低温烧结Zn(Nb0.9V0.1)2O6微波介质陶瓷的结构与性能

对低温烧结Zn(Nb0.9V0.1)2O6微波介质陶瓷进行了研究,讨论了V离子取代Nb离子进入铌酸锌晶格后对材料结构与微波性能的影响以及V5+取代后材料结构与性能之间的关系.实验结果表明少量V5+取代Nb5+后材料的烧结温度可从未取代时的1150℃显著降至取代后的950℃;V离子进入铌酸锌晶格,材料晶体结构仍为铌铁矿结构;低温烧结后ZnNb0.9(V0.1)2O6微波介质材料具有圆柱状微结构和部分玻璃相物质;Zn(Nb0.9V0.1)2O6微波介质材料950℃烧结后具有最佳微波介电性能(介电常数为25,Q×f值为29 500GHz,谐振频率温度系数为-44×10-6/℃).     

添加玻璃料对BaSm_2Ti_4O_(12)微波介质陶瓷烧结行为和介电性能的影响

利用固相法制备BaSm_2Ti_4O_(12)(BST)微波介质陶瓷.研究了复合添加Li_2CO_3-B_2O_3-SiO_2-CaO-Al_2O_3(LBSCA)和BaO-B_2O_3-SiO_2(BBS) 玻璃料对BaSm_2Ti_4O_(12)微波介质陶瓷的烧结性能、介电性能、相组成和微观结构的影响.研究表明:复合掺杂10% LBSCA和2%～5% BBS可使烧结温度降至900 ℃.XRD分析表明复合掺杂两种玻璃料的BST陶瓷主晶相为BaSm_2Ti_4O_(12)相,玻璃料以玻璃相的形式存在陶瓷晶粒间.复合掺杂10% LBSCA+3%BBS玻璃料的BST陶瓷可在900 ℃、保温2 h条件下烧结致密,微波介电性能为:ε_r =55.63,Q_f = 4266 GHz,τ_f= -13.5×10~(-6)℃~(-1),这种陶瓷材料有望与纯Ag电极共烧,制作各种多层微波频率元器件.     

B_2O_3添加对(Zn_(0.5)Mg_(0.5))Nb_2O_6陶瓷微波介电性能的影响

研究了B_2O_3助烧剂对(Zn_0.5Mg_0.5)Nb_2O_6陶瓷的烧结温度、微观结构、相结构及微波介电性能的影响.结果表明,助烧剂B_2O_3的添加有助于降低(Zn_0.5Mg_0.5)Nb_2O_6陶瓷的烧结温度,可以将(Zn_0.5Mg_0.5)Nb_2O_6陶瓷的烧结温度降低到950 ℃.其中掺杂2%B_2O_3(质量分数,下同)的(Zn_0.5Mg_0.5)Nb_2O_6陶瓷,在950 ℃烧结可获得结构致密的烧结体,并且具有较佳的介电性能:ε_r = 20.7,Q×f= 60156 GHz.     

SPS制备致密碳化硼陶瓷的结构及性能

以富硼碳化硼粉体为原料,采用放电等离子烧结(SPS)制备致密碳化硼陶瓷体,研究了SPS工艺对碳化硼陶瓷结构和性能的影响.结果表明,SPS烧结工艺可以低温快速烧结得到致密度达到99.7%的碳化硼陶瓷体,烧结温度和烧结时间对碳化硼的致密度和晶粒尺寸都有影响.烧结过程中样品晶粒表面产生玻璃相,玻璃相的存在使碳化硼断裂机制由穿晶断裂过渡为沿晶断裂,有助于提高材料断裂强度和断裂韧性.SPS制备的致密碳化硅陶瓷材料具有良好的力学性能,其中致密度达到99.6%,抗弯强度达到550.1 MPa,硬度39.52 GPa.     

微波LTCC环行器用热压烧结SrFe_(12)O_(19)铁氧体的低温烧结特性（英文）

为了与低温共烧陶瓷(LTCC)技术兼容,采用热压烧结工艺在870℃制备了添加不同Bi_2O_3含量的SrFe_(12)O_(19)铁氧体材料,着重研究了材料的晶相组成、烧结密度、气孔率和磁性能等低温烧结特性。研究结果表明,材料在870℃烧结时,Bi_2O_3的添加促进了SrFe_(12)O_(19)晶相结构的形成,提高了材料的烧结致密度和磁性能。当Bi_2O_3的添加量(质量分数)为2%~4%,材料可以获得致密的结构,烧结密度达到4.65 g·cm~(-3)以上,气孔率低于10%,材料的饱和磁化强度Ms和内禀矫顽力Hci较高,分别达到252.4 k A·m~(-1)和312.9k A·m~(-1)以上。此外,基于SrFe_(12)O_(19)材料的低温烧结特性讨论了该材料在微波LTCC环行器当中的应用。     

微波无压烧结Fe-Cu-WC基金属结合剂

分别采用常规无压烧结和微波无压烧结法,以Fe、Cu、Sn等金属粉以及WC粉作为原料制备金属烧结体,研究不同烧结工艺对金属烧结体的微观组织形貌、致密度和抗弯强度的影响。结果表明:对比常规无压烧结,微波无压烧结可提高金属烧结体的致密度及力学性能;当烧结温度为900℃时,致密度和抗弯强度均达到最大,分别为90.6%、93.9%和753 MPa、816 MPa;通过样品微观形貌分析,微波无压烧结可以使烧结体元素分布更均匀,降低烧结体的孔隙率。在达到同等级力学性能的前提下,微波无压烧结可以降低烧结温度,避免高温损伤金刚石强度。      

放电等离子烧结MoSi_2陶瓷的微观结构与力学性能

以微米级MoSi_2粉末为原料,利用放电等离子烧结技术制备致密度达99%的MoSi_2陶瓷材料。研究烧结温度对MoSi_2陶瓷的致密化、微观结构和力学性能的影响。结果表明:SPS烧结技术制备的MoSi_2陶瓷由MoSi_2、少量的Mo_5Si_3和SiO_2组成;随着烧结温度的升高,材料的致密化效果明显加强;当烧结温度为1600℃时,材料的综合性能最优,相对密度和抗弯强度达到98.9%和417 MPa。但当烧结温度达到1800℃时,致密度基本保持不变,MoSi_2晶粒长大明显,材料抗弯强度降低。     

Transient Liquid-Phase Sintering Characteristic of W-Ni-Fe Alloy via Microwave-Assisted Heating

研究了W-Ni-Fe合金在2.45 GHz微波炉中瞬时液相烧结的致密化行为和力学性能。结果表明:微波辅助热场下的93W-Ni-Fe合金显示出优异的力学性能和快速的致密化过程,其压缩试样在1500℃下烧结5 min后,拉伸强度、延伸率、相对密度和硬度(HRC)分别是1200 MPa,16.6%,98.6%和42.0;在微波辅助热场下,试样烧结可以减少80%的烧结时间;微波辅助热场下的瞬时液相烧结有利于减少烧结时间,加快致密化过程,并且有利于钨晶粒的细化,获得组织均匀和综合性能高的W-Ni-Fe合金。     

微波辅助热场下W-Ni-Fe合金的瞬时液相烧结特性（英文）

研究了W-Ni-Fe合金在2.45 GHz微波炉中瞬时液相烧结的致密化行为和力学性能。结果表明:微波辅助热场下的93W-Ni-Fe合金显示出优异的力学性能和快速的致密化过程,其压缩试样在1500℃下烧结5 min后,拉伸强度、延伸率、相对密度和硬度(HRC)分别是1200 MPa,16.6%,98.6%和42.0;在微波辅助热场下,试样烧结可以减少80%的烧结时间;微波辅助热场下的瞬时液相烧结有利于减少烧结时间,加快致密化过程,并且有利于钨晶粒的细化,获得组织均匀和综合性能高的W-Ni-Fe合金。     

掺杂FeVO4低温烧结ZnO-Nb2O5-TiO2微波介质陶瓷

研究了FeVO4对ZnO-Nb2O5-TiO2微波介质陶瓷的烧结特性、介电性能、相组成和微观结构的影响.研究表明添加3 ω/%～10ω/%FeVO4可使烧结温度从1200℃降低到960℃,XRD与EDS分析表明FeVO4固溶入主晶相ZnTiNb2O8,导致晶格畸变,缺陷增加,促进传质,在液相和固溶体协同作用下降低烧结温度;随FeVO4添加量的增加,Zn0.15Nb0.3Ti0.55O2相和TiO2相含量增大,介电常数εr基本不变,Q·f值由于晶体缺陷增多和晶粒尺寸不均而下降;FeVO4添加量为4 ω/%的ZnO-Nb2O5-TiO2陶瓷可在940 ℃,2 h条件下致密烧结,微波介电性能为εr=40,Q·f=10 200 GHz(3GHz),τf=-9×10-6/℃,可用于制备各种多层微波频率器件.     

Effect of annealing on microstructure of CuO-doped (Zr0.8Sn0.2)TiO4

Zirconium tin titanate ceramics, and specifically the (Zr_0.8Sn_0.2)TiO₄ (ZST) are the preferred materials for use in resonators or filters working at microwave frequency. However, the problem with these materials is their high sintering temperature which is as high as 1550 °C. In this research, the influence of different amounts of CuO additions on the densification and microstructure evaluations of ZST ceramics modified with 1 wt% ZnO has been studied in two different states: before and after annealing. Results showed that annealing process at 1250 °C resulted in some changes in density, grain size and shape due to the rearrangement of liquid phase and its reactivation, but no secondary phase was detected. Also, variations in lattice parameters during annealing compared to those of as-sintered specimens suggested the possibility of disorder-order transformation during long time high temperature heat treatment process.     

Sintering response of austenitic (316L) and ferritic (434L) stainless steel consolidated in conventional and microwave furnaces

This study compares the effect of heating mode on the densification, microstructure, strength and hardness of austenitic and ferritic stainless steel. The compacts were sintered in a radiatively heated (conventional) and a 2.45 GHz microwave furnace. Both 316L and 434L compacts couple with microwaves and heat up to the sintering temperature rapidly (45 °C/min). The overall processing time was reduced by about 90% through microwave sintering. While the microwave sintered compacts exhibit a finer microstructure, there is no corresponding improvement in densification and mechanical properties. This has been correlated with elongated and irregular pore structure.     

烧结温度对Micro-FAST制备钛微型齿轮致密化的影响

将新颖的多物理场活化烧结微成形技术(Micro-FAST)引入到钛微型齿轮的制备中,研究了烧结温度对Micro-FAST制备钛微型齿轮致密化的影响。结果表明,在1200℃烧结保温4 min,体系的相对密度即可达到90.5%。Micro-FAST的烧结致密化过程大致可分为4个阶段:预热阶段、低温保温阶段、快速升温阶段和烧结保温阶段,钛粉末的致密化过程主要发生在快速升温阶段。对烧结体系的收缩动力学曲线研究发现,在电场、力场和温度场的耦合作用下,粉末体系在450℃发生了塑性变形,在1032℃生成了局部液相。研究表明,与传统烧结法相比,多物理场活化烧结法是一种新型和高效的制备钛微型零件的良好方法。     

微波烧结WC-Co硬质合金致密化与晶粒生长

分别采用微波烧结和常规烧结制备WC-8Co硬质合金,通过1 000~1 400℃温度范围烧结以及1 400℃保温0~240 min的微波和常规烧结实验,测量各样品的收缩率、密度和晶粒尺寸,分析其致密化行为和晶粒生长,研究烧结温度和保温时间对合金致密化和晶粒生长的影响。结果表明,与常规烧结比较,微波烧结促进YG8硬质合金的致密化,且获得的合金组织均匀,晶粒细小。另外,保温时间对微波烧结YG8硬质合金的晶粒生长几乎没有影响。     

Microstructure and microwave dielectric properties of ZnO-B2O3 added （Ca0.254Li0.19Sm0.14）TiO3 ceramics

The effects of ZnO-B2O3 (ZB2) on the sintering behavior and microwave dielectric properties of (Ca0.254Li0.19Sm0.14)TiO3 ceramics were investigated.The densities of the specimens reached the maximum value by adding 3 wt.% ZB2 and then decreased.The sintering temperature of the specimens was lowered from 1300 to 1100°C without degradation of the microwave dielectric properties.The (Ca0.254Li0.19Sm0.14)TiO3 + 3 wt.% ZB2 sintered at 1100°C for 3 h showed good microwave dielectric properties,εr = 108.2,Qf = 6545 GHz,and τf = 6.5 ppm/°C,respectively,indicating that ZB2 was an effective sintering aid to improve the densification and microwave dielectric properties of (Ca0.254Li0.19Sm0.14)TiO3 ceramics.     

W-Ni-Fe合金的放电等离子烧结致密化与微观组织演变(英文)

采用放电等离子烧结(SPS)技术固结成形W-5.6Ni-1.4Fe(质量分数,%)混合粉末,研究不同加热速率对烧结致密化行为和微观组织演变规律的影响。结果表明,W-5.6Ni-1.4Fe合金的SPS致密化过程可以划分为三个阶段。初始不收缩阶段,快速加热导致粉末颗粒接触区产生瞬间放电,并在颗粒表面产生局部高温,强化后续烧结致密化;致密化过程主要发生在中期固相烧结阶段,缓慢加热有助于扩散更加充分;在后期瞬时液相烧结阶段,钨晶粒球化并迅速长大,且快速加热可获得更为细小的晶粒。     

溶胶-喷雾干燥超细/纳米晶W-20Cu复合粉末的烧结行为

采用喷雾干燥-氢气还原法制备超细/纳米晶W-20Cu(质量分数,%)复合粉末,粉末压坯直接从室温推入高温区烧结不同时间后直接取出水淬,研究其烧结致密化和显微组织的变化。结果表明,超细/纳米晶W-20Cu粉末在1000～1200℃烧结时发生迅速致密化。粉末压坯在1200℃烧结60min,其材料致密度已达到96.4%。1420℃烧结90min时致密度达到99%以上。1100～1420℃烧结时其烧结致密化活化能不断减小,从1100℃时的276.3kJ/mol减小到1420℃时的29.1kJ/mol。当温度低于1200℃时,W晶粒长大不明显,当温度超过1300℃时,W晶粒开始有明显长大。随温度的升高W晶粒发生显著球形化,1420℃烧结时发现其晶粒长大符合G3=kt的Ostwald机制,此时晶粒长大动力学系数K仅为0.024μm3/min。     

高密度活化钨粉低温烧结近全致密化行为

采用物理化学方法制备超细高密度活化钨粉(W-0.1%Ni复合粉末,质量分数),研究球磨时间对活化钨粉形貌及其物理性能的影响,探讨球磨处理对该高密度活化钨粉烧结致密化行为的影响,并与超细纯钨粉末的烧结致密化行为进行对比。结果表明:微量活化元素镍的添加及球磨处理能明显加速钨粉的低温烧结收缩速率,显著促进钨粉的烧结致密化程度;球磨5 h后,活化钨粉在1 600℃下烧结即可达到近全致密化(致密度为99.4%),此外,镍元素的添加和球磨处理也能显著促进钨晶粒的长大。     

Microstructure evolution and densification kinetics of Al2O3/Ti(C,N) ceramic tool material by microwave sintering

The microstructure evolution and densification kinetics of Al₂O₃/Ti(C,N) ceramic tool material during microwave sintering were studied. The density and grain growth significantly increases at the temperatures higher than 1400 °C. The calculated kinetics parameter n indicates that volume diffusion is the main densification mechanism when the sintering temperature is below 1300 °C, while grain boundary diffusion plays a leading role in the densification process when the sintering temperature is higher than 1300 °C. The grain growth activation energy of Al₂O₃/Ti(C,N) composite is 48.82 KJ/mol, which is much lower than those of monolithic Al₂O₃ in the microwave sintering and conventional sintering. The results suggested that the Al₂O₃/Ti(C,N) ceramic tool material with nearly full densification and fine grains can be prepared by two-step microwave sintering.