观结构和性能的影响。结果表明: 采用纯无机碳源(碳黑), 制备的碳化硅陶瓷具有较为细小的碳化硅晶粒结构, 但致密度较低; 添加有机碳源(酚醛树脂)时, 随着其裂解碳添加量的增加, 碳化硅的晶粒逐步长大, 碳在材料中的分布更加均匀, 材料的致密度提高, 力学性能增强。当有机碳源裂解碳添加量达3wt%时, 材料的致密度最高, 并具有最大的弹性模量468 GPa, 断裂韧性达4.65 MPa·m^1/2。当有机碳源裂解碳添加量大于3wt%时, 碳化硅晶粒发生局部异常长大现象, 材料的弯曲强度与断裂韧性进一步增加。同时, 对材料的热扩散系数随碳源添加种类和比例变化的规律也进行了分析与讨论。     

氮掺杂导电碳化硅陶瓷研究进展EI北大核心CSCD

可电火花加工的导电碳化硅(SiC)陶瓷不仅可以克服传统高电阻率SiC陶瓷难加工的突出缺点,而且能够保留传统高电阻率SiC陶瓷的其他优异性能,在结构陶瓷领域取代传统的高电阻率SiC陶瓷具有突出优势。本文阐述了粉末烧结制备氮掺杂导电SiC陶瓷的原理,归纳总结分析了其粉末烧结制备方法、烧结助剂的种类及其所获得SiC陶瓷的热电和力学性能。同时,探讨了SiC陶瓷的电性能影响因素,为调控SiC陶瓷的电性能提供了参考依据。最后,指出了氮掺杂导电SiC陶瓷面临的主要挑战,在未来研究中,应聚焦于发展新烧结技术与烧结添加剂体系以及澄清电性能调控机制,为制备电阻率可控的高性能导电SiC陶瓷奠定技术基础。     

掺钇(Ba,Ca)(Ti,Zr)O_3电容器陶瓷抗还原性的研究

对掺钇的(Ba,Ca)(Ti,Zr)O3(BCTZ)电容器陶瓷进行了抗还原性研究,研究了不同摩尔分数的钇的掺杂对BCTZ电容器陶瓷的介电性能、显微结构和密度的影响。结果表明,随着Y2O3掺杂量的增加,BCTZ陶瓷的室温介电常数、介质损耗逐渐减小,居里温度向低温方向移动,同时绝缘电阻率升高,BCTZ陶瓷抗还原性能提高;Y2O3的掺入能够促进BCTZ陶瓷的致密化,并有利于抑制BCTZ陶瓷的晶粒生长。     

ZrO2颗粒状态对SiC/金刚石复相陶瓷结构、性能的影响

本文用不同水解时间辅以氨水沉淀制备了不同颗粒尺寸的纳米(9nm ) ZrO₂ (Y₂O₃) 粉体。以其为增韧相, 在高温(1350℃) 超高压(5GPa) 条件下烧结ZrO₂ (Y₂O₃) + SiC+ 金刚石超硬复相陶瓷, 用TEM、SEM、XRD、冲击韧性测定和磨耗比测定研究了ZrO₂ (Y₂O₃) 颗粒形状特征及对超硬复相陶瓷相结构及机械性能的影响。结果表明, ZrO₂ (Y₂O₃) 制备的水解时间≥50h, ZrO₂ (Y₂O₃) 颗粒均一, 在复相陶瓷内均一分布, 以100% t 相存留, 断裂过程中t →m 转变量≥20vo l% , 使超硬复相陶瓷具备较高韧性及耐磨性。      

烧结温度对包混/复合添加工艺制备多孔SiC陶瓷性能的影响

采用包混工艺合成了核壳结构的先驱体粉体,并引入一定量Al2O3、SiO2和Y2O3复合添加剂,通过成型、炭化和烧结工艺制备了多孔碳化硅陶瓷;分析了样品的物相、表面形貌、孔隙率、热导率、热膨胀系数、抗弯强度和抗热震性能。结果表明,在较低的烧结温度下制得了多孔碳化硅陶瓷,在1650℃烧结的多孔碳化硅陶瓷综合性能较好。     

Y_2O_3和TiO_2烧结剂对制备β-Sialon陶瓷烧结性能的影响

以金属Al粉、单质Si粉、α-Al_2O_3微粉为主要原料,高温氮化反应制备β-Sialon陶瓷。通过在反应物中分别添加不同含量的Y_2O_3和TiO_2烧结剂,研究分析和对比了Y~(3+)和Ti~(4+)对β-Sialon陶瓷晶相组成、晶格常数、微观结构及烧结性能的影响。采用SEM及EDS对试样的微观形貌进行观察与分析,利用X'Pert Plus软件分析晶相的晶格常数,采用半定量法计算试样晶相组成。结果表明:Y_2O_3和TiO_2可显著降低高温氮化法制备β-Sialon陶瓷试样中β-Sialon相的生成温度。伴随着Y_2O_3和TiO_2的引入,Al_2O_3在Si3N4中的固溶度提高,β-Sialon晶相的生成量增加,晶格常数和晶胞体积增大,烧结性能得到改善。综合对比分析,Y_2O_3和TiO_2均对制备β-Sialon陶瓷具有良好的促烧结作用,用成本较低的TiO_2代替传统的稀土氧化物作为助烧结剂无压烧结制备β-Sialon陶瓷是可行的。     

熔盐辅助合成Dy3Si2C2包裹SiC粉体及其陶瓷的烧结行为

碳化硅陶瓷因自身优良的物理化学性能而具有广泛的应用前景。碳化硅的化学键结合特性决定了其难以烧结成型, 因此如何制备高质量碳化硅陶瓷是领域内的难点之一。本研究以三元稀土碳化物Dy₃Si₂C₂作为新型SiC陶瓷的烧结助剂, 依据Dy-Si-C体系的高温相转变原位促进碳化硅的烧结致密化。采用放电等离子烧结技术, 利用金属Dy与SiC反应生成Dy₃Si₂C₂, 对Dy₃Si₂C₂包裹的SiC粉体进行烧结。在1800 ℃、45 MPa的烧结条件下, 得到了致密度为99%、热导率为162.8 W·m ^-1·K ^-1的高纯度碳化硅陶瓷。进一步的研究表明, 高温下Dy₃Si₂C₂与SiC发生共晶反应, 在晶界处产生的液相促进了SiC陶瓷的致密化, 表明稀土层状碳化物Re₃Si₂C₂ (Re=La, Ce…)有助于SiC的烧结致密。     

成型温度对多孔SiC陶瓷性能的影响

以包混工艺合成了核-壳结构的先驱体粉体,并引入少量Al<,2>O<,3>,SiO<,2>和Y<,2>O<,3>作为复合添加剂,通过模压成型、炭化和烧结工艺制备了多孔碳化硅陶瓷;研究了成型温度对样品的孔隙率、密度、热膨胀系数、抗弯强度和热震性能的影响.结果表明:成型温度对多孔碳化硅陶瓷的孔隙率、密度、抗弯强度及热震性能均...     

Synthesis of SiC/BN nanocomposite powders by carbothermal reduction and nitridation of borosilicate glass, and the properties of their sintered composites

A new synthetic method for the fabrication of SiC/BN nanocomposites was devised to attain strong machinable ceramics. SiC/BN nanocomposites that contained 10, 20, and 30?vol% hexagonal BN (h-BN) were successfully fabricated by sintering SiC-BN nanocomposite powders by carbothermal reduction and nitridation of borosilicate glass powders. Homogeneous mixtures of silica (SiO(2)), boric acid (H(3)BO(3)), and carbon powder were heated in a nitrogen atmosphere to synthesize SiC-BN nanocomposite powders. Borosilicate glass was obtained by reacting SiO(2) and B(2)O(3) above 800?°C, and SiC and turbostratic BN (t-BN) were obtained by reacting borosilicate glass with carbon powder and nitrogen gas at 1500?°C. Carbothermal reduction followed by nitridation yielded SiC-BN nanocomposite powder composed of nanosized SiC and t-BN. By hot-pressing nanocomposite SiC-BN powders containing 7?wt% Al(2)O(3) and 2?wt% Y(2)O(3), machinable SiC/BN nanocomposites were obtained without a significant decrease in their fracture strength.     

Al2O3陶瓷制备及性能分析

以纯Al2O3粉、Mg(NO3)2·6H2O、Y(NO3)3·6H2O为原料,于1500℃、1600℃和1700℃常压制备了高纯Al2O3陶瓷,研究了烧结温度和烧结助剂的含量对Al2 O3陶瓷密度、硬度及微观结构的影响.结果表明,添加剂的作用受烧结温度的影响较大,进而影响了烧结体的硬度.     

氧化铁粉末化学组成对合成SHS复合弯管内衬陶瓷的影响

基于重力分离SHS法制备陶瓷内衬复合弯管 ,研究了氧化铁粉末化学组成对SHS复合弯管内衬陶瓷的影响 .研究发现在铝热剂相同质量分数条件下 ,存在于工业原料Fe2 O3 粉末的杂质比SiO2 添加剂对燃烧过程的稀释效应更为强烈 .在工业原料Fe2 O3 +Al体系中加入适量的Fe3 O4+Al体系 ,使燃烧温度、蔓延速率及SHS反应转化率均有所升高 ;但加入过量的Fe3 O4+Al体系 ,虽然使蔓延速率进一步增大 ,但却引起燃烧温度和SHS反应转化率有所下降 .实验表明 ,在工业原料Fe2 O3 +Al体系中加入 1 5 %的Fe3 O4+Al体系 ,使复合弯管内衬陶瓷性能达到并超过用分析纯Fe2 O3+Al体系所制备的复合弯管内衬陶瓷性能 .     

新型基片材料——C/SiC复合材料

阐述了目前常用的3大类基片材料,即塑料基、金属基和陶瓷基材料,比较了3类材料的性能,得出了陶瓷基材料是综合性能较好的基片材料的结论,并比较了目前陶瓷基片材料中的Al2O3、AlN、BeO、SiC的性能,认为SiC作为基片材料具有良好的发展前景;针对单相SiC陶瓷固有脆性导致难以大尺寸成型的问题,提出了使用C/SiC复合材料制备基片材料的可能性,并综述了C/SiC复合材料的制备工艺,比较了3种工艺(PIP、CVI、LSI)所制备的材料的性能,认为液相渗硅(LSI)C/SiC复合材料制备大尺寸封装基片材料是未来最具前景的发展方向。     

SiC对烧结堇青石材料性能的影响

以高岭土、滑石和工业氧化铝为矿物原料烧结制备了堇青石陶瓷,通过X射线衍射仪、扫描电镜、万能材料试验机和热膨胀仪等测试手段,研究了添加不同含量SiC对烧结堇青石陶瓷相组成和性能的影响,并比较了添加不同颗粒尺寸的SiC对烧结陶瓷强度的影响。试验表明,随着SiC添加量的增加,堇青石陶瓷的弯曲强度、致密度和热膨胀系数逐渐增大。当添加SiC的质量分数为5%、粒径为5.0μm时,烧结堇青石陶瓷的强度较未添加时增大了41.9%,而热膨胀系数的增幅不大。     

ZnO基导电陶瓷的溶胶掺杂制备

用Ｃｏ、Ｎｂ、Ｙ元素对ＺｎＯ材料进行掺杂制备出ＺｎＯ基导电陶瓷样品。研究了掺杂含量及掺杂方式对ＺｎＯ基导电陶瓷电阻率的影响。用溶胶一凝胶法制得Ｙ（ＮＯ３）３含Ｔｉ掺杂剂溶胶且与Ｙ２Ｏ３固相氧化物掺杂进行了比较。结果表明,Ｙ（ＮＯ３）３含Ｔｉ溶胶掺杂可制备出室温电阻率很低的ＺｎＯ基导电陶瓷,其室温电阻率可达３．３８ｘ１０－２Ω·ｍ,溶胶引入量为０．０５％ｍｏｌ。     

A Coprecipitation Coating Synthesis of SiC/YAG Composites

The α-SiC in 0.5μm size powders were coated with Al_2O_3 and Y_2O_3 by a coprecipitation coating (CPC) method forfabrication of SiC/YAG composites. The same powder preparation was carried out by conventional mechanical mixing(MM) method for comparison. Two kinds of SiC/YAG composites were manufactured by pressureless sintering usingthe different powders, named CPC composite and MM composite thereafter respectively. It is shown that the CPCcomposite has the advantages of homogeneous distribution of YAG phase and of being sintered to high density ata low temperature, 100℃ lower than that of MM composite. The strength (573 MPa) and hardness (23.3 GPa) ofthe CPC composite are significantly higher than those (323 MPa and 13.5 GPa) of the MM composite, respectively.